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  • 1.
    Anthony, Richard
    et al.
    The University of Greenwich.
    Chen, DeJiu
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Systems.
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Systems.
    Scholle, Detlef
    Enea Data AB.
    Sanfridson, Martin
    Volvo Technology AB.
    Rettberg, Achim
    University of Paderborn/C-LAB.
    Qureshi, Tahir Naseer
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Systems.
    Persson, Magnus
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Systems.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Systems.
    Autonomic Middleware for Automotive Embedded Systems2009In: Autonomic Communication / [ed] Vasilakos, Athanasios V.; Parashar, Manish; Karnouskos, Stamatis; Pedrycz, Witold, Springer US , 2009, p. 169-210Chapter in book (Refereed)
    Abstract [en]

    This chapter describes DySCAS: an advanced autonomic platform-independent middleware framework for automotive embedded systems. The concepts and architecture are motivated and described in detail, focusing on the need for, and achievement of, high flexibility and automatic run-time reconfiguration. The design of the middleware is positioned with respect to the way it overcomes the specific technical, environmental, and performance challenges of the automotive domain. Self-management is achieved in terms of automatic configuration for context-aware behavior, resource-use efficiency, and self-healing to handle run-time detected faults. The self-management is governed by the use of policies distributed throughout the middleware components. The simulation techniques that have been used for extensive validation are described and some key results presented. A reference implementation is presented, illustrating the way in which the various concepts and mechanisms can be realized and orchestrated.

  • 2.
    Chen, DeJiu
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Lönn, Henrik
    Volvo Trucks Technology.
    Tolvanen, Juha-Pekka
    MetaCase.
    Advances in Automotive System Modeling: EAST-ADL2013In: EETimes Europe Automotive, article id 222902939Article in journal (Other academic)
  • 3.
    Chen, DeJiu
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Feng, Lei
    Volvo Group Trucks Technology.
    Naseer Qureshi, Tahir
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Lönn, Henrik
    Volvo Group Trucks Technology.
    Hagl, Frank
    Continental Automotive DE.
    An architectural approach to the analysis, verification and validation of software intensive embedded systems2013In: Computing, ISSN 0010-485X, E-ISSN 1436-5057, Vol. 95, no 8, p. 649-688Article in journal (Refereed)
    Abstract [en]

    EAST-ADL is a domain specific Architecture Description Language (ADL) for safety-critical and software-intensive embedded systems. The language allows a formalized and traceable description of a wide range of engineering concerns throughout the entire lifecycle of system development. This makes it possible to fully utilize the leverage of state-of-the-art methods and tools for the development of correct-by-construction system functions and components in a seamless and cost efficient way. This paper focuses on the recent advancement of EAST-ADL in supporting an architecture-centric analysis, verification&validation of complex behaviors for the purposes of requirements engineering, application design, and safety engineering. The approach is architecture centric because all behavior descriptions are formalized and connected to a set of standardized design artifacts sitting at multiple levels of abstractions. We present the language design to support this, the theoretical underpinning and tool implementation. To show the capability of EAST-ADL, we also introduce an algorithm and its implementation for transforming the EAST-ADL behavior models to SPIN models for logic model checking. Exploiting mature state-of-the-art technologies from computer science, electronic engineering, and other related domains for a model-based incremental system development, the contribution enables the developers of embedded systems and software to maintain various engineering concerns coherently using EAST-ADL.

  • 4.
    Chen, DeJiu
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Mahmud, Nidhal
    University of Hull, United Kingdom.
    Walker, Martin
    University of Hull, United Kingdom.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Lönn, Henrik
    Volvo Technology AB, Sweden.
    Papadopoulos, Yiannis
    University of Hull, United Kingdom.
    Systems Modeling with EAST-ADL for Fault Tree Analysis through HiP-HOPS2013In: IFAC Proceedings Volumes: (IFAC-PapersOnline), 2013, Vol. 4, p. 91-96Conference paper (Refereed)
    Abstract [en]

    EAST-ADL is a domain-specific modeling framework with methodology and language supportfor the engineering of automotive embedded systems. In regard to functional safety, it aims toprovide the maximum possible support for ISO 26262 so that all safety related information can beconsolidated seamlessly in a common system model together with the requirements specification.This paper describes the EAST-ADL support for the modeling of plausible error behaviors as anorthogonal system view. We introduce in particular an integration of such EAST-ADL modelswith the HiP-HOPS method for automated temporal fault tree analysis.

  • 5.
    Chen, DeJiu
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Persson, Magnus
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Qureshi, Tahir Naseer
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Towards Model-Based Engineering of Self-Configuring Embedded Systems2010In: Model-based engineering of embedded real-time systems / [ed] Giese, H; Karsai, G; Lee, E; Rumpe, B; Schatz, B, Springer Berlin/Heidelberg, 2010, 1st Edition, Vol. 6100, p. 345-353Conference paper (Refereed)
    Abstract [en]

    In self-configuring embedded systems, upgrades, attachment of devices, relocation ofapplications and adjustment of performance parameters can be carried out during run-timefor the purposes of information/function integration, maintenance, performance, resourceefficiency, and robustness. We describe a model-based engineering approach to support thedevelopment of such systems. Essential ingredients include a combined usage of a systemmodel, simulation combined with a number of formal techniques, and run-time models used as a basis for on-line decision making, with the overall goal to ascertain flexible, yet dependable, system behavior.

  • 6. Chen, Li
    et al.
    Song, Zhijie
    Feng, Lei
    Design and Manufacturing Integration Laboratory, Department of Mechanical and Industrial Engineering, The University of Toronto, 5 King's College Road, Toronto, Ont., Canada M5S 3G8.
    Internet-Enabled Real-Time Collaborative Assembly Modeling via An e-Assembly System: Status and Promise2004In: Computer-Aided Design, ISSN 0010-4485, E-ISSN 1879-2685, Vol. 36, no 9, p. 835-847Article in journal (Refereed)
    Abstract [en]

    Collaborative CAD systems enabling collaboration in computer-aided design processes among distributed designers are gaining more and more attention. Yet, such systems, especially in support of collaborative assembly modeling, are hardly achievable. Targeting this gap, this paper addresses an Internet-enabled real-time collaborative assembly modeling system, named e-Assembly. This emerging system allows a group of geographically dispersed designers to jointly build an assembly model in real time over the Internet. In particular, this paper proposes a new assembly representation, called Collaborative Assembly Representation, for Internet-based collaborative assembly modeling. Also, collaborative assembly constraint satisfaction is addressed based on three coordination rules embedded in e-Assembly. Furthermore, the system architecture and realization of e-Assembly are provided. Finally, a prototypic implementation of e-Assembly is presented for demonstration and discussion.

