Power assistance on slope of an omnidirectional hybrid walker and wheelchair

In this paper, first we briefly present an overview of our developed electric powered user-propelled hybrid walker and wheelchair robot. Then we focus on analysis and investigation of a movement in which the robot starts to ascend and to descend a slope. We originally point out that in such motion the users walking speed and the robots traveling speed are inevitably different since the robot is undergoing a planar motion. This explains why the load of the user suddenly increases/decreases when a user-propelled walker or wheelchair starts to ascend/descend a slope. Note that as far as our knowledge this is the first time clarifying the intrinsic nature of the movement. Further we propose two speed compensation approaches under an admittance based interaction control to let the user get a smooth “load feeling” as the user utilizing the robot on a horizontal plane. The experiments verify the effectiveness of the proposed approaches.