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  • 1.
    Aftab, Ahmad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Khan, Suleman
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    A stiffness modeling methodology for simulation-driven design of haptic devices2014In: Engineering with Computers, ISSN 0177-0667, E-ISSN 1435-5663, Vol. 30, no 1, p. 125-141Article in journal (Refereed)
    Abstract [en]

    Efficient development and engineering of high performing interactive devices, such as haptic robots for surgical training benefits from model-based and simulation-driven design. The complexity of the design space and the multi-domain and multi-physics character of the behavior of such a product ask for a systematic methodology for creating and validating compact and computationally efficient simulation models to be used in the design process. Modeling the quasi-static stiffness is an important first step before optimizing the mechanical structure, engineering the control system, and performing hardware in the loop tests. The stiffness depends not only on the stiffness of the links, but also on the contact stiffness in each joint. A fine-granular Finite element method (FEM) model, which is the most straightforward approach, cannot, due to the model size and simulation complexity, efficiently be used to address such tasks. In this work, a new methodology for creating an analytical and compact model of the quasi-static stiffness of a haptic device is proposed, which considers the stiffness of actuation systems, flexible links and passive joints. For the modeling of passive joints, a hertzian contact model is introduced for both spherical and universal joints, and a simply supported beam model for universal joints. The validation process is presented as a systematic guideline to evaluate the stiffness parameters both using parametric FEM modeling and physical experiments. Preloading has been used to consider the clearances and possible assembling errors during manufacturing. A modified JP Merlet kinematic structure is used to exemplify the modeling and validation methodology.

  • 2.
    Aftab, Ahmad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Khan, Suleman
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Kinematics and Dynamics of a novel 6-DoF TAU Haptic Device2011In: Proceedings of the 2011 IEEE International Conference on MechatronicsInternational Conference on Mechatronics, April 13-15, 2011, Istanbul, Turkey, IEEE conference proceedings, 2011, p. 719-724Conference paper (Refereed)
    Abstract [en]

    This paper presents the kinematics and dynamics modeling of a novel hybrid kinematic concept, i.e. the TAU haptic device. This new concept was obtained from the modification of TAU-2 structure proposed by Khan et al. First a kinematic model for inverse and forward kinematics was developed and analyzed. Then an algorithm to solve the close form inverse dynamics is presented using Lagrangian formulation. Numerical simulation was carried out to examine the validity of the approach and accuracy of the technique employed. A trigonometric helical trajectory of 5th order spline was developed in Cartesian space for each degree of freedom of the moving platform in order to verify and simulate the inverse dynamics; the motion of the platform is such that the tool centre point remains on this trajectory while its orientation is changing constantly in roll, pitch and yaw.

  • 3.
    Ahmad, Aftab
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    A comparative study of friction estimation and compensation using extended, iterated, hybrid, and unscented kalman filters2013In: Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference - 2013, ASME Press, 2013Conference paper (Refereed)
    Abstract [en]

    Transparency is a key performance evaluation criterion for haptic devices, which describes how realistically the haptic force/torque feedback is mimicked from a virtual environment or in case of master-slave haptic device. Transparency in haptic devices is affected by disturbance forces like friction between moving parts. An accurate estimate of friction forces for observer based compensation requires estimation techniques, which are computationally efficient and gives reduced error between measured and estimated friction. In this work different estimation techniques based on Kalman filter, such as Extended Kalman filter (EKF), Iterated Extended Kalman filter (IEKF), Hybrid extended Kalman filter (HEKF) and Unscented Kalman filter (UKF) are investigated with the purpose to find which estimation technique that gives the most efficient and realistic compensation using online estimation. The friction observer is based on a newly developed friction smooth generalized Maxwell slip model (S-GMS). Each studied estimation technique is demonstrated by numerical and experimental simulation of sinusoidal position tracking experiments. The performances of the system are quantified with the normalized root mean-square error (NRMSE) and the computation time. The results from comparative analyses suggest that friction estimation and compensation based on Iterated Extended Kalman filter both gives a reduced tracking error and computational advantages compared to EKF, HEKF, UKF, as well as with no friction compensation.

  • 4.
    Ahmad, Aftab
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    A deterministic and probabilistic approach for robust optimal design of a 6-DOF haptic device2014In: Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference--2013: Volume 3 B, 2013, ASME Press, 2014, p. V03BT03A032-Conference paper (Refereed)
    Abstract [en]

    This work suggests a two-stage approach for robust optimal design of 6-DOF haptic devices based on a sequence of deterministic and probabilistic analyses with a multi-objective genetic algorithm and the Monte-Carlo method. The presented model-based design robust optimization approach consider simultaneously the kinematic, dynamic, and kinetostatic characteristics of the device in both a constant and a dexterous workspace in order to find a set of optimal design parameter values for structural configuration and dimensioning. Design evaluation is carried out based on local and global indices, like workspace volume, quasi-static torque requirements for the actuators, kinematic isotropy, dynamic isotropy, stiffness isotropy, and natural frequencies of the device. These indices were defined based on focused kinematic, dynamic, and stiffness models. A novel procedure to evaluate local indices at a singularity-free point in the dexterous workspace is presented. The deterministic optimization approach neglects the effects from variations of design variables, e.g. due to tolerances. A Monte-Carlo simulation was carried out to obtain the response variation of the design indices when independent design parameters are simultaneously regarded as uncertain variables. It has been observed that numerical evaluation of performance indices depends of the type of workspace used during optimization. To verify the effectiveness of the proposed procedure, the performance indices were evaluated and compared in constant orientation and in dexterous workspace.

