Abstract
The CNS has various means of to regaulate the impedances at muscle level, such as variable viscoelastic properties of muscles and stretch reflex. Hawever the motion tasks to be controlled are usually given about end-point coordinates. The mechanical properties of the musculoskeletal system which transfer the muscle impedance into the end-point one is the key of fine regulations of the motor impedance in the human movements.
In this paper, the mechanical properties and the impedance regulations of the musculoskeletal system are discussed. First, the impedance relationships among muscle, joint and end-point levels are formulated and it is shown that these impedances specify the inverse kinematic solutions of redundant arms. Then the manipulation ability of end-point via muscle forces is defined by ellipsoids and an estimation method of muscle forces required for a given end-point movement is presented. It is shown that the manipulation ability of end-point is affected largely by the mechanical properties of the musculoskeletal system, especially the redundancy of joints and muscles.
