The Experts below are selected from a list of 112398 Experts worldwide ranked by ideXlab platform

Dongjun Lee - One of the best experts on this subject based on the ideXlab platform.

  • passive bilateral control and Tool dynamics rendering for nonlinear Mechanical teleoperators
    IEEE Transactions on Robotics, 2005
    Co-Authors: Dongjun Lee
    Abstract:

    We propose a passive bilateral teleoperation control law for a pair of n-degree-of-freedom (DOF) nonlinear robotic systems. The control law ensures energetic passivity of the closed-loop teleoperator with power scaling, coordinates motions of the master and slave robots, and installs useful task-specific dynamics for inertia scaling, motion guidance, and obstacle avoidance. Consequently, the closed-loop teleoperator behaves like a common passive Mechanical Tool. A key innovation is the passive decomposition, which decomposes the 2n-DOF nonlinear teleoperator dynamics into two robot-like systems without violating passivity: an n-DOF shape system representing the master-slave position coordination aspect, and an n-DOF locked system representing the dynamics of the coordinated teleoperator. The master-slave position coordination is then achieved by regulating the shape system, while programmable apparent inertia of the coordinated teleoperator is achieved by scaling the inertia of the locked system. To achieve this perfect coordination and inertia scaling, the proposed control law measures and compensates for environment and human forcing. Passive velocity field control and artificial potential field control are used to implement guidance and obstacle avoidance for the coordinated teleoperator. The designed control is also implemented in an intrinsically passive negative semidefinite structure to ensure energetic passivity of the closed-loop teleoperator, even in the presence of parametric model uncertainties and inaccurate force sensing. Experiments are performed to validate the properties of the proposed control framework.

  • Passive bilateral feedforward control of linear dynamically similar teleoperated manipulators
    IEEE Transactions on Robotics and Automation, 2003
    Co-Authors: Dongjun Lee, Perry Y. Li
    Abstract:

    Presents a passive bilateral feedforward control scheme for linear dynamically similar (LDS) teleoperated manipulators with kinematic scaling and power scaling. The proposed control law renders the teleoperator as a passive rigid Mechanical Tool with programmable apparent inertia to the human operator and the work environment by utilizing bilateral force feedforward and kinematic feedback control. The passivity of the closed-loop system is robust to force measurement inaccuracies and model uncertainty. Thus, interaction stability of the teleoperator with any passive environment is guaranteed. Coordination error and the overall motion aspects of teleoperation are controlled individually. The proposed control law is also applicable to general nonlinear robotic teleoperators if sufficiently high kinematic feedback gains are used. The proposed control schemes have been validated experimentally for both LDS and non-LDS systems.

Toshio Fukuda - One of the best experts on this subject based on the ideXlab platform.

  • human machine cooperative telemanipulation with motion and force scaling using task oriented virtual Tool dynamics
    International Conference on Robotics and Automation, 2000
    Co-Authors: T Itoh, Kazuhiro Kosuge, Toshio Fukuda
    Abstract:

    We propose an alternative control algorithm for a scaled telemanipulation system using the task-oriented virtual Tool dynamics. The aim of the proposed virtual Tool approach is to realize the ideal relationship for the human-oriented collaboration between a human operator and a controlled robot in a human-robot environment system. In the proposed cooperative system, a telemanipulator is controlled so that it has semi-autonomous virtual Tool dynamics designed appropriately for a given task. It assists a human operator semi-autonomously during the task as if it were a real Mechanical Tool and improves the maneuverability and the efficiency in the teleoperation. The stability is analyzed based on the passivity of the resultant system, and the total stability is guaranteed for a human operator and a passive environment with unknown dynamics. The algorithm is experimentally applied to a telemanipulator. The results illustrate the validity of the system.

Perry Y. Li - One of the best experts on this subject based on the ideXlab platform.

  • Passive bilateral feedforward control of linear dynamically similar teleoperated manipulators
    IEEE Transactions on Robotics and Automation, 2003
    Co-Authors: Dongjun Lee, Perry Y. Li
    Abstract:

    Presents a passive bilateral feedforward control scheme for linear dynamically similar (LDS) teleoperated manipulators with kinematic scaling and power scaling. The proposed control law renders the teleoperator as a passive rigid Mechanical Tool with programmable apparent inertia to the human operator and the work environment by utilizing bilateral force feedforward and kinematic feedback control. The passivity of the closed-loop system is robust to force measurement inaccuracies and model uncertainty. Thus, interaction stability of the teleoperator with any passive environment is guaranteed. Coordination error and the overall motion aspects of teleoperation are controlled individually. The proposed control law is also applicable to general nonlinear robotic teleoperators if sufficiently high kinematic feedback gains are used. The proposed control schemes have been validated experimentally for both LDS and non-LDS systems.

Radova Kovacevic - One of the best experts on this subject based on the ideXlab platform.

  • thermo Mechanical model with adaptive boundary conditions for friction stir welding of al 6061
    International Journal of Machine Tools & Manufacture, 2005
    Co-Authors: Vijay Soundararaja, Srdja Zekovic, Radova Kovacevic
    Abstract:

    Abstract Thermo-Mechanical simulation of friction stir welding can predict the transient temperature field, active stresses developed, forces in all the three dimensions and may be extended to determine the residual stress. The thermal stresses constitute a major portion of the total stress developed during the process. Boundary conditions in the thermal modeling of process play a vital role in the final temperature profile. The heating and cooling rates with the peak temperature attained by the workpiece determine the thermal stress. Also, predicting realistic peak temperature becomes important as the operating temperature at the interface of Tool-workpiece is very close to the solidus temperature of the aluminum workpiece. The convection heat-transfer coefficients of the surfaces exposed to air can be theoretically determined using Newton's law of cooling. Contact conductance depends on the pressure at the interface and has a non-uniform variation. The actual pressure distribution along the interface is dependent on the thermal stress from local temperature and non-linear stress–strain state. Therefore, applying an adaptive contact conductance can make the model more robust for process parameter variations. A finite element thermo-Mechanical model with Mechanical Tool loading was developed considering a uniform value for contact conductance and used for predicting the stress at the workpiece and backplate interface. This pressure distribution contours are used for defining the non-uniform adaptive contact conductance used in the thermal model for predicting the thermal history in the workpiece. The thermo-Mechanical model was then used in predict stress development in friction stir welding.

T Itoh - One of the best experts on this subject based on the ideXlab platform.

  • human machine cooperative telemanipulation with motion and force scaling using task oriented virtual Tool dynamics
    International Conference on Robotics and Automation, 2000
    Co-Authors: T Itoh, Kazuhiro Kosuge, Toshio Fukuda
    Abstract:

    We propose an alternative control algorithm for a scaled telemanipulation system using the task-oriented virtual Tool dynamics. The aim of the proposed virtual Tool approach is to realize the ideal relationship for the human-oriented collaboration between a human operator and a controlled robot in a human-robot environment system. In the proposed cooperative system, a telemanipulator is controlled so that it has semi-autonomous virtual Tool dynamics designed appropriately for a given task. It assists a human operator semi-autonomously during the task as if it were a real Mechanical Tool and improves the maneuverability and the efficiency in the teleoperation. The stability is analyzed based on the passivity of the resultant system, and the total stability is guaranteed for a human operator and a passive environment with unknown dynamics. The algorithm is experimentally applied to a telemanipulator. The results illustrate the validity of the system.