  • 7.
    Feng, Lei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Cai, Kai
    Wonham, W. M.
    A structural approach to the non-blocking supervisory control of discrete-event systems2009In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 41, no 11-12, p. 1152-1168Article in journal (Refereed)
    Abstract [en]

    Many practical and important systemic properties of manufacturing systems, like deadlock freeness, liveness, and reversibility, can be formulated as the non-blocking property of discrete-event systems. It can be difficult, however, to verify non-blocking or design a supervisor to guarantee non-blocking control because of state size explosion in the concurrency model. In this paper, we present sufficient conditions for the computation of (small) model abstractions that preserve the non-blocking property. As a consequence, hierarchical and decentralized control structures can be flexibly integrated, and the proposed approach can synthesize maximally permissive and non-blocking control with reduced computational effort. The solution is a group of decentralized supervisors that transparently displays control logic and admits relatively simple implementation.

  • 8.
    Feng, Lei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Systems.
    Chen, DeJiu
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Systems.
    Lönn, Henrik
    Volvo Technology AB.
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Systems.
    Verifying System Behaviors in EAST-ADL2 with the SPIN ModelChecker2010Conference paper (Refereed)
    Abstract [en]

    EAST-ADL2 is a domain-specific architecture descriptionlanguage to support the model-based developmentof automotive embedded systems. It emerged to manage thecomplexity of software and electronics in advanced automotiveapplications. The language focuses on the structural definitionfor functional specifications. Behavior is defined only on thecomponent level, in terms of functional blocks and their triggersand interfaces. The behavioral definition inside each functionalblock is not prescribed. This paper shows one approachto augment the language with precise syntax and semanticsfor behavior, and develops a procedure that transforms thecomposed behavioral model to the SPIN model for logicmodel checking. The contribution improves the modeling andverification capability of EAST-ADL2.

  • 9.
    Feng, Lei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Chen, DeJiu
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Self Configuration of Dependent Tasks for Dynamically Reconfigurable Automotive Embedded Systems2008In: Proceedings of the IEEE Conference on Decision and Control, IEEE conference proceedings, 2008, p. 3737-3742Conference paper (Refereed)
    Abstract [en]

    The configurations of an automotive embedded system are normally fixed in production and remain static over the vehicle lifetime. Future scenarios, however, call for more flexible configuration support. DySCAS (Dynamically Self-Configuring Automotive Systems) project aims to introduce context-awareness and self-management features into automotive embedded systems via middleware technologies. Contributing to online configuration decisions, this paper formalizes a fundamental self-configuration problem. It forms a basis for managing the cross interdependencies of configurational items, assessing the system-wide impacts of changes, and making dynamic decisions about new configurations.

  • 10. Feng, Lei
    et al.
    Chen, Li
    Achieving online coordination in real-time collaborative assembly modeling: A supervisory control approach2006In: Journal of Computing and Information Science in Engineering, ISSN 1530-9827, E-ISSN 1944-7078, Vol. 6, no 3, p. 252-262Article in journal (Refereed)
    Abstract [en]

    A real-time collaborative assembly modeling process involves the teamwork of multiple designers. Without adequate coordination, this multi-user based modeling process could be more time consuming, or even divergent, than the conventional single-user-based process. This paper thus presents a supervisory control approach to achieving online operational coordination of the multi-user based assembly modeling process. In this approach, we treat the real-time collaborative modeling process as a discrete-event system (DES) and then obtain an effective coordinator for the process control via the supervisory control theory (SCT). Our work extends the framework of SCT to this new application so that the assembly modeling operations and its desired operational behaviors can be modeled and controlled by a set of automata. With them, we further propose a modular supervision approach to find a group of modular supervisors. These supervisors compose the online coordinator to enforce the control specifications and to yield a nonblocking controlled process. The results show much promise for SCT in the new application domain of collaborative CAD (CCAD).

  • 11.
    Feng, Lei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Lundmark, Simon
    Meinke, Karl
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Niu, Fei
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Sindhu, Mudassar A.
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Wong, Peter Y. H.
    Case studies in learning-based testing2013In: Testing Software and Systems: 25th IFIP WG 6.1 International Conference, ICTSS 2013, Istanbul, Turkey, November 13-15, 2013, Proceedings, Springer, 2013, p. 164-179Conference paper (Refereed)
    Abstract [en]

    We present case studies which show how the paradigm of learning-based testing (LBT) can be successfully applied to black-box requirements testing of industrial reactive systems. For this, we apply a new testing tool LBTest, which combines algorithms for incremental black-box learning of Kripke structures with model checking technology. We show how test requirements can be modeled in propositional linear temporal logic extended by finite data types.We then provide benchmark performance results for LBTest applied to three industrial case studies.

  • 12.
    Feng, Lei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Innovative Centre for Embedded Systems, ICES.
    Wonham, W. M.
    On the Computation of Natural Observers in Discrete-Event Systems2010In: Discrete event dynamic systems, ISSN 0924-6703, E-ISSN 1573-7594, Vol. 20, no 1, p. 63-102Article in journal (Refereed)
    Abstract [en]

    Natural projections with the observer property have proved effective in reducing the computational complexity of nonblocking supervisory control design, and the state sizes of the resulting controllers. In this paper we present an algorithm to verify this property, or if necessary to achieve it. A natural projection is a special type of general causal reporter map; for the latter an algorithm is already known for verification and modification. This algorithm could be used to verify the observer property of a natural projection, but if the natural projection is not an observer the algorithm is not applicable to modify it to an observer. Also, while a general reporter map always admits a unique smallest refinement with the observer property, a natural projection does not. Indeed there may exist several minimal extensions to the original observable event set of a natural projection. We show that the problem of finding a minimal extension is NP-hard, but propose a polynomial-time algorithm that always finds an acceptable extension. While not guaranteed to be minimal, it is in practice often reasonably small.

  • 13. Feng, Lei
    et al.
    Wonham, W. M.
    Supervisory control architecture for discrete-event systems2008In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 53, no 6, p. 1449-1461Article in journal (Refereed)
    Abstract [en]

    A flexible decentralized and hierarchical architecture is presented to reduce computational effort in designing optimal nonblocking supervisors for discrete-event systems (DES). We organize a DES into modular subsystems that embody internal interacting dependencies. Verification of, and coordination among modular subsystems are achieved through their model abstractions. Sufficient conditions are presented to guarantee that coordinators and modular supervisors result in maximally permissive and nonblocking control. A medium-sized example demonstrates the computational effectiveness of our approach.

