Autonomous Creeping Mode Control for Traction Enhancement and Energy Optimization in Self-Reconfigurable Wheeled Mobile Robots

Multimode motion capability in self-reconfigurable wheeled mobile robots (SRWMRs) can be achieved by designing various control modes and the corresponding switching strategies adapted to different motion objectives. While SRWMR is capable of strong traction and moving at a fast speed by utilizing robot creeping (RC) and wheel rolling (WR) modes, respectively, the autonomous RC mode control is challenging due to the parameter definition of mode-switching control (MSC). Therefore, to obtain the main control parameters in an SRWMR, an ROSTDyn Vortex platform is developed to analyze the traction, slippage, and sinkage variation of the modes on varied soil terrains. To autonomously activate the RC mode while the robot is in WR mode, an MSC method is proposed by utilizing fuzzy logic algorithms, taking into account the slip ratio of wheels and their change in rate. Furthermore, for RC mode, to enhance the motion efficiency by adaptively changing the wheelbase length on different types of soil terrains, the control indices on energy consumption and forward movement are presented with the consideration of the defined slip ratio indices. According to the results of simulation experiments, including climbing slopes and escaping from the wheel sinking on the designed soil terrains with varied sloping degrees and stiffness, the autonomous RC control was effectively achieved by the proposed MSC, leading to body traction enhancement. In addition, a 31% reduction in energy consumption was achieved by RC mode with adjustable parameters, compared to the regular RC control.