DESIGN OF ROBUST STATE FEEDBACK CONTROLLERS FOR REHABILITATION IN PARKINSONS TREMOR: A SIMULATION STUDY WITH UNCERTAIN MODEL OF BASAL GANGLIA

Deep brain stimulation ( DBS) is one of the most effective neurosurgical procedures to reduce Parkinsons tremor. The conventional method of DBS is open loop stimulation of one area of basal ganglia ( BG). On the other hand, existing feedback causes the reduction of additional stimulatory signal delivered to the brain which results in the reduction of the side effects caused by the excessive stimulation intensity. Actually, the stimulatory intensity of the controllers is reduced proportionally by the reduction of hands tremor, which is in fact the intended rehabilitation of the disease. The meaningful objective of this study is to design an architecture of controllers to decrease three criteria. The first one is the hand's tremor, the second one is the level of delivered stimulation signal to brain in disease condition and the third one is the ratio of the level of delivered stimulation signal in health condition to disease condition. In order to achieve these objectives, a new architecture of a closed loop control system to stimulate two areas of BG at the same time is presented. One area ( STN: subthalamic nucleus) is stimulated with a state feedback ( SF) controller ( pole placement method) and the other area ( GPi: globus pallidus internal) is stimulated with a partial state feedback controller ( PSFC). Considering these criteria, the results illustrate that stimulating two areas leads to a suitable performance. Simulation results show that the PSF and SF controllers are robust enough to the variations of the system parameters. Moreover, we are able to estimate the parameters of BG model in real time; it is a valuable method to update the time variable parameters of this model.