Task-oriented impedance adjustments of human arm movements

This paper discusses task-oriented control strategies and their dynamic formation in movements of human arm, with the impedance adjustment as the fundamental control method in its redundant degree-of-freedom (DOF) muscular-skeletal structure. Impedance adjustment mechanisms and dynamic characteristics for the muscular-skeletal and spinal reflection systems are described. It is also shown that the impedance adjustment at the joint and muscular levels plays an important role in the manipulation of objects. Dynamic impedance properties (stiffness and viscosity) of the actuating structure, together with the equilibrium trajectory profile of the structure, is defined to be the expression of the motion skill. Then, a task-oriented iterative impedance adjusting algorithm based on Variant Calculus is proposed, and simulation examples on a three-DOF planar arm are presented to show that the task-oriented motion skills can be formed under naturally specified simple objective functions