Study On Semi-Active Torsion Vibration Isolator Based On Combined Positive And Negative Stiffness

With the development of the automobile industry, especially some technology applications such as engine lightweight,turbo boost,common rail direct injection, automobile power performance and fuel economy is improved significantly, but the vibration and noise of vehicle driveline worsened in certain degree. Conventional torsion vibration isolator in the driven plate of clutch gradually cannot meet the needs of the transmission system on vibration and noise reduction. Torsion vibration isolator dual mass flywheel has good damping effect, but there are elastic elements easy to wear, yet localization issues. In order to reduce torsion vibration of automobile transmission, the concept of semi-active torsion vibration isolator combined positive and negative stiffness is put forward in the paper that is funded by the National Natural Science Foundation. Many issues were studied, including structure design, dynamic characteristics, isolation mechanism, control system, parameter optimization, prototype development and tests. The main research contents and achievements are as follows:(1) By analyzing the damping element of automotive driveline torsion vibration isolator, the concept of semi-active torsion vibration isolator combined positive and negative stiffness was proposed and its operation principle was discussed. The design of main structure of the isolator was completed, including elastic element, damping elements, and control systems. The stiffness expression of the elastic element was established and its elastic characteristics were analyzed. The dynamics simulation about isolator was carried out with ADAMS software and the result shows that semi-active torsion vibration isolator combined positive and negative stiffness has extremely low natural frequency, can effectively inhibit the driveline torsional vibration at idling condition.(2) The isolation mechanism of semi-active torsion damper combined positive and negative stiffness was revealed by analyzing the damper stiffness characteristics. The mathematical model of damper was established and its natural frequency was analyzed. Aiming at the strong nonlinearity of the established model of the damper, the damping performances, such as the dynamic response of steady condition, were analyzed by using stiffness approach method and the incremental harmonic balance method. By plotting the amplitude-frequency characteristic curve, dynamic bifurcation diagram, the stability analysis of damper was carried out.(3) Based on hybrid system theory, an automatic switching control system model of the semi-active torsion damper combined positive and negative stiffness was established. By using on-off control strategic and sliding mode variable structure control strategic respectively, the damping performances of dynamic condition of the damper was simulated. The results show that compared with the on-off control strategic, the sliding mode variable structure control strategic can greatly reduce the vibration impact caused by the stiffness mutation of the damper system by using on-off control strategic.(4) Based on the torsion stiffness matching principle, a design method of the semi-active torsion damper combined positive and negative stiffness was proposed. Then the optimization design of the parameters of the elastic element, damping element and control system of the semi-active torsion damper was developed and the prototype of the semi-active torsion damper combined positive and negative stiffness was designed.(5) Ameasuring system for the prototype of the semi-active torsion damper combined positive and negative stiffness was designed and built. The tests of the prototype of the damper at idling、no- load, load, and control conditions were implemented separately. The test results show the damper can effectively reduce torsional vibration of the vehicle transmission at all conditions, but also verifies the correctness of study onr theory modeling and related theory analysis for the semi-active torsion damper combined positive and negative stiffness.