Front Steering System Research Articles

Integrated control of ground vehicles dynamics via advanced terminal sliding mode control

ABSTRACTAn integrated vehicle dynamics control (IVDC) algorithm, developed for improving vehicle handling and stability under critical lateral motions, is discussed in this paper. The IVDC system utilises integral and nonsingular fast terminal sliding mode (NFTSM) control strategies and coordinates active front steering (AFS) and direct yaw moment control (DYC) systems. When the vehicle is in the normal driving situation, the AFS system provides handling enhancement. If the vehicle reaches its handling limit, both AFS and DYC are then integrated to ensure the vehicle stability. The major contribution of this paper is in improving the transient response of the vehicle yaw rate and sideslip angle tracking controllers by implementing advanced types of sliding mode strategies, namely integral terminal sliding mode and NFTSM, in the IVDC system. Simulation results demonstrate that the developed control algorithm for the IVDC system not only has strong robustness against uncertainties but also improves the transient response of the control system.

Chassis integrated control for active suspension, active front steering and direct yaw moment systems using hierarchical strategy

ABSTRACTThis paper proposes a novel integrated controller with three-layer hierarchical structure to coordinate the interactions among active suspension system (ASS), active front steering (AFS) and direct yaw moment control (DYC). First of all, a 14-degree-of-freedom nonlinear vehicle dynamic model is constructed. Then, an upper layer is designed to calculate the total corrected moment for ASS and intermediate layer based on linear moment distribution. By considering the working regions of the AFS and DYC, the intermediate layer is functionalised to determine the trigger signal for the lower layer with corresponding weights. The lower layer is utilised to separately trace the desired value of each local controller and achieve the local control objectives of each subsystem. Simulation results show that the proposed three-layer hierarchical structure is effective in handling the working region of the AFS and DYC, while the quasi-experimental result shows that the proposed integrated controller is able to improve the lateral and vertical dynamics of the vehicle effectively as compared with a conventional electronic stability controller.

A mechanical integral steering system for increasing the stability and handling of motor vehicles

The article deals with the design, modeling, and simulation of an innovative four-wheel steering system for motor vehicles. The study is focused on the steering box of the rear wheels, which is a cam-based mechanism, while the front steering system uses a classical pinion—rack gearbox. In the proposed concept, the four-wheel steering aims to improve the vehicle stability and handling performances by considering the integral steering law, which is formulated in terms of correlation between the steering angles of the front and rear wheels. In this regard, a double-profiled cam is designed, in correlation with the input motion law applied to the steering wheel. The cam profile dictates (prescribes) the translational movement of the rear follower, which is connected to the left and right steering tierods, turning—as appropriate—the rear wheels in the same direction (for stability) or in opposite (for handling) to the front wheels. The cam-based mechanism is able to carry out complex motion laws, providing accurate integral steering law. The dynamic modeling and simulation of the four-wheel steering vehicle was performed by using the Multi-Body Systems package Automatic Dynamic Analysis of Mechanical Systems of MSC.Software, the full-vehicle model containing also the front and rear wheels suspension systems, as well the vehicle chassis (car body). The dynamic simulations in virtual environment have resulted in important results that demonstrate the handling and stability performances of the proposed four-wheel steering system by reference to a classical two-wheel steering vehicle.

Gain-Scheduled Vehicle Handling Stability Control Via Integration of Active Front Steering and Suspension Systems

This paper proposes an integrated vehicle dynamics control system that aims to enhance vehicles handling stability and safety performance by coordinating active front steering (AFS) and active suspension systems (ASS). The integrated controller design is based on the lateral stability region described by phase plane approach that is employed to bound the vehicle stability and coordinate AFS and ASS. During normal steering conditions, the vehicle states lie inside the lateral stability region, only the AFS is involved for vehicle steerability enhancement. Whereas, when the vehicle reaches the handling limits and the vehicle states go outside the lateral stability region under extreme steering maneuvers, both AFS and ASS collaborate together to improve vehicle handling stability. The linear parameter-varying (LPV) polytopic vehicle model is built, which depends affinely on the time-varying longitudinal speed that is described by a polytope with finite vertices. The resulting gain-scheduling state-feedback controller is designed and solved utilizing a set of linear matrix inequalities derived from quadratic H∞ performance. Simulation using matlab/simulink-carsim® is carried out to evaluate the performance of the integrated controller. The simulation results show the effectiveness of the proposed controller.

