Research On The Method Of Simulation And Test Measurement For Wheel Turn Center

Steering system design and steering performance analysis and evaluation is one of keyfactors for vehicle handling design. As the speed of vehicles increases, the bad dynamicphenomenon appears gradually, such as stability getting worse. Therefore, people put forwardhigher requirements for steering performance. Modern vehicles’ steering design is mainlybased on Ackerman Principle, by optimizing the steering trapezoidal mechanism, an idealallocation of steering angles can be achieved. Researches show that wheels are not movingaround a single instantaneous center when the car is on turn. The common multi-axles vehicleshave no systemic steering design theory, so they are designed with the equivalent axle basedon Ackerman Principle, which results in the wheels cannot move harmoniously, then lead totire wire badly, bad steering stability and so on. In order to seek for a Scientific and reasonablesolution, steering performance evaluation methods are investigated, which shows that thecommon steering performance evaluation methods simplify vehicle as a rigid body, theresponses of the whole car are regarded as evaluation indexes. Because the movements ofwheels are not considered, the phenomenon of wheels’ moving harmoniously cannot bedescribed, and the steering coordination cannot be evaluated and optimized.According to this problem, our team came up with the Wheel Turn Center(WTC) theorypreliminary in the past research, try to analyzing steering coordination and suspensionmatching and verified on the sedan cars and three axles vehicles. The verification show thatWTC theory is not only effective on multi-axles vehicles, but also useful on sedan cars.Base on the WTC theory, according to the limitation of WTC calculating method whenthe car is in the instantaneous turning state, the thesis mainly researched the wheelinstantaneous turn center calculating method. Meanwhile, in order to measure WTC accuratelywhen a real car is running, the thesis researched WTC test measurement method. Considered the recent test conditions, the real car test verification was made on a sedan car. The researchcontent of this thesis is organized as follows:First, the dynamics model of an A-class vehicle has been established. By using ADAMSsoftware, an A-class vehicle has been established. Then the model was proved consistencywith the real car in the comparison between the results of simulation and test on handling, andthe model had a good consistency with real car. So the model provided a simulation basis forthe future research.Second, the calculation method of the WTC in instantaneous steering process has beenresearched. Particle curvature method and rigid space instantaneous axle method wereresearched to calculate wheel turn centers. By theory analysis and simulation comparison,particle curvature method was proved to be effective in steady state, while rigid spaceinstantaneous axle method can calculate wheel turn centers accurately both in steady andinstantaneous state.Third, the test measurement method for wheel turn centers was researched and proved onreal car test. Investigating the measure ability of the test equipment, the velocity, angularvelocity and acceleration of wheels which are used in WTC calculation cannot be gained fromequipment directly. So the evaluation method for wheels’ movement state was came up withbased on multibody dynamics theory. By using the parameters which can be measured in test,the movement state of wheels is evaluated. The method is the basic for the test design. Thepositions of WTC were calculated by using particle curvature method and rigid spaceinstantaneous axle method respectively. The results show that the WTC calculated by twomethods were consistent in steady state. Rigid space instantaneous axle method is effectiveboth in steady and instantaneous state and it is the ideal method to calculate wheel turn centers,while the evaluation of wheels’ angular velocity is complex. Although the particle curvaturemethod is not effective in instantaneous state, because of its simple measurement, it is a goodmethod for WTC calculation in steady state. The thesis realized the simulation calculation andtest measurement for WTC and established the basis for the future researches on real cars.