An H∞, control model of human postural control in quiet upright standing

An understanding of human postural control in quiet upright standing is very valuable for human being. This paper proposes a new control model of human postural control in quiet upright standing. An H_∞ state feedback control problem is proposed as a mathematical model of human postural control during quiet upright standing. An inverted pendulum controlled by a joint torque is used to model the human body and an H_∞ state feedback controller is used to model the central nervous system (CNS). At the same time, time-varying delay is considered. Then, the problem addressed here is design of a state feedback H_∞ controller so that the closed-loop system is exponentially stable with a prescribed H_∞ performance and can simulate human CNS in postural control in term of linear matrix inequality (LMI). Finally, the Stabilogram Diffusion Function (SDF) is used to analyze the results, which demonstrates the validity of the proposed design approach. The major contributions of this method are that an H_∞ state feedback controller is commendably used to model human CNS of postural control in quiet upright standing and synchronously varying time delay is considered.