A two-way model for motor control of redundant systems

The biological motor control system is an adaptive system exhibiting vast redundancy at all its hierarchical levels. Redundancy improves reliability and flexibility and might be the salient reason for the superb dexterity of human motor control. However, introducing redundancy in an inversely controlled object results in an ill-posed problem. We describe a general two-way model for redundancy control. This model includes the selection of a single solution by the dynamics of the system at the lower level, and a multiple controller that can use different solutions under different circumstances at the higher level. We demonstrate the role of the system dynamics in facilitating the stereotypical features of rapid movements, and suggest an architecture as well as a theoretical framework for many-to-one function approximation and inversion.