Active Front Wheel Steering Research Articles

Composite Nonlinear Feedback Control for Path Following of Four-Wheel Independently Actuated Autonomous Ground Vehicles

This paper investigates the path-following control problem for four-wheel independently actuated autonomous ground vehicles through integrated control of active front-wheel steering and direct yaw-moment control. A modified composite nonlinear feedback strategy is proposed to improve the transient performance and eliminate the steady-state errors in path-following control considering the tire force saturations, in the presence of the time-varying road curvature for the desired path. Path following is achieved through vehicle lateral and yaw control, i.e., the lateral velocity and yaw rate are simultaneously controlled to track their respective desired values, where the desired yaw rate is generated according to the path-following demand. CarSim–Simulink joint simulation results indicate that the proposed controller can effectively improve the transient response performance, inhibit the overshoots, and eliminate the steady-state errors in path following within the tire force saturation limits.

Integral Sliding Mode-Based Composite Nonlinear Feedback Control for Path Following of Four-Wheel Independently Actuated Autonomous Vehicles

This paper presents an accurate, fast, and robust path-following control approach for four-wheel independently actuated (FWIA) autonomous vehicles via integrated control of the active front-wheel steering (AFS) and direct yaw-moment control (DYC). The path following is realized through simultaneously converging the yaw rate and lateral velocity to their respective desired values which are generated according to the path-following demand. A novel integral sliding mode (ISM)-based composite nonlinear feedback (CNF) control technique considering the multi-input multi-output and the time-varying tracking reference is proposed, which has combined the advantages of CNF control in improving the transient performance and ISM control in guaranteeing good robustness. Chattering is avoided using a continuous ISM controller instead of generally adopted discontinuous ones based on a multivariable super-twisting algorithm (STA). System uncertainties, tire fore saturations, and variation of the desired-path curvature are compositively considered in the ISM-CNF controller design, with the stability of the overall system proved using Lyapunov method. CarSim–Simulink simulations have verified the effectiveness of the proposed controller in improving the transient path-following performance, inhibiting the overshoots, eliminating the steady-state errors, and rejecting the lumped disturbance considering the tire forces saturations and the varying path curvature.

Output Constraint Control on Path Following of Four-Wheel Independently Actuated Autonomous Ground Vehicles

The path-following problem for four-wheel independently actuated autonomous ground vehicles is investigated in this paper. A novel output constraint controller is proposed to deal with the lateral offset control in path following and maintain the vehicle lateral stability in the presence of tire sliding effects. The innovations of this work lie in the following two aspects: 1) A novel output constraint control strategy, namely, the hyperbolic projection method, is proposed to strictly bound the lateral offset to prevent the vehicle from transgressing the safety bound in path following; 2) an adaptive and robust linear quadratic regulator controller is adopted to obtain the optimal active front-wheel steering and direct yaw-moment control inputs with vehicle lateral stability consideration and to eliminate the effect of parameter uncertainties. CarSim–Simulink joint simulation results indicate that the proposed controller can compactly bound the lateral offset to avoid transgressing the safe boundary during path following, particularly in extreme driving conditions, in the presence of tire sliding effects and system uncertainties.

Active front wheel steering model and controller for integrated dynamics control systems

We report a model and controller for an active front-wheel steering (AFS) system. Two integrated dynamics control (IDC) systems are designed to investigate the performance of the AFS system when integrated with braking and steering systems. An 8-degrees-of-freedom vehicle model was employed to test the controllers. The controllers were inspected and compared under different driving and road conditions, with and without braking input, and with and without steering input. The results show that the AFS system performs kinematic steering assistance function and kinematic stabilisation function very well. Three controllers allowed the yaw rate to accurately follow a reference yaw rate, improving the lateral stability. The two IDC systems improved the lateral stability and vehicle control and were effective in reducing the sideslip angle.

Active Steering Actuator Fault Detection for An Automatically-steered Electric Ground Vehicle

In this paper, we investigate the actuator fault detector design problem for an electric ground vehicle (EGV) that is equipped with an active front-wheel steering system. Since the EGV can be steered by a motor automatically, it is desired to design a fault detector for the steering actuator for safety reasons. A two degree of freedom lateral nonlinear vehicle model is established. The nonlinear vehicle model is converted to a linear-parameter-varying (LPV) form and the scheduling vector is related to the vehicle longitudinal velocity. Since it is not easy to measure the longitudinal velocity precisely, the uncertain measurement on the longitudinal velocity is considered and the weighting factors of LPV submodels are subject to uncertainties. Based on the uncertain LPV model, a gain-scheduling fault detector is proposed and an augmented system is obtained. The desired steering angle and the faulty steering angle are both involved in the augmented system. As the steering angle generally has a low-frequency working range, the steering angle amplitude spectrums of three different maneuvers are studied, and the frequency working range is determined. The stability, the $\mathcal {H}{\_}$ performance, and the $\mathcal {H}_{\infty }$ performance of the augmented system are all exploited. Based on the analysis results, the mixed $\mathcal {H}{\_}$ / $\mathcal {H}_{\infty }$ fault detector design method is developed. An experimental test is used to show the performance of the designed fault detector.

