A Neural Model as an Internal Inverse Model in the Brain for Controlling the Standing Balance Based on a Fuzzy Intermittent Strategy

Human body during upright stance is an unstablesystem which needs to be stabilized through activation ofinvolved muscles. In this paper, a novel control strategy utilizinga fuzzy intermittent mechanism and a self-tuning PD controllerhas been proposed to address the issue of human upright posturestabilization. In this research, balance control using the anklestrategy is desired. Therefore, if the COP signal and its firstderivative (COP velocity), as the sensory information related toa healthy subject, to be considered as the controller input signals,it is expected that the controller output is similar to the anklemuscle activation profile elicited by the neural commands. If itcan be proved, it can be claimed that the proposed controlstrategy can imitate the behavior of the internal Inverse modelin the brain that is assigned for controlling the posture balanceduring the quiet standing. The COP signal and GastrocnemiusEMG signal of a healthy subject were recorded during the quietstanding. Quantitative evaluations show that the controlleroutput matches the muscle activation profile extracted from theelectromyogram signals recorded simultaneously with the inputsignals.