  • 14. Feng, Lei
    et al.
    Wonham, W. M.
    Thiagarajan, P. S.
    Designing communicating transaction processes by supervisory control theory2007In: Formal methods in system design, ISSN 0925-9856, E-ISSN 1572-8102, Vol. 30, no 2, p. 117-141Article in journal (Refereed)
    Abstract [en]

    A Communicating Transaction Process (CTP) is a computational model that serves as a high level specification language for reactive embedded system components and their interactions. It consists of a network of communicating processes coordinating their behaviors via common actions and the common actions are refined as a set of guarded Message Sequence Charts (MSCs). There has been little work devoted to developing CTP models systematically. This paper takes the first step towards bridging this gap. In our work, communicating processes of embedded components are modeled and controlled as Discrete-Event Systems (DES). The control logic among communicating components is derived by Supervisory Control Theory (SCT), so as to guarantee that the communicating processes meet all predefined constraints and possess other desirable system behavioral properties. The control logic is then translated into propositional formulas for guarded MSCs which then results in a CTP model with guaranteed behavioral properties.

  • 15.
    Khodabakhshian, Mohammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Börjesson, Stefan
    Lindgärde, Olof
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Reducing Auxiliary Energy Consumption of Heavy Trucks by Onboard Prediction and Real-time Optimization2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 188, p. 652-671Article in journal (Refereed)
    Abstract [en]

    The electric engine cooling system, where the coolant pump and the radiator fan are driven by electric motors, admits advanced control methods to decrease auxiliary energy consumption. Recent publications show the fuel saving potential of optimal control strategies for the electric cooling system through offline simulations. These strategies often assume full knowledge of the drive cycle and compute the optimal control sequence by expensive global optimization methods. In reality, the full drive cycle is unknown during driving and global optimization not directly applicable on resource-constrained truck electronic control units. This paper reports state-of-the-art engineering achievements of exploiting vehicular onboard prediction for a limited time horizon and minimizing the auxiliary energy consumption of the electric cooling system through real-time optimization. The prediction and optimization are integrated into a model predictive controller (MPC), which is implemented on a dSPACE MicroAutoBox and tested on a truck on a public road. Systematic simulations show that the new method reduces fuel consumption of a 40-tonne truck by 0.36% and a 60-tonne truck by 0.69% in a real drive cycle compared to a base-line controller. The reductions on auxiliary fuel consumption for the 40-tonne and 60-tonne trucks are about 26% and 38%, respectively. Truck experiments validate the consistency between simulations and experiments and confirm the real-time feasibility of the MPC controller. © 2016 Elsevier Ltd

  • 16.
    Khodabakhshian, Mohammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Fuel Saving Potential of Optimal Engine Cooling System2014Conference paper (Refereed)
    Abstract [en]

    The engine cooling system in trucks is one of the main sources of parasite load. Thus optimal control of the engine thermal management system with the objective of minimizing energy consumption can substantially improve fuel efficiency. Existing methods on the engine thermal control system concentrate mainly on regulating the engine coolant temperature within a safety range. This paper explicitly calculates the energy consumption of the cooling system using the optimal control methods to decide the trajectories of the control values of the cooling system. During the optimal operation, the engine cooling system serves as another energy buffer to balance the engine workload in conventional trucks. To expose the maximal fuel saving potential of the optimal engine thermal control system, we apply dynamic programming in the investigation and the results are compared with a simple state feedback controller.

  • 17.
    Khodabakhshian, Mohammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Improvement of fuel efficiency and drivability using simple prediction for gear changing2013In: IFAC Proceedings Volumes (IFAC-PapersOnline), 2013, no PART 1, p. 518-523Conference paper (Refereed)
    Abstract [en]

    Decreasing fuel consumption and emissions in automobiles has been an active research topic in recent years. A promising technology is the hybridization of powertrain. The main focus in this area is usually on the development of optimal power management control methods. For parallel HEVs (hybrid electric vehicle), the primary control variable is the torque split between the internal combustion engine and the electric motor but gear number can also be considered as a control parameter. ECMS (equivalent consumption minimization strategy) is one of the well-known real time power management strategies and has been used extensively in different works; however, using ECMS for controlling gearbox cannot always lead to optimal fuel consumption and drivability. The slow dynamics of gearbox might introduce unnecessary gear changing, which leads to suboptimal fuel efficiency and degraded drivability. In this paper, a simple prediction strategy is implemented to improve fuel efficiency and drivability. The presented prediction method does not use any information from the environment and does not need any extra sensor. The strategy is not computationally heavy compared to other predictive methods. The simplicity of the method makes it suitable for implementations.

  • 18.
    Khodabakhshian, Mohammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Improving Fuel Economy and Robustness of an Improved ECMS Method2013In: 2013 10th IEEE International Conference on Control and Automation  (ICCA), IEEE , 2013, p. 598-603Conference paper (Refereed)
    Abstract [en]

    Hybrid electric vehicles have shown significant improvement for both fuel efficiency and emission reduction, and attracted many researchers. Paramount for the fuel efficiency of HEVs is the energy management control strategies. ECMS (equivalent consumption minimization strategy) is one of the well-known real time power management strategies and has been used extensively in different works; however, its intrinsic difficulty is to find the optimal equivalent factor, which in theory is determined by the a priori knowledge of the complete driving cycle. Different methods have been proposed to solve this issue, but each one has its own pros. and cons. Especially, the applicability of each method for different cycles as well as the computation overhead are two main concerns in the methods presented so far. In this paper, a new method is presented for calculating equivalent factor in the ECMS method. The method does not rely on any prediction nor the a priori knowledge of driving cycles. Its robustness is demonstrated through different driving cycles with distinct characteristics. Our new method will improve the effectiveness and robustness of the ECMS method.

  • 19.
    Khodabakhshian, Mohammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    One-step prediction for improving gear changing control of HEVs2014In: Journal of Robotics and Mechatronics, ISSN 0915-3942, Vol. 26, no 6, p. 799-807Article in journal (Refereed)
    Abstract [en]

    Decreasing fuel consumption and emissions in automobiles continues to be an active research problem. A promising technology is powertrain hybridization. Study in this area usually focuses on the development of optimal power management control methods. The equivalent consumption minimization strategy (ECMS) is a widely used real-time control method used for determining the optimal trajectory of the power split between the engine and motor. Reports also cover applying ECMS to find an optimal gear changing strategy, but results are not always satisfactory in fuel economy and drivability. One possible reason for this is that gearbox dynamics are slow, but ECMS is based on instant optimization and neglects this time delay. This paper proposes a simple prediction strategy for improving ECMS performance used with gear changing control. The proposed controller improves fuel efficiency and drivability without the need of adding extra sensors to the automobile. The proposed method’s simplicity makes it suitable for implementation.

