On-line control of continuous walking of wearable robot coordinating with user´s voluntary motion

In this paper, we propose a cooperative control of a wearable robot for paraplegics. The control system adjusts the stride length and walking velocity of a robot according to user´s voluntary movement while generating a continuous walking pattern. We assume that the desired stride length and walking speed correspond to the preceding motion of a walking aid (walker), and the motion of the walker by the user was measured by a laser range sensor and an accelerometer. The continuous walking pattern during a step was planned by optimization of joint trajectories under inequality conditions. To perform continuous walking, the desired trajectory is required before the walker movement. To adjust the foot placement according to the walker movement, the desired walking pattern in the late swing phase is replanned. For the latest movement distance of the walker, the posture at heel strike is modified by Newton-like iterative calculations. We confirmed that a normal subject could walk continuously with a wearable robot controlled by our system while changing the stride length and walking speed.