Simulation Analysis And Control Of Vehicle Electronic Control Air Suspension Based On CAN-BUS

The ECAS Control strategy and Algorithm are researched with the project: Research on the Control Strategy and Algorithm of Electronic Control Air Suspension System for Heavy Truck. The format of the message of CAN-BUS control system is constituted,based on the SAE J1939 protocol, and the relevant software is designed.Based on the development demands of truck airspring suspension system, firstly confirmed the topology of CAN-BUS and the configuration of truck suspension: the front bridge with leafsprings and the rear bridge with airsprings. Refered to the driving conditions, defined three standard levels: H0,H1,H2, and four work modules: the whole body level adjusting, maintaining the body level stability, the listing and pitching carriage control, the body vertical vibration control. The double-CAN module of the BUS-Controller circuit is used as the control module of the CAN-BUS system, the SJA1000 circuit is used as CAN-bus controller, the 89C52 as CPU of the system nodes, and the PCA82C250 circuit as the interface circuit connecting CAN-bus controller with CPU together. The priority, cycle and address of the node are designed, and the format of the message of CAN-BUS control system is constituted, based on the SAE J1939 agreement.The control strategy in driving and the fuzzy control Algorithm to the root mean square value of the vehicle vertical vibration acceleration are instituted, based on the air suspension fuction of vehicle. By the method of making the algorithm parameters followed the error, carry out the fuzzy control process. The self-modulability and self-optimization of fuzzy formula are carried out by the ITAE integral.Refer to the different body carriage and the control demands, defined Start-Stop mode, Load-Unload mode, general driving stability control, and the driving carriage control. The seven-freedom vehicle model is created. Refer to the automobile Theory and some other articles, created the road input of white noise, the B and D class road and the mixture of the two class roads. The simulation models of the vehicle suspension, and the fuzzy control process were created, the airspring level control with Matlab/Simulink toolboxes and modules.The result indicates that the fuzzy control had less help to the body vibration on the good rood such as B class road, and had the better benefit on the bad road such as D class road.Based on the vehicle dynamic model and the control strategy, The ECAS test-bed of heavy truck is designed with the WABCO products such as solenoid values and level sensors, and the ECU of the Electronic Control Air Suspension system.The conclusion indicated that the airspring control strategy and Algorithm constructed had better effect to improve the body stability. The fuzzy control algorithm can make the effective improvement to the body vertical vibration acceleration. The ECAS constructed can response to the real driving conditions quickly, which realized the control strategy effectively.