  • 5.
    Ahmad, Aftab
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    A model-based and simulation driven design approach for haptic devices2013In: Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference--2013, ASME Press, 2013, p. V02BT02A014-Conference paper (Refereed)
    Abstract [en]

    The output from a design process of high precision and reliable haptic devices for surgical training like bones and teeth is a complex design. The complexity is largely due to the multi-criteria and conflicting character of the functional requirements. These requirements include high stiffness, large workspace, high manipulability, small inertia, low friction, and high transparency. The requirements are a basis for generating design concepts. The concept evaluation relies to a large extent on a systematic usage of kinematic, dynamic, stiffness, and friction models. The design process can benefit from a model-based and simulation driven approach, where one starts from an abstract top-level model that is extended via stepwise refinements and design space exploration into a complete realization of the system. Such an approach is presented and evaluated through a test case where a haptic device, based on a Stewart platform, has been designed and realized. It can be concluded, based on simulation and experimental results that the performance of this optimally designed haptic device satisfies the stated user requirements. This indicates that the methodology can support the development of an optimal haptic device. However, more test cases are needed to further verify the presented methodology.

  • 6.
    Ahmad, Aftab
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    An approach to stiffness analysis methodology for haptic devices2011In: 2011 3rd International Congress on Ultra Modern Telecommunications and Control Systems and Workshops (ICUMT), IEEE conference proceedings, 2011, , p. 8p. 1-8Conference paper (Refereed)
    Abstract [en]

    In this work a new methodology is proposed to model the static stiffness of a haptic device. This methodology can be used for other parallel, serial and hybrid manipulators. The stiffness model considers the stiffness of; actuation system; flexible links and passive joints. For the modeling of the passive joints a Hertzian contact model is introduced for both spherical and universal joints and a simply supported beam model for universal joints. For validation of the stiffness model a modified JP Merlet kinematic structure has been used as a test case. A parametric Ansys FEM model was developed for this test case and used to validate the resulting stiffness model. The findings in this paper can provide an additional index to use for multi-objective structural optimization to find an optimum compromise between a lightweight design and the stiffness performance for high precision motion within a larger workspace.

  • 7.
    Ahmad, Aftab
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    An Optimization Approach Toward a Robust Design of Six Degrees of Freedom Haptic Devices2015In: Journal of mechanical design (1990), ISSN 1050-0472, E-ISSN 1528-9001, Vol. 137, no 4, article id 042301Article in journal (Refereed)
    Abstract [en]

    This work presents an optimization approach for the robust design of six degrees of freedom (DOF) haptic devices. Our objective is to find the optimal values for a set of design parameters that maximize the kinematic, dynamic, and kinetostatic performances of a 6-DOF haptic device while minimizing its sensitivity to variations in manufacturing tolerances. Because performance indices differ in magnitude, the formulation of an objective function for multicriteria performance requirements is complex. A new approach based on Monte Carlo simulation (MCS) was used to find the extreme values (minimum and maximum) of the performance indices to enable normalization of these indices. The optimization approach presented here is formulated as a methodology in which a hybrid design-optimization approach, combining genetic algorithm (GA) and MCS, is first used. This new approach can find the numerical values of the design parameters that are both optimal and robust (i.e., less sensitive to variation and thus to uncertainties in the design parameters). In the following step, with design optimization, a set of optimum tolerances is determined that minimizes manufacturing cost and also satisfies the allowed variations in the performance indices. The presented approach can thus enable the designer to evaluate trade-offs between allowed performance variations and tolerances cost.

  • 8.
    Ahmad, Aftab
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Kjell, Andersson
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    A model-based and simulation-driven methodology for design of haptic devices2014In: Mechatronics (Oxford), ISSN 0957-4158, E-ISSN 1873-4006, Vol. 24, no 7, p. 805-818Article in journal (Refereed)
    Abstract [en]

    High precision and reliable haptic devices are highly complex products. The complexity that has to be carefully treated in the design process is largely due to the multi-criteria and conflicting character of the functional and performance requirements. These requirements include high stiffness, large work-space, high manipulability, small inertia, low friction, high transparency, as well as cost constraints. The requirements are a basis for creating and assessing design concepts. Concept evaluation relies to a large extent on a systematic usage of kinematic, dynamic, stiffness, friction, and control models. The design process can benefit from a model-based and simulation-driven approach, where one starts from an abstract top-level model that is extended via stepwise refinements and design space exploration into a detailed and integrated systems model that can be physically realized. Such an approach is presented, put in context of the V-model, and evaluated through a test case where a haptic device, based on a Stewart platform, is designed and realized. It can be concluded, based on simulation and experimental results that the performance of this deterministically optimized haptic device satisfies the stated user requirements. Experiences from this case indicate that the methodology is capable of supporting effective and efficient development of high performing haptic devices. However, more test cases are needed to further validate the presented methodology.

  • 9.
    Ahmad, Aftab
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Kjell, Andersson
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    An optimization approach towards a robust design of 6-DOF haptic devicesManuscript (preprint) (Other academic)
  • 10.
    Ahmad, Aftab
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Kjell, Andersson
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Model-based control strategy for 6-DOF haptic devicesManuscript (preprint) (Other academic)
  • 11.
    Ahmad, Aftab
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Kjell, Andersson
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Boegli, Max
    Evaluation of friction models for haptic devices2013Conference paper (Refereed)
    Abstract [en]

    In this work different friction models are evaluated to determine how well these models are suited for performance simulation and control of a 6-DOF haptic device. The studied models include, Dahl model, LuGre model, Generalized Maxwell slip model (GMS), smooth Generalized Maxwell slip model (S-GMS) and Differential Algebraic Multistate (DAM) friction model. These models are evaluated both numerically and experimentally with an existing 6-DOF haptic device that is based on a Stewart platform. In order to evaluate how well these models compensate friction, a model-based feedback friction compensation strategy along with a PID controller were used for position fracking accuracy The accuracies of the friction compensation models are examined separately for both low-velocity and high-velocity motions of the system. To evaluate these models, we use criteria based on fidelity to predict realistic friction phenomena, easiness to implement, computational efficiency and easiness to estimate the model parameters. Experimental results show that friction compensated with GMS, S-GMS and DAA4 models give better accuracy in terms of standard deviation, Root Mean Squared Error, and maximum error between a reference and measured trajectory. Based on the criteria of fidelity, ease of implementation and ease to estimate model parameters, the S-GMS model, which represents a smooth transition between sliding and pre-sliding regime through an analytical set of differential equations, is suggested.

