Design of a Novel Nonlinear Observer to Estimate Sideslip Angle and Tire Forces for Distributed Electric Vehicle

Abstract

For four-wheel independently driven (4WD) distributed electric vehicle (DEV), vehicle dynamics control systems such as direct yaw moment control (DYC) can be easily achieved. Accurate estimation of vehicle state variables and uncertain parameters can improve the robustness of vehicle dynamics control system. Various sensors are generally equipped to the acquisition of the vehicle dynamics. For both technical and economic reasons, some fundamental vehicle parameters, such as the sideslip angle and tire-road forces, can hardly be obtained through sensors directly. Therefore, this paper presented a state observer to estimate these variables based on Unscented Kalman Filter (UKF). To improve the accuracy of UKF, measurement noise covariance is also self-adaptive regulated. In addition, a nonlinear dynamics tire model is utilized to improve the accuracy of tire lateral force estimation. The simulation and experiment results show that the proposed observer can provide the precision values of the vehicle state.

Virtual tyre force sensors: An overview of tyre model-based and tyre model-less state estimation techniques

“…In research papers, 28,32–34,73,104,105 longitudinal forces are obtained employing a state estimator based on the wheel rotating dynamics. In Song et al, 28 an open loop observer structure based on the direct computation of the tyre rotating dynamics, equation (58), is proposed. The wheel torque and wheel speed are measured directly from an electric motor.…”

“…Finally, to conclude with this discussion on lateral tyre force estimation, tyre model- based 3,10,27,28,52,59,74,113,114, 125,126 approaches are presented in the following. Some of these works have been introduced previously and will be revisited in this section to address the particularities of the lateral force case.…”

“…While the previous approaches were based on constant or adaptive linear models, nonlinear tyre models have been employed in other appropaches. 3,10,27,28,52,59,114,125 In Doumiati et al, 3,10,59 a Dugoff model is employed to compute the lateral forces from the lateral wheel slips and tyre vertical loads. In this case, longitudinal slips are not considered and a relaxation length approach is used to model the tyre’s transient dynamics.…”

“…Concerning observation-based approaches, two trends are clearly differentiated depending on whether a specific tyre model is employed: tyre model-based approaches and tyre model-less approaches, Figure 3. In the former group, an empirical 27 or physical 3,10,28 tyre model is used to compute the tyre forces from a number of tyre states (normally longitudinal slip κ, lateral slip α, vertical force F z and wheel inclination angle γ), 29 and the tyre model parameters need to be known a priori. Depending on the model complexity and the differences between the tyre characterisation testbed and the real functioning conditions, the force estimation will be subjected to a degree of uncertainty.…”

Design of an Interacting Multiple Model‐Cubature Kalman Filter Approach for Vehicle Sideslip Angle and Tire Forces Estimation

“…Therefore the curve, which reflects the relationship between the tire force and the wheel slip angle, is initially linear. Many algorithms, such as the variable forgetting factor recursive least squares algorithm [5], Luenberger linear Observer [6], ∞ filtering [7], and Kalman filters [8,9], based on the linear model have been used to estimate the vehicle state parameters. However, the vehicle cannot always be under normal driving condition.…”