Optimization Matching Design And Test Research For Bus Air Suspension System

With the rapid development of economic and technological level, the vehicleperformance requirements are increasing. This phenomenon promoted the popularization andapplication of new technology and equipment in auto industry objectively, and electronicallycontrolled air suspension system is one of them. Compared to other forms of suspensionsystems, air suspension has a lower natural frequency. With the reasonable match betweencomponents of automotive systems, air suspension system enables vehicle to get a better ridecomfort and handling stability. Although the air suspension with the disadvantage ofcomplex structure, difficult to manufacturing and high cost, it is widely used in auto industrybecause of the excellent performance that can not be replaced, and the forward design ideasfor key technologies of electronical controlled air suspension is expounded in this paper. Themain contents include the following six parts:In the first part, a lot of the research literature on the air springs has been cited, and theresearch domestic and international air suspension was introduced. Combined with theexperience of suspension development and design, the in-depth detailed analysis of theperformance characteristics of air suspension has been described in this article, which canprovided a reference for air suspension design.The second part explains the key technique of the electric control air suspension matchaccording to the positive design thinking. First of all, the performance indexes of the vehicleride comfort and operation stability are defined in the suspension system design and thesuspension system design scheme is determined. Air springs are classified in the matchingdesign. The static and dynamic performances of the air springs are discussed. The dynamicstiffness formula of the air spring is deduced according to the air state equation theory andthe performance is analyzed. The formula of the spring stiffness from the test curve is deduced. The calculation formula of the air spring suspension stiffness is deduced inmechanical angles. The matching principle of the air spring and stopper is proposed. Theeffect of the guide arm to wheel positioning parameters is analyzed through suspension K&Cperformance modeling in the guide arm matching design. The clearance check of the guidearm and FEM analyses are done. In the matching design of the rubber mount, the distributionprinciple of the longitude stiffness, lateral stiffness and torsional stiffness are described. Inthe absorbed matching design, the damping matching and route design of the absorber aredescribed and performance curve is given. In the stabilized bar matching design thecalculation method of the body roll angle, guide arm roll angle stiffness and stabilized barangle stiffness are described. In the matching design of the ECAS system, the systemcomponent, operation principle, relative merits and attitude sensor matching design principleare described and checked. In the air pipe matching design, the matching principle of theconnecting of the pressure sensor, pipe diameter and length and tank capacity are describedand system pressure consumption test is introduced. The design flow and method of theECAS are integrity introduced through the above work.The third part firstly introduces multi-body dynamics modeling theory and methods,and then through defined the virtual prototype of the kinematics model parameters, qualityparameters, mechanical properties in the SIMPACK software, I established the vehiclemulti-body dynamics model which based on the relevant data of the vehicle. It mainlyinclude double wishbone suspension model steel air spring, spring plate side-acting rearsuspension model, rack and pinion steering system model, road surface model based on themagic formula and tire model with the experimental data and the superposition methodbased on harmonic, and simulated the K&C characteristics of the front suspension with thissimulation model, which carried out a detailed analysis of the same-direction jumping of thewheel and the working condition of rolling simulation results. In the vehicle steeringstability analysis, simulated the steering angle step input, steering angle pulse input andsteady-state rotation. At last compared the simulation results with the real-vehicle test results,the result shows that:all the simulation agree well with experimental results, proved the vehicle virtual prototype of the kinematics simulation model in this paper has a goodsimulation accuracy, and can accurately simulate the various simulation conditions of avehicle, and it also can meet the requirements of the follow-up optimization and controllinganalysis.In the fourth part, at first I introduce the basic theory of multiple target optimize and thearithmetic of multiple target inherit optimize, then expound how evaluation index ofsuspension system, such as automobile body vertical acceleration, wheel dynamic load andsuspension dynamic deflection ,effect automobile performance in detail. Analysis the effectof spring stiffness and absorber damp to suspension characters thoroughly. Expound thechange essence of load, speed and road condition and the inner relationship between springstiffness and absorber damp and the evaluation index of suspension system. To solve thecontradiction between the evaluation index of suspension system and the selection criteria ofabsorber damp, I put forward a combine project, which use optimization and control method,set three-level air spring stiffness and absorber damp. Then I build the optimize model baseon NSGA-II inherit arithmetic, which let automobile body acceleration as the target function,let air spring stiffness and absorber damp as the optimize variable, let dynamic deflection ofsuspension system , dynamic load of wheel and damping ratio of suspension system as theconstraint condition. At last, I design a optimize project base on the matching between the"soft/medium/hard"character of absorber damp and the"low/medium/high"gears of airspring stiffness, which establish the foundation to optimize the control of suspension system.The fifth part introduces the control theory of PID Neural network at first, thenaccording to the characteristic of air spring and controllable three gear damper, connectingM×Q×3 BP Network with traditional PID controller, designing an incremental PID Neuralnetwork controller, according to test the input and output of the controlled system, afterlearning and training, finally the proper incremental of stiffness and damping are determined,when the increments accumulate to a certain extend, the inflatable and deflatable devices ofair spring and the shift device of controllable damper will shift ,which can satisfy demandsof suspension stiffness and damping characteristic to different driving conditions. At last, on the vehicle dynamics model which the paper has already set, conducting simulation about thethree typical conditions including Straight-line driving, Turn and Break. The simulationproves that: the controllable suspension system based on PID neutral network can efficientlydecrease the acceleration amplitude of Body vertical \roll and pitch and then improve theride comfort of car; at the same time it also can efficiently decrease the amplitude of Bodylateral acceleration \roll angle \yaw rate, and then improve the handling and stability of car.The last part is to verify the match design effect of air suspension system and find itsshortcomings. Based on high-level bus and vehicles in same level with leaf spring, the matchdesign work proceed mainly on the vehicle ride comfort and handling stability to make thefull comparison test and analysis, of which the vehicle ride comfort tests contain pulse inputtest,random input test, suspension partial frequency, damping ratio test and dynamic stroketest. It can be seen from the test result that the effect of vibration cushioning and damping forair suspension is obviously better than leaf spring suspension, meanwhile the design ofdynamic stroke is reasonable; The vehicle handling stability tests contain steady staticcircular test, angle step input test, angle pulse input test, steering portability test, steeringreturnability test and snake-shaped test. It can easily be found from the test result that thehandling stability for air suspension is better than the leaf spring suspension. From all above,we can say the match design is correct and efficient.