  • 12.
    Andersson, Kjell
    KTH, Superseded Departments, Machine Design.
    A REQUIREMENT-DRIVEN PRODUCT DEVELOPMENT PROCESS2004In: 7th Workshop on Product Structuring: Product platform Development / [ed] J. Malmqvist, 2004, p. 37-48Conference paper (Refereed)
    Abstract [en]

    Product development is often described as an iterative process of finding solutions that match specific requirements. The many dimensions of this process include time, organization, product-specific elements such as the level of abstraction and detail, and analysis to verify the product’s properties.

    Many types of software tools are used to generate and visualize the concept shape. These include CAD (computer-aided design) tools; tools to simulate and verify product properties, such as FE (finite element analysis) and MBS (multibody systems); and tools for handling product data such as PDM (product data management). This paper focus on the effective use of simulation software such as FE and MBS tools to support the process of verifying that a product meets the formulated requirements. The simulation software can be used for such things as selecting alternative solutions or as a final check or optimization of a solution concept. Its can be used even more effectively if it is supported by a framework for handling the information created during the verification process.

    This paper presents a proposal for an information framework that can support traceability and reuse of partial results created during the verification of a specific required attribute. This framework also facilitates study of the effects of changes in the specification on product properties. The framework is illustrated in a modeling and simulation scenario for a lifting unit on a wheel loader produced by Volvo CE. This scenario focus on modeling and simulation activities and how these can be supported in a question-and-answer driven process that investigates the behavior of the lifting unit. 

  • 13.
    Andersson, Kjell
    KTH, Superseded Departments, Machine Design.
    An iterative question-answer driven process to support product design2004In: PROCEEDINGS OF NORDDESIGN 2004: PRODUCT DEVELOPMENT IN CHANGING ENVIRONMENT / [ed] Lehtonen, T, TAMPERE: TAMPERE UNIV TECH PRODUCT DEVELOPMENT LABORATORY , 2004, p. 173-182Conference paper (Refereed)
    Abstract [en]

    Product development is often described as an iterative process of finding solutions that match specific requirements. The many dimensions of this process include time, organization, product-specific elements such as the level of abstraction and detail, and analysis to verify the product's properties. Many types of software tools are used to generate and visualize the concept shape. These include CAD (computer-aided design) tools; tools to simulate and verify product properties, such as FE (finite element analysis) and MBS (multibody systems); and tools for handling product data such as PDM (product data management). This paper focus on the effective use of simulation software such as FE and MBS tools to support the process of verifying that a product meets the formulated requirements. The simulation software can be used for such things as selecting alternative solutions or as a final check or optimization of a solution concept. Its can be used even more effectively if it is supported by a framework for handling the information created during the verification process. This paper presents a proposal to a question-answer driven process for verification of product requirements. This process is based on the framework presented by the author in [Andersson 2004a, 2004b]. The process is illustrated in a modeling and simulation scenario of a lifting unit in a wheel loader from Volvo CE. This scenario focus on modeling and simulation activities and how these can be supported in a question-answer driven process that investigates the behavior of the lifting unit.

  • 14.
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Evaluation of a model based learning approach for engineering design2015In: INTERNATIONAL DESIGN ENGINEERING TECHNICAL CONFERENCES AND COMPUTERS AND INFORMATION IN ENGINEERING CONFERENCE, 2015, VOL 3, 2015, article id UNSP V003T04A013Conference paper (Refereed)
    Abstract [en]

    Project-based education in combination with problem based learning has been very successful, and has contributed to the popularity of engineering design education among students at technical universities. The close connection to industrial problems by the use of industry-connected projects has boosted this popularity still further and to get an insight of future working environments after graduation is very inspiring for the students.

    The curriculum of the Machine Design capstone course at KTH Department of Machine Design covers the whole process from idea generation to manufacturing and testing a final prototype. A major part of the course consists of project work where students develop a product prototype in close cooperation with an industrial partner or with a research project at the department. This means that a major part of the course uses project-based learning as a teaching strategy. In addition, a model-based design methodology is introduced which enables the students to evaluate and "experience" many different behaviors of the product using digital models in a virtual environment. In this way, students can see that many undesirable concepts and flaws can be avoided even before a prototype is manufactured.

    This paper evaluates the use and learning outcome of model-based design in a capstone course in the Engineering Design MSc program at KTH Department of Machine Design. The approach has been used during a period of three years and the effect on the students' learning has been evaluated by a questionnaire after each course. I this paper we compare the results of these questionnaires and discuss implications and general conclusions about this learning approach.

  • 15.
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Impact of model-based design in engineering design education2013In: Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference - 2013, ASME Press, 2013, p. V001T04A022-Conference paper (Refereed)
    Abstract [en]

    Project-based education in combination with problem-based learning has been very successful, and has contributed to the popularity of engineering design among students at technical universities. And when the project work addresses real industrial problems, offers insight into post-graduation working environments and gets direct feedback from professionals in industry, students can see the immediate relevance of their education - an invaluable boost to their learning experience. Students taking MF2004, a capstone course at KTH Department of Machine Design, learn the whole process from idea generation to manufacturing and testing a final prototype built in close collaboration with an industrial partner or a research group at the department. The benefits of using real prototypes cannot be stressed enough - students find out for themselves why a product must be designed in a certain way (e.g. to make it possible to assemble). The course uses project based learning as a teaching strategy and introduces a model based design methodology which enables the students to evaluate and "experience" many different behaviors of the product using digital models in a virtual environment. In this way, students can see that many undesirable concepts and flaws can be avoided even before a prototype is manufactured. This paper focuses on the introduction of the model-based design methodology and evaluation of its impact on learning in a capstone course in the Engineering Design MSc programme at KTH Department of Machine Design. A questionnaire was used to evaluate the effects on the students' learning, as well as to assess how feasible they consider this methodology to be. On the basis of this, in combination with the weekly meetings with the project teams, we can report a positive attitude among the students and improved learning outcomes.

