Workspace control of a wheel-legged mobile robot for gyrating locomotion with movable leg

We discuss motion generation problems of a wheel-legged mobile robot (WLMR) with movable legs. We consider and solve two problems of inverse kinematics of WLMRs. The first problem occurs in the generation of steering commands for WLMRs, which is due to the mechanism of the structure of the wheels. In general, inverse kinematics for WLMRs are applied in the velocity level. However, in our case, it is not possible to generate the proper steering motion. To solve this problem, we show that for WLMRs, the application of inverse kinematics in the acceleration level is effective. The second problem addressed is a singularity problem that occurs when controlling the contact point of legs during the wheeled locomotion of the WLMR. We show that this singularity problem can be avoided by utilizing the redundancy present in the wheel-leg mechanism. Finally, the effectiveness of our motion generation schemes is validated by conducting precise, three-dimensional simulations.