Suspension Design And Full Vehicle Experimental Optimization Based On VPD Technique

VPD (Virtual Product Development) technology has already became the important tool using in automobile product development aboard, it passed through each product development step, especially preliminary pre-development. Through using VPD technology in automobile product development, may enormous reduce development cost and cycle, understand the product performance in advance, avoid developing risk. The experimental optimization techniques has became an advanced design method in modern design method as a result of its remarkable merit, it's used by US, Japan, Europe and so on each big car companies.All the work of this thesis is supported by science and technology development plan key project of JiLin Province"the research of vehicle chassis integration development platform and the key technologies", as well as the project"the SUV handling stability and ride comfort simulation and experiment study"cooperated with a domestic car enterprise. Conducted quite comprehensive and thorough research on suspension system design method as well as full vehicle performance optimization using VPD technology and experiment optimization techniques.1. Suspension kinematics and elastokinematics simulation, test, evaluation Analyzed the typical suspension systems kinematics and elastokinematics mechanism. Established a comprehensive suspension virtual prototype database using VPD technology. Elaborated simulation and test method on suspension kinematics and the elastokinematics systematically. Proposed a comprehensive suspension kinematics and elastokinematics evaluation target. Constructed suspension integration development platform initially by merging the simulation, experiment, evaluation, optimization into one organic.First, carried on kinematics and elastokinematics analysis to each kind of structural style suspension which are widespread applicated in domestic and foreign at present stage, established a virtual prototype database including dozens kind of suspension forms. Using the database may construct specific parameter suspension virtual prototype conveniently. Provided a contrast analyze platform for different structural style suspension, as well as identical structural style and different parameter suspension.Next, proposed suspension kinematics and elastokinematics simulation method comprehensively. These methods Including: parallel wheel travel simulation, reverse wheel travel simulation, single wheel travel simulation, roll simulation and load simulation. Then, elaborated suspension kinematics and elastokinematics bench test method. Introduced structure, principle of work and survey ability of typical suspension K&C test platform in detail.Finally, put forward all-around suspension kinematics and elastokinematics evaluation target according to simulation and test methods. Pointed out more than twenty suspension parameters to evaluate kinematics and elastokinematics characteristic, these parameters reflected wheel alignment, compliance steering, body pitches and roll, wheel returnability, steering efforts and tire attrition separately. Elaborated the influence of these parameters on full vehicle performance and its reasonable change tendency and scope.2. Simulation and experiment study on suspension and full vehicleTook a home made SUV as study object based on the suspension virtual prototype database. Constructed suspensions and full vehicle virtual prototype, developed a set of virtual test platform for suspension nature frequency and ride comfort virtual test facility for full vehicle, carried on virtual prototype analysis, experimental study and performance evaluation of suspensions and full vehicle using the method of virtual simulation and physical vehicle test. Confirmed the virtual prototype and the virtual test platforms, discovered two main problems existed in the vehicle: bad anti-dive performance when brake as well as the tends to over steering when lateral acceleration greatly.First, established front and rear suspension virtual prototype of this vehicle based on the database, carried on simulation and K&C experiment study to them using simulation and bench test methods. Established full vehicle virtual prototype which including steering system, power transmission, tire and body etc on the basic of front and rear suspension virtual prototype.Second, carried on many handling stability simulation and experiment study to virtual prototype and physical vehicle separately, and done processing and evaluation to the test result. On one hand confirmed the simulation model which will be used in the following optimize design, on the other hand discovered faults of full vehicle. The test results showed that the simulation and experiment fit well. The results of pylon course slalom test, steering wheel angle step input test, steering wheel angle pulse input test and returnability test quite to be ideal, meet or surpass the design requirements. But in steady static circular test, both simulation and experiment are demonstrated bad, the vehicle tends to be over steering when lateral acceleration is big, this problem must be solved.Third, established a set of virtual test platform for suspension nature frequency test, and a random road surface input virtual test facility for ride comfort. Carried on corresponding virtual experiment to full vehicle virtual prototype using the virtual test platform and the virtual test facility. Carried on suspension nature frequency test, B level