Roll Control Of Commercial Vehicles And Application Of Zero Moment Point In Its Evaluation

With the development of national economy and the improvement of road facilities,the production and sales of commercial vehicles in China have been on the rise in the past ten years,and the number of commercial vehicles on the road is also increasing.However,commercial vehicles have great potential safety hazards due to their high quality,high center of gravity and large volume.Once rollover occurs,it will have serious consequences.Investigation shows that the proportion of casualties caused by vehicle rollover is several times higher than that caused by rollover accidents.Therefore,vehicle rollover stability,as an urgent problem,has attracted the attention and research of experts and scholars at home and abroad.Among them,the use of lateral anti-roll bar to reduce vehicle roll has become one of the key points.In order to improve the vehicle stability by using the anti-roll bar,this paper mainly does the following research:Firstly,in order to better study the vehicle stability,a vehicle roll stability evaluation index based on zero moment point is proposed.The distance between zero moment point and vehicle axis is used as the judgment criterion of vehicle roll level and recorded as vehicle roll coefficient.In order to adapt to different models and simulations,the specific positions of zero moment points are deduced on two different vehicle models: rigid and roll.The accuracy of the roll index is verified by simplifying and comparing with other existing evaluation indicators.Secondly,a nine-degree-of-freedom dynamic model based on vehicle roll motion is set up,using "magic formula" tire model and corresponding road excitation.Taking 19-seats Iveco commercial vehicles as the research object,carry out a slalom test according to GB/T6323-2014 to verify the validity of the model.The results of the test and simulation were basically coincided.It showed that the model could reflect the actual state of vehicles to a certain extent,and ensure the accuracy of the model,which laid a foundation for the follow-up study.Finally,based on the analysis of the characteristics of passive anti-roll bar,in order to further improve the stability of vehicles,semi-active and active lateral anti-roll bars are designed,and the performance of these two kinds of stabilizer bars is analyzed.The semi-active anti-roll bar uses magnetorheological damper as actuator.The mechanical characteristics of magnetorheological damper are analyzed and the mechanical equation is given.In order to ensure the stability of the system,the H_method is chosen to synthesize the controller,and the control system model is built in Simulink.In order to make the simulation more accurate,the whole vehicle model is built in Trucksim and simulated jointly with the controller model in Simulink.Three different roll-prone working conditions are adopted in the simulation.The comparison of the parameters such as body roll angle,lateral acceleration and the evaluation index proposed in Chapter 2 prove that the semi-active stabilizer bar can reduce the roll of the vehicle to a certain extent.The core of the active stabilizer is mainly composed of actuator and control system.Active anti-roll bar adopts electro-hydraulic proportional control system as actuator,which can balance the chassis space and anti-roll moment of vehicle well.For control strategy,use PID + feedforward control stagety,and moth flame optimization algorithm is used to optimize its parameters.In order to compare the effect of lateral control,the simulation method is the same as that of semi-active anti-roll bar.The values of stability evaluation indexes under semi-active and active stabilizing bars are calculated and compared with the four parameters obtained by simulation.The anti-roll effects of two different systems are analyzed.The results show that the active stabilizer can better control the roll state of the vehicle.