Electromechanical Exoskeleton Control Model Using the Constraint Stabilization Method

The electromechanical model of exoskeleton with three controlled mobile links is considered in the article. Every link is hinged with the neigbouring one by a cylindrical hinge, in which there is an electric drive implementing the required control torque. The main feature of this model is that bottom point of exoskeleton is mobile. This feature corresponds to exoskeleton supporting point slippage on the surface in the situation when the value of friction coefficient is insufficient, for example, when the model is on a snow-covered or ice-covered surface. The exoskeleton acquires two additional degrees of freedom, relating to translational motion of the exoskeleton bottom point, in this case. Since the considered model features fairly large number of freedom degrees, the issue of error accumulation arises when the Cauchy problem is solved numerically. Therefore, the control system of exoskeleton programmed motion, using the constraint stabilization method, has been developed for the considered model. The equations of programmed constraints are introduced for their stabilization. The possible deviations, triggered by external disturbances, and by the results of the system numerical simulation, are described by the constraint disturbance equations. The Lyapunov function is introduced, and the solution asymptotic stability is considered. The practical significance of the obtained results lies in the possibility of designing a more precise exoskeleton motion control system with minimal deviation of link movements from the specified trajectories.