Stabilizing Vehicle Lateral Dynamics with Considerations of State Delay of AFS for Electric Vehicles via Robust Gain‐Scheduling Control

AbstractThis paper presents a robust gain‐scheduled H∞ controller to improve lateral stability and handling of four‐wheel‐independent‐drive electric vehicles possessing active front steering system with considerations of state delay. The time delay for the state is assumed as uncertain time‐invariant but has a known constant bound. By considering the tyre cornering stiffness represented by the norm‐bounded uncertainty and the time‐varying longitudinal velocity described by a polytope with finite vertices, and the vehicle lateral dynamics model is converted into the uncertain vehicle linear parameter‐varying (LPV) state‐delayed system. The resulting delay‐dependent robust gain‐scheduling state feedback H∞ controller is finally designed utilizing the constructed Lyapunov‐Krakovskii functional, and solved via a set of delay‐dependent linear matrix inequalities (LMIs). Simulations for various driving scenarios are implemented using MATLAB/SIMULINK‐CARSIM. The simulation results show the effectiveness of the proposed controller.

Adaptive Fuzzy-PI Control for Active Front Steering System of Armoured Vehicles: Outer Loop Control Design for Firing On The Move System

An armoured vehicle tends to lose its dynamic mobility when firing on the move. This is due to the effect of the firing force that reacts at the centre of the weapon platform, which creates an unwanted yaw moment at the vehicle’s centre of gravity. In order to enhance the mobility performance of the armoured vehicle, a control strategy, i.e. yaw rejection control, is designed and test on an armoured vehicle model. The purpose of the control strategy is to maintain the directional mobility of the armoured vehicle by providing a steering correction angle to the pitman arm steering system. The control strategy proposed in this study consists of two main structures: yaw rate feedback control using a Proportional-Integral-Derivative (PID) controller and Lateral Force Rejection Control (LFRC) using an adaptive Fuzzy-Proportional-Integral (adaptive Fuzzy-PI) controller. The simulation results in terms of yaw and lateral motions were observed, and the proposed control strategy was shown to successfully improve the directional mobility of the armoured vehicle after firing. The benefit of the proposed control strategy with adaptive fuzzy-PI control is evaluated by comparing its performance to fuzzy-PI and proportional-integral (PI) control strategies.

Generalized internal model robust control for active front steering intervention

Because of the tire nonlinearity and vehicle’s parameters’ uncertainties, robust control methods based on the worst cases, such as H ∞, µ synthesis, have been widely used in active front steering control, however, in order to guarantee the stability of active front steering system (AFS) controller, the robust control is at the cost of performance so that the robust controller is a little conservative and has low performance for AFS control. In this paper, a generalized internal model robust control (GIMC) that can overcome the contradiction between performance and stability is used in the AFS control. In GIMC, the Youla parameterization is used in an improved way. And GIMC controller includes two sections: a high performance controller designed for the nominal vehicle model and a robust controller compensating the vehicle parameters’ uncertainties and some external disturbances. Simulations of double lane change (DLC) maneuver and that of braking on split-µ road are conducted to compare the performance and stability of the GIMC control, the nominal performance PID controller and the H ∞ controller. Simulation results show that the high nominal performance PID controller will be unstable under some extreme situations because of large vehicle’s parameters variations, H ∞ controller is conservative so that the performance is a little low, and only the GIMC controller overcomes the contradiction between performance and robustness, which can both ensure the stability of the AFS controller and guarantee the high performance of the AFS controller. Therefore, the GIMC method proposed for AFS can overcome some disadvantages of control methods used by current AFS system, that is, can solve the instability of PID or LQP control methods and the low performance of the standard H ∞ controller.

Composite Nonlinear Feedback Control with Multi-objective Particle Swarm Optimization for Active Front Steering System

The purpose of controlling the vehicle handling is to ensure that the vehicle is in a safe condition and following its desire path. Vehicle yaw rate is controlled in order to achieve a good vehicle handling. In this paper, the optimal Composite Nonlinear Feedback (CNF) control technique is proposed for an Active Front Steering (AFS) system for improving the vehicle yaw rate response. The model used in order to validate the performance of controller is nonlinear vehicle model with 7 degree-of-freedom (DOF) and a bicycle model is implemented for the purpose of designing the controller. In designing an optimal CNF controller, the parameter estimation of linear and nonlinear gain becomes very important to produce the best output response. An intelligent algorithm is designed to minimize the time consumed to get the best parameter. To design an optimal method, Multi Objective Particle Swarm Optimization (MOPSO) is utilized to optimize the CNF controller performance. As a result, transient performance of the yaw rate has improved with the increased speed of in tracking and searching of the best optimized parameter estimation for the linear and the nonlinear gain of CNF controller.

