A New Trajectory Tracking Framework for Autonomous Vehicles with In-wheel Motors

The coordinated control of autonomous electric vehicles with in-wheel motors is classified as over-actuated control problems requiring a precise control allocation strategy. This paper addresses the trajectory tracking problem of autonomous electric vehicles equipped with four independent in-wheel motors and active front steering. Unlike other available methods presenting optimization formulation to handle the redundancy, in this paper, the constraints have been applied directly using the kinematic relations of each wheel. Four separate sliding mode controllers are designed in such a way that they ensure the convergence of tracking errors. The lateral controller is also designed to determine the front steering angles to eliminate lateral tracking errors. To appraise the performance of the proposed control strategy, a co-simulation is carried out in MATLAB/Simulink and Carsim software. The results show that the proposed control strategy has enabled the vehicle to follow the reference path. The tracking errors of longitudinal and lateral positions and the velocity are limited to [-2.6, 4] cm, [-4.5, 3.3] cm, and [-0.2, 0.4] m/s, respectively and the error signals for the heading angle and yaw rate lie in the bounds of ±0.3° and ±2.7°/s, respectively. Furthermore, the proposed control system shows promising results in the presence of uncertainties including the mass and moment of inertia, friction coefficient, and the wind disturbances.