  • 16.
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Modular simulation models as a key enabler for a question-answer driven verification process2006In: 1st Nordic Conference on Product Lifecycle Management: NordPLM'06, 2006, p. 99-110Conference paper (Refereed)
  • 17.
    Andersson, Kjell
    KTH, Superseded Departments, Machine Design.
    Simulation in product design: An iterative question-answer driven process2004In: Design 2004: Proceedings of the 8th International Design Conference, Vols 1-3 / [ed] Marjanovic, D, 2004, p. 91-98Conference paper (Refereed)
  • 18.
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Using Model-Based Design In Engineering Design Education2012In: Proceedings of the ASME Design Engineering Technical Conferences And Computers And Information In Engineering Conference, Vol 7, ASME Press, 2012, p. 69-76Conference paper (Refereed)
    Abstract [en]

    Project-based education in combination with problem-based learning has been one of the key factors for the popularity of engineering design education among students at technical universities. The use of industry-connected projects has boosted this popularity still further. To get feedback from professionals in industry is very stimulating and in this way students also get confirmation that their education is related to industrial needs. In the Machine Design capstone course at KTH Department of Machine Design, the curriculum covers the whole process from idea generation to manufacturing and testing a final prototype. A major part of the course consists of project work where students will develop a product prototype in close cooperation with an industrial partner or with a research project at the department. The benefits of using real prototypes cannot be stressed enough. This is a very efficient way to explain to the students why a product must be designed in a certain way, e.g. to make it possible to assemble. This means that a major part of the course is using project-based learning as a teaching strategy. In addition, the use of model-based design is introduced as a methodology that enables the students to evaluate and "experience" many different behaviors of the product using digital models in a virtual environment. In this way many undesirable concepts and flaws can be avoided even before a prototype is manufactured. This paper describes a model-based methodology for product development. It also shows the application of this methodology in project work in a capstone course in engineering design at KTH, and discusses the effects on student motivation and learning.

  • 19.
    Andersson, Kjell
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Hagnestål, Anders
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM).
    A flexible chain proposal for winch based point absorbers2018In: Proceedings of the ASME 2018 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2018: August 26-29, 2018, Quebec City, Quebec, Canada, 2018Conference paper (Refereed)
    Abstract [en]

    Ocean wave power is a promising renewable energy source for future energy production. It has however been difficult to find a cost-effective solution to convert the wave energy into electricity. The harsh marine environment and the fact that wave power is delivered with high forces at low speeds makes design of durable mechanical structures and efficient energy conversion challenging. The dimensioning forces strongly depend on the wave power concept, the Wave Energy Converter (WEC) implementation and the actual Power TakeOff (PTO) system. A WEC using a winch as a Power Take-Off system, i.e. a Winch Based Point Absorber (WBPA), could potentially accomplish a low Levelized Cost Of Energy (LCOE) if akey component - a low-cost, durable and efficient winch that can deal with high loads - can be developed. A key problem for achieving a durable winch is to find a force transmitting solution that can deal with these high loads and handle up to 80 million cycles. In this article we propose a design solution for a force transmitting chain in a WBPA system where elastomeric bearings are used as a means to achieve the relative motion between the links in the chain. With this solution no sliding is present and the angular motion is achieved as a deformation in the elastomeric bearing when the chain is winded on a drum. The link was designed primarily to minimize the number of joints in the chain: Thereby the maximum allowed relative angle between the links when rolled up over the drum should be as large as possible within practical limits. The angle is to be handled by the elastomeric bearing. A detailed strength analysis of the link has been performed as well as topology optimization to increase the strength to weight ratio. A test rig for a first proof of concept testing has been developed and the first preliminary test results indicate that this concept with using elastomeric bearings can be a potential solution for a durable chain and should be analyzed further for fatigue conditions and under water operations. 

  • 20.
    Andersson, Kjell
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Hagnestål, Anders
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Design of a flexible chain for winch based point absorbers2018In: Proceedings of NordDesign: Design in the Era of Digitalization, NordDesign 2018, 2018Conference paper (Refereed)
  • 21.
    Andersson, Kjell
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Reality-driven virtual wheel loader operation2005In: Proceedings of Virtual Concept 2005, 2005Conference paper (Refereed)
  • 22.
    Baez, Federico
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Ismoilov, Abbos
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Löfgren, Björn
    Skogforsk.
    Multi-objective performance optimization of pendulum-arm suspensions for forestry machines2014Conference paper (Other academic)
  • 23.
    Hagnestål, Anders
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Durable winch-based point absorbers2017In: Proceedings of the 12th European Wave and Tidal Energy Conference 27th Aug - 1st Sept 2017, Cork, Ireland, European Wave and Tidal Energy Conference , 2017Conference paper (Refereed)
    Abstract [en]

    Wave power could give a significant contribution to a

    future sustainable energy system if the Levelized Cost Of Energy

    can be reduced to a competitive level. Winch-based point

    absorbers could potentially accomplish this if a key component –

    a low-cost, durable and efficient winch that can deal with high

    loads – can be developed. In this article the possibilities of winchbased

    point absorbers and the challenges that need to be

    overcome are described. Further, the possibilities to design such

    winches are explored and several different design approaches are

    evaluated and compared. At present, we believe that such a

    winch solution can be found although more research is needed to

    develop a full concept, and the most promising solutions so far

    involve inverted tooth chains, flat UHMwPE fiber (Dyneema)

    bands and flat carbon fibre structures.

