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  • 201.
    Tumova, Jana
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Marzinotto, Alejandro
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Kragic, Danica
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Maximally Satisfying LTL Action Planning2014Inngår i: 2014 IEEE/RSJ International Conference on Intelligent Robots and Systems, (IROS 2014), IEEE , 2014, s. 1503-1510Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We focus on autonomous robot action planning problem from Linear Temporal Logic (LTL) specifications, where the action refers to a "simple" motion or manipulation task, such as "go from A to B" or "grasp a ball". At the high-level planning layer, we propose an algorithm to synthesize a maximally satisfying discrete control strategy while taking into account that the robot's action executions may fail. Furthermore, we interface the high-level plan with the robot's low-level controller through a reactive middle-layer formalism called Behavior Trees (BTs). We demonstrate the proposed framework using a NAO robot capable of walking, ball grasping and ball dropping actions.

  • 202.
    van de Hoef, Sebastian
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Tsiotras, Panagiotes
    Spectral analysis of extended consensus algorithms for multiagent systems2014Inngår i: Decision and Control (CDC), 2014 IEEE 53rd Annual Conference on, 2014, s. 2204-2209Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We analyze an extension of the well-known linear consensus protocol for agents moving in two dimensions, where the standard consensus feedback is multiplied with a rotation matrix. This leads to a richer family of trajectories, and if only the new feedback term is applied, periodic solutions emerge. For special configurations of the controller gains, the form of the system trajectories is given in terms of the eigenvalues and eigenvectors of the closed-loop system matrix. We characterize the resulting closed-loop trajectories for specific choices of the controller gains and of the communication graph topology. Furthermore, the control strategy is extended to agents with double integrator dynamics. It is shown that stability is achieved with sufficiently large velocity feedback. The effect of this feedback on the overall system performance is further investigated. We finally provide simulations to illustrate the theoretical results.

  • 203.
    van de Hoef, Sebastian
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Computing Feasible Vehicle Platooning Opportunities for Transport Assignments2016Inngår i: IFAC PAPERSONLINE, 2016, Vol. 49, nr 3, s. 43-48Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Vehicle platooning facilitates the partial automation of vehicles and can significantly reduce fuel consumption. Mobile mummification infrastructure makes it possible to dynamically coordinate the formation of platoons en route. We consider a centralized system that provides trucks with routes and speed profiles allowing them to dynamically form platoons during their journeys. For this to work, all possible pairs of vehicles that can platoon based on their location, destination, and other constraints have to be identified. The presented approach scales well to large vehicle fleets and realistic road networks by extracting features from the transport assignments of the vehicles and rules out a majority of possible pairs based on these features only. Merely a small number of remaining pairs are considered in depth by a complete and computationally expensive algorithm. This algorithm conclusively decides if platooning is possible for a pair based on the complete data associated with the two vehicles. We derive appropriate features for the problem and demonstrate the effectiveness of the approach in a simulation example.

  • 204. van de Hoef, Sebastian
    et al.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Coordinating Truck Platooning by Clustering Pairwise Fuel-Optimal Plans2015Inngår i: IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC, IEEE conference proceedings, 2015, s. 408-415Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider the fuel-optimal coordination of trucks into platoons. Truck platooning is a promising technology that enables trucks to save significant amounts of fuel by driving close together and thus reducing air drag. We study how fuel-optimal speed profiles for platooning can be computed. A first-order fuel model is considered and pairwise optimal plans are derived. We formulate an optimization problem that combines these pairwise plans into an overall plan for a large number of trucks. The problem resembles a medoids clustering problem. We propose an approximation algorithm similar to the partitioning around medoids algorithm and discuss its convergence. The method is evaluated with Monte Carlo simulations. We demonstrate that the proposed algorithm can compute a plan for thousands of trucks and that significant fuel savings can be achieved.

  • 205.
    van de Hoef, Sebastian
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Efficient Dynamic Programming Solution to a Platoon Coordination Merge Problem With Stochastic Travel Times2017Inngår i: IFAC-PapersOnLine, ISSN 2405-8963, Vol. 50, nr 1, s. 4228-4233Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The problem of maximizing the probability of two trucks being coordinated to merge into a platoon on a highway is considered. Truck platooning is a promising technology that allows heavy vehicles to save fuel by driving with small automatically controlled inter-vehicle distances. In order to leverage the full potential of platooning, platoons can be formed dynamically en route by small adjustments to their speeds. However, in heavily used parts of the road network, travel times are subject to random disturbances originating from traffic, weather and other sources. We formulate this problem as a stochastic dynamic programming problem over a finite horizon, for which solutions can be computed using a backwards recursion. By exploiting the characteristics of the problem, we derive bounds on the set of states that have to be explored at every stage, which in turn reduces the complexity of computing the solution. Simulations suggest that the approach is applicable to realistic problem instances.

  • 206.
    van de Hoef, Sebastian
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Fuel-optimal centralized coordination of truck platooning based on shortest paths2015Inngår i: Proceedings of the American Control Conference, IEEE , 2015, s. 3740-3745Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Platooning is a way to significantly reduce fuel consumption of trucks. Vehicles that drive at close inter-vehicle distance assisted by automatic controllers experience substantially lower air-drag. In this paper, we deal with the problem of coordinating the formation and the breakup of platoons in a fuel-optimal way. We formulate an optimization problem which accounts for routing, speed-dependent fuel consumption, and platooning decisions. An algorithm to obtain an approximate solution to the problem is presented. It first determines the shortest path for each truck. Then, possible platoon configurations are identified. For a certain platoon configuration the optimal speed profile is the solution to a convex program. The algorithm is illustrated by a realistic example.