Braking and steering performance analysis of a road vehicle with active independent front steering

Active front steering (AFS) systems help achieve target handling performance through simultaneous applications of steering corrections to both the wheels, but may exhibit limited performance during high-speed manoeuvres. This study explores the effectiveness of an active independent front steering (AIFS) system under application of braking to demonstrate that it could not only overcome the limitation of the AFS but also provide sufficient adhesion reserve for generating longitudinal forces. A simple AIFS controller is synthesised using the yaw rate feedback and the tyres' saturation limits. The simulation results are obtained under a wide range of braking-in-turn manoeuvres in different road conditions. Comparisons of the results with those obtained with the conventional AFS suggested greater effectiveness of the AIFS under high-speed manoeuvres. A parametric study is subsequently conducted to study the robustness of the AIFS performance. The results demonstrated enhanced braking-in-turn performance of the AIFS under conditions where the understeer handling characteristic exists.

Integrated control of active front steering and electric power steering system with EKF estimation of lateral force

Good vehicle handling characteristics are essential to ensure traffic safety. In the integrated system of electric power steering (EPS) and active front steering (AFS), the steering wheel torque may change abruptly with the interference of active steering. The additional front road wheel angle generated by AFS gives rise to the change of tyre lateral force, which results in the change of steering wheel torque finally. Although the tyre forces are difficult to measure, the extended Kalman filter (EKF) algorithm can be used to estimate it. The problem of steering wheel torque change can be resolved by tyre forces estimate based on the EKF observer in nonlinear system. The vehicle nonlinear mathematical model is presented and a nonlinear tyre lateral force estimator is also established basing on EKF. The estimated tyre lateral forces can be applied to compensate the abrupt change of steering wheel torque, which realises the combination of vehicle states estimation and vehicle control. The simulation results in MATLAB/Simulink show the effectiveness of proposed control strategy.

Robust guaranteed cost state-delayed control of yaw stability for four-wheel-independent-drive electric vehicles with active front steering system

A robust guaranteed cost state-delayed control design for four-wheel-independent-drive electric vehicles with active front steering system is presented in this paper. The main control objective is to deal with the time delay problem and improve yaw stability and handling performance of vehicle. To address the challenge of time delay problem, the time delay of steering system is assumed to be concentrated in vehicle state. In terms of the feasibility of a sequence of linear matrix inequalities (LMIs) derived from the selected Lyapunov-Krakovskii functional, the guaranteed cost memoryless state-delayed controller is designed, which ensures the corresponding closed-loop system is asymptotically stable with a guaranteed cost performance. Simulations for various operating manoeuvres are carried out using the platform of Matlab/Simulink-Carsim®. It is found from the simulation results that the proposed controller can effectively attenuate the delayed effect of steering system and preserve vehicle yaw stability.

An independently controllable active steering system for maximizing the handling performance limits of road vehicles

This study explores the effectiveness of an active independent front steering system capable of applying a corrective steering at each wheel selectively and in an independent manner. In doing this, it is possible to generate the required adhesion force for active steering control while ensuring that none of the tyres approaches saturation. A non-linear yaw-plane model of a two-axle truck with a limited number of roll degrees of freedom is used to evaluate the effectiveness of the active independent front steering under a range of steering manoeuvres. A simple proportional–integral controller is synthesized to track the reference response based on the neutral steering system as well as to limit the steering correction considering the saturation limit of the tyres, which is defined from the normalized cornering stiffness properties of the tyres. The directional responses obtained for the vehicle model integrating the active independent front steering controller are compared with those of the conventional active front steering system for each of the selected manoeuvres. The results show that, while both the control strategies can effectively track the target yaw rate of the vehicle, the proposed active independent front steering control can yield enhanced performance limits without any of the tyres approaching the saturation limit, irrespective of the road condition and the steering manoeuvre. Furthermore, the active independent front steering design permits some adhesion reserve for each wheel for generating additional traction and braking forces during a severe steering manoeuvre.

Robust control of hand wheel torque for active front steering system

Active front steering (AFS) system has been used as a promising technology which improves the steering portability and handing stability of vehicles. It employs a steering motor to realize the functions of variable steering ratio and vehicle stability control. However, it has a serious problem of unexpected reaction hand wheel torque caused by the additional steering angle. In this paper, the optimum hand wheel torque is designed based on the linear tire model. Considering the uncertainty and disturbance of the steering system and vehicle, an H∞ controller is developed to make sure the hand wheel torque follows the reference torque accurately and quickly. The simulation shows that the proposed controller can compensate the unnatural reaction torque and provide a good steering feel for the driver.