Modeling, validation and firing-on-the-move control of armored vehicles using active front-wheel steering

It is a well-known fact that an armored vehicle will lose its directional stability when firing a large-caliber gun while moving. The instability is caused by the impulse force from firing, acting at the center of a weapons platform that produces a yaw moment at the center of gravity of the armored vehicle. In order to improve the stability, this paper introduces a firing-on-the-move technology for armored vehicles using an active front-wheel steering (AFS) system. The AFS system is proposed to maintain the directional stability of the armored vehicle by providing an electronically controlled correction to the steering mechanism. The steering correction is designed to reject the unwanted yaw motion and bring the vehicle back to its intended direction of travel after firing. The proposed control strategy of the AFS system in this study consists of yaw rate feedback with lateral force rejection control. The AFS system controller is developed on a validated 10-degrees-of-freedom armored vehicle. The results indicate that the developed control strategy can effectively maintain the directional stability, in terms of yaw and lateral motions, of the armored vehicle after firing. The superiority of the proposed AFS system controller is also evaluated by comparing its performance to an AFS system without lateral force rejection control as well as to a conventional armored vehicle without AFS.

Robust [formula omitted] output-feedback yaw control for in-wheel motor driven electric vehicles with differential steering

This paper investigates the yaw control issue for in-wheel-motor (IWM) electric ground vehicles (EGVs) based on the differential steering in the presence of the complete failure of the active front-wheel steering. Differential steering is an emerging steering mechanism, generated from the differential torque between the left and right wheels in IWM EGVs. In case that the regular steering system is defective, differential steering can be utilized to act as the sole steering power, and thus avoid dangerous consequences for vehicles. For this purpose, a robust H∞ output-feedback controller based on differential steering is designed to achieve yaw stabilization, considering that the desired steering angle is uncertain and hard to obtain. Parameter uncertainties for the cornering stiffnesses and the external disturbances are considered to make vehicle robust to different driving conditions. CarSim-Simulink joint simulation results based on a high-fidelity and full-car model verify the effectiveness of the proposed controller to guarantee the equal vehicle handling and stability.

Integrated control of in-wheel motor electric vehicles using a triple-step nonlinear method

To improve the vehicle stability of an electric vehicle with four in-wheel motors, an integrated control scheme with active front wheel steering and direct yaw moment is proposed using a triple-step nonlinear method. The method handles the nonlinear tire characteristics explicitly and actualizes a decoupling control for the considered two-input two-output nonlinear system, in the sense that the closed-loop error dynamics evolve independently. The design procedure is formalized as a triple-step deduction, and the derived controller consists of three parts: steady-state-like control, feedforward control considering reference variations, and state-dependent error feedback control. Finally, the designed controller is evaluated in a realistic seven DOF vehicle model and results are satisfying.

Design and Evaluation of Active Front Wheel Steering System Model and Controller

Design and Evaluation of Active Front Wheel Steering System Model and Controller

Research on Vehicle Stability Based on DYC and AFS Integrated Controller

A new vehicle stability control method integrated direct yaw moment control (DYC) with active front wheel steering (AFS) was proposed. On the basis of the vehicle nonlinear model, vehicle stable domain was determined by the phase plane of sideslip angle and sideslip angular velocity. When the vehicle was outside the stable domain, DYC was firstly used to produce direct yaw moment, which can make vehicle inside the stable domain. Then AFS sliding mode control was used to make the sideslip angle and yaw rate track the reference vehicle model. The simulation results show that the integrated controller improves vehicle stability more effectively than using the AFS controller alone.

Control Methods of Active Front Wheel Steering for 4WD Electric Vehicle

Based on two freedom degrees of vehicle model, control method which takes yaw rate and sideslip angle as system state, and front wheel corner and direct yaw moment as control input is put forward. Considering uncertainty of velocity and direct yaw moment, feedforward-feedback controllers are designed. Four wheel drive force are allocated by using feedforward compensation and yaw moment which is formed by driving force difference value. It makes yaw rate and sideslip well of tracking the desirable model when the vehicle drive steering. Finally, vehicle handling stability is studied on conditions of step input and sine input by simulation.