  • 207.
    van de Hoef, Sebastian
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Mårtensson, Jonas
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    A predictive framework for dynamic heavy-duty vehicle platoon coordination2019Inngår i: ACM Transactions on Cyber-Physical Systems, ISSN 2378-962X, Vol. 4, nr 1, artikkel-id A5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article describes a system to facilitate dynamic en route formation of heavy-duty vehicle platoons with the goal of reducing fuel consumption. Safe vehicle platooning is a maturing technology that leverages modern sensor, control, and communication technology to automatically regulate the inter-vehicle distances. Truck platooning has been shown to reduce fuel consumption through slipstreaming by up to 10% under realistic highway-driving conditions. To further benefit from this technology, a platoon coordinator is proposed, which interfaces with fleet management systems and suggests how platoons can be formed in a fuel-efficient manner over a large region. The coordinator frequently updates the plans to react to newly available information. This way, it requires a minimum of customization with respect to the logistic operations.We discuss the system architecture in detail and introduce important underlying methodological foundations. Plans are derived in computationally tractable stages optimizing fuel savings from platooning. The effectiveness of this approach is verified in a simulation study. It shows that the coordinated platooning system can improve over spontaneously occurring platooning even under the presence of disturbances. A real demonstrator has also been developed. We present data from an experiment in which three vehicles were coordinated to form a platoon on public highways under normal traffic conditions. It demonstrates the feasibility of coordinated en route platoon formation with current communication and on-board technology. Simulations and experiments support that the proposed system is technically feasible and a potential solution to the problem of using vehicle platooning in an operational context.

  • 208.
    Varnai, Peter
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Prescribed performance control guided policy improvement for satisfying signal temporal logic tasks2019Inngår i: Proceedings of the American Control Conference, Institute of Electrical and Electronics Engineers (IEEE), 2019, s. 286-291, artikkel-id 8814999Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Signal temporal logic (STL) provides a user-friendly interface for defining complex tasks for robotic systems. Recent efforts aim at designing control laws or using reinforcement learning methods to find policies which guarantee satisfaction of these tasks. While the former suffer from the trade-off between task specification and computational complexity, the latter encounter difficulties in exploration as the tasks become more complex and challenging to satisfy. This paper proposes to combine the benefits of the two approaches and use an efficient prescribed performance control (PPC) base law to guide exploration within the reinforcement learning algorithm. The potential of the method is demonstrated in a simulated environment through two sample navigational tasks.

  • 209.
    Verginis, Christos
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Bechlioulis, Charalampos
    Dimarogonas, Dimos V
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Kyriakopoulos, Kostas
    Decentralized 2-D Control of Vehicular Platoons under Limited Visual Feedback2015Inngår i: IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Hamburg, Germany, Sept. 28 2015-Oct. 2 2015, IEEE conference proceedings, 2015, s. 3566-3571Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider the two dimensional (2-D) predecessor-following control problem for a platoon of unicycle vehicles moving on a planar surface. More specifically, we design a decentralized kinematic control protocol, in the sense that each vehicle calculates its own control signal based solely on local information regarding its preceding vehicle, by its on-board camera, without incorporating any velocity measurements. Additionally, the transient and steady state response is a priori determined by certain designer-specified performance functions and is fully decoupled by the number of vehicles composing the platoon and the control gains selection. Moreover, collisions between successive vehicles as well as connectivity breaks, owing to the limited field of view of cameras, are provably avoided. Finally, an extensive simulation study is carried out in the WEBOTS realistic simulator, clarifying the proposed control scheme and verifying its effectiveness.

    Fulltekst (pdf)
    fulltext
  • 210.
    Verginis, Christos
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Adaptive Leader-Follower Coordination of Lagrangian Multi-Agent Systems under Transient Constraints2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a novel control methodologyfor the coordination of a multi-agent system with 2nd orderuncertain Lagrangian dynamics, while guaranteeing collisionand connectivity properties in the transient state. More specifically,we consider that a leader agent aims at tracking adesired pose, while all the agents must avoid collisions witheach other. Motivated by cooperative tasks, we also considerthat a subset of the initially connected agents must remainconnected, in the sense of a connected sensing graph.We employa key property of the incidence matrix and integrate potentialfields with discontinuous adaptive control laws to compensatefor unknown dynamic parameters of the model and externaldisturbances. Simulation results in a realistic dynamics engineillustrate the theoretical findings.

    Fulltekst (pdf)
    fulltext
  • 211.
    Verginis, Christos
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS. KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Asymptotic Stability of Uncertain Lagrangian Systems with Prescribed Transient Response2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper considers the asymptotic trackingproblem for 2nd-order nonlinear Lagrangian systems subjectto predefined constraints for the system response, such asmaximum overshoot or minimum convergence rate. In particular,by employing discontinuous adaptive control protocolsand nonsmooth analysis, we extend previous results on funnelcontrol to guarantee at the same time asymptotic trajectorytracking from all the initial conditions that are compliant withthe given funnel. The considered system contains parametricand structural uncertainties, with no boundedness or approximation/parametric factorization assumptions. The response ofthe closed loop system is solely determined by the predefinedfunnel and is independent from the control gain selection.Finally, simulation results verify the theoretical findings.

    Fulltekst (pdf)
    fulltext
  • 212.
    Verginis, Christos
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Closed-Form Barrier Functions for Multi-Agent Ellipsoidal Systems With Uncertain Lagrangian Dynamics2019Inngår i: IEEE Control Systems LettersArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract—In this paper, we design a decentralized controlprotocol for the collision avoidance of a multi-agent system,which is comprised of 3D ellipsoidal agents that obey 2nd-orderuncertain Lagrangian dynamics. More specifically, we derivea novel closed-form smooth barrier function that resemblesa distance metric between 3D ellipsoids and can be used byfeedback-based control laws to guarantee inter-agent collisionavoidance. Discontinuities and adaptation laws are incorporatedin the control protocol to deal with the uncertainties of thedynamic model. The control laws are decentralized, in the sensethat each agent uses only local sensing information. Simulationresults verify the theoretical findings.

