HOPF BIFURCATION CHARACTERISTICS OF A HIGH-SPEED TRAIN WITH ACTIVE LATERAL SUSPENSION CONTROL

To study the Hopf bifurcation characteristics of high-speed vehicles with active lateral suspension, a 7DOFs nonlinear simplify dynamics model is established. Based on the traditional skyhook control principle, the nonlinear control strategy of skyhook/groundhook damping and stiffness control law is proposed, which means that the ideal active force of the lateral damper is expressed as a cubic polynomial function of the lateral vibration displacement or velocity of the vehicle carbody or the bogie. Theoretical study of the effects of the state feedback quantity and control gain on the Hopf bifurcation velocity, the limit cycle amplitude and the hunting motion frequency of the vehicle system. The results shows that the passive suspension parameters hardly balance the first hunting motion and the second hunting motion. The primary and cubic term gain of the groundhook damping and stiffness law have little influence on the bifurcation characteristics of the first hunting motion; Optimizing the primary and cubic term gain of the groundhook damping and stiffness law can increase the critical speed of second hunting motion and the effect of the groundhook damping law is more significantly; Increasing the cubic term gain of the groundhook damping law can significantly reduce the limit cycle amplitude without changing the frequency of hunting motion, and the cubic term gain of the groundhook stiffness law does not affect the bifurcation characteristics of second hunting motion; Increasing the primary term gain of the skyhook damping and stiffness law can effectively inhibit the first hunting motion, mainly because of changing the body suspension modal damping ratio and frequency, however, the skyhook stiffness low will reduce the critical speed of the second hunting motion; In conclusion, the reasonable design of skyhook/groundhook damping and stiffness control laws and their parameters can effectively regulate the bifurcation speed and limit cycle amplitude of the vehicle system. The study can provide theoretical basis and reference for the coordinated control of hunting motion stability and ride quality of the EMU based on active lateral suspension technology.