Invariant points of semi-active suspensions

Abstract

The invariant points of the quarter vehicle model shape many properties concerned in vehicle suspension design. Although they have been studied for years, the invariant points are still confusing for their different traits. Hence, the existing invariant points are sorted and analysed. Meanwhile, the invariant points of the semi-active suspension were introduced. In this article, a further study on the invariant points of the semi-active suspension is conducted, which provides insight for suspension optimization. In detail, an equivalent linear approximation model, derived from the transformation of the semi-active suspension model, is utilized to analyse the invariant points of the semi-active suspension. With the equivalent linear approximation model, the invariant points of the sky-hook semi-active suspension are proved to be highly dependent on the adjustable damping range. In fact, the frequencies and magnitudes of the invariant points, as the limit of the semi-active suspension, are determined by the adjustable damping range. Consequently, the influence rule of the adjustable damping range on semi-active suspension performance is revealed, which provides insight for the optimization of the damping for different demands. Experimental study shows that the invariant points are real, not just exist in the theoretical analysis.

PID Controller of a Car with Quarter Body Active Suspension System

“…All powers of vehicles have amount and direction depends on the size of bump that hits the wheel, where the wheels are exposed to a vertical height when passing the road curves [7]. In fact, the vehicle suspension system is part of the structure and combines all important systems at the bottom of the vehicle which includes the Frame, suspension system, guidance system [8]- [9].…”

Dynamic response of multi-degree-of-freedom systems with a Coulomb friction contact under harmonic excitation

“…In these points, the response amplitude is independent of the damping, which is represented in this case by the friction ratio. The presence of invariant points in the transmissibility curves is regarded as an important aspect in the design of mechanical systems such as dynamic vibration absorbers [48][49][50] and car suspensions [51,52]. In particular, according to the Den Hartog's theory illustrated in reference [53], these points can be used to determine the optimal configuration of a viscous damper acting as vibration absorber for a main undamped SDOF system.…”

Dynamic response of multi-degree-of-freedom systems with a Coulomb friction contact under harmonic excitation

“…In these points, the response amplitude is independent of the damping, which is represented in this case by the friction ratio. The presence of invariant points in the transmissibility curves is regarded as an important aspect in the design of mechanical systems such as dynamic vibration absorbers [51][52][53] and car suspensions [54,55]. In particular, according to the Den Hartog's theory illustrated in reference [56], these points can be used to determine the optimal configuration of a viscous damper acting as vibration absorber for a main undamped SDOF system.…”