    Fulltekst (pdf)
    fulltext
  • 213.
    Verginis, Christos K.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Dimarogonas, Dimos V.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Robust Decentralized Abstractions for Multiple Mobile Manipulators2017Inngår i: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper addresses the problem of decentralized abstractions for multiple mobile manipulators with 2nd order dynamics. In particular, we propose decentralized controllers for the navigation of each agent among predefined regions of interest in the workspace, while guaranteeing at the same time inter-agent collision avoidance and connectivity maintenance for a subset of initially connected agents. In that way, the motion of the coupled multi-agent system is abstracted into multiple finite transition systems for each agent, which are then suitable for the application of temporal logic-based high level plans. The proposed methodology is decentralized, since each agent uses local information based on limited sensing capabilities. Finally, simulation studies verify the validity of the approach.

  • 214.
    Verginis, Christos K.
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Timed abstractions for distributed cooperative manipulation2018Inngår i: Autonomous Robots, ISSN 0929-5593, E-ISSN 1573-7527, Vol. 42, nr 4, s. 781-799Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper addresses the problem of deriving well-defined timed abstractions for the decentralized cooperative manipulation of a single object by N robotic agents. In particular, we propose a distributed model-free control protocol for the trajectory tracking of the cooperatively manipulated object without necessitating feedback of the contact forces/torques or inter-agent communication. Certain prespecified performance functions determine the transient and steady state of the coupled object-agents system. The latter, along with a region partition of the workspace that depends on the physical volume of the object and the agents, allows us to define timed transitions for the coupled system among the derived workspace regions. Therefore, we abstract its motion as a finite transition system and, by employing standard automata-based methodologies, we define high level complex tasks for the object that can be encoded by timed temporal logics. In addition, we use load sharing coefficients to represent potential differences in power capabilities among the agents. Finally, realistic simulation studies verify the validity of the proposed scheme.

  • 215.
    Verginis, Christos K.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Nikou, Alexandros
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Communication-based Decentralized Cooperative Object Transportation Using Nonlinear Model Predictive Control2018Inngår i: 2018 European Control Conference, ECC 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, s. 733-738, artikkel-id 8550305Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper addresses the problem of cooperative transportation of an object rigidly grasped by N robotic agents. We propose a decentralized Nonlinear Model Predictive Control (NMPC) scheme that guarantees the navigation of the object to a desired pose in a bounded workspace with obstacles, while complying with certain input saturations of the agents. The control scheme is based on inter-agent communication and is decentralized in the sense that each agent calculates its own control signal. Moreover, the proposed methodology ensures that the agents do not collide with each other or with workspace obstacles as well as that they do not pass through singular configurations. Finally, simulation results illustrate the validity and efficiency of the proposed method.

  • 216.
    Verginis, Christos K.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Nikou, Alexandros
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Position and Orientation Based Formation Control of Multiple Rigid Bodies with Collision Avoidance and Connectivity Maintenance2017Inngår i: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 411-416Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper addresses the problem of position-and orientation-based formation control of a class of second-order nonlinear multi-agent systems in a 3D workspace with obstacles. More specifically, we design a decentralized control protocol such that each agent achieves a predefined geometric formation with its initial neighbors, while using local information based on a limited sensing radius. The latter implies that the proposed scheme guarantees that the initially connected agents remain always connected. In addition, by introducing certain distance constraints, we guarantee inter-agent collision avoidance as well as collision avoidance with the obstacles and the boundary of the workspace. Finally, simulation results verify the validity of the proposed framework.

  • 217.
    Verginis, Christos
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Mastellaro, Matteo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Robust Cooperative Manipulation Without Force/Torque Measurements: Control Design and Experiments2019Inngår i: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents two novel control methodologies for the cooperative manipulation of an object by  N robotic agents. First, we design an adaptive control protocol which employs quaternion feedback for the object orientation to avoid potential representation singularities. Second, we propose a control protocol that guarantees predefined transient and steady-state performance for the object trajectory. Both methodologies are decentralized, since the agents calculate their own signals without communicating with each other, as well as robust to external disturbances and model uncertainties. Moreover, we consider that the grasping points are rigid and avoid the need for force/torque measurements. Load distribution is also included via a grasp matrix pseudoinverse to account for potential differences in the agents’ power capabilities. Finally, simulation and experimental results with two robotic arms verify the theoretical findings.

  • 218.
    Verginis, Christos
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Nikou, Alexandros
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Robust formation control in SE(3) for tree-graph structures with prescribed transient and steady state performance2019Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 103, s. 538-548Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a novel control protocol for distance and orientation formation control of rigid bodies, whose sensing graph is a static and undirected tree, in the special Euclidean group SE(3). The proposed control laws are decentralized, in the sense that each agent uses only local relative information from its neighbors to calculate its control signal, as well as robust with respect to modeling (parametric and structural) uncertainties and external disturbances. The proposed methodology guarantees the satisfaction of inter-agent distance constraints that resemble collision avoidance and connectivity maintenance properties. Moreover, certain predefined functions characterize the transient and steady state performance of the closed loop system. Finally, simulation results verify the validity and efficiency of the proposed approach.

