SUMMARY Based mainly on English language literature, information relating to the design of automobile suspension systems for ride comfort and control of wheel load variations for frequencies below body structure resonances is reviewed. The information is interpreted in the context of vehicles which travel through a wide speed range on roads of markedly differing quality, which do so carrying different loads and which are required to possess good handling qualities. Sections are devoted to describing road surfaces, modelling vehicles and setting up performance criteria, and to passive, active, semi-active and slow-active system types. Methods for deriving active system control laws are outlined. Strengths and weaknesses of the various systems are identified and their relative performance capabilities and equipment requirements are discussed. Attention is given to adaptation of the suspension or control system parameters to changing conditions. Remaining research needs are considered.

Road Vehicle Suspension System Design - a review

Stochastic optimal preview control of a vehicle suspension

SUMMARY An adaptive control scheme for a two-degree-of-freedom vehicle model with active suspension is proposed. The performance goal is to minimize the variance of vehicle body acceleration under inequality constraints imposed on the variance of either tire or suspension deflection. An active suspension is adapted to the changes in vehicle velocity and the type of road (or terrain) surface which is assumed to be reconstructable from the accelerometer measurements. The control gain factors are obtained by the iterative method taking advantage of stochastic linear control theory. The performance of the system is evaluated and compared to that of an active system with constant gain factors and a passive system with adjustable parameters.

Adaptive Control of Vehicle Suspension

Active suspensions in vehicles can apply a vertical force between the wheel and the vehicle body in order to reduce vehicle body motion over road obstacles, enhancing ride comfort. In this study, new methods are developed to generate a preview road height profile using vehicle sensors and to control the active suspension using this information. To control the actuators, two concepts are developed: a feedforward disturbance compensation, calculated from the preview signal, combined with a feedback loop without preview and a preview model predictive control approach. After defining a desired road height profile as input for the designed control algorithms, a sensor-fixed and an inertial coordinate system to compile the road height profile from sensor measurements are proposed. Methods to transform the sensor data from one time step to another, to accumulate redundant measurements, and a filtering technique to shape the road signal are developed. To test the algorithms, a simulation from the road signal generation to the suspension control is designed, and additionally, an observer is derived to determine the road height profile from vehicle motion in order to verify the preview signal. Simulation results and measurements of vehicle implementation are presented.

Road Profile Estimation and Preview Control For Low-Bandwidth Active Suspension Systems

This study concerns with multi-objective H ∞/GH 2 preview control of active vehicle suspensions. This control scheme has two main aspects: first, it allows constrained outputs of the system to vary freely as long as they remain within their given bounds, in order that the best possible performance could be delivered. Secondly, the optimisation as well as constraint fulfilment is done for the worst-case road disturbances to cover all road types. To design a system to perform satisfactorily for a wide range of road irregularities, H ∞-norm is used wherever minimisation is required, and generalised H 2-norm is used to care for the constraints on suspension working space. Moreover, to ensure desired stability margins for the system, pole location constraints are considered in the design. The proposed approach is evaluated on a quarter-car model and compared with the state-of-the-art preview control algorithm in the literature, namely, Linear quadratic Gaussian preview. Simulation results demonstrate the effec...

Output feedback H ∞/GH 2 preview control of active vehicle suspensions: a comparison study of LQG preview

SUMMARY In vehicles with traditional passive suspension, the spring and damping elements between car body and axles have a fixed characteristic. This means that when the suspension is adjusted, a compromise between comfort and safety has to be arrived at. With active suspension, on the other hand, both these criteria can be enhanced at the same time. Moreover, further improvements in driving behaviour can be made which are not possible with passive suspension. In this case, the time delay between front and rear axle excitation is represented by a fade approximation, which means that linear controller design methods in the state space (Riccati controller, Kalman filter) can be used to implement active vehicle suspension. A spatial model of a medium-range passenger vehicle is augmented by a disturbance model (stochastic dual track excitation of the road surface with excitation delay time, if need be with irregularity sensors), a perception filter (weighting of human sensitivity to vibration) and a filter fo...

R. Kasper

Papers

Design of an active suspension for a passenger vehicle model using input processes with time delays