Development and Control of Four-Wheel Independent Driving and Modular Steering Electric Vehicles for Improved Maneuverability Limits 2019-01-0459
Electric vehicles are capable of more flexible drivetrain configurations, such that driving dynamics of each wheel could be controlled independently to increase its stability and maneuverability bounds. We hereby propose a configuration consisting of four wheel independent driving and front and rear axle modular steering. The vehicle implements drive-by-wire technology, which means the controlling program running on vehicle control computer will have direct control authority of the vehicle under normal driving conditions, based on inputs of higher level systems such as human drivers and autonomous driving programs. Both the torque allocation on four wheels and the steering allocation on axles are completely independent on the mechanical hardware level, thus the vehicle is able to harness adverse contact conditions with confidence. A self-adaptive controlling method for torque allocation and steering control is proposed