  • 219.
    Verginis, Christos
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS.
    Vrohidis, Constantinos
    Bechlioulis, Charalampos
    Kyriakopoulos, Kostas
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS.
    Reconfigurable Motion Planning and Control in Obstacle Cluttered Environments under Timed Temporal Tasks2019Inngår i: 2019 International Conference on Robotics And Automation (ICRA): 2019 International Conference on Robotics and Automation, ICRA 2019; Palais des Congres de Montreal, Montreal; Canada; 20 May 2019 through 24 May 2019, Institute of Electrical and Electronics Engineers (IEEE), 2019, s. 951-957, artikkel-id 8794000Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This work addresses the problem of robot navigation under timed temporal specifications in workspaces cluttered with obstacles. We propose a hybrid control strategy that guarantees the accomplishment of a high-level specification expressed as a timed temporal logic formula, while preserving safety (i.e., obstacle avoidance) of the system. In particular, we utilize a motion controller that achieves safe navigation inside the workspace in predetermined time, thus allowingus to abstract the motion of the agent as a finite timed transition system among certain regions of interest. Next, we employ standard formal verification and convex optimization techniques to derive high-level timed plans that satisfy the agent’s specifications. A simulation study illustrates and clarifies the proposed scheme.

  • 220.
    Vizins, Kim
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimons
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Wahlberg, Bo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Modeling and control of dual arm robotic manipulators using decentralized navigation functions2012Inngår i: IFAC Proc. Vol. (IFAC-PapersOnline), 2012, s. 241-246Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We apply multi-agent systems' techniques to the control of dual arm robotic manipulators. The paper is divided into two separate subproblems: the first one considers decentralized navigation of a non-holonomic two-agent system with collision avoidance, corresponding to the end effectors of the robotic arms. For this problem, a controller that guarantees convergence to an arbitrarily small region around the desired destination is proposed. The second subproblem considers decentralized connectivity preserving control of a holonomic multi-agent system of fingers associated with the end effectors. Here, the goal is to account for the angle constraints that are necessary to describe the relationship between fingers connected to the same hand. For this case, both connectivity and convergence are shown with the proposed controller.

  • 221.
    Wei, Jieqiang
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Verginis, Christos
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Wu, J.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Asymptotic and finite-time almost global attitude tracking: Representations free approach2018Inngår i: 2018 European Control Conference, ECC 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, s. 3126-3131, artikkel-id 8550190Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, the attitude tracking problem is considered using the rotation matrices. Due to the inherent topological restriction, it is impossible to achieve global attractivity with any continuous attitude control system on SO(3). Hence in this work, we propose some control protocols achieving almost global tracking asymptotically and in finite time, respectively. In these protocols, no world frame is needed and only relative state information are requested. For finitetime tracking case, Filippov solutions and non-smooth analysis techniques are adopted to handle the discontinuities. Simulation examples are provided to verify the performances of the control protocols designed in this paper.

  • 222. Wiget, R.
    et al.
    Andersson, G.
    Andreasson, Martin
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dynamic simulation of a combined AC and MTDC grid with decentralized controllers to share primary frequency control reserves2015Inngår i: 2015 IEEE Eindhoven PowerTech, PowerTech 2015, IEEE conference proceedings, 2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The use of multi-terminal HVDC grids is a promising option to tackle the coming challenges in long distance power transmission, but the combined operation of HVDC and AC grids will bring certain challenges. The dynamic interaction from the fast controllable converter station with the rotational inertia dependent AC grids has to be investigated in detail, as well as how the converter stations will be controlled in the static and dynamic case. This paper will focus on the dynamic case and proposes a decentralized controller structure to control the HVDC converter power set-points. The proposed controller does not rely on real-time communication nor on a slack bus. A simulation study is presented to demonstrate the implementation of the controller.

  • 223.
    Yang, Tao
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Meng, Ziyang
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Periodic Behaviors for Discrete-Time Second-Order Multiagent Systems With Input Saturation Constraints2016Inngår i: IEEE Transactions on Circuits and Systems - II - Express Briefs, ISSN 1549-7747, E-ISSN 1558-3791, Vol. 63, nr 7, s. 663-667Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This brief considers the existence of periodic behaviors for discrete-time second-order multiagent systems with input saturation constraints. We first consider the case where the agent dynamics is a double integrator and then establish conditions on the feedback gains of the linear consensus control law for achieving periodic behaviors. This, in turn, shows that the previously established sufficient condition for reaching global consensus has a necessary aspect since these two conditions are exclusive. We further consider all other second-order agent dynamics and show that these multiagent systems under the linear consensus law exhibit periodic solutions provided the feedback gains satisfy certain conditions. Simulation results are used to validate the theoretical findings.

  • 224.
    Yang, Tao
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Meng, Ziyang
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Global consensus for discrete-time multi-agent systems with input saturation constraints2014Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 50, nr 2, s. 499-506Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider the global consensus problem for discrete-time multi-agent systems with input saturation constraints under fixed undirected topologies. We first give necessary conditions for achieving global consensus via a distributed protocol based on relative state measurements of the agent itself and its neighboring agents. We then focus on two special cases, where the agent model is either neutrally stable or a double integrator. For the neutrally stable case, any linear protocol of a particular form, which solves the consensus problem for the case without input saturation constraints, also solves the global consensus problem for the case with input saturation constraints. For the double integrator case, we show that a subset of linear protocols, which solve the consensus problem for the case without saturation constraints, also solve the global consensus problem for the case with input saturation constraints. The results are illustrated by numerical simulations.

  • 225.
    Yang, Tao
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Meng, Ziyang
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Global consensus in homogeneous networks of discrete-time agents subject to actuator saturation2013Inngår i: 2013 European Control Conference, ECC 2013, IEEE , 2013, s. 244-249Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we give necessary conditions for achieving global consensus in homogeneous networks of discrete-time linear time-invariant agents with input saturation constraints under fixed undirected topologies. For two special cases, where the agent model is either neutrally stable or a double integrator, these necessary conditions together with a gain condition are also sufficient. We show this by designing a linear protocol based on the combination of state differences between the agent and its neighbors. In particular, for the neutrally stable case, we show that any linear protocol of a particular form which solves the consensus problem for the case without input saturation constraints also solves the global consensus problem for the case with input saturation constraints. For the double integrator case, we show that a subset of linear protocols which solve the consensus problem for the case without saturation constraints also solve the global consensus problem in the presence of input saturation. The results are illustrated by numerical simulations.

