A New Monitoring Strategy and Automatic Speed Reduction for PI Slip Control in Autonomous Electric Vehicles with In-Wheel Motors: Experimental results

A new monitoring strategy for PI slip control in an autonomous electric vehicle with two independent in-wheel motors is presented. The distributed motors are employed to regulate the longitudinal speed and yaw-rate. Based on such regulation errors, each motor is given a suitable tire-slip/angular-speed set point. To drive independently each motor to its reference speed, the individual control loops lead to the online steady-state estimation of each actual wheel load-torque which is compensated. Simultaneous information on each tire torque-slip pair allow for a steady-state monitoring of tire operations on force-slip characteristics. An automatic longitudinal speed reduction action is performed to prevent tire forces saturation. An experimental setup is designed on a 1:10 scale autonomous vehicle equipped with 2-rear in-wheel DC brushless motors, aiming to show the reliability of such tire operation monitoring from rear wheel speed real measurements, conditioned by a Kalman filter. A path-following algorithm is developed for the autonomous guidance. The experiment illustrates the automatic speed reduction when the vehicle encounters an adherence jump.