Hardware in the loop simulation of active front wheel steering control for yaw disturbance rejection

This paper introduces an Active Front Wheel Steering (AFWS) control for the purpose of reducing unwanted yaw motion. Side wind forces are considered to be the sources of yaw disturbance in this study. The proposed control strategy for the AFWS is a lateral directional control with yaw rate feedback. The AFWS controller was implemented on Hardware in the Loop Simulation (HILS) using an AFWS test rig. From the simulation and experimental results, AFWS control is able to perform the task of yaw disturbance attenuation by providing additional steering correction for maintaining the original direction of the vehicle.

Design of Active Front Steering (AFS) system with QFT control

This paper investigates a control strategy of active front wheel steering based on quantitative feedback theory (QFT). By incorporating feedback from yaw rate sensor into active steering system, the control system improves the dynamic responses of the vehicle. A multi degree-of-freedom nonlinear vehicle model is co-simulated with MATLAB Simulink and ADAMS/CAR. The performance of the control system is evaluated under various emergency manoeuvres and road conditions. The results show that the designed robust control algorithm has good control performance and can efficiently improve the handing qualities and stability characteristics.

Yaw stability control of a steer-by-wire equipped vehicle via active front wheel steering

A novel yaw stability control algorithm with active front wheel steering control of a vehicle equipped with a steer-by-wire system is presented in this paper. The proposed algorithm achieves the decoupling of the lateral and yaw motion of a vehicle and the vehicle’s yaw damping simultaneously by the feedback of both yaw rate and front steering angle. A trade-off is then made between the robust decoupling and yaw rate damping through the adjustment of the feedback gains with respect to vehicle speed. With this trade-off, the gain scheduled steering controller provides the desired yaw rate damping while keeping the yaw-lateral motion decoupled. The robustness of the yaw-lateral decoupling is achievable when arbitrary yaw damping is not required. The proposed control system is implemented on a steer-by-wire vehicle, and the experimental results are presented illustrating the benefits.

Lateral dynamics emulation via a four-wheel steering vehicle

In this paper, we examine the lateral dynamics emulation capabilities of an automotive vehicle equipped with four-wheel steering. We first demonstrate that the lateral dynamics of a wide range of vehicles can be emulated, either with little or with no modification on the test vehicle. Then we discuss a sliding mode controller for active front and rear wheel steering, in order to track some given yaw rate and side-slip angle. Analytically, it is shown that the proposed controller is robust to plant parameter variations by±10%, and is invariant to unmeasurable wind disturbance. The performance of the sliding mode controller is evaluated via computer simulations to verify its robustness to vehicle parameter variations and delay in the loop, and its insensitivity to wind disturbance. Finally, the emulation of a bus, a van, and two commercially available passenger vehicles is demonstrated in an advanced nonlinear simulator.

Vehicle-handling quality evaluation through model-based driver steering behaviour

This study proposes a method to evaluate vehicle-handling quality based on the steering characteristics that are identified by a simple driver model using measured time histories of steering behaviour and vehicle motion during lane change. On the basis that drivers adapt to the vehicle-handling characteristics during a manoeuvre, their steering behaviour reflects the vehicle-handling characteristics and plays an important role in the evaluation of handling quality. Thus, the handling parameters in the model indicate the handling quality of the vehicle. This method is applied successfully to investigate the effects of the active front-wheel steering and direct yaw moment control on driver's handling quality evaluation of the vehicles.

Robust Active Steering System Taking Account of Nonlinear Dynamics

The objective of this study is to design an active front wheel steering system in which the steering characteristics do not vary for changes of environment. It is based on the Robust Model Matching (RMM) algorithm which realizes desired frequency characteristics between the driver's steering angle and vehicle yaw rate. This makes the frequency characteristics robust for parameter errors and non linear dynamics. The effectiveness of the proposed system is verified by computer simulation of vehicle behavior running under various velocities and road surface friction conditions.

Crosswind Feedforward Control – A Measure to Improve Vehicle Crosswind Behaviour

SUMMARY The theory of crosswind feedforward control was explained using the example of a vehicle with active front-wheel steering. Beforehand, the calculation formulas and frequency responses of the transient crosswind force and of the wind yaw moment acting on the vehicle were derived using the example of a simple vehicle fluid model. The influence of the transiency of crosswind disturbance on the dynamic crosswind behaviour of a vehicle was then presented. The results of simulation confirmed the analyses carried out in the frequency domain for feedforward control with front, rear and all-wheel steering. With front-wheel steering, the influence of crosswind on one of the vehicle movement variables (lateral acceleration or yaw rate) could be almost completely compensated by dynamic feedforward control. With rear-wheel steering, it is only possible to compensate directly for the influence on the yawing rate. Due to the setting of the side force in the same direction as the lateral wind force at the start, ...