  • 226.
    Yang, Tao
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Meng, Ziyang
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Periodic behaviors in multi-agent systems with input saturation constraints2013Inngår i: 2013 IEEE 52nd Annual Conference on Decision and Control (CDC), IEEE conference proceedings, 2013, s. 4467-4472Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we give conditions for the existence of periodic behaviors in a multi-agent system of identical discrete-time double integrators with input saturation constraints. If the feedback gain parameters of the controllers, which are based on relative state measurements of the agent itself and its neighboring agents, are bounded by a value depending on the largest eigenvalue of the Laplacian matrix, then the multi-agent system exhibits a periodic solution for certain initial conditions.

  • 227.
    Yang, Tao
    et al.
    Northeastern Univ, State Key Lab Synthet Automat Proc Ind, Shenyang, Liaoning, Peoples R China..
    Meng, Ziyang
    Tsinghua Univ, Dept Precis Instrument, Beijing, Peoples R China..
    Wan, Yan
    Univ Texas Arlington, Dept Elect Engn, Arlington, TX 76019 USA..
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Ren, Wei
    Univ Calif Riverside, Dept Elect Engn, Riverside, CA 92521 USA..
    Lewis, Frank L.
    Univ Texas Arlington, Dept Elect Engn, Arlington, TX 76019 USA..
    Guest Editorial: Distributed Optimisation and Learning for Networked Systems2019Inngår i: IET Control Theory & Applications, ISSN 1751-8644, E-ISSN 1751-8652, Vol. 13, nr 17, s. 2725-2729Artikkel i tidsskrift (Annet vitenskapelig)
  • 228. Yang, Y.
    et al.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Hu, X.
    Opinion consensus under external influences2018Inngår i: Systems & control letters (Print), ISSN 0167-6911, E-ISSN 1872-7956, Vol. 119, s. 23-30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As a means to regulate the continuous-time bounded confidence opinion dynamics, an exo-system to the original Hegselmann–Krause model is added. Some analysis is made about the properties of the combined system. Two theorems are provided in this article in terms of sufficient conditions of the exo-system that can guarantee opinion consensus for any initial conditions. Two more corollaries are given to describe the resulting synchronized opinions. 

  • 229.
    Yang, Yuecheng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori.
    Dimarogonas, Dimos
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Hu, Xiaoming
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori.
    Shaping up crowd of agents through controlling their statistical moments2015Inngår i: 2015 European Control Conference, ECC 2015, Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 1017-1022Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In a crowd model based on leader-follower interactions, where positions of the leaders are viewed as the control input, up-to-date solutions rely on knowledge of the agents' coordinates. In practice, it is more realistic to exploit knowledge of statistical properties of the group of agents, rather than their exact positions. In order to shape the crowd, we study thus the problem of controlling the moments instead, since it is well known that shape can be determined by moments. An optimal control for the moments tracking problem is obtained by solving a modified Hamilton-Jacobi-Bellman (HJB) equation, which only uses the moments and leaders' states as feedback. The optimal solution can be solved fast enough for on-line implementations.

  • 230.
    Yang, Yuecheng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Hu, Xiaoming
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Opinion consensus of modified Hegselmann-Krause models2012Inngår i: 2012 IEEE 51st Annual Conference on Decision and Control (CDC), IEEE , 2012, s. 100-105Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider the opinion consensus problem using a multi-agent setting based on the Hegselmann-Krause (H-K) Model. Firstly, we give a sufficient condition on the initial opinion distribution so that the system will converge to only one cluster. Then, modified models are proposed to guarantee convergence for more general initial conditions. The overall connectivity is maintained with these models, while the loss of certain edges can occur. Furthermore, a smooth control protocol is provided to avoid the difficulties that may arise due to the discontinuous right-hand side in the H-K model.

  • 231.
    Yang, Yuecheng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Hu, Xiaoming
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Opinion consensus of modified Hegselmann-Krause models2014Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 50, nr 2, s. 622-627Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider the opinion consensus problem using a multi-agent setting based on the Hegselmann-Krause (H-K) Model. Firstly, we give a sufficient condition on the initial opinion distribution so that the system will converge to only one cluster. Then, modified models are proposed to guarantee convergence for more general initial conditions. The overall connectivity is maintained with these models, while the loss of certain edges can occur. Furthermore, a smooth control protocol is provided to avoid the difficulties that may arise due to the discontinuous right-hand side in the H-K model.

  • 232.
    Yang, Yuecheng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Hu, Xiaoming
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori.
    Optimal leader-follower control for crowd evacuation2013Inngår i: 2013 IEEE 52nd Annual Conference on Decision and Control (CDC), IEEE conference proceedings, 2013, s. 2769-2774Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Crowd evacuation has become a primary safety issue in many public places in a metropolitan area. Experts from different fields have worked on modeling and designing evacuating policies by using different tools and methods. In this paper, an optimal control approach is used to derive guiding strategies for the rescue agents under different circumstances. Various optimal control problems are formulated to handle different assumptions of the scenario. Both the analytic solutions and the numerical simulation confirm the efficiency of this approach, which in turn can be potentially used as decisionmaking support in practical applications.

