Servo hypotheses for the biological control of movement

An analysis is made of equilibrium-point models for motor control, describing these models in the context of servo control mechanisms. We considered issues of speed and stiffness scaling that are incompatible with current formulations of the equilibrium-point models. A modification of the equilibrium-point models is proposed in which the central nervous system controls velocity as well as positions during the course of fast limb movements. Numerical simulations are presented that verify that such a servo control mechanism could successfully produce fast limb movements, as observed in human subjects.