  • 20.
    Khodabakhshian, Mohammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Optimization of gear shifting and torque split for improved fuel efficiency and drivability of HEVs2013In: SAE Technical Papers: Volume 2, 2013, S A E Inc , 2013, Vol. 2, p. 2013-01-1461-Conference paper (Refereed)
    Abstract [en]

    Decreasing fuel consumption and emissions in automobiles has been an active research topic in recent years. Vehicles with alternative powertrain systems, especially hybrid-electric vehicles (HEVs), have shown significant reduction in fuel consumption and emissions, and therefore have attracted many researchers to this field. The focus is usually on the development of optimal power management control methods. For parallel HEVs, the primary control variable is the torque split between the internal combustion engine and the electric motor. More advanced approaches also simultaneously search for the optimal gear number and engine on/off state, which can further reduce the fuel consumption but also complicate the problem. In the literature on HEVs, the emphasis is typically only on fuel efficiency and sometimes the emissions. The drivability of the vehicle is usually not considered during the optimization process. Furthermore, gearbox models do not usually reflect the real behavior of vehicle due to over simplification in vehicle models. This paper studies the energy management problem of parallel HEVs. Fuel consumption and drivability are optimized through an integrated optimization process by searching optimal torque split and gear number simultaneously. Intelligent filters are designed to stabilize the values of gear number to avoid frequent oscillation. The method is suitable for real-time implementation and has been tested in the simulation software Autonomie.

  • 21.
    Khodabakhshian, Mohammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Predictive control of the engine cooling system for fuel efficiency improvement2014In: Automation Science and Engineering (CASE), 2014 IEEE International Conference on, IEEE conference proceedings, 2014, p. 61-66Conference paper (Refereed)
    Abstract [en]

    The engine cooling system in trucks is one of the main sources of parasite load. Thus fuel efficiency can be improved by optimal control of engine thermal management system considering fuel consumption minimization as the objective. Although several optimal control methods have been proposed for the engine cooling system, their main emphasize is on regulating engine and coolant temperature in an acceptable range rather than minimizing fuel consumption. In contrast, this paper investigates the fuel saving potential of predictive optimal control methods for the engine cooling system of conventional trucks. Our method exploits the idea of energy buffers in the automotive system, where the engine cooling system and the battery serve as energy buffers. The advantages of this approach are the recovery of brake energy and the balance of energy sources so that the total energy loss is minimized. A model predictive controller is used as the real time controller, and the results are compared with a simple state feedback controller and a global optimal solution obtained by dynamic programming. The results show limited but notable improvement in fuel efficiency. The results also construct a base for ongoing research on energy buffer control in conventional heavy trucks.

  • 22.
    Khodabakhshian, Mohammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Fuel efficiency improvement in HEVs using electromechanical brake system2013In: 2013 IEEE Intelligent Vehicles Symposium (IV), IEEE , 2013, p. 322-327Conference paper (Refereed)
    Abstract [en]

    Today, two of the main concerns in transportation industry are reducing fuel consumption and emissions, and tough regulations are put on the vehicle manufacturers in these regards. One of the main approaches towards reducing CO2 emissions is hybridization of the powertrain system. Substantial R&D in this area over the last couple of years has resulted in rather optimal components and control strategies, and hence that further substantial improvements are difficult. This motivates research on other energy consuming vehicle subsystems, e.g. pneumatic and hydraulic systems. In this paper, the brake system of a hybrid city bus is studied. A complete electrification of the primary brake system would eliminate the use of low efficiency pneumatics for braking. It is therefore interesting to investigate how much energy can be saved by using electrically actuated and controlled primary brakes. The study is based on simulations in Autonomie which is a MATLAB/SIMULINK based vehicle simulation software package. Different representative driving cycles are studied. It is shown that fuel consumption can be reduced in the range of 0.5 to 1.5% by substituting the pneumatic brake system with a mechatronic one. This may seem limited, but can, combined with substitution of also other less efficient subsystems with their mechatronic counterparts, result in a substantial environmental and economic improvement.

  • 23.
    Li, Yuchao
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Duan, Anqing
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Gratner, Alexander
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    A Geometric Programming Approach to the Optimization of Mechatronic Systems in Early Design Stages2016In: 2016 IEEE INTERNATIONAL CONFERENCE ON ADVANCED INTELLIGENT MECHATRONICS (AIM), IEEE conference proceedings, 2016, p. 1351-1356Conference paper (Refereed)
    Abstract [en]

    This paper evaluates geometric programming as a solver to optimize mechatronic system design in a holistic manner to aid early design decisions. Mechatronic systems design optimization requires complex and often non-convex functions as design objectives and constraints. Currently the solutions are primarily based on randomized search methods, e.g., genetic algorithms, and they are time-consuming. This paper converts complex constraints and objectives into approximate posynomial forms, which can then be used with disciplined convex optimization to significantly reduce the computation time for optimization. The approach is compared to the previous research using a mechatronic servo system design case study consisting of a motor, a shaft, two planetary gears and a rotational load. The result confirms that the geometric programming approach improves both computation speed and accuracy.

  • 24.
    Li, Yuchao
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Wang, Yu
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
    A cascade control approach to active suspension using pneumatic actuators2019In: Asian journal of control, ISSN 1561-8625, E-ISSN 1561-8625, p. 1-19Article in journal (Refereed)
    Abstract [en]

    Operators of forest machinery suffer from intensive whole body vibrations, which are big threats to their health. Therefore, it is important to investigate effective seat undercarriages and control methods for vibration reduction. This paper addresses the control problem of a novel seat undercarriage with pneu-matic actuators customized for forest machinery. A two-layer cascade controlstructure is developed, where the top layer consists of a group of proportional controllers to regulate the position of pneumatic actuators and the bottom layeris a sliding mode controller for force and stiffness tracking. The advantage ofthe sliding mode control is to achieve robust control performance with coarse system models. The paper demonstrates that the proposed control structure is better than a traditional PID controller. The robust stability of the sliding mode controller is proved by the Lyapunov's method. Experiments show its capability of reducing at least 20% amplitude of seat vibrations from 0.5 to 1 Hz.

  • 25. Lindgärde, O.
    et al.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Tenstam, A.
    Soderman, M.
    Optimal Vehicle Control for Fuel Efficiency2015In: SAE International Journal of Commercial Vehicles, ISSN 1946-391X, E-ISSN 1946-3928, Vol. 8, no 2, p. 682-694Article in journal (Refereed)
    Abstract [en]

    CONVENIENT is a project where prediction and integrated control are applied on several subsystems with electrified actuators. The technologies developed in this project are applied to a long-haul tractor and semi-trailer combination. A Volvo truck meeting the Eu6 emission standard is rebuilt with a number of controllable electrified actuators. An e-Horizon system collects information about future road topography and speed limits. Controllable aerodynamic wind deflectors reduce the wind drag. The tractor is also equipped with a full digital cluster for human machine interface development. A primary project goal is to develop a model-based optimal controller that uses predictive information from the e-Horizon system in order to minimize fuel consumption. Several energy buffers are controlled in an integrated and optimal way using model predictive control. Several buffers are considered, such as the cooling system, the battery, and the vehicle kinetic energy. This paper presents details on the model predictive controller of the battery system and of the cooling system. Another project goal is to reduce fuel consumption by using adaptive aerodynamics. Controllers are developed that automatically sets an optimal roof deflector angle and the optimal side deflector angle. The results presented in this paper are encouraging. A third focus is the human machine interface and especially the communication between the driver and the control system during driving. This project develops a driver interface that encourages the driver to use the adaptive cruise controller when appropriate. The CONVENIENT project will be finalized this year. This paper presents the main project findings.