  • 233.
    Yi, Xinlei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Liu, Kun
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Distributed Dynamic Event-Triggered Control for Multi-Agent Systems2017Inngår i: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017, IEEE, 2017, s. 6683-6688Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose two distributed dynamic triggering laws to solve the consensus problem for multi-agent systems with event-triggered control. Compared with existing triggering laws, the proposed triggering laws involve internal dynamic variables which play an essential role to guarantee that the triggering time sequence does not exhibit Zeno behavior. Some existing triggering laws are special cases of our dynamic triggering laws. Under the condition that the underlying graph is undirected and connected, it is proven that the proposed dynamic triggering laws together with the event-triggered control make the state of each agent converges exponentially to the average of the agents’ initial states. Numerical simulations illustrate the effectiveness of the theoretical results and show that the dynamic triggering laws lead to reduction of actuation updates and inter-agent communications.

    Fulltekst (pdf)
    fulltext
  • 234.
    Yi, Xinlei
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Liu, Kun
    Beijing Inst Technol, Sch Automat, Beijing 100081, Peoples R China..
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Dynamic Event-Triggered and Self-Triggered Control for Multi-agent Systems2019Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 64, nr 8, s. 3300-3307Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We propose two novel dynamic event-triggered control laws to solve the average consensus problem for first-order continuous-time multiagent systems over undirected graphs. Compared with the most existing triggering laws, the proposed laws involve internal dynamic variables, which play an essential role in guaranteeing that the triggering time sequence does not exhibit Zeno behavior. Moreover, some existing triggering laws are special cases of ours. For the proposed self-triggered algorithm, continuous agent listening is avoided as each agent predicts its next triggering time and broadcasts it to its neighbors at the current triggering time. Thus, each agent only needs to sense and broadcast at its triggering times, and to listen to and receive incoming information from its neighbors at their triggering times. It is proved that the proposed triggering laws make the state of each agent converge exponentially to the average of the agents' initial states if and only if the underlying graph is connected. Numerical simulations are provided to illustrate the effectiveness of the theoretical results.

  • 235.
    Yi, Xinlei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Wei, Jieqiang
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Formation Control for Multi-Agent Systems with Connectivity Preservation and Event-Triggered Controllers2017Inngår i: IFAC-PapersOnLine, ISSN 1045-0823, E-ISSN 1797-318X, Vol. 50, nr 1, s. 9367-9373Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, event-triggered controllers and corresponding algorithms are proposed to establish the formation with connectivity preservation for multi-agent systems. Each agent needs to update its control input and to broadcast this control input together with the relative state information to its neighbors at its own triggering times, and to receive information at its neighbors' triggering times. Two types of system dynamics, single integrators and double integrators, are considered. As a result, all agents converge to the formation exponentially with connectivity preservation, and Zeno behavior can be excluded. Numerical simulations show the effectiveness of the theoretical results.

    Fulltekst (pdf)
    fulltext
  • 236.
    Yoo, Jaehyun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES). KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Molin, Adam
    Jafarian, Matin
    KTH, Skolan för teknikvetenskaplig kommunikation och lärande (ECE). KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Esen, Hasan
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Event-triggered Model Predictive Control with Machine Learning for Compensation of Model Uncertainties2017Inngår i: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 5463-5468Konferansepaper (Fagfellevurdert)
    Abstract [en]

    As one of the extensions of model predictive control (MPC), event-triggered MPC takes advantage of the reduction of control updates. However, approaches to event-triggered MPCs may be subject to frequent event-triggering instants in the presence of large disturbances. Motivated by this, this paper suggests an application of machine learning to this control method in order to learn a compensation model for disturbance attenuation. The suggested method improves both event-triggering policy efficiency and control accuracy compared to previous approaches to event-triggered MPCs. We employ the radial basis function (RBF) kernel based machine learning technique. By the universial approximation property of the RBF, which imposes an upper bound on the training error, we can present the stability analysis of the learningaided control system. The proposed algorithm is evaluated by means of position control of a nonholonomic robot subject to state-dependent disturbances. Simulation results show that the developed method yields not only two times less event triggering instants, but also improved tracking performance.

  • 237.
    Yu, Pian
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Explicit computation of sampling period in periodic event-triggered multi-agent control2018Inngår i: Proceedings of the American Control Conference, Institute of Electrical and Electronics Engineers Inc. , 2018, s. 3038-3043Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper investigates the synchronization of nonlinear sampled-data multi-agent systems. The purpose is to obtain an explicit formula for the maximum allowable sampling period (MASP) that guarantees exponential synchronization. Two implementation scenarios are considered. We first propose an approach on finding the MASP for periodic time-triggered sampled-data control. Then, a periodic event-triggered communication and control strategy is formulated, where a communication function and a control function are designed for each agent to determine whether or not the sampled data or the control input should be transmitted at each sampling instant. It is shown that there is a tradeoff between the sampling frequency and the convergence performance. The theoretical results are illustrated in simulations.

  • 238.
    Yu, Pian
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Explicit computation of sampling period in periodic event-triggered multi-agent control under limited data rate2019Inngår i: IEEE Transactions on Control of Network Systems, E-ISSN 2325-5870, Vol. 6, nr 4, s. 1366-1378Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper investigates the coordination of nonlinear sampled-data multi-agent systems subject to data rate constraint. The purpose is to design resource-efficient communication and control strategies that guarantee exponential synchronization. Two implementation scenarios are considered, the period time-triggered control and the period event-triggered control. One of the main difficulties of the problem is to obtain an explicit formula for the maximum allowable sampling period (MASP). To this end, an approach on finding the MASP for periodic time-triggered control is proposed first. Then, an asynchronous period event-triggered control strategy is formulated, a communication function and a control function are designed for each agent to determine respectively whether or not the sampled data and the control input should be transmitted at each sampling instant. Finally, the constraint of limited data rate is considered. An observer-based encoder-decoder and a finite-level quantizer are designed respectively for the Sensor-Controller communication and the Controller-Actuator communication such that certain constraint on the data rate is satisfied. It is shown that exponential synchronization can still be achieved in the presence of data rate constraint. A simulation example is given to illustrate the effectiveness of the theoretical results

