Experiment of vehicle passive skyhook damping suspension system

Abstract: In recent years, the inerter was used to different mechanical vibration networks to improve the vibration isolation performance. In order to improve the vehicle suspension system's performance of vibration isolation and develop passive suspension system, the suspension system with inerter was studied. A passive realization method was presented for ideal skyhook damping to solve the technical problem in connecting the damper with the inertial reference system. This method took use of the anti-resonance phenomenon in the inerter-spring-mass system. The passive realization method of ideal skyhook damping was applied to the vehicle suspension system. Based on the inerter-spring-damper mechanical system, a passive skyhook damping suspension system with inerter was proposed, which could achive the main function of the ideal skyhook damping suspension.There was two -stage structure in the passive skyhook damping suspension system. The first stage had a coil spring and a damper in parallel, the same as the conventional passive suspension. The second stage had a coil spring, a damper and an inerter in parallel which could realize the ideal skyhook damping performance. The experimental prototype of passive skyhook damping suspension was designed and installed to the back of the test vehicle instead of the conventional passive suspension. The two-stage series passive skyhook damping suspension needed more vertical space when installed to the vehicle than the conventional passive suspension. So it was not suitable for the car. In order to solve the problem, the two-stage series suspension was folded in half to reduce the total height. Then the improved suspension was installed to the test vehicle with a rocker arm. The rocker arm was an equal armed lever which could change the direction of force but not change the magnitude. The test system was designed based on the MTS 320 type simulator with four-channel road coupled by tire. A gyroscope was used to acquire the body vertical, pitch and roll acceleration signal. Two PCB acceleration sensors were used to acquire the left rear body vertical acceleration and the left rear wheel vertical acceleration signals. Frequency response characteristics test of rear suspension, bump pulse response test, random excitation response test were carried out. And the test results were compared to the conventional passive suspension in order to verify the characteristics of the passive skyhook damping suspension. The test results of frequency response characteristics of rear suspension showed that the resonant peak value of the left rear body vertical acceleration was reduced by 35.7% within the frequency of 1-3 Hz. At the same time, the left rear wheel vertical acceleration had no significant deterioration. The test results of bump pulse response showed that the peak-to-peak values of body vertical acceleration, body pitch acceleration and left rear wheel vertical acceleration were reduced by 7.52%, 11.82% and 31.48% respectively. The test results of random excitation response showed that the power spectral densities of body vertical, body pitch, body roll, left rear body vertical and left rear wheel vertical acceleration were reduced obviously within the frequency of 1-3 Hz. In different roads the root mean square (RMS) of body vertical acceleration was reduced by about 12% with different speeds. The RMS of body pitch, body roll, and left rear wheel vertical acceleration were all reduced by no more than 10%. It was shown from the test results that the low frequency response characteristics of vehicle could be improved by the proposed passive skyhook damping suspension. Meanwhile, the vertical, pitch and roll vibration of vehicle body within the frequency of 1-3 Hz could be inhibited obviously. So, the vehicle performance of ride comfort could be improved markedly. Compared with the conventional passive suspension, the passive skyhook damping suspension had better performance. The test results also indicated that the passive realization method of ideal skyhook damping was correct and feasible. The conclusion provides an important reference for the investigation of new passive suspension system with inerter.