Defining performance tradeoffs for multi-degree-of-freedom bilateral teleoperators with LQG control

Two main objectives of feedback design for bilateral teleoperators are position coordination between the master and slave and accurate haptic display of environment forces to the human operator. We demonstrate that, for multi-degree-of-freedom teleoperation, certain directional haptic distortions may occur unless the controller creates an isotropic impedance between the master and slave. On the other hand, a strictly isotropic impedance controller may sacrifice position coordination performance. Thus, it is desirable to find a control design that achieves the best possible simultaneous position coordination and accurate haptic display. We provide quantitative measures of these goals and provide a solution to the feedback design problem through novel application of optimal Linear-Quadratic-Gaussian (LQG) control to multi-degree-of-freedom teleoperation. An experimental study demonstrates the tradeoff between the goals of position coordination and isotropic impedance when a teleoperator is subject to realistic bandwidth constraints due to intrinsic hardware limitations.