  • 239.
    Yu, Pian
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Time-constrained multi-agent task scheduling based on prescribed performance control2018Inngår i: 2018 IEEE CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2018, s. 2593-2598Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The problem of time-constrained multi-agent task scheduling and control synthesis is addressed. We assume the existence of a high level plan which consists of a sequence of cooperative tasks, each of which is associated with a deadline and several Quality-of-Service levels. By taking into account the reward and cost of satisfying each task, a novel scheduling problem is formulated and a path synthesis algorithm is proposed. Based on the obtained plan, a distributed hybrid control law is further designed for each agent. Under the condition that only a subset of the agents are aware of the high level plan, it is shown that the proposed controller guarantees the satisfaction of time constraints for each task. A simulation example is given to verify the theoretical results.

  • 240.
    Yu, Pian
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Fischione, Carlo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Distributed Event-Triggered Communication and Control of Linear Multiagent Systems Under Tactile Communication2018Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 63, nr 11, s. 3979-3985Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This note is concerned with the consensus of linear multiagent systems under tactile communication. Motivated by the emerging tactile communication technology where extremely low latency has to be supported, a distributed event-triggered communication and control scheme is proposed for the data reduction of each agent. First, an event-triggered data reduction scheme is designed for the communication between neighbors. Under such a communication scheme, a distributed event-triggered output feedback controller is further implemented for each agent, which is updated asynchronously with the communication action. It is proven that the consensus of the underlying multiagent systems is achieved asymptotically. Furthermore, it is shown that the proposed communication and control strategy fulfils the reduction of both the frequency of communication and controller updates as well as excluding Zeno behavior. A numerical example is given to illustrate the effectiveness of the proposed control strategy.

  • 241.
    Yu, Pian
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Event-Triggered Output Feedback Control for Linear Systems under Tactile Communication2017Inngår i: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 5451-5456Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper investigates an event-triggered output feedback control strategy of linear systems under tactile communication, for which two different frameworks are considered. Motivated by the emerging tactile communications technology where latencies are very small but at the price of limited message sizes, a perception-based deadband principle is proposed for the data reduction of communication. In each framework, under an assumption that the deadband factor is upper bounded with respect to the system model, it is proven that global asymptotic stability of the closed loop system is achieved. Then, an event-triggered output feedback controller under tactile communication is further introduced. It is shown that the designed controller is capable of reducing the frequency of controller updates as well as excluding Zeno behavior. Numerical examples are given to illustrate the effectiveness of the proposed control algorithm.

  • 242.
    Zambelli, Martina
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Karayiannidis, Yiannis
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Posture regulation for unicycle-like robots with prescribed performance guarantees2015Inngår i: IET Control Theory & Applications, ISSN 1751-8644, E-ISSN 1751-8652, Vol. 9, nr 2, s. 192-202Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study aims to address the regulation problem for the unicycle model while guaranteeing prescribed performance. Different controllers based either on polar coordinates or time-varying laws are proposed. The main contribution is the combination of the standard control laws that allow to achieve posture regulation for the unicycle, with the prescribed performance control technique that imposes time-varying constraints to the system coordinates. To apply prescribed performance to the unicycle system which is subject to a non-holonomic constraint, the authors design a specific transformation function that is instrumental in the proof of asymptotic convergence with prescribed guaranties.

  • 243. Zareh, M.
    et al.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Franceschelli, M.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Seatzu, C.
    Consensus in multi-agent systems with non-periodic sampled-data exchange and uncertain network topology2014Inngår i: Proceedings - 2014 International Conference on Control, Decision and Information Technologies, CoDIT 2014, 2014, s. 411-416Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper consensus in second-order multi-agent systems with a non-periodic sampled-data exchange among agents is investigated. The sampling is random with bounded inter-sampling intervals. It is assumed that each agent has exact knowledge of its own state at any time instant. The considered local interaction rule is PD-type. Sufficient conditions for stability of the consensus protocol to a time-invariant value are derived based on LMIs. Such conditions only require the knowledge of the connectivity of the graph modeling the network topology. Numerical simulations are presented to corroborate the theoretical results.

  • 244. Zareh, M.
    et al.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Franceschelli, M.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Seatzu, C.
    Consensus in multi-agent systems with second-order dynamics and non-periodic sampled-data exchange2014Inngår i: 19th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2014, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper consensus in second-order multi-agent systems with a non-periodic sampled-data exchange among agents is investigated. The sampling is random with bounded inter-sampling intervals. It is assumed that each agent has exact knowledge of its own state at all times. The considered local interaction rule is PD-type. The characterization of the convergence properties exploits a Lyapunov-Krasovskii functional method, sufficient conditions for stability of the consensus protocol to a time-invariant value are derived. Numerical simulations are presented to corroborate the theoretical results.

  • 245.
    Ótão Pereira, Pedro Miguel
    et al.
    KTH, Skolan för elektro- och systemteknik (EES).
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES).
    Collaborative Transportation of a Bar by Two Aerial Vehicles with Attitude Inner Loop and Experimental Validation2017Inngår i: 2017 IEEE 56TH ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2017, s. 1815-1820Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose a control law for stabilization of a bar tethered to two aerial vehicles, and provide conditions on the control law's gains that guarantee exponential stability of the equilibrium. Given the proposed control law, we analyze the stability of the equilibrium for two cases, specifically, for a bar of known and unknown mass. We provide lower bounds on the attitude gains of the UAVs' attitude inner loop that guarantee exponential stability of the equilibrium. We also include an integral action term in the control law, so as to compensate for battery drainage and model mismatches, and we provide a lower bound on the integral gain that guarantees stability of the equilibrium. We present an experiment that demonstrates the stabilization and that validates the robustness of the proposed control law.

