Pitch Motion Control of Vehicles Based on Fully Active Suspension

During straight-line driving, the driver’s acceleration and braking maneuvers induce pitching motion of the vehicle body. Frequent attitude changes are prone to causing motion sickness of passengers and adversely affect the handling experience. To suppress this adverse pitch response, focusing on the problem of vehicle body pitch attitude control under driving and braking conditions, this paper conducted research on modeling and control algorithms based on a fully active suspension system, and verified the control effect through real-vehicle tests. Firstly, a four-degree-of-freedom vehicle pitch model was developed, with particular emphasis on the effects of suspension anti-dive and anti-lift characteristics, the location of the sprung mass’s pitch center, and the differences in the transmission paths of driving and braking forces. The model was validated via CarMaker co-simulations. Subsequently, a vehicle body attitude control algorithm based on feedforward-feedback architecture was designed, for which a nonlinear pitch model was used in place of real vehicle state feedback, achieving decoupling between the driving/braking force inputs and the disturbances caused by vertical road displacement. This approach effectively prevents road undulations and gradients from interfering with the suspension control force output. Furthermore, based on the control objective of zero pitch angle, a feedforward and PID feedback controller was designed, and an optimization method for the feedforward controller that is easy to implement in engineering was proposed, which resolves the issue of high-frequency chattering in the output force of the theoretical feedforward controller. Finally, real-vehicle tests were conducted on a prototype vehicle equipped with fully active suspension, and the results demonstrate that the proposed control strategy significantly attenuates vehicle pitch response under full-throttle acceleration and emergency braking conditions, reducing pitch angle RMS by up to 89.2% and 77.7%, respectively, thereby enhancing ride comfort and handling stability.