Simulation study of human posture control under external perturbation

A 4-segment human mechanical model with sensory and actuator dynamics has been developed to investigate the human postural control under external perturbations. The model contains the major nonlinear dynamics of the physiological system and the time delays in the sensory feedback pathways. A Smith predictor is implemented to compensate for the sensory delays. Then a linear quadratic regulator is designed to simulate the human control of postural stability. The model simulates the control of an upright posture under an external perturbation which is a short duration pulling force applied at the pelvic level. The model simulation produced controls and perturbation responses that reasonably matched experimental data. In both the human experiment and the model simulation we find that the knowledge of the perturbation is important for improved performance. We also find that the formulation of an effective controller relies heavily on the availability of sensory information from the foot such as the center of pressure. The possible application of this model in functional neural stimulation is discussed