Swing motion control of lower extremity exoskeleton based on admittance method

To solve the problem of the pilot motion intent's identification and tracking during the swing motion of lower extremity exoskeleton, a control algorithm based on admittance method was proposed at first. This control method used the admittance characteristics between the force and velocity of moving object. And the interaction force between pilot and lower extremity exoskeleton was converted into the desired motion trajectories via the reasonable design of admittance parameters. Then the traditional control was employed to track these trajectories accurately. Finally the coordinated movement of pilot and exoskeleton was achieved. The human-machine system model including interaction force information was established and the simulations were conducted according to the system model. The results show that the interaction force between pilot and exoskeleton is reduced by 85% compared with the unpowered exoskeleton under the normal swing frequency, and the accurate tracking to pilot's motion trajectories is implemented successfully with the error ranged from -0.3° to 0.3°.