Optimal Trajectory Planning for 2-DOF Adaptive Transformable Wheel

Steps are frequently encountered while mobile robots move in indoor environments; thus, the ability to overcome a step is essential to indoor mobile robots. In this study, a new adaptive transformable wheel is conceptually proposed to effectively overcome steps of different sizes. The center trajectory of the proposed wheel is optimally designed to minimize its fluctuations while the robot overcomes a step. For this purpose, a kinematic analysis of the proposed wheel is performed to identify the points that its center must pass while the robot overcomes a step. The center trajectory is optimized with an objective function to evaluate the mobile stability of the proposed wheel under kinematic constraints to avoid undesired interferences between the wheel and the step. Extensive simulations with different steps verify that the optimal trajectory ensures stable and effective overcoming of steps. The experiment using the prototype of mobile robot equipped with the proposed wheel verifies the smoothness of resulting trajectory of wheel center.