Active Variable Geometry Suspension robust control for improved vehicle ride comfort and road holding

Abstract

Abstract-This paper investigates the design of robust H∞ control for road vehicle Series Active Variable Geometry Suspension (SAVGS). The objective is to improve ride comfort and road holding, while guaranteeing operation inside existing physical constraints. The study utilizes a nonlinear quarter car model that represents accurately the vertical dynamics and geometry of one quarter of a high performance car with a double wishbone suspension. The control objective is to reduce the body vertical acceleration, tire deflection and suspension travel under the impact of road perturbations. Therefore, the selection of the weighting functions for a linear H∞ control, designed for the linearized quarter car, is based on these objectives. The proposed controller is then applied to the nonlinear quarter car model and investigated by nonlinear simulation for a range of road disturbance inputs. The results show that the designed controller when applied on the SAVGS is effective in improving the vehicle ride comfort and road holding.

Quarter-Car Experimental Study for Series Active Variable Geometry Suspension

“…In previous studies of active suspensions, linear models with two pure vertical motions are widely applied, in which the geometric nonlinearity is not considered. In [12], a nonlinear model is first built and then linearized at a trim state of θ SL = 90°to synthesize an H-infinity control for the SAVGS quarter car. However, the linear model obtained in this way is not accurate when a large single-link offset is required.…”

“…The performance of active suspensions can be further improved and realize its full potential by integration of advanced sensors and intelligent controls, such as road preview control [4]. More recently, a series active variable geometry suspension (SAVGS) has been proposed and theoretically proven as a valid alternative to existing solutions [5]- [12]. Fig.…”

Kinematic Analysis of SAVGS

“…The vibration, which reduced the vehicle frame life and affected biological passengers [2], is aimed to be eliminated as much as possible. Regarding these, especially for passenger comfort, the active suspensions are widely assessed that they provided the best capabilities among the aforementioned types [3].…”

“…The active suspensions encouraged to equip in the luxury vehicle are continuously studied on their performance improvement, the essential approach is started from the quarter-car model [1], [3]- [11], typically utilizing linear and non-linear models. However, in the real application, the suspension lower end-strut is seldom connected to the center mass of unsprung mass, which leads the suspension system to be non-linear.…”

“…In [12], it has been reported that the variation of the double-wishbone lower arm significantly influenced the suspension performance. In addition, a few controllers have been proposed with the promising result; LQR [4]- [6], [9], [13]- [15]; LQG [7], [8]; and robust control H-infinity [1], [3], [10]- [12] Nonetheless, active suspension in vehicle production still fails, especially for the high bandwidth, due to the several drawbacks, such as energy demand, lower compactness, and complexity [11]. Moreover, the passive suspension has limited capability due to the limited suspension stroke [8], less adjustability of force, and damping coefficient.…”