Ride Comfort Simulation And Optimization Of Full Vehicle Based On Taguchi Method

Taguchi Method has became an advanced design method in modern design as a result of its remarkable merit, it's invented by Dr. Genichi Taguchi in 1970s and used by every engineers in Japan, and each big car companies in the world, it is a important branch of design of experiment (DOE), VP(Virtual Prototype Technology) has already became the important tool using in automobile product development aboard, Through using VP technology and Taguchi Method in automobile product development, may enormous reduce development cost and cycle, understand the performance in advance, avoid developing risk.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 MPV modification design and experiment study"cooperated with a domestic car enterprise. Conducted research on the full vehicle ride comfortable (especially under multi-running case)simulation, test and optimization using vehicle dynamics and multi-body system dynamics, Give a new ride comfortable evaluate method named Robust Method, Signal to Noise Ratio (SNR) of smaller-the-best character is used to evaluate ride comfortable of full vehicle in multi-running case. Through using Taguchi Method and VP technology, test and design were integrated,The paper mainly carries on from following several aspects:1. Modeling of full vehicle ride comfort using multi-body systems dynamicsPaper used CAD software CATIA to establish some MPV full vehicle three dimensional solid model including front and rear suspension system, steering system, frame and so on. The vehicle three dimensional CAD model in CATIA was transformed to multi-body dynamics simulation model in ADAMS/Car. In the switching process the bodys which do not have relative motion will be treated as a rigid body, using corresponding hinge and restraint to connect these rigid bodys, and tire simulation model, helical spring elasticity characteristic simulation model as well as shock absorber non-linear damping characteristic simulation model will join to full vehicle model, simultaneously made stabilizer bar as flexible body and used bushing to connect the elastic connection point in full vehicle, so that the full vehicle model is more precise.2. Full vehicle ride comfort simulation and analysis and experimental studyUsing the simulation model, We analyzed suspension systems kinematics parameters such as Camber-angle, toe angle, Caster Angle, Kingpin Inclination Angle, Roll stiffness and anti-dive ratio. All these parameters is meet the design except anti-dive ratio of front suspension, then ride comfort performance simulation analysis to the MPV on full load and light load operating situation was done. The results indicated that the simulation model is accuracy, explained that using large-scale mechanical system dynamics software ADAMS on computer to establish MPV virtual prototype and carry on forecast to its ride comfort performance is feasible, three main problems were discovered at the same time: bad anti-dive performance when brake, roll stiffness distribution is unreasonable as well as the front and rear suspension stiffness distribution is not meet the Olley Criteria.3. The optimization design of the suspension system of the vehicleIn order to solve the problem of the ride comfort pertormances during the improve design of this MPV vehicle; An optimization model was proposed and feasibale direction optimization method was used as well as a new evaluate index which is calculated by the square-root acceleration at two point of vehicle was puts forward, and vertical; pitch and roll vibration were considered in the index. The optimization design of the suspension system of the MPV vehicle is completed for 54 running cases.Taguchi Method was first used in the suspension system design under the multi running case, With the reasonable parameters and its range based on vehicle theory and calculation ,the control factors and levels of Taguchi Method were confirmed, the speed, load and road irregularity were defined as noise factors. The SNR of smaller-the-best performance was used to evaluate the ride comfort, through virtual experiment a group parameters with the best robustness were discovered and the unreasonable stiffness distribution was solve perfectly. A new ride comfortable evaluate method named Robust Method was given at the same time.4. Anti-dive performance analysis and simulationIn order to solve the problem of bad anti-dive performance when brake of the MPV, suspension geometry parameters which affected the full vehicle longitudinal stability was inspected, found the reasons of the bad anti-dive performance. A fomula about the relationship between inclination angles of front suspension arms axis and anti-dive angle was given, the formula indicated that the affect to the anti-dive angle of sub-arm's inclination angle is more markedness than the up-arm's. Different inclination angle arrangement schemes of front suspension arms axis experimental plan was proposed, simulation result indicated that the formula is correct and superior angles was confirmed .5. Experimental studyApplied the parameters after optimized to the full vehicle ride comfort virtual prototype model, carried on the contrast analysis to the origin model and the modified model. The automobile body vertical acceleration, have improved distinctly and the suspension dynamic deflection and the wheel relative moving load were in allowance range after optimization, confirmed accuracy of the Taguchi Method used in ride comfort parameter design and optimization. Finally, conduct the experimental study to the full vehicle ride comfort and handling performances after optimization, the ride comfort performance has improved distinctly seeing from the test results. The parameters of the optimized suspension system have no big effect on the vehicle handling performance for the steady-state steer in characteristics.