  • 26. Lindgärde, O.
    et al.
    Söderman, M.
    Tenstam, A.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Optimal Complete Vehicle Control for Fuel Efficiency2016Conference paper (Refereed)
    Abstract [en]

    CONVENIENT is a project where prediction and integrated control are applied on several subsystems with electrified actuators. The technologies developed in this project are applied to a long-haul tractor and semi-trailer combination. A Volvo truck meeting the Eu6 emission standard is rebuilt with a number of controllable electrified actuators. An e-Horizon system collects information about future road topography and speed limits. Controllable aerodynamic wind deflectors reduce the wind drag. The tractor is also equipped with a full digital cluster for human machine interface development. A primary project goal is to develop a model-based optimal controller that uses predictive information from the e-Horizon system in order to minimize fuel consumption. Several energy buffers are controlled in an integrated and optimal way using model predictive control. Several buffers are considered, such as the cooling system, the battery, and the vehicle kinetic energy. This paper presents details on the model predictive controller of the battery system and of the cooling system. Another project goal is to reduce fuel consumption by using adaptive aerodynamics. Controllers are developed that automatically sets an optimal roof deflector angle and the optimal side deflector angle. The results presented in this paper are encouraging. A third focus is the human machine interface and especially the communication between the driver and the control system during driving. This project develops a driver interface that encourages the driver to use the adaptive cruise controller when appropriate. The CONVENIENT project will be finalized this year. This paper presents the main project findings.

  • 27. Liu, Junhui
    et al.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Li, Zhiwu
    The Optimal Road Grade Design for Minimizing Ground Vehicle Energy Consumption2017In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 10, no 5, article id 700Article in journal (Refereed)
    Abstract [en]

    Reducing energy consumption of ground vehicles is a paramount pursuit in academia and industry. Even though the road infrastructural has a significant influence on vehicular fuel consumption, the majority of the R&D efforts are dedicated to improving vehicles. Little investigation has been made in the optimal design of the road infrastructure to minimize the total fuel consumption of all vehicles running on it. This paper focuses on this overlooked design problem and the design parameters of the optimal road infrastructure is the profile of road grade angle between two fixed points. We assume that all vehicles on the road follow a given acceleration profile between the two given points. The mean value of the energy consumptions of all vehicles running on the road is defined as the objective function. The optimization problem is solved both analytically by Pontryagin's minimum principle and numerically by dynamic programming. The two solutions agree well. A large number of Monte Carlo simulations show that the vehicles driving on the road with the optimal road grade consume up to 31.7% less energy than on a flat road. Finally, a rough cost analysis justifies the economic advantage of building the optimal road profile.

  • 28.
    Liu, Tong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Hellgren, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Increasing Fuel Efficiency of a Hybrid Electric Competition Car by a Binary Equivalent Consumption Minimization Strategy2018In: 2018 IEEE 14th International Conference on Automation Science and Engineering (CASE), IEEE, 2018Conference paper (Refereed)
    Abstract [en]

    To improve the fuel efficiency of a hybrid electric car with special powertrain features racing in Shell Eco-marathon, a computationally efficient online control system is developed by solving hierarchical optimal control problems. The top-level computes the optimal velocity trajectory based on the given competition track in advance. The lower-level then finds the best instantaneous engine state and torque allocation by the equivalent consumption minimization strategy (ECMS). The special design of the competition car reduces the ECMS into a binary optimization problem. The new controller can run in real-time on low-cost microprocessors and improves the car's fuel efficiency by 50% while maintaining the state of charge of the electrical energy buffer.

  • 29.
    Persson, Magnus
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    A Timed Automata Formalism for Modeling Resource Management and Quality of Service in Real-Time Contexts2009Report (Other academic)
    Abstract [en]

    Quality of service (QoS) and resource management play important roles in embeddedsystems. In this report, a formalism to describe QoS properties in real-time systemsis presented. The formal model is extensible and can be used to model both resourceavailability and resource needs. The formalism focuses rather on organization andstructuring of data than providing novel analysis techniques. An instantiation of theformalism in the context of DyLite, an adaptive middleware implementation developedat KTH, is explained as a modeling guideline and help to future instantiators of theframework.

  • 30.
    Persson, Magnus
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    García, Javier
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Qureshi, Tahir Naseer
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Chen, DeJiu
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    DyLite: Design, Implementation and Experiences of a Light-Weight Middleware for Adaptive Embedded Systems2009Report (Other academic)
    Abstract [en]

    Within this document, we introduce the architecture and detailed design of the DyLitemiddleware. DyLite was created at the Mechatronics Lab during fall 2008 and earlyspring 2009 to further validate the configurational aspects of the architectural frameworkproduced within the DySCAS project. The focus of the implementation is to build alow-overhead, simple implementation of the main concepts in the DySCAS referencearchitecture. Its primary purpose is to validate the parts of the DySCAS system closelyrelated to the (re-)configuration algorithms and quality of service (QoS) mechanisms, andas a basis for the demonstrator built on the SAINT truck. DyLite has been developed in thecontext of automotive systems.Following the work on DyLite, it has been confirmed that the DySCAS ideas areimplementable in real middleware. The DyLite implementation is very compact - thefootprint is only 15 kB - which clearly makes it deployable even in very small-scalemicrocontrollers.

  • 31.
    Qureshi, Tahir Naseer
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Chen, DeJiu
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Persson, Magnus
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    On Mapping UML™ Models to Simulink® /SimEvents™:  A Case Study of Dynamically Self-Configuring Middleware2009Report (Other academic)
    Abstract [en]

    Due to the increased usage of electronics and software the complexity of systems such as automotive as well as their development process is also increasing. One possible solution to reduce and manage this complexity is model-based and component based development approach. One of the major key features of model-based development is model transformation. This report presents an effort towards the model-based development in automotive systems with a dynamically self-configuring middleware as case study. A mapping scheme from UML™ (Unified modeling language) to SimEvents™ an extension of Simulink® for discrete event simulations is the major outcome of this work. The focus of this work is on the behavior of the middleware components specified by state machines and activity diagrams using UML™. Identification of the requirements and challenges in model transformations for self-configuring systems and a library for the middleware core services for SimEvents™ is also part of this work.

