Preview Control of Slow-active Suspension Systems

Preview control is investigated for active suspension systems. Two preview concepts are used: (1) look-ahead preview, where the information relating to roadway disturbances about to be encountered by the moving vehicle is assumed to be sensed, and (2) wheelbase preview, where knowledge of the front wheel states is used to improve performance at the rear of the vehicle. A method based on optimal control theory is presented to find the control laws for a half-car equipped with both fully active and slow-active systems under preview. The random road profile is assumed to be the output of a filtered white-noise process. Human perception of vibration is considered in the design of the active suspension systems. The design of the preview controller is reduced to the classical linear quadratic regulator of the original system and the previewed road inputs. Integral constraints are included in the performance index to achieve better body attitude control. The effect of preview control on vehicle performance characteristics in terms of ride comfort, suspension deflections and road-holding ability is investigated. The results show that the use of wheelbase preview along with look-ahead preview improves all aspects of the suspension performance.