Jean-Charles Cadiou

H/sub /spl infin//-force control of a hydraulic servo-actuator with environmental uncertainties

This paper deals with the application of the H/sub /spl infin//-approach to robustly control the force exerted by a hydraulic servo-actuator on its environment. In order to evaluate the system stability and the performance, large environmental uncertainties and disturbances are introduced by use of a particular workpiece. The major nonlinearities of the system are pointed out through experimental tests and parameters estimation results. Then, a linear time-invariant model for control is defined with respect to both system dynamics and application requirements. Experimental and simulation control results are presented and the achievement of a stability/performance trade-off is discussed.

ADAPTIVE SLIDING MODE CONTROL OF VEHICLE TRACTION

Abstract In this paper we present a sliding mode based vehicle control strategy, which includes anti-lock braking and anti-spin acceleration. This strategy uses the slip velocity as controlled variable instead of wheel slip. The sliding mode control is integrated with an adaptation process for the unknown and varying adhesion coefficient of the tire/road interface. The proposed control method is verified through one-wheel simulation model with a “Magic formula” tire model. Simulations results show the effectiveness of this controller scheme.

Friction force estimation and adaptive control for tire-road contact

It is important to estimate the friction force in tire-road contact in order to improve the control performance of a vehicle in critical motions. In this paper, an estimation of a friction force is proposed by using a pressure distribution in 3D. Then, an adaptive control for friction compensation is presented to validate the proposed model.

Transversal tyre road characteristic estimation

Abstract This paper presents two methods for lateral tyre/road characteristic identification. The proposed methods are estimation based on simulation (EBS) and estimation based on observer (EBO). The first method is based on the development of a vehicle dynamics simulation whereas the second is based on a vehicle dynamics observation. In the EBS method, a vehicle simulator is used to replay certain road tests assuming that only the side force characteristic is unknown. The EBO method uses an observer to reconstruct vehicle dynamics and thus estimate tyre forces. For both methods a tyre characteristic described by a reduced Bakker—Pacjeka tyre model is used to characterize the tyre / road interface. The principle of the proposed procedures consists in the use of an iterative process based on the minimization of quadratic error in order to find the optimal tyre characteristic. To evaluate the proposed procedures, some experimental results were performed. The results are obtained off line on the basis of a set of test data. The originality of these approaches is to have a simple method and a less expensive technique for the characterization of the tyre/road interface.

Compensation of stick-slip effect in an electrical actuator

In some mechanical systems which make very small motions like industrial wagons or constructor robots, the dispositive of their control usually presents some imperfections, a succession of jumps and stops, when the static friction force is larger than the dynamic friction force. This effect is called the stick-slip phenomenon. In this paper, we develop a nonlinear observer in order to estimate the friction force of the contact during the motion, and to compensate the effects which cause the stick-slip phenomenon.

Vehicle/road interaction and tyre lateral performance identification

We propose a procedure to identify a basic Pacejka tyre model (H. Pacejka, 1996) based on the use of the vehicle dynamics simulation and measurements. The model uses the seven main coefficients of the lateral Pacejka model. The principle of the procedure consists of an optimization with a trajectory criterion on the coefficient of the lateral tyre model. The trajectory reference is the real trajectory of an instrumented experimental vehicle. The simulator uses the same conditions of the test and only transversal performances are considered unknown. The method allows a good reconstruction of the lateral tyre model for slip angle in the range of 0 to 2 degrees.

Four-wheeled vehicle modelling toward on board dynamics observer

This paper applies the step by step algorithm based on sliding mode observer to estimate tire forces. To define an observer, a model of a four-wheeled vehicle has been developed. The model is a rigid-body model with 10 degrees-of-freedom, including individual wheel speeds. Then a vehicle dynamic state is defined with the tire forces treated as vehicle variables with unknown dynamics. A field of test results is used to demonstrate the validity of this technique.

Longitudinal Tire Force Estimation Based on Sliding Mode Observer

Abstract This paper presents an estimation method for vehicle longitudinal dynamics, particularly the tractive/braking force. The estimation can be used to detect a critical driving situation to improve security. It can be used also in several vehicle control systems. The main characteristics of the vehicle longitudinal dynamics were taken into account in the model used to design an observer and computer simulations. The state variables are the angular wheel velocity, vehicle velocity and the longitudinal tire force. The proposed differential equation of the tractive/braking force is derived using the concept of relaxation length. The observer designed is based on the sliding mode approach using only the angular wheel velocity measurement. The proposed method of estimation is verified through a one-wheel simulation model with a “Magic formula” tire model. Simulations results show an excellent reconstruction of the tire force.