Feedback and predictive motion control strategies for the off-road locomotion of the three-wheeled personal vehicle Falcon-III

Falcon-III is a robotic personal vehicle that has been designed for uneven terrain usage. It has a two-degree-of-freedom suspension mechanism that allows the passenger´s seat orientation (pitch and roll) to be controlled by actively adjusting the height of its wheels. This paper discusses the motion control of such a vehicle on rough terrain. In particular, we show that a feedback control law that measures the vehicle seat attitude and acts to correct it, aiming at maintaining the horizontal seat posture during the traversing of uneven terrain, is by itself insufficient to provide satisfactory performance on certain types of terrain. Therefore, we propose a predictive motion control strategy, in addition to the feedback control law, that dynamically controls the vehicle suspension in order to facilitate the negotiation of obstacles - the motion executed is somewhat similar to that performed by a cyclist when overcoming a step-like obstacle. When tall step-like obstacles have to be negotiated, it may be necessary to dynamically lift one of the wheels from the ground, in which case a gait pattern emerges.