Analysis and Design of Suspension State Observer for Wheel Load Estimation 2024-01-2285

Tire forces and moments play an important role in vehicle dynamics and safety. X-by-wire chassis components including active suspension, electronic powered steering, by-wire braking, etc can take the tire forces as inputs to improve vehicle’s dynamic performance. In order to measure the accurate dynamic wheel load, most of the researches focused on the kinematic parameters such as body longitudinal and lateral acceleration, load transfer and etc. In this paper, the authors focus on the suspension system, avoiding the dependence on accurate mass and aerodynamics model of the whole vehicle. The geometry of the suspension is equated by the spatial parallel mechanism model (RSSR model), which improves the calculation speed while ensuring the accuracy. A suspension force observer is created, which contains parameters including spring damper compression length, push rod force, knuckle accelerations, etc., combing the kinematic and dynamic characteristic of the vehicle. Subsequently, the wheel load can be obtained by solving the above nonlinear system using Extended Kalman Filtering (EKF). Validation experiments are conducted on a quarter-suspension model as well as a Formula Student race car under standard working conditions. The car is equipped with sensors for the signals required by the algorithm as well as signal processing units. While calculations are performed, the conventional acceleration-based estimation method is used for comparison. The experimental results show that the measurement error of the method in this paper is significantly smaller than that of the traditional method, and it has higher sensitivity to dangerous conditions such as bumps and rollovers, which is of greater significance for the usage of wheel load for vehicle control and active safety.