Chouki Sentouh

A New Control Strategy of an Electric-Power-Assisted Steering System

The control of electric-power-assisted steering (EPAS) systems is a challenging problem due to multiple objectives and the need for several pieces of information to implement the control. The control objectives are to generate assist torque with fast responses to drivers torque commands, ensure system stability, attenuate vibrations, transmit the road information to the driver, and improve the steering wheel returnability and free-control performance. The control must also be robust to modeling errors and parameter uncertainties. To achieve these objectives, a new control strategy is introduced in this paper. A reference model is used to generate an ideal motor angle that can guarantee the desired performance, and then, a sliding-mode control is used to track the desired motor angle. This reference model is built using a dynamic mechanical EPAS model, which is driven by the driver torque, the road reaction torque, and the desired assist torque. To implement the reference model with a minimum of sensors, a sliding-mode observer with unknown inputs and robust differentiators are employed to estimate the driver torque, the road reaction torque, and the systems states. With the proposed control strategy, there is no need for different algorithms, rules for switching between these algorithms, or fine-tuning of several parameters. In addition, our strategy improves system performance and robustness and reduces costs. The simulation results show that the proposed control structure can satisfy the desired performance.

Integrated Driver–Vehicle–Infrastructure Road Departure Warning Unit

In this paper, a road-departure warning unit taking into account driver-vehicle-infrastructure (DVI) interactions is proposed. The longitudinal and lateral vehicle dynamics limits are analyzed to detect the road departure on loss of control. Vehicle positioning and time to lane crossing (TLC) are used to detect the road departure on a defect of guidance. Prevention of excessive longitudinal speed is handled through the computation of a critical longitudinal speed when approaching a curve and speed profile generation in the straight road section preceding the curve. For the lateral mode, the vehicle oversteering or understeering, the yaw motion, and the lateral acceleration are analyzed. The vehicle lateral displacement and the TLC values are also examined when the vehicle dynamics are not excessive. Necessary data for detection algorithms, which are not available from measurements, are estimated using an extended Kalman filter. The system consists of several subsystems, which work in parallel and provide warning through a dedicated human-machine interface (HMI). This road-departure warning system is experimentally tested on a test track using a prototype vehicle. It is found to be efficient and robust.

Control of an Electric Power Assisted Steering system using reference model

This paper presents a new control strategy of Electric Power Assisted Steering (EPAS) systems to ensure several control objectives. First, a reference model is employed to generate ideal motor angle that can guarantee the control objectives, assist torque generation, fast response to drivers torque command, vibration attenuation, supplying road information to the driver, improving steering wheel returnability and free control performance. Second, a sliding mode control law is used to track the desired motor angle. Finally, a sliding mode observer with unknown inputs and robust differentiators are designed to implement the reference model. Simulation results show that the proposed control structure can satisfy the desired performance.

Cooperative Steering Assist Control System

The paper deals with the design of lateral shared vehicle control taking into account the interaction between the driver and the assistance system. The shared control system is designed in such a way to ensure a good transfer of the control authority without generating negative interference. For that a driver model that allows making valid predictions on the driver behaviour is integrated in the design process of the controller. In order to avoid complex conflict situations such as during lane change maneuver, a decision making algorithm for the control authority shifting is also proposed and implemented. Experimental results provided in the paper, using interactive simulator, show the effectiveness of the approach to ensure shared lateral vehicle control.

Driver torque and road reaction force estimation of an Electric Power Assisted Steering using sliding mode observer with unknown inputs

Driver torque and steering reaction force are important information in the designing of EPAS (Electric Power Assisted Steering) system. The driver torque determines the amount of assisted torque and the reaction force can be used to improve the steering feeling and the vehicle stability or introduce a new assist torque control. Since, in practice, they are not usually measureable; a sliding mode observer with unknown inputs is introduced to estimate the driver torque and the road reaction force of an EPAS system by using other measured signals which are normally available. A state space formulation for EPAS system with brushed motor is used for the synthesis of observer with unknown inputs. The proposed observer is applied to state and unknown input estimation of EPAS. Simulation results demonstrate the effectiveness of the proposed observer which improves the EPAS system performance and also reduces system cost and complexity.

Fuzzy Takagi-Sugeno LQ controller for lateral control assistance of a vehicle

This paper describes a concept of lane keeping assistance system based on the fuzzy Takagi-Sugeno (T-S) optimal controller. Nonlinearities due to longitudinal velocity variation in the lateral dynamics are considered to give a T-S representation and Linear Matrix Inequalities (LMI) are used to reach the appropriate T-S optimal controller that insure the global stability of the closed loop system. In conclusion the effectiveness of the proposed approach is illustrated in Matlab/Simulink and experimental tests carried out on the ”SHERPA” (Simulateur Hybride dEtude et de Recherche de PSA pour lAutomobile) simulator.

Control of electric power assisted steering system using sliding mode control

This paper presents a robust control design of Electric Power Assisted Steering (EPAS) system. The control is synthesized using integral sliding mode control to ensure the control objectives, such as the steering assist torque generation, the dampening compensation and the robustness to the parameters uncertainty, modeling errors, nonlinearity and disturbances. The driver torque needed to determine the amount of the assist torque and the other information needed to implement the controller are estimated. So, the proposed controller can be implemented without additional sensors. Simulation results show the effectiveness and the robustness of the proposed control.

Human-Machine Interaction in Automated Vehicle: The ABV Project

Abstract The work described in this paper is part of a research program named ABV (Low Speed Automation) where the goal is the automation of road vehicle at low speed while ensuring the sharing of driving between the driver and the assistance. This paper focuses on the problem of human-machine cooperation in the specific context of vehicle driving, with a view of shared control between driver and automation, considering the acceptability of the system and the driver distractions and drowsiness.

Fuzzy Takagi-Sugeno LQ controller for a shared control of vehicle

In this paper we propose an assistance system that share the lateral control of a vehicle based in fuzzy Takagi-Sugeno (T-S) optimal control solving a Linear Quadratic Regulator (LQR) problem. The T-S controller is based in a T-S modelization of the vehicle that takes into account longitudinal velocity variation. A decision making algorithm that manage the authority between the driver and the controller is implemented.

The H 2 -optimal preview controller for a shared lateral control

This paper proposes a concept of human-centered lane keeping assistance system using the H2-optimal preview controller. In order to successfully share lateral control of the vehicle between human driver and controller, a dynamic pre-compensation control unit (forcing control) with reference model is added to the resulting controller which combines state feedback control and feedforward control. The driver steering torque is used as input of the reference model and is estimated using a robust Proportional Integral observer with unknown input. A more precise estimation of vehicle states and driver torque provides an accurate values for computing the optimal preview steering controller from the driver-vehicle system. Simulation results are presented here to demonstrate the effectiveness of the proposed structure to ensure a shared lateral control between human driver and assistance.