Design, Control and Experiments of An Agile Omnidirectional Mobile Robot with Active Suspension.

Omnidirectional vehicles (ODVs) have wide applications, but most of them (e.g., mobile robots with omni-, Mecanum, or spherical wheels) are mainly designed for indoor use on flat and smooth terrains. Literature review indicates that mobile robots based on the "self-sustained" active split offset caster (ASOC) module design that uses conventional wheels (e.g., rubber tires) is more suitable to execute agile maneuvers in unstructured rough terrains. However, these robots often have time delay and synchronization issues caused by the wireless transmission of control signals and the wheel-terrain contact-breaking issues (some wheels are lifted off from the ground), which often lead to poor motion control and trajectory tracking performance when executing high speed turns. To solve these problems, through improved ASOC module design, active suspension design, and control algorithm design, we develop an ASOC-based mobile robot capable of active body posture control and agile omnidirectional mobility. We give detailed explanations of its design philosophy and working principle. Experiment results indicate that our proposed robot can achieve much better performance in challenging tests such as negotiating uneven ground and executing very sharp turns at high speed.