Motion control of a walking support robot considering pressure and thrust from users

A walking support machine (WSM) has been developed for the people with walking disabilities. To safely and accurately assist users to their destination, the path and trajectory tracking accuracy of WSM must be guaranteed. However, path and trajectory tracking accuracy of the WSM is seriously affected by acting forces from users. To address these issues, in this paper, an analysis about the acting forces from users on WSM was conducted. The acting forces were assumed to be the pressure on the vertical plane and the thrust on the horizontal plane. The thrust was treated as external disturbances and the pressure was considered as equivalent mass that user imposes on the WSM. Then, a more accurate dynamic model of the WSM was derived considering the acting force. A digital acceleration controller was proposed to address the issue of thrust which is unmolded. However, the design of this controller required the real time position of center of gravity (COG) and mass of robot system (considering the effect of user). Therefore, four force sensors were equipped under the armrest to measure the pressure from user on the robot to calculate the position of COG and mass of load. Finally, experiments were conducted that the WSM was used to support the subject to follow a pre-desired path, and the results showed that the proposed controller was effective to deal with the problems of acting force.