| Electronically controlled air suspension(ECAS)can adjust the rigidity of the suspension according to different working conditions,which can improve the overall performance of the vehicle.The traditional vehicle control unit uses the serial development mode,which can no longer meet the update speed of electronic products.The hardware-in-the-loop simulation technology provides a convenient and effective way for the development of the controller.In this paper,the ECAS system with auxiliary air chamber is taken as the research object,based on the existing modified vehicles in the laboratory,the fuzzy PID control strategy is proposed and the simulation test is carried out.The test vehicle carried out the road test of the whole vehicle and verified the effectiveness of the control strategy.The main contents and results of this article are as follows:(1)In order to obtain the mechanical characteristics of the bladder air spring,the air spring selected for the test vehicle was used as the research object,and the finite element model of the bladder air spring was established using ABAQUS software,and the load of the air spring under different initial internal pressures was analyzed.The relationship between the curve and the displacement has been verified by experiments to verify the accuracy of the finite element model simulation.(2)In order to carry out dynamic analysis of the ECAS system of the whole vehicle,according to the vehicle dynamics and engineering thermodynamics theory,a four-wheel randomly excited road model and an air spring model with an auxiliary air chamber were established,and Simulink was used to build an auxiliary air the seven-degree-of-freedom mathematical model of the ECAS system in the laboratory.(3)In order to improve the overall performance of the vehicle traveling straight,a fuzzy PID controller was designed,and the volume value of the auxiliary air chamber was optimized using fuzzy rules.The fuzzy PID controller and the uncontrolled ECAS vehicle system with auxiliary air chamber were carried out respectively.Compared with the simulation test,the results show that: compared with the uncontrolled ECAS vehicle system,the fuzzy PID control reduces the root mean square value of the body vertical acceleration,pitch angle acceleration and roll angle acceleration by 14.47%,3.4%,25.19%.The root mean square values of suspension dynamic deflection are reduced by 25%,37.5%,34.04%and 4.76% respectively.The root mean square values of tire dynamic load were increased by7.33%,11.03%,2.75% and 16.43% respectively.In order to further verify the effectiveness of the designed control strategy,a joint simulation platform was built through Car Sim and Simulink software.The simulation results show that the comprehensive performance of the ECAS vehicle system under fuzzy PID control has been significantly improved.(4)To verify the impact of the control strategy on vehicle performance,an ECAS hardware-in-the-loop simulation test platform was designed and built.The ECAS hardware object was connected to the simulation model,and the ECAS actuator was controlled by an industrial computer to control the additional gas chamber.For volume,a static vehicle height model and a road driving model were built respectively,and hardware-in-the-loop simulation tests were conducted.(5)In order to verify the effectiveness of the control strategy designed in this paper in the actual environment,the test vehicle was reasonably modified,and the vehicle ride test was carried out before and after the modification.The vertical acceleration time domain characteristic curve of the vehicle body was obtained by using DASP software The sum amplitude-frequency characteristic curve and the relationship between the root-mean-square value of the vehicle's total weighted acceleration and speed show that the smoothness of ECAS under fuzzy PID control has been improved by road tests. |
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