Composite Nonlinear Feedback for Vehicle Active Front Steering

In this paper, Composite Nonlinear Feedback (CNF) is applied on Active Front Steering (AFS) system for vehicle yaw stability control in order to have an excellent transient response performance. The control method, which has linear and nonlinear parts that work concurrently capable to track reference signal very fast with minimum overshoot, fast settling time, and without exceed nature of actuator saturation limit. Beside, modelling of 7 degree of freedom for typical passenger car with magic formula to represent tyre nonlinearity behaviour is also presented to simulate controlled vehicle as close as possible with a real situation. An extensive computer simulation is performed with considering a various profile of cornering manoeuvres with external disturbance to evaluate its performance in different scenarios. The performance of the proposed controller is compared to conventional Proportional Integration and Derivative (PID) for effectiveness analysis.

A new robust control method for active front steering considering the intention of the driver

The influence of the active front steering system on the driver’s intention and the trade-off between the robustness and the performance of the active front steering controller have not been adequately addressed by current research studies. A new robust control method based on the normalized left coprime factorization model including uncertainty and perturbations is introduced, and the robustness of this method against high speeds and variations in the cornering stiffness without changing the intention of the driver is guaranteed by the design of the feedforward controller and the feedback controller. A single-step method is adopted to solve the feedforward robust controller and the feedback robust controller. The resulting controllers obtained by the proposed robust control method have a simple structure and do not require online optimization. Furthermore, simulations of the double-lane-change manoeuvre and of braking on a split- μ road are conducted to compare the performance and the stability of the new robust control method with those of the proportional–integral–derivative controller and the standard H∞ controller. Simulation results show that, in comparison with the other two control methods, the established new robust control method can enhance the vehicle stability and handling, and the tracking rapidity is improved by the introduction of feedforward control so that the active steering intervention does not affect the driver’s intention, regardless of the external interferences or emergency evasive manoeuvres.

Variable structure controller design for steer-by-wire system of a passenger car

The electric power steering (EPS) system was developed and the steer-by-wire (SBW) system achieves the purposes of EPS. The advantages of SBW are packaging flexibility, advanced vehicle control system, and superior performance. No mechanical linkage exists between the steering gear and steering column in the SBW system. The steering wheel and front-wheel steering can be controlled independently. The SBW system consists of two motors controlled by an electronic control unit (ECU). One motor is in the steering wheel and develops the steering feel of the driver and the other motor is in the steering linkage and improves vehicle maneuverability and stability. Moreover, the active front steering (AFS) system can be added to the SBW system. AFS reduces the difference between actual and estimated vehicle yaw rate. Up-to-date information from the steering wheel enables drivers to identify road conditions through the tire force, which should be fed back to the steering wheel. Furthermore, several control algorithms related to the vehicle and motor can be used together through the self-aligning torque, which is fed back to the steering wheel. This study proposes a method to control the vehicle yaw rate through an SBW system. This control method is based on a PID control method for the steering-wheel-motor controller, as well as on a sliding mode control (SMC) method for the front-wheel-motor controller and yaw stability controller. The SBW system is modeled using a bond graph method. Results imply that the controllers are robust enough when in contact with nonlinear properties of tire and road conditions. This study is expected to guide further research on the SBW system.

Optimal Composite Nonlinear Feedback Controller for an Active Front Steering System

Yaw stability control is the most popular topics in the automotive field. Several studies have been done in searching the effective method in controlling yaw moment. Hence, an integration of the active front steering system (AFS) with Composite Nonlinear Feedback controller is presented in this paper. Recently, this controller has been used by a lot of researchers in controlling their system performance due to its main advantage that can be seen in transient response which demonstrate super fast tracking. An optimal CNF feedback control problem is formulated as a parameter optimization problem with performance index and restrictions on stability. To handle such restrictions and constraint, the particle swarm optimization algorithm is applied to solve parameter optimization problems.

Optimal combination of design parameters for improving the kinematics characteristics of a midsize truck through design of experiment

This paper optimizes the combination of design parameters for improving the kinematic characteristics of a midsize truck using both design of experiment and computer simulation. A computational model of the front suspension and steering system of a midsize truck is developed for analyzing kinematic and compliance characteristics. A taper leaf spring is modeled as a flexible body using finite elements. A bump mode test is performed to validate the reliability of the developed computational model. Mean absolute values of the toe angle and wheel base change are used as objective functions. Modifiable hard points are selected as design parameters. An optimal combination of design parameters for improving kinematic characteristics is suggested based on analyses of variance and factor effects using a table of orthogonal arrays.

Study and Simulation on Truck Front Suspension Using ADAMS

The mechanical system dynamics software,ADAMS,is used to establish multi-body dynamics system model for a truck front suspension and steering system. Through the simulation test of wheel travel, front wheel alignment parameters changing along with the wheel travel was obtained.

Research on the Control Strategy of Active Front Steering System

Research on the Control Strategy of Active Front Steering System