  • 32.
    Qureshi, Tahir Naseer
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Chen, DeJiu
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Persson, Magnus
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Experiences in Simulating a Dynamically Self-Configuring Middleware: A Case Study of DySCAS2009Report (Other academic)
    Abstract [en]

    The increased usage of electronic components, wired and wireless networks, software and advanced telematics systems in modern automotive systems has raised the overall complexity in terms of both the system functionalities and their development and maintenance. One way to handle a few of the complexities is the use of middlewares and introduction of self-management mechanisms. This report presents the experiences and efforts for verification and proof of concepts by simulations of a dynamically self-configuring middleware for automotive systems. A brief overview of the architecture and control flow of the simulated middleware, requirements for a self-managing systems and their simulation platform are also presented.

  • 33.
    Qureshi, Tahir Naseer
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Persson, Magnus
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Chen, DeJiu
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Model-Based Development of Middleware forSelf-Configurable Embedded Real Time Systems: Experiences from the DySCAS Project2009Conference paper (Refereed)
    Abstract [en]

    This paper presents experiences from the model-based development of a framework for a middleware targeting the needs for self-management and context awareness in automotive systems. The major focus is on a simulation platform and a reference implementation of the middleware architecture. We also discuss challenges and possible future extensions.

  • 34. Rashidinejad, Aida
    et al.
    Reniers, Michel
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Supervisory Control of Timed Discrete-Event Systems Subject to Communication Delays and Non-FIFO Observations2018In: IFAC PAPERSONLINE, ISSN 2405-8963, Vol. 51, no 7, p. 456-463Article in journal (Refereed)
    Abstract [en]

    Conventional supervisory control synthesis techniques are not adequate anymore when a network between the plant and the supervisor introduces communication delays. This paper presents a method to synthesize a networked supervisor handling delays in both observation and control channels. To deal with the problem of delayed observations, we propose an automaton modeling the behaviour of the plant observed by a supervisor through a network, called observed plant. In this automaton, events observed by a supervisor are delayed from those occurring in the plant. Moreover, since observation channels are considered not to have the first in first out (FIFO) characteristic, events may not be necessarily observed in the same order as they occurred within the plant. A safe, observable, controllable and nonblocking supervisor is synthesized for the observed plant by means of an adapted synthesis algorithm for timed discrete-event systems (TDES). By enabling the achieved supervisor to predict the effects of control delays, it will be further transformed to a networked supervisor. The networked supervisor makes decisions ahead of time to ensure that the commands will be applied on the right (plant) state.

  • 35.
    Sandberg, Anders
    et al.
    Mecel AB.
    Chen, DeJiu
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Lönn, Henrik
    Volvo Technology AB.
    Johansson, Rolf
    Mentor Graphics Corp..
    Feng, Lei
    Volvo Technology AB.
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Torchiaro, Sandra
    Centro Ricerche Fiat.
    Tavakoli-Kolagari, Ramin
    Volvo Technology AB.
    Abele, Andreas
    Continental Automotive GmbH.
    Model-Based Safety Engineering of Interdependent Functions in Automotive Vehicles Using EAST-ADL22010In: COMPUTER SAFETY, RELIABILITY, AND SECURITY, Springer, 2010, Vol. 6351Conference paper (Refereed)
    Abstract [en]

    For systems where functions are distributed but share support forcomputation, communication, environment sensing and actuation, it is essentialto understand how such functions can affect each other. Preliminary HazardAnalysis (PHA) is the task through which safety requirements are established.This is usually a document-based process where each system function isanalyzed alone, making it difficult to reason about the commonalities of relatedfunctional concepts and the distribution of safety mechanisms across a systemof-systems. This paper presents a model-based approach to PHA with theEAST-ADL2 language and in accordance with the ISO/DIS 26262 standard.The language explicitly supports the definition and handling of requirements,functions and technical solutions, and their various relations and constraints as acoherent whole with multiple views. We show in particular the engineeringneeds for a systematic approach to PHA and the related language features forprecise modeling of requirements, user functionalities, system operationcontexts, and the derived safety mechanisms.

  • 36. Shoaei, M. R.
    et al.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Lennartson, B.
    Abstractions for nonblocking supervisory control of Extended Finite Automata2012In: Automation Science and Engineering (CASE), 2012 IEEE International Conference on, IEEE , 2012, p. 364-370Conference paper (Refereed)
    Abstract [en]

    An abstraction method for Extended Finite Automata (EFAs), i.e., finite automata extended with variables, using transition projection is presented in this work. A manufacturing system modeled by EFAs is abstracted into subsystems that embody internal interacting dependencies. Synthesis and verification of subsystems are achieved through their model abstractions rather than their global model. Sufficient conditions are presented to guarantee that supervisors result in maximally permissive and nonblocking control. An examples demonstrate the computational effectiveness and practical usage of the approach.

  • 37. Shoaei, M. R.
    et al.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Lennartson, B.
    On the computation of natural observers for extended finite automata2014In: IFAC Proceedings Volumes (IFAC-PapersOnline), 2014, p. 2448-2455Conference paper (Refereed)
    Abstract [en]

    Compared to finite automata, Extended Finite Automata (EFAs) allows us to efficiently represent discrete-event systems that involve non-trivial data manipulation. However, the complexity of designing supervisors for such systems is still a challenge. In our previous works, we have studied model abstraction for EFAs using natural projections with observer property on events as well as data. In this paper, we provide sufficient conditions for verifying the observer properties and further enhance the EFAs when the property does not hold. To this end, we introduce symbolic simplification techniques for data and generalize existing algorithms in the literature for the events to compute natural observers for EFAs. The importance of this combined abstraction and symbolic simplification method is demonstrated by synthesis of a nonblocking controller for an industrial manufacturing system.

  • 38. Shoaei, M. R.
    et al.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Lennartson, B.
    Supervisory control of extended finite automata using transition projection2012In: Decision and Control (CDC), 2012 IEEE 51st Annual Conference on, IEEE , 2012, p. 7259-7266Conference paper (Refereed)
    Abstract [en]

    A limitation of the Ramadge and Wonham (RW) framework for the supervisory control theory is the explicit state representation using finite automata, often resulting in complex and unintelligible models. Extended finite automata (EFAs), i.e., deterministic finite automata extended with variables, provide compact state representation and then make the control logic transparent through logic expressions of the variables. A challenge with this new control framework is to exploit the rich control structure established in RW's framework. This paper studies the decentralized control structure with EFAs. To reduce the computational complexity, the controller is synthesized based on model abstraction of subsystems, which means that the global model of the entire system is unnecessary. Sufficient conditions are presented to that guarantee the decentralized supervisors result in maximally permissive and nonblocking control to the entire system.