random road surface test and typical road surface test to physical vehicle. Done processing and evaluation to the result of simulation and test, the results met well and the vehicle ride comfort is good. The virtual test platform and the virtual test facility were confirmed, which are effective method for ride comfort simulation.3. Suspension influence on vehicle longitudinal stability and optimization.Applied research on the question of bad anti-dive performance when brake of the SUV. Inspected suspension parameters which affected the full vehicle longitudinal stability, found the reasons of the bad anti-dive performance, and carried on the experimental optimization design in the virtual prototype, discovered the superior plan, confirmed the optimization plan feasibility through the virtual experiment finally.First, analyzed front and rear suspension pitch center and its computational method, established vehicle longitudinal stability model when brake. Researched suspensions and full vehicle parameter which affect anti-dive angle, infered the ideal anti-dive angle and its reasonably choose principle and method. Found the reasons and pointed out many arrangement schemes to enhance anti-dive performance.Then, utilized virtual prototype technology to carry on the experimental design on different inclination angle arrangement schemes of front suspension arms axis, proposed four kinds experimental plans, designed four kinds of arrangements to each plan, discovered the superior plan through contrasting test results.Finally, carried on handling stability test in full vehicle virtual prototype to one superior plan, the test result demonstrated that: the influence was very small to the full vehicle handling stability after the adjustment to arms axis of front suspension, the modification is confirmed feasibility.4. Suspension influence on vehicle steady circular response and optimization.Conducted research on over steering question which appears in steady circular test of the SUV. Analyzed vehicle construction parameter which influence steady circular response. Found methods to improve steady-state characteristic, and introduced experimental optimization method into full vehicle virtual prototype. Solved theproblem successfully after using the optimized result on physical vehicle finally.First, in view of the fact that front and rear suspension roll rate match is unreasonable which were discovered in suspension simulation and experimental study. Discovered the factors which influence steady circular response embarking from steady circular response inherent laws. Analyzed suspension influence on steady circular response with emphasis. Analyzed vehicle parameter which influence steady circular response through establishing four wheelers mathematical model. Discovered that the reasonable match of stabilizer bars rate may change full vehicle characteristic to a great extent, found the front and rear stabilizers rate unreasonable match is the primary reason. Statement: Increases the front suspension stabilizer bar rate or reduces the rear suspension stabilizer bar rate, or both also carry on around, then adjusts the roll rate match of front and rear suspension.Then, carried on the experimental design to the virtual prototype by introducing experiment optimization design method. Took the steady circular test synthetic evaluation value N W (N anNUNφ) 3= ++as the experimental target, took the front and rear stabilizer bars diameter as the experimental factors, constructed a two factors four levels experimental plan, selected L1 6(42) orthogonal array to establish experiment plan, carried on the experimental optimization in the virtual prototype.Finally, determined front stabilizer bar diameter 28mm and rear stabilizer bar diameter 17mm as the superior plan. And carry on the steady circular response test to the modified vehicle, the test result demonstrated a good under steering characteristic, the existence problem are solved successfully. 5. Intension check and structure optimization on suspension partsDiscussed the application of VPD technology in the suspension system part design embarking from the aspect of structure. Carried on the structure optimize design to the control arm of rear suspension system. Established structure finite element model of the front sub-frame and carried on intensity analysis, discovered weak regions in the part and analyzed reasons, proposed the improvement methods. Mainly includes following two aspects:On structure optimization aspect, analyzed the characteristic of four structure optimization techniques (Topology optimization, Shape optimization, Size optimization, Topography optimization). Carried on structure optimization design to suspension control arm, carried on contrast analysis of intensity and rigidity to optimized under control arm in four operating situations. Results indicated: The controls arm after optimization compare to the original design not only in the weight has 31.3% depression, moreover, the rigidity and intensity all have great scope enhancement.On intensity examination aspect, carried on four kinds of virtual simulations to suspension and full vehicle virtual prototype under brake, road surface impact, left-turn and right-turn. Tested strength and moment of force received by front sub-frame which come from the control arm. Then carried on intensity analysis to front sub-frame under the corresponding situations. Discovered weak region in the components, analyzed reasons and proposed structure optimization design method.