Study on possible control algorithms for lower limb rehabilitation system

In this paper, one of the possibilities of introduction of variable stiffness in a rehabilitation manipulator for lower limbs, is described. Mechanical design and working principle of a proposed system are presented. The following control algorithms for manipulators with flexible joints are suggested: the position control and the active impedance control. The tracking performance is experimentally studied for sinusoidal and polynomial reference trajectories. Obtained results confirm that both control strategies are suitable for controlling a rehabilitation manipulator with changeable stiffness.