  • 39. Sun, Tao
    et al.
    Lian, Binbin
    School of Mechanical Engineering, Tianjin University, China.
    Song, Yimin
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Elasto-dynamic Optimization of A 5-DoF Parallel Kinematic Machine Considering Parameter Uncertainty2019In: IEEE/ASME transactions on mechatronics, ISSN 1083-4435, E-ISSN 1941-014XArticle in journal (Refereed)
    Abstract [en]

    Geometric errors, vibration and elastic deformation are the main causes for inaccuracy of parallel kinematic machines (PKMs). Instead of tackling these inaccuracies after the prototype has been built, this paper proposes a design optimization method to minimize vibration and deformation considering the effects of geometric errors before constructing the PKM. In the presented study, geometric errors are described as parameter uncertainty because they are unknown in design stage. A 5 degree-of-freedom (DoF) PKM is taken to exemplify this method. Elasto-dynamic model is firstly formulated by a step-by-step strategy. On this basis, dynamic performances, including natural frequency, elastic deformation and maximum stress, are analyzed. These analytical results are verified by finite element simulation and experiment. Then, the necessity of concerning parameter uncertainty in optimization is addressed. Next, parameter uncertainty is added to the formulation of objectives and constraints by Monte Carlo simulation (MCS) and response surface method (RSM). Finally, elasto-dynamic optimization of the 5-DoF PKM is implemented to rebuild a prototype which is robust to geometric errors and has minimal vibration and deformation. The proposed method can also be applied to accuracy improvement of any machines in practical applications.

  • 40.
    Svensson, Lars
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Masson, Lola
    Mohan, Naveen
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Ward, Erik
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, perception and learning, RPL.
    Pernestål Brenden, Anna
    KTH, School of Industrial Engineering and Management (ITM), Centres, Integrated Transport Research Lab, ITRL.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Safe Stop Trajectory Planning for Highly Automated Vehicles:An Optimal Control Problem Formulation2018In: 2018 IEEE Intelligent Vehicles Symposium (IV), Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 517-522, article id 8500536Conference paper (Refereed)
    Abstract [en]

    Highly automated road vehicles need the capabilityof stopping safely in a situation that disrupts continued normaloperation, e.g. due to internal system faults. Motion planningfor safe stop differs from nominal motion planning, since thereis not a specific goal location. Rather, the desired behavior isthat the vehicle should reach a stopped state, preferably outsideof active lanes. Also, the functionality to stop safely needs tobe of high integrity. The first contribution of this paper isto formulate the safe stop problem as a benchmark optimalcontrol problem, which can be solved by dynamic programming.However, this solution method cannot be used in real-time. Thesecond contribution is to develop a real-time safe stop trajectoryplanning algorithm, based on selection from a precomputedset of trajectories. By exploiting the particular properties ofthe safe stop problem, the cardinality of the set is decreased,making the algorithm computationally efficient. Furthermore, amonitoring based architecture concept is proposed, that ensuresdependability of the safe stop function. Finally, a proof of conceptsimulation using the proposed architecture and the safe stoptrajectory planner is presented.

  • 41.
    Tao, Sun
    et al.
    Tianjin University.
    Lian, Binbin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Yimin, Song
    Tianjin University.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Elasto-dynamicoptimization of a 5-DoF parallel kinematic machine considering parameteruncertainty2019In: IEEE/ASME transactions on mechatronics, ISSN 1083-4435, E-ISSN 1941-014X, no 1, p. 315-325Article in journal (Refereed)
    Abstract [en]

    Geometric errors, vibration, and elastic deformation are the main causes for inaccuracy of parallel kinematic machines (PKMs). Instead of tackling these inaccuracies after the prototype has been built, this paper proposes a design optimization method to minimize vibration and deformation considering the effects of geometric errors before constructing the PKM. In this paper, geometric errors are described as parameter uncertainty because they are unknown in design stage. A five degree-of-freedom (DoF) PKM is taken to exemplify this method. Elastodynamic model is first formulated by a step-by-step strategy. On this basis, dynamic performances, including natural frequency, elastic deformation, and maximum stress, are analyzed. These analytical results are verified by finite-element simulation and experiment. Then, the necessity of concerning parameter uncertainty in optimization is addressed. Next, parameter uncertainty is added to the formulation of objectives and constraints by Monte Carlo simulation and response surface method. Finally, elastodynamic optimization of the 5-DoF PKM is implemented to rebuild a prototype which is robust to geometric errors and has minimal vibration and deformation. The proposed method can also be applied to accuracy improvement of any machines in practical applications.

  • 42.
    Vahdati, Pouya Mahdavipour
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Design Optimization of Cyber-Physical Systems by Partitioning and Coordination: A Study on Mechatronic Systems2018In: Proceedings - 21st Euromicro Conference on Digital System Design, DSD 2018, IEEE, 2018, p. 304-311311, article id 8491832Conference paper (Refereed)
    Abstract [en]

    Cyber-Physical Systems are inherently complex. Reducing the design complexity of such systems, is beneficial for scalability of the design. In this paper, a method for design optimization of these systems is proposed to facilitate the decomposition of the optimization problem for the whole system into smaller sub-problems and coordination of modular solutions to reach the desired optimum. The coordinated solutions are either identical to the optimal solution of the complex optimization problem for the system as a whole or within an acceptable error margin of it. To demonstrate the efficacy of the method, it is applied to a mechatronic case study. The results provide evidence for the potential feasibility of the methodology in terms of meeting the requirements on the solutions, while reducing the computational demand of the design process.

  • 43.
    Zhang, Huimin
    et al.
    School of Electro-Mechanical Engineering, Xidian University, Xi'an China.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Li, Zhiwu
    School of Electro-Mechnical Engineering, Xidian University, Xi'an China.
    A learning-based synthesis approach to the supremal nonblocking supervisor of discrete-event systems2018In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 63, no 10, p. 3345-3360Article in journal (Refereed)
    Abstract [en]

    The paper presents a novel approach to synthesize supremal nonblocking supervisors of discrete-event systems (DES), when the automaton models of specifications are not available. Extending the L* learning algorithm, an S* algorithm is developed to infer a tentatively correct supervisor. If the tentatively correct supervisor is nonblocking, it is indeed the supremal nonblocking supervisor with respect to the plant and specifications. Otherwise, the blocking automaton is regarded as a new plant, and the specification is the nonblocking property. Then, the supremal nonblocking supervisor with respect to the new problem is computed using supervisory control theory of DES. Two simplification rules are introduced to the S* algorithm to decrease the computational cost. Finally, the S* algorithm is implemented based on the LearnLib framework, and experiments are performed to verify the proposed approach.

