Georg Roll

Sidewise Adaptive Single-Track Vehicle Model for ESC

Electronic Stability Control (ESC) typically compares the reference yaw rate (desired yaw rate) and the measured yaw rate (actual yaw rate) and then makes the required interventions. The reference yaw rate will normally be calculated with a symmetric vehicle reference model. But many vehicles have different dynamics for left and right curve driving. In this case the symmetric vehicle reference model will acquire large problems to gain the correct reference yaw rate. Recently, Continental has developed a new procedure to identify the asymmetry of the vehicle dynamics and to apply the sidewise adaptive parameters for calculation of the reference yaw rate. The vehicle dynamics and the handling performances are normally described with a mathematical vehicle model and dependent on many vehicle parameters. To simplify the computation complexity, Continental has selected the quasi linear single-track model as the vehicle reference model. For this single-track vehicle model only some important vehicle parameters are used, which have direct influence on the vehicle behaviour such as oversteering or understeering. Vehicles in their initial state from series production normally have symmetric dynamics. Some of these parameters can be measured directly and the others can be identified with appropriate driving manoeuvres and methods. For the real usage of vehicles the parameters may be very different from the initial ones and the vehicles may have strong asymmetric dynamics. In such cases, the single-track model with constant parameters may cause too many wrong or too late required interventions. To improve the ESC performances for such reasons Continental has developed a new sidewise adaptive single-track vehicle model. The most important parameter for the single-track model is the tire-side stiffness of the rear axle. During driving the vehicle dynamics will be monitored permanently. Under certain conditions the tire-side stiffness will be continually calculated online for two different driving directions. These newly identified parameters will then be verified, limited and transmitted to the former ones. In this way the parameters will be permanently updated online so that the ESC has always the correct parameters for the actual driving situation. Practice has already shown that using this sidewise adaptive single-track model the reference yaw rate can be calculated more precisely. The ESC performance is improved significantly especially for vehicles with asymmetric characteristics. The number of faulty and unnecessary ESC interventions is largely reduced. This procedure can be applied to all passenger cars and light trucks with an ESC system.