  • 246.
    Ótão Pereira, Pedro Miguel
    et al.
    KTH, Skolan för elektro- och systemteknik (EES).
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES).
    Control Framework for Slung Load Transportation with Two Aerial Vehicles2017Inngår i: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 4254-4259Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We model a point mass load tethered to two aerial vehicles, and propose a control strategy that guarantees that the load tracks a desired position trajectory. Our framework consists in designing an input and a state transformation which converts the quadrotors-load system into three decoupled subsystems: one concerning the position of the load, with dynamics similar to those of an under-actuated aerial vehicle; one concerning the angle between the cables, with double integrator dynamics; and another concerning the yaw motion of the plane formed by the cables, also with double integrator dynamics. Once the decoupling is done, controllers from the literature can be leveraged, which we take advantage of when controlling the subsystem with dynamics similar to those of an under-actuated aerial vehicle. Simulations are presented which validate the proposed algorithm.

  • 247.
    Ótão Pereira, Pedro Miguel
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Lyapunov-based Generic Controller Design for Thrust-Propelled Underactuated Systems2016Inngår i: 2016 EUROPEAN CONTROL CONFERENCE (ECC), IEEE , 2016, s. 594-599Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present a controller for an underactuated system which is driven by a one dimensional linear acceleration/thrust along a direction vector, by a time-varying gravity, and by the angular acceleration of the direction vector. We propose state and time-dependent control laws for the linear and angular accelerations that guarantee that the position of the system is steered to the origin. The proposed control law depends on (i) a bounded control law for a double integrator system; and (ii) on a Lyapunov function that guarantees asymptotic stability of the origin for the double integrator system when controlled with the previous bounded control law. As such, the control law forms a family of control laws depending on (i) and (ii). The complete state space of the system, under the proposed control laws, has two equilibria, and by proper control design, a trajectory of the system is guaranteed to converge to only one of those. The overall design provides a common framework for controlling different systems, such as quadrotors and slung load transportation systems.

  • 248.
    Ótão Pereira, Pedro Miguel
    et al.
    KTH, Skolan för elektro- och systemteknik (EES).
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES).
    Nonlinear Pose Tracking Controller for Bar Tethered to Two Aerial Vehicles with Bounded Linear and Angular Accelerations2017Inngår i: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 4260-4265Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider a system composed of a bar tethered to two aerial vehicles, and develop a controller for pose tracking of the bar, i.e., a controller for position and attitude tracking. Our first control step is to provide an input and a state transformations which convert the system vector field into one that highlights the cascaded structure of the problem. We then design a controller for the transformed system by exploring that cascaded structure. There are three main contributions: i) we provide bounds on the linear and angular acceleration of the bar that guarantee well-posedness of the controller, and such bounds can be used when selecting the gains and saturations of bounded controllers for both three dimensional and unit vector double integrators; ii) the proposed control law includes a degree of freedom which can be used to regulate the relative position between the aerial vehicles; and iii) the proposed control law for the throttle guarantees that the cascaded structure of the problem is preserved. Simulations are presented which validate the proposed algorithm.

  • 249.
    Ótão Pereira, Pedro Miguel
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH Royal Inst Technol, Sch Elect Engn & Comp Sci, SE-10044 Stockholm, Sweden..
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Pose stabilization of a bar tethered to two aerial vehicles2020Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 112, artikkel-id 108695Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work focuses on the modeling, control and analysis of a bar, tethered to two unmanned aerial vehicles, which is required to stabilize around a desired pose. We derive the equations of motion of the system, we close the loop by equipping each UAV with a PID control law, and finally we linearize the closed-loop vector field around some equilibrium points of interest. When requiring the bar to stay on the horizontal plane and under no normal stress, we verify that the bar's motion is decomposable into three decoupled motions, namely a longitudinal, a lateral and a vertical: for a symmetric system, each of those motions is further decomposed into two decoupled sub-motions, one linear and one angular; for an asymmetric system, we provide relations on the UAVs' gains that compensate for the system asymmetries and which decouple the linear sub-motions from the angular sub-motions. From this analysis, we provide conditions, based on the system's physical parameters, that describe good and bad types of asymmetries. Finally, when requiring the bar to pitch or to be under normal stress, we verify that there is a coupling between the longitudinal and the vertical motions, and that a positive normal stress (tension) has a positive effect on the stability, while a negative normal stress (compression) has a negative effect on the stability.

  • 250.
    Ótão Pereira, Pedro Miguel
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Stability of load lifting by a quadrotor under attitude control delay2017Inngår i: Proceedings - IEEE International Conference on Robotics and Automation, Institute of Electrical and Electronics Engineers Inc. , 2017, s. 3287-3292Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose a control law for stabilization of a quadrotor-load system, and provide conditions on the control law's gains that guarantee exponential stability of the equilibrium. The system is composed of a load and an unmanned aerial vehicle (UAV) attached to each other by a cable of fixed length, which behaves as a rigid link under tensile forces; and the control input is composed of a three dimensional force requested to the UAV, which the UAV provides with or without delay. Given the proposed control law, we analyze the stability of the equilibrium in two separate parts. In the first, the system is modeled assuming that the UAV provides the requested control input without delay, and we verify that the equilibrium is exponentially stable. In the second part, the UAV is modeled as possessing an attitude inner loop, and we provide a lower bound on the attitude gain for which exponential stability of the equilibrium is preserved. An integral action term is also included in the control law, which compensates for battery drainage or model mismatches, such as an unknown load mass. We present experiments for different scenarios that demonstrate and validate the robustness of the proposed control law.

23456 201 - 250 of 255
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