  • 24.
    Ismoilov, Abbos
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM).
    MODEL-BASED PERFORMANCE COMPARISON OF TRACKED FORWARDERSArticle in journal (Other academic)
    Abstract [en]

    The predominant forest harvesting method in northern Europe is the cut-to-length (CTL) harvesting methodthat is performed by specialized two-machines, a harvester and a forwarder, and both machines are usually sixoreight wheeled machines with pairs of wheels mounted on bogies. Under soft ground or snow conditions, bogietracks and bogie chains are used to improve mobility and tractive performance. The main engineering challengewhen developing the next generation of forwarders is to reduce whole-body vibrations and soil damage. Due tothe small global market for CTL-machines, these challenges preferably should be addressed with a singlemachine architecture.The focus of this study is to analyse and compare the interaction with very soft soil and the dynamicperformance on hard rough terrain of a medium-sized forwarder equipped with two conceptually differentforwarder track units, namely a track unit with pendulum arm suspended ground wheels and bogie suspendedground wheels, with the performance of a wheeled and bogie-type of forwarder.The simulation results show that tracked forwarders have less negative impact on the soil than wheeledforwarders due to its significantly larger footprint area. Furthermore, it is shown that tracked forwardersequipped with pendulum-arm suspended road wheels are slightly gentler for the operator in terms of whole-bodyvibrations, when operating on hard rough terrain, compared to wheeled forwarders. Furthermore, they are alsosignificantly better than the bogie-type of track unit.

  • 25.
    Ismoilov, Abbos
    et al.
    KTH, School of Industrial Engineering and Management (ITM).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Löfgren, Björn
    A comparison of novel chassis suspended machines for sustainable forestry2015In: Journal of terramechanics, ISSN 0022-4898, E-ISSN 1879-1204, Vol. 58, p. 59-68Article in journal (Refereed)
    Abstract [en]

    Cut-to-length logging (CTL) is a mechanized harvesting process where trees are delimbed and cut to length directly at the stump. The main challenges for the manufacturers of forestry machines for CTL logging are to address new customer demands and tougher health and environmental legislations by finding means that: (1) further increase the harvesting and log transportation productivity, e.g. by enabling operation on eco-soils, (2) reduce the damage to the soil, e.g. by controlling the ruts depth and preserving the root layer, (3) reduce exhaust emissions, e.g. by reducing the rolling resistance, and (4) reducing the daily vibration dosage for the machine operators, e.g. by active chassis and cabin damping. This paper presents of a number of passive forwarder chassis suspension concepts and compares their performance from three perspectives: their gentleness to terrain and operator, as well as their potential for improved fuel efficiency. Based on multi-body dynamics simulations, it is shown that a passive pendulum arm suspension can reduce the lateral accelerations in a passively suspended cabin with 50% compared to traditional bogie machines when travelling in rough hard terrain.

  • 26.
    Ismoilov, Abbos
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Löfgren, Björn
    Skogforsk.
    Four wheeled active suspended design concept for forestry machines on soft and rough terrain2014Conference paper (Other academic)
  • 27.
    Ismoilov, Abbos
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Pirnazarov, Abdurasul
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Anderson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Löfgren, B.
    Investigating the dynamic behavior of a mid-sized forestry machine on sloped rough terrain2014In: 18th International Conference of the ISTVS, 2014Conference paper (Refereed)
    Abstract [en]

    High-performing forestry machines, such as forwarders, must be able to handle large loads and to operate rough and sloped terrains. Present forwarders are almost exclusively six-or eight-wheeled machines with pairs of wheels mounted on bogies. Consequently, they have very limited chassis damping and levelling capabilities. Traditional forestry machine chassis design is unfavourable from an active machine levelling and operator full body vibration control standpoint. This paper analyses the dynamic behaviour of an existing mid-sized forwarder. The multi-objective concept performance is studied with multi-body simulations and response analysis. The main focus is to identify critical design issues of the machine, specifically while traveling in sloped terrain, and to compare its off-road performance with a new pendulum arm suspended forwarder, referred to as the XT28 machine. The main purpose of the presented investigation is to suggest criteria for assessing the performance of off-road forestry machines when operating on sloped and rough terrain. The target is to assist future research on the newly developed XT28 forwarder that is planned to be in the initial full scale test during the coming year.

  • 28.
    Khan, Suleman
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Aftab, Ahmad
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Design Optimization of the Tau Haptic Device2011In: ICUMT: Ultra Modern Telecommunications and Control Systems and Workshops (ICUMT), 2011 3rd International Congress on, IEEE , 2011, p. 1-8Conference paper (Refereed)
    Abstract [en]

    The work presented in this paper is motivated by the use of haptics in medical simulation, particularly simulation of surgical procedures in hard tissue such as bone structures. In this context, characteristics such as motion, stiffness, workspace-to-footprint ratio, and low inertia are key factors in the design of a haptic device. This paper introduces a procedure for design optimization of haptic devices based on a hybrid mechanism. For design optimization, performance indices such as workspace volume, kinematic isotropy and static torque requirements indices are defined. A new multi-criteria objective optimization (MOO) function is introduced to define the optimization problem. Multi-objective algorithms are used to solve this optimization problem using the defined objective function. Furthermore sensitivity analysis of the performance indices against each design parameter is presented as a basis for selecting a final set of design parameters to develop a prototype. Finally, a CAD model and prototype of the device is developed based on the simulation results.

