Dynamic-boundary-based lateral motion synergistic control of distributed drive autonomous vehicle

To improve the path tracking accuracy and yaw stability of distributed drive autonomous vehicles (DDAVs) under extreme working conditions, a cooperative lateral motion control method based on the dynamic boundary is proposed to prevent different road adhesion conditions from affecting the motion stability of DDAVs. Based on the analysis of the DDAV lateral dynamics system coordination mechanism, a dynamic boundary considering the pavement adhesion coefficient is proposed, and the Lateral Motion Synergistic Control System (LMSCS) is designed. The LMSCS is divided into the coordination, control, and executive layers. The coordination layer divides the control domain into the stable, quasi-stable, and unstable domains by the dynamic boundary, and coordinates the control strength of the path following control and yaw stability control. In the control layer, the path following control and yaw stability control laws are designed based on the global fast terminal sliding mode. The executive layer estimates the expected steering wheel angle and expected additional wheel torque. Joint simulations under double line shifting conditions confirmed that LMSCS reflects the impact of the road attachment conditions and improves the path tracking accuracy and vehicle yaw stability. The LMSCS has better overall performance than existing lateral motion control methods.

Decoupling control of active suspension and four-wheel steering based on Backstepping-ADRC with mechanical elastic wheel

Mechanical elastic wheel (MEW) has the advantages of explosion-proof and prick-proof, which is conducive to the safety and maneuverability of the vehicle. However, the research on the performance of the full vehicle equipped with MEW is rare. Considering the particular properties of the radial and cornering stiffness of MEW, this paper aims to take into account both ride comfort and yaw stability of the vehicle equipped with the MEW through a nonlinear control method. Firstly, a 9-DOF nonlinear full vehicle model with the MEW tire model is constructed. The tire model is fitted based on experimental data, which corrects the impacts of vertical load on the cornering characteristic of the MEW. Then the full vehicle system is decoupled into four subsystems with a single input and a single output each according to active disturbance rejection control (ADRC) technology. In this process, the coupling relationship between different motions of the original system is regarded as the disturbance. Afterward, a novel nonlinear extended state observer is proposed, which has a similar structure of traditional linear extended state observer but smaller estimation error. Next, the control law of Backstepping-ADRC for different subsystems are derived respectively based on the Lyapunov theory. For the first time, the Backstepping-ADRC method is applied to the decoupling control of four-wheel steering and active suspension systems. Furthermore, the parameters of the controllers are adjusted through a multi-objective optimization scheme. Finally, simulation results validate the effectiveness and robustness of the proposed controller, especially when encountering some disturbances. The indices of vehicle body attitude and ride comfort are improved significantly, and also the yaw stability is guaranteed simultaneously.

An Adaptive Nonsingular Fast Terminal Sliding Mode Control for Yaw Stability Control of Bus Based on STI Tire Model

Due to the bus characteristics of large quality, high center of gravity and narrow wheelbase, the research of its yaw stability control (YSC) system has become the focus in the field of vehicle system dynamics. However, the tire nonlinear mechanical properties and the effectiveness of the YSC control system are not considered carefully in the current research. In this paper, a novel adaptive nonsingular fast terminal sliding mode (ANFTSM) control scheme for YSC is proposed to improve the bus curve driving stability and safety on slippery roads. Firstly, the STI (Systems Technologies Inc.) tire model, which can effectively reflect the nonlinear coupling relationship between the tire longitudinal force and lateral force, is established based on experimental data and firstly adopted in the bus YSC system design. On this basis, a more accurate bus lateral dynamics model is built and a novel YSC strategy based on ANFTSM, which has the merits of fast transient response, finite time convergence and high robustness against uncertainties and external disturbances, is designed. Thirdly, to solve the optimal allocation problem of the tire forces, whose objective is to achieve the desired direct yaw moment through the effective distribution of the brake force of each tire, the robust least-squares allocation method is adopted. To verify the feasibility, effectiveness and practicality of the proposed bus YSC approach, the TruckSim-Simulink co-simulation results are finally provided. The co-simulation results show that the lateral stability of bus under special driving conditions has been significantly improved. This research proposes a more effective design method for bus YSC system based on a more accurate tire model.

Observation of Dynamic State Parameters and Yaw Stability Control of Four-Wheel-Independent-Drive EV

Vehicle yaw stability control is an important part of the active safety of electric vehicles. In order to realize the yaw stability control of vehicles, this paper takes 4-WID electric vehicles as the research object, studies the nonlinear estimation of the state parameters of the lateral stability dynamic system and the yaw stability control strategy. The vehicle state parameter estimation strategy, based on the unscented Kalman filter (UKF) algorithm and the model predictive control algorithm, are designed to control the vehicle yaw stability, which realizes the safe and stable driving of the vehicle. Through CarSim–Simulink joint simulation and hardware-in-the-loop (HIL) experiments based on MicroAutoBox, the effectiveness and real-time performance of the designed control strategy are fully verified, which accelerate the development process of the vehicle controller, and realizes the safe and stable driving of the vehicle.

Cooperative control of yaw and roll motion for in-wheel motor vehicle with semi-active suspension

A new vehicle motion control strategy is proposed, which synthesizes the rolling and yaw performance of vehicle by cooperating the damping force of semi-active suspension and yaw moment. To address the coupled dynamic behavior of roll and yaw motion, the modeling approach for nonlinear roll and yaw coupled dynamics is firstly employed. Furthermore, considering that the yaw and roll controllers are located in different electronic control units in practice, a distributed structure of cooperative control is presented. The key of cooperative control is that the damping force of semi-active suspension is controlled to adjust the roll dynamic, the front- and rear-axle load transfer cooperating the yaw motion; the yaw stability controller is designed to improve the yaw dynamic performance. To design the suspension damping force controller, the effect of the suspension damping force on roll and yaw dynamic behavior is discussed, and the piecewise-linear damping-force model with drive current as input is established. Moreover, the optimal suspension drive current is designed to alter roll performance and load transfer. To enhance the yaw dynamic performance, the yaw stability controller based on a sliding mode method is explored, and the optimal sliding-surface parameter is discussed to synthesize the settling time and overshoot of the yaw rate. Simulation and hardware-in-loop (HIL) test results show that the cooperative control combines the roll and yaw dynamics performance well; the overshoot and oscillation of yaw rate and lateral speed can be restrained.