ABSTRACT
This chapter concentrates on the control of human biped stance and balancing as relatively simple prototypes of posture and movement control in general. The simplicity is mainly owing to the fact that the physics of the body sway resembles that of a single or double inverted pendulum. Clinically, postural control is often equated to equilibrium control of stance. However, posture control does not end with body-on-feet balancing. Rather, we balance the head on the trunk, the trunk on the hips, or make the trajectory of an arm during reaching movements resist gravity. Admittedly, there are differences among these tasks, depending on which muscle groups, joints, etc. are concerned. Yet, basic function principles resemble each other when viewed from a ‘systems control perspective’. At this level, the muscles are abstracted as actuators. Furthermore the movements of body parts are formalized according to the rules of physics, and the balancing represents the neural control task. Such abstractions help to grasp the essence of the function principles.
