Development of multi-wheel drivetrain control system for future electric combat vehicle

Abstract

In modern times, electric vehicle and autonomous driving control technology have been rapidly evolving for use in civilian passenger vehicles. They bring forth many benefits in improved mobility, cost savings and life-preserving benefits – all of which can be extended to military vehicles. In this thesis, a comprehensive drivetrain control system for a future fully-electric 8x8 multi-wheeled combat vehicle with autonomous navigation functionality is developed. The proposed combat vehicle is equipped with eight independently-actuated wheels using individual in-wheel driving motors and linear actuators for steering. The control system is intended to harness the flexibility of the electric drivetrain to enable different driving configurations over a range of conditions to maximize mobility, deployability and survivability. The system comprises of autonomous navigation via path preview sensors and a driver model, torque vectoring and skid steering through a single LQR-based active yaw controller, and feedforward zero side-slip rear-wheel steering control. Separate feedforward controllers were also developed for skid steering and rear-wheel steering to mimic existing mechanical implementations for comparison. Vehicle performance evaluation using the control system was divided into low-speed autonomous operation and high-speed manned operation. Under low-speed autonomous operation, the control system achieved stable skid steering up to 40 km/h with significantly reduced driver input effort compared to a conventional combat vehicle. In high-speed manned operation, the LQR torque vectoring controller performed well in stabilizing the vehicle motion over reduced friction conditions. Feedforward zero-side slip control steering the fourth axle improved cornering precision and yaw response below 50 km/h, and improved lateral motion stability steering all wheels up to a recommended operating speed of 80 km/h.