Research On Matching Damping To Suspension Of Heavy Commercial Tractor

Automotive driving modes such as braking, cornering, or road roughness canlead to intense vehicle body vibration which will consequently cause uncomfortablefelling of passengers and damage goods. Suspension shock absorber is one of themajor parts that can attenuate such automotive vibrations.The damping characteristics of suspension system of the vehicle are highlydependent on the requirements of handling stability as well as riding comfort.However, these requirements vary within different driving modes. Therefore, it isnecessary to take into account different requirements in matching the dampingcharacteristics of suspension system within different automotive driving modes.Damping force provided by shock absorber follows the changes of the motion ofshock absorber. The shock absorber moves according to the suspension while themotion of suspension depends on automotive driving modes. Therefore, the techniquefor matching damping characteristics of suspension mainly includes three issues:(1)ideal damping force of suspension under certain automotive driving modes;(2) therelationship between automotive driving modes and the motion of suspension shockabsorber;(3) determination of the relationship between the ideal damping force andmotion characteristics of the shock absorber. Currently, domestic studies focus onideal suspension damping force under certain automotive driving modes and the effectof internal structure of shock absorber on characteristics of shock absorber. There areonly few reports about the relationship between automotive driving modes and themotion of suspension shock absorber which need to be analyzed in detail.Based on former study, this paper focuses on the damping matching technologyfor heavy commercial tractor to improve the vehicle riding comfort. The relationshipbetween the automotive driving modes and the shock absorber movement wereanalyzed to make up defect of damping matching technology in domestic research.The structure scheme of manually adjustable shock absorber for damping matchingwas presented and methods for adjusting the damping characteristics were simulated. This layout the foundation of vehicle tests for damping matching. The main work andachievements of this dissertation include the following aspects:1. The significance of studying the suspension damping matching is expounded;the development of riding comfort evaluation methods and damping matchingtechnology are summarized; and the shortcomings in the present study are pointedout.2. The TruckSim model and the seven degree-of-freedom mathematical modelfor the target vehicle are established. The reliability of the two models is validated bycomparing the simulation results of the two automotive simulation models.3. Typical driving modes are defined based on riding comfort. The effects offront axle’s damping coefficient on the riding comfort of the whole vehicle aresimulated by using the TruckSim model. Then the ideal damping coefficients of thetypical conditions and relationships between motion parameters of shock absorber andtypical driving modes are determined. Results show that ideal damping characteristicsof shock absorber strongly depends on the change of vibration frequency amplitudeand vibration displacement amplitude. The value of damping coefficient of shockabsorber should be larger when there is a smaller value of the amplitude of vibrationfrequency and larger value of the amplitude of vibration displacement, vice versa.4. The orthogonal experimental design is use to establish the appropriatesimulation test schemes:(1) the influence of both left and right side damping of thefront axle suspension and their interactions on riding comfort;(2) the influence of thefront axle suspension stiffness and damping coefficients, balanced suspensionstiffness and damping coefficients, and their interactions on the riding comfort. Baseon the results, the ideal damping of automotive driving modes is determined. Thenideal damping characteristics of shock absorber is established by considering therelationship between the damper motion and automotive driving modes, and the idealdamping force and vibration velocity amplitude in ideal driving modes.5. In this dissertation, a structure scheme for manual adjustable shock absorberfor matching damping characteristics was proposed, and the AMESim model forshock absorber is established for determining the main structure parameters thatwould influence the damping characteristic of shock absorber. This results forms a groundwork for damping matching through automotive test.