Attitude Control of the Vehicle with Six In-Wheel Drive and Adaptive Hydro Pneumatic Suspensions

The ability of actively adjusting attitude provides a great advantage for those vehicles used in special environments such as off-road environment with extreme terrains and obstacles. It can improve vehicles’ stability and performance. This paper proposes an attitude control system for realizing the active attitude adjustment and vehicle motion control in the same time. The study is based on a vehicle with six wheel independent drive and six independent suspensions (6WIDIS), which is a kind of unmanned vehicle with six in-wheel drives and six independent hydro pneumatic suspensions. With the hydro- pneumatic suspensions, the vehicle’s attitude can be actively adjusted. This paper develops a centralized- distributed control strategy with attitude information obtained by multi-sensor fusion, which can coordinate the complex relationship among the six wheels and suspensions. The attitude control system consists of three parts. The first part is the attitude determination that includes attitude sensors and a method to measure any quantity sensitive to attitude and determine the real-time vehicle status. The second part is the attitude adjustment that computes the input torques to follow the desired roll and pitch angles. The third part is an attitude actuator that determines a desired force for each hydro pneumatic suspension. In order to simulate the practical vehicle more realistically, a dynamic model with 18 degrees of freedom is established. A torque vector controller is also developed to provide the excellent steering ability, skid-resistance and robustness for the 6WIDIS, which is the basis of the attitude control. Simulation tests are conducted to evaluate the performance of the proposed attitude control system. The simulation results show that the performance of the proposed attitude control system is good and it can improve the obstacle performance, mobility and flexibility of the vehicles.