DYNAMIC TIRE FORCE CONTROL BY SEMIACTIVE SUSPENSIONS

This paper presents a semiactive suspension control algorithm to reduc e dynamic tire forces and it includes the development and application of observers for bilinear systems with unknown disturbances. The peak dynamic tire forces, which are greatly in excess of static tire forces , are highly dependent on the dynamic characteristics of vehicle suspe nsions. One way to reduce dynamic tire forces is to use advanced suspe nsion systems such as semiactive suspensions. Semiactive control laws to reduce dynamic tire forces are investigated and a bilinear observer structure for bilinear systems with unknown disturbances is formulate d such that the estimation error is indePendent of the unknown externa l disturbances and the error dynamics are stable for bounded inputs. T he motivation for the development of a disturbance decoupled bilinear observer comes from the state estimation problem in semiactive suspens ions. An experimental study on the performance of a semiactive suspens ion to reduce the dynamic tire forces is made via a laboratory vehicle test rig. The semiactive suspension has been implemented by using a m odulable damper, accelerometers and a personal computer. Experimental studies show that the performance of the semiactive suspension is clos e to that of the best passive suspension for all frequency ranges in t he sense of minimizing the dynamic tire forces and that the dynamic ti re force can be replaced by the estimated one. The dynamic tire forces for both passive and semiactive control test cases are compared to sh ow the potential of a semiactive suspension to reduce the dynamic tire forces.