P. Pudlo

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.

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.

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.

Controller Design for Discrete-Time Descriptor Models: A Systematic LMI Approach

This paper provides a systematic way to generalize the controller design for discrete-time nonlinear descriptor models. The controller synthesis is done using a Takagi-Sugeno representation of the descriptor models and linear matrix inequalities. We propose approaches to exploit the discrete-time nature of the problem by using delayed Lyapunov functions, which allow delayed controller gains. In addition, the well-known Finslers Lemma is used to avoid the explicit substitution of the closed-loop dynamics. Examples are provided to show the effectiveness of the proposed results.

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.

Optimization approach for the simulation of car accessibility movement

The objective of this study is to develop a numeric simulator able to quantify the discomfort during the automobile accessibility movement. An experimental protocol and device were set up in order to record the automobile accessibility movement using the motion analysis system Vicon. A biomechanical human model composed of rigid bodies articulated was also proposed to simulate it. After reconstruction of the ingress/egress movement, a position error exists between the simulated and the experimental trajectories of the hands and feet. This error could imply collisions with the vehicle. In order to correct this error, an optimization procedure is suggested. This method modifies the experimental joint angles so that the simulated trajectories of the limb extremities fit to the experimental data.

A new method for simulating the car-entering movement

This article proposes a four-step method for simulating the car-entering movement. These four steps are: 1) build a corrected motion database, containing the motions in which the feet follow their measured trajectory, 2) identify and characterise the motion strategies of the car-entering movement, with each strategy being synthesised for a representative subject with known kinematic attributes, 3) model a segment of the predicted motion (e.g., the foot trajectories) using the motion strategies identified in Step 2, 4) compute the joint angles and simulate the car-entering movement of a new subject. The results of the motion simulation demonstrate a good correlation between the corrected and simulated joint angles, with the distance between these angles increasing with the distance between the simulated subject and the representative subject.

Virtual Prototyping of an Electric Power Steering Simulator

This paper presents a simulation tool for an electrical steering system whose aim is twofold: 1) to investigate the possibility of designing a minimum clearance mechatronic platform with sensorless control methods and 2) to evaluate assistance torque control feedback by considering technological specifications and human factor consideration. The choice has been made for a driving simulator having at least a real steering system with an electrical power steering (EPS) device and an adequate motor to reproduce the rack load force resulting from tire/road contact, as in a real driving situation. These components are gathered to form a virtual simulator platform, which serves as a basis for future realization. Our main contributions concern the vehicles front assembly kinematics modeling and the evaluation of the load rack force resulting from tire/road interaction. In addition, a real application of the most recent virtual sensor algorithms, arising from the sliding-mode observer theory for states and unknown input estimation, is described.

Rack force feedback for an electrical power steering simulator

This paper presents a force feedback control approach to enhance the realism and the fidelity of an electric power steering simulator. This simulator includes a real steering system with its electric assistance and a DC motor intended for the load rack force restitution. This motor allows to compensate for the lack of real tires and to simulate the tire/road contact as in a real driving situation. Besides, two different scenarios case study are introduced to prove the effectiveness of the various algorithms: virtual sensor based on sliding mode observer for the unknown input estimation and a sliding mode control for the force feedback.

Variations in expert rower coordination when rate increases on ergometer concept2

Continuous relative phase (CRP) represents at each time a quantitative valuation of coordination between two body segments (Burgess-Limerick et al. 1993) or two joints (Scholz 1993). In 1998, Pudlo et al. (1998), via an adapted using of CRP, has shown up technical weakness of two French local rowers. In 2004, Découfour and Pudlo (2004) have computed CRP between elbow and knee for 11 French national level rowers. Authors’ results are based on the best rower and show that is on recovery phase the coordination changes when stroke rate increases. Nevertheless, authors were not able to conclude objectively on the effect of stroke rate increase on the movement of expert rowers. The aim of this paper is to use these numerical data to conclude on coordination modifications when stroke rate increases in the light of results for the expert rowers population.