  • 29.
    Khan, Suleman
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    A design Methodology for haptic devices2011In: Proceedings of the 18th International Conference on Engineering Design (ICED11), Vol. 4 / [ed] Culley, S.J.; Hicks, B.J.; McAloone, T.C.; Howard, T.J. & Lindemann, U., 2011, p. 288-298Conference paper (Refereed)
    Abstract [en]

    This paper presents a design methodology for optimal design of haptic devices, considering aspects form all involved engineering domains. The design methodology is based on parametric modeling, iterative and integrated design approach that leads to easier design space exploration for global optimal design and initial verification in the conceptual design phase. For global optimization, performance indices such as; workspace volume, isotropy, stiffness, inertia and control of the device were from all involved engineering domains were considered. To handle this complex and non-linear optimization problem, a multi-objective algorithm together with a new developed optimization function was used, to obtain a global optimum solution. A case study, where the methodology has been applied to develop a parallel haptic device is presented in detail in this paper. The results obtain from the test case model show significant improvements in the performances of the device.

  • 30.
    Khan, Suleman
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Andersson, Kjell
    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.
    A Design Approach for a New 6-DoF Haptic Device Based on Parallel Kinematics2009In: 2009 IEEE INTERNATIONAL CONFERENCE ON MECHATRONICS, NEW YORK: IEEE , 2009, p. 195-200Conference paper (Refereed)
    Abstract [en]

    This paper presents an approach to a methodology for design, analysis and optimization of haptic devices. This approach roughly divides the design process into; device requirements, conceptual design, device design, control design and finally building a prototype of the device. In addition, we have applied the first two phases of this methodology, i.e. device requirements and conceptual design on the development of a new 6-DoF haptic device. The intended application area for this device is medical simulations and this research is one important component towards achieving manipulation capabilities and force/torque feedback in six degrees of freedom during medical simulations. Three candidate concepts, all based on parallel kinematic structures, have been investigated and analyzed. The performance parameters being analyzed have covered workspace analysis and force/torque requirements to fulfill the specified TCP force performance. The initial analysis of these three concepts has shown, after a smaller modification of one of the concepts that all concepts seem to satisfy, the initially stated requirements.

  • 31.
    Khan, Suleman
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Andersson, Kjell
    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.
    Design Optimization and Performance Evaluation of a 6-DOF Haptic DeviceIn: Journal of mechanical design (1990), ISSN 1050-0472, E-ISSN 1528-9001Article in journal (Other academic)
  • 32.
    Khan, Suleman
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Dynamic based control strategy for haptic devices2011In: World Haptics Conference (WHC), 2011 IEEE Issue Date: 21-24 June 2011 / [ed] IEEE, 2011, p. 131-136Conference paper (Refereed)
    Abstract [en]

    Transparency is a key performance measure for haptic devices. In this paper, we investigate a control strategy to increase the transparency of a haptic device. This control strategy is based on careful analysis of the dynamics of the haptic device, computed torque feed forward control and current feedback based force control. The inverse dynamic equation of motion for the device is derived using Lagrangian formalism and the dominating terms are identified for some representative motion trajectories. The user contact dynamic model is identified using experiments on the device with different users. A PI controller using motor current measurements is used to follow the reference force from the virtual environment. Experimental results illustrate the effectiveness of the control strategy.

  • 33.
    Khan, Suleman
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Investigation of parallel kinematic mechanism structures for haptic devices2009In: 2nd Nordic Conference on Product Lifecycle Management – NordPLM’09, Gothenburg January 2009., 2009Conference paper (Refereed)
    Abstract [en]

    Today modeling and simulation tools like FE (Finite Element) and MBS (Multi Body Systems) simulation tools are commonly used within mechanical engineering. These types of tools offer capabilities of Virtual prototyping (VP) with the possibility to investigate and explore a product before a physical prototype is manufactured. This can reduce the number of physical prototypes needed and save both time and money. These tools are also well known to be an effective means to support the process of verification of formulated requirements. They can be used e.g. for evaluation and selection of alternative solutions or as a final check or optimisation of a solution concept. The use of these kinds of tools can be even more effective if an information framework for handling the information created during the verification process can support them.

    The outline of such an information framework has been presented by Andersson [1], [2], which support traceability and reuse of partial result created during the verification of a specific requirements attribute as well as a possibility to study the effects that changes in the requirements specification have on product properties. This type of framework need a fine granularity of information, to be able to reuse partial results e.g. component simulation models but also that the models are structured such that we can reuse them in new model configurations.

    This paper presents an investigation of 6-dof haptic devices based on parallel structure that can be used in a surgical training simulator for temporal bone milling or as a 6-dof input- output teleoperated haptic master device. This investigation follows the verification process outlined by Andersson [1], [2], where the haptic devices in this case the product concept to be evaluated. The basic idea behind these concepts is to develop a haptic device with a large workspace and high stiffness within this workspace based on modeling and analysis of two different concepts. The study will concentrate to find a way to measure performance parameters to be able to evaluate and compare different structures.

  • 34.
    Khan, Suleman
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Jacobian Matrix Normalization - A Comparison of Different Approaches in the Context of Multi-Objective Optimization of 6-DOF Haptic Devices2015In: Journal of Intelligent and Robotic Systems, ISSN 0921-0296, E-ISSN 1573-0409, Vol. 79, no 1, p. 87-100Article in journal (Refereed)
    Abstract [en]

    This paper focuses on Jacobian matrix normalization and the performance effects of using different criterion and techniques. Normalization of the Jacobian matrix becomes an issue when using kinematic performance indices and the matrix contains elements with non-homogenous physical units, i.e. representing both translational and rotational motions. Normalization is necessary in multi objective optimization if kinematic performance indices are used based on the full Jacobian matrix. Different methods have been proposed in literature for defining a scaling factor used to normalize the Jacobian. Based on a comparison of a few of these methods, we conclude that it is better to have the scaling factor as a design variable in the multi objective optimization. However, as an alternative, a new scaling factor is proposed based on the relationship between linear actuator motion range in joint space and rotational end effector motion in task space, a proposal underpinned by simulation, analysis and comparison of optimization results using existing normalization techniques. For optimization, performance indices for workspace, kinematic sensitivity, device isotropy and inertia are considered. To deal with the multi-objective optimization problem, genetic algorithms are employed together with a normalized multi-objective optimization function. The performances of different device configurations (depending on the normalization method and the global isotropy index used) are presented in this article.