  • 44.
    Zhang, Huimin
    et al.
    Guangxi Normal University.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Li, Zhiwu
    Control of Black-Box Embedded Systems by Integrating Automaton Learning and Supervisory Control Theory of Discrete-Event Systems2019In: IEEE Transactions on Automation Science and Engineering, ISSN 1545-5955, E-ISSN 1558-3783, p. 1-14Article in journal (Refereed)
    Abstract [en]

    The paper presents an approach to the control of black-box embedded systems by integrating automaton learning and supervisory control theory (SCT) of discrete-event systems (DES), where automaton models of both the system and requirements are unavailable or hard to obtain. First, the system is tested against the requirements. If all the requirements are satisfied, no supervisor is needed and the process terminates. Otherwise, a supervisor is synthesized to enforce the system to satisfy the requirements. To apply SCT and automaton learning technologies efficiently, the system is abstracted to be a finite-discrete model. Then, a C* learning algorithm is proposed based on the classical L* algorithm to infer a Moore automaton describing both the behavior of the system and the conjunctive behavior of the system and the requirements. Subsequently, a supervisor for the system is derived from the learned Moore automaton and patched on the system. Finally, the controlled system is tested again to check the correctness of the supervisor. If the requirements are still not satisfied, a larger Moore automaton is learned and a refined supervisor is synthesized. The whole process iterates until the requirements hold in the controlled system. The effectiveness of the proposed approach is manifested through two realistic case studies.

  • 45.
    Zhang, Huimin
    et al.
    School of Electro-Mechanical Engineering, Xidian University.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Wu, Naiqi
    Institute of Systems Engineering, Macau University of Science and Technology.
    Li, Zhiwu
    School of Electro-Mechanical Engineering, Xidian University.
    Integration of Learning-Based Testing and Supervisory Control for Requirements Conformance of Black-Box Reactive Systems2018In: IEEE Transactions on Automation Science and Engineering, ISSN 1545-5955, E-ISSN 1558-3783, Vol. 15, no 1, p. 2-15Article in journal (Refereed)
    Abstract [en]

    A fundamental requirement of the supervisory control theory (SCT) of discrete-event systems is a finite automaton model of the plant. The requirement does not hold for black-box systems whose source code and logical model are not accessible. To apply SCT to black-box systems, we integrate automaton learning technology with SCT and apply the new method to improve the requirements conformance of software reuse. If the reused software component does not satisfy a requirement, the method adds a supervisor component to prevent the black-box system from reaching ''faulty sections.'' The method employs learning-based testing (LBT) to verify whether the reused software meets all requirements in the new context. LBT generates a large number of test cases and iteratively constructs an automaton model of the system under test. If the system fails the test, the learned model is applied as the plant model for control synthesis using SCT. Then, the supervisor is implemented as an executable program to monitor and control the system to follow the requirement. Finally, the integrated system, including the supervisory program and the reused component, is tested by LBT to assure the satisfiability of the requirement. This paper makes two contributions. First, we innovatively integrate LBT and SCT for the control synthesis of black-box reactive systems. Second, software component reuse is still possible even if it does not satisfy user requirements at the outset.

  • 46.
    Zhang, Xinhai
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Chen, De-Jiu
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Design-Space Reduction for Architectural Optimization of Automotive Embedded Systems2015In: High Performance Computing and Communications (HPCC), 2015 IEEE 7th International Symposium on Cyberspace Safety and Security (CSS), 2015 IEEE 12th International Conferen on Embedded Software and Systems (ICESS), 2015 IEEE 17th International Conference on, IEEE Computer Society, 2015, , p. 7p. 1103-1109Conference paper (Refereed)
    Abstract [en]

    A key decision for the synthesis of automotiveembedded systems is the allocation of application softwarecomponents to ECUs. Design Space Exploration (DSE) supportsthe decision by automatically characterizing and evaluating alarge number of possible design alternatives, and thereby suggestingthe optimal ones. A primary challenge for applying DSEmethods to support this decision is to reduce the computationtime of the DSE process while maintaining the generality andoptimality. This paper exploits legacy system architectures andthe AUTOSAR standard to preemptively reduce the design space,because both artifacts limit the flexibility of certain designvariables. A new DES formulation incorporating the constraintsof the legacy system architectures and the AUTOSAR standardis proposed in this paper. Computation result shows a largereduction of the computation time comparing to traditionalmodeling and formulations. The scalability of our method is alsoanalyzed by testing it on a set of random problem instances.

  • 47.
    Zhang, Xinhai
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Chen, DeJiu
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Formulating Customized Specifications for Resource Allocation Problem of Distributed Embedded Systems2016In: 2016 IEEE/ACM INTERNATIONAL CONFERENCE ON COMPUTER-AIDED DESIGN (ICCAD), Institute of Electrical and Electronics Engineers (IEEE), 2016Conference paper (Refereed)
    Abstract [en]

    There are plentiful attempts for increasing the efficiency, generality and optimality of the Design Space Exploration (DSE) algorithms for resource allocation problems of distributed embedded systems. Most contemporary approaches formulate DSE as an optimization or SAT problem, based on a set of predefined constraints. In this way, the end users lose the flexibility to guide and customize the exploration based on specifics of their actual problem. Besides, during the design of the DSE algorithms, manual formulation is time consuming and error-prone. To solve these problems, 1) a formal representation is defined for capturing customized architectural constraints based on a combination of propositional logic and Pseudo-Boolean (PB) formulas; 2) A process is designed to automatically translate these architectural constrains into corresponding Integer Linear Programming (ILP) constraints, commonly used for DSE. The translation process is also optimized to create ILP formulation with less introduced variables so as to reduce computation time. The results show that the generated constraints correctly reflect the corresponding specification with decent efficiency.

  • 48.
    Zhang, Xinhai
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Song, Xinwu
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Chen, Lei
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    A Case Study on Achieving Fair Data Age Distribution in Vehicular Communications2017In: PROCEEDINGS OF THE 23RD IEEE REAL-TIME AND EMBEDDED TECHNOLOGY AND APPLICATIONS SYMPOSIUM (RTAS 2017) / [ed] Parmer, G, IEEE , 2017, p. 307-317Conference paper (Refereed)
    Abstract [en]

    In vehicular communication protocol stacks, received messages may not always be decoded successfully due to the complexity of the decoding functions, the uncertainty of the communication load and the limited computation resources. Even worse, an improper implementation of the protocol stack may cause an unfair data age distribution among all the communicating vehicles (the receiving bias problem). In such cases, some vehicles are almost locked out of the vehicular communication, causing potential safety risk in scenarios such as intersection passing. To our knowledge, this problem has not been systematically studied in the fields of vehicular communication and intelligent transport systems (ITS). This paper analyzes the root of the receiving bias problem and proposes architectural solutions to balance data age distribution. Simulation studies based on commercial devices demonstrate the effectiveness of these solutions. In addition, our system has been successfully applied during the Grand Cooperative Driving Challenge, where complicated scenarios involving platooning maneuvering and intersection coordination were conducted.

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