Browse Publications Technical Papers 2018-01-1895

Identification and Resolution of Vehicle Pull and Steering Wobble Using Virtual Simulation and Testing 2018-01-1895

A vehicle drifts due to several reasons from its intended straight path even in the case of no steering input. Vehicle pull is a condition where the driver must apply a constant correction torque to the steering wheel to maintain a straight-line course of the vehicle. This paper presents an investigation study into the characteristics of a vehicle experiencing steering drift. The aim of the work is to study vehicle stability and the causes of vehicle drift/pull during straight line to minimize vehicle pull level and hence optimize safety measures. A wobble in the steering wheel feels like the wheel is shaking to the left and right. This may get worse if increase in speed. This paper focuses on modeling and evaluating effects of suspension parameters, differential friction, brake torque variation, Unbalanced mass in the wheel assembly and C.G. location of the vehicle under multibody dynamic simulation environment. Asymmetry of geometry and compliance between left and right side is considered cause of drift. The sensitivities of the suspension parameters are presented for each driving condition. In case of acceleration, the interaction of differential friction and driveshaft stiffness and their influence on drift are also studied. For braking condition, suspension parameters such as initial toe, camber and caster variation of front suspension are studied including the braking force difference. The factors influencing steering pull and steering wobble include the compliance properties of the suspension and steering parameters are studied. The mechanics of the brake force interactions with these steering and suspension properties are explained here. Simulation provides an excellent tool to examine and quantify these interactions. The SUV simulation model, MSC.ADAMS/CAR is used to show the importance of linkage compliance as a primary variable and the interactions with other steering and suspension properties. It will be shown that jounce steer and/or brake steer can be used to compensate for the unbalanced effects arising from the linkage asymmetry.


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