  • 35.
    Khan, Suleman
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Andersson, Kjell
    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.
    Multi-objective Optimal Design of a 6-DOF Haptic Device Based on Jacobian NormalizationIn: IEEE transactions on robotics and automation, ISSN 1042-296XArticle in journal (Other academic)
  • 36.
    Khan, Suleman
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Optimal Design of a 6-DoF Haptic device2011In: Mechatronics (ICM), 2011 IEEE International Conference on, IEEE , 2011Conference paper (Refereed)
    Abstract [en]

    The work presented in this paper is motivated by the use of haptics in applications of medical simulation, particularly simulation of surgical procedures in hard tissue such as bone structures. In such a scenario haptic device characteristics such as stiffness, motions, suitable workspace and device footprint are key design factors. This paper presents a procedure for optimal design of a parallel kinematic structure for a 6-Dof haptic device. For optimization, performance indices such as workspace volume, kinematic isotropy and static actuator force requirements are defined. A specific Jacobian matrix normalization is introduced for defining the kinematic isotropy and actuator force requirement indices. For defining the optimization problem, a novel multi-criteria objective function is introduced. Based on this objective function, a genetic algorithm is used to solve the multi-objective and non-linear optimization problem. Also, sensitivity analysis of the performance indices against each design parameter is presented as a basis for selecting a final set of design parameters for prototype development. Finally, using these results, a prototype was implemented.

  • 37.
    Pirnazarov, Abdurasul
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Wijekoon, Madura
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Löfgren, Björn
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Modeling of the bearing capacity of Nordic forest soil2012In: 12th European Conference of the ISTVS, 2012Conference paper (Other academic)
  • 38.
    Ramachandran, Praveen
    et al.
    KTH, School of Industrial Engineering and Management (ITM).
    Ismoilov, AbbosKTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).Sellgren, UlfKTH, School of Industrial Engineering and Management (ITM).Löfgren, BjörnSwedish Forestry Research Institute, Skogforsk.Andersson, KjellKTH, School of Industrial Engineering and Management (ITM).
    MODEL-BASED ANALYSIS OF A TRACKED FORWARDER FOR SUSTAINABLE FORESTRY2015Conference proceedings (editor) (Other academic)
    Abstract [en]

    Cut-to-length logging (CTL) is a mechanized harvesting process where trees are delimbed and cut to length directly at the stump. CTL is typically a two-man, two-machine operation with a harvester felling, delimbing, and bucking trees, and a forwarder transporting the cut logs from the felling area to a landing area accessible by trucks, or trains. The main challenges for the manufacturers of forestry machines for CTL logging are to address new customer demands and tougher ergonomic and environmental legislations by finding means that: (1) further increase the harvesting and log transportation productivity, e.g. by enabling operation on eco-soils, (2) reduce the damage to the soil, e.g. by controlling the rut depth and preserving the root layer, (3) reduce exhaust emissions, e.g. by reducing the rolling resistance and evening the contact and tractive forces between all traction units and ground, and (4) reduce the daily vibration dosage for the machine operators, e.g. with efficient chassis and cabin suspension solutions.This paper presents a model-based study of a novel tracked medium-sized forestry machine. The machine is a standard eight-wheeled forwarder of bogie type with the four bogies replaced with four passively suspended track units adapted from an off-road military vehicle. The paper briefly summarize how a tracked forwarder can be modelled and simulated using multi-body simulation software like Adams ATV and how the performance parameters can be evaluated.

  • 39.
    Sellgren, Ulf
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Ismoilov, Abbos
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Baez, Federico
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Löfgren, B.
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Model-based verification of a pendulum-arm suspended forwarder for sustainable forestry2014In: 18th International Conference of the ISTVS, 2014Conference paper (Refereed)
    Abstract [en]

    Cut-to-length logging (CTL) is a mechanized harvesting process where trees are delimbed and cut to length directly at the stump. CTL is typically a two-machine operation with a harvester felling, delimbing, and bucking trees, and a forwarder transporting the cut logs from the felling area to a landing area that is accessible by trucks, or trains. A major challenge for the manufacturers of forestry machines for CTL logging is to (1) further increase the harvesting and log transportation productivity, e.g. by enabling operation with higher transportation speed and on eco-soils, (2) reduce the damage to the soil, e.g. by controlling the rut depth and preserving the root layer, and (3) reduce the daily vibration dosage for the machine operators, e.g. by active chassis and cabin suspensions. This paper presents a study of a novel all-wheel-drive pendulum-arm suspended medium-sized forestry machine, with several upgrade performance steps, e.g. passive and active chassis suspensions. The dynamic performance of the new concept are quantified with simulations and compared with a present bogie solution. The simulations show an 80% reduction of whole body vibrations with an active suspension system compared to present passive bogie solutions when operating on a standardized test ground.

  • 40.
    Sellgren, Ulf
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Pirnazarov, Abdurasul
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Löfgren, Björn
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Model-Based Development of machines for sustainable forestry2012In: 12th European Conference of the ISTVS, 2012Conference paper (Other academic)
  • 41.
    Sun, Xuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Design optimization of haptic device - A systematic literature reviewIn: Article in journal (Refereed)
    Abstract [en]

    Performance requirements for high-performing haptic devices are usually multi-criteria. Sometimes the requirements are interacting, and several of them are conflicting. Optimization is one of the main approaches to scrutinize the design space and to search for a design that satisfies all requirements. Many researchers have used and published optimization approaches to search for an optimal haptic device design. However, predicting the performance of a high-performing haptic device usually involves computationally intensive simulations and analyses with complex and heterogeneous models. In order to study what are the common design and performance requirements of haptic devices and what optimization approaches have been used to improve optimization effectiveness and efficiency, a literature review on the present state-of-the-art in these areas has been performed. The most commonly used performance requirements presented in the literature are the number of degrees-of-freedom, dynamic inertia, kinematic isotropy, stiffness, peak and continuous force, position/force resolution, and bandwidth. Furthermore, parallel and hybrid kinematic structures are more commonly used than serial structures. Multi-objective optimization (MOO) is a commonly used approach to simultaneously optimize all performance criteria. The most common optimization targets, as presented in published literature, are to maximize workspace, kinematic isotropy, as well as the peak force/torque provided by the device, and to minimize the dynamic inertia. Commonly used indices to constrain the design space are a minimum workspace, avoidance of singularities and motion limits of active and passive joints. The number of design variables varies from 2 to 9, and the most commonly used design variables are a set of mechanical parameters, such as the lengths and diameters of the mechanical components. To increase the efficiency of complex and multi-criteria optimization tasks, the Pareto-front approach combined with multidisciplinary design optimization (MDO) and metamodel techniques are recommended.

  • 42.
    Sun, Xuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    The search for an efficient design optimization methodology for haptic devicesIn: Engineering with Computers, ISSN 0177-0667, E-ISSN 1435-5663Article in journal (Refereed)
    Abstract [en]

    Design optimization of haptic devices must manage multiple objectives,complex models, and time-consuming simulations. This paper proposes amethodology to eciently and eectively optimize the design of a high-performing6-degree-of-freedom (DOF) haptic device. The proposed methodology adapts ametamodel selection method called Predictive Estimation of Model Fidelity (PEMF)method, and integrates it with metamodel-based design optimization (MBDO)process in a multi-tool framework. A 6-DOF TAU haptic device, with two designobjectives, the global isotropy index (GII) and the dexterous workspace volumeindex (VI), is used to exemplify and verify the methodology. Two additional studiesare made to nd the most suitable sample size for metamodel training, and tostudy the eects of metamodel combinations on the solution accuracy. The generalityof the ndings is veried with MBDO of a completely dierent 6-DOF hapticdevice based on a Stewart Platform. The proposed metamodel-based methodologyreduces the computational time about 27 times as compared to using the fullmodel. For the specied design optimization problem, 300 sample points are ableto provide accurate enough metamodels and system solutions. The combination ofthe best-t metamodel for each design objective, Kriging (KR) for GII and RadialBasis Functions (RBF) for VI, can provide suciently accurate solutions whichlikely are applicable for all types of 6-DOF haptic devices.

  • 43.
    Sun, Xuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Towards a Methodology for multidisciplinary Design Optimization of Haptic Devices2015In: Proceedings of the ASME 2015 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2015, 2015Conference paper (Refereed)
  • 44.
    Sun, Xuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Efficient and situated design of haptic devicesIn: Article in journal (Refereed)
    Abstract [en]

    It is a challenging task to develop and optimize a high-performing haptic device for, e.g., medical training,because of the multi-objective performance requirements, and the complex relations between the design variablesand the performance objectives. Consequently, the solution space is scrutinized with efficient optimization techniques,and the cause-effect relations are preferably represented in a way that enables further reasoning in amulti-discipline setting, e.g., as Pareto-front curves and surfaces. Furthermore, if we have found a Pareto-optimalsolution, how can we benefit from the knowledge and optimization results obtained in that process if we are facinga trailing challenge (a new design situation) to re-design the initial solution to another application and/or otherrequirements, i.e. how can we address this new situation by efficiently re-using as much as possible of the initialsolutions? In this paper, we first present multi-objective optimizations of a 6-degree-of-freedom TAU haptic device.To investigate how we efficiently can address new design situations, by making use of the initial solutions, we havedefined, solved and analyzed six re-design cases. For the different cases, it is shown what can be reused and inwhat way that can be done. The six studied cases are then analyzed and a generic process for situated designoptimization, based on available knowledge and Pareto-optimal solutions, is proposed.

  • 45.
    Sun, Xuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Situated Design Optimization of Haptic Devices2016In: Procedia CIRP, Elsevier, 2016, Vol. 50, p. 293-298Conference paper (Refereed)
    Abstract [en]

    It is a complex task to develop and optimize a high-performing haptic device. Design optimization scenarios with predefined and fixed sets of performance requirements are presented in literature. However, the early design optimization phases for haptic devices are characterized by requirement conflicting requirements with uncertainties. With a lack of knowledge, and/or an ill-defined design problem, the challenges are not only to find a high quality solution with reasonable computational effort. In this paper, a previously proposed model-based framework and methodology for multi-disciplinary design optimization of haptic devices is further developed to enable situated design scenarios, i.e. design cases that may be characterized by changing requirements, constraints, and/or performance objectives, driven by the knowledge gained in the design and optimization process itself. To provide both precision and computational efficiency, the proposed situated, i.e. flexible and adaptable, framework is based on an approach that combines design-of-experiments (DOE) with meta-modelling methods for multi-objective optimization problems. The proposed methodology is described and verified with a 6 degree-of-freedom (DOF) TAU haptic device optimization scenario, with changing ranges for the design variables and the constraints. Results from the case study strongly indicate that a thoroughly balanced and sequential DOE and metamodelling process is capable of being both effective and efficient in a situated design scenario. It is shown that the knowledge gained in the process, e.g. the number of sampling points and the most appropriate training method, may be used to efficiently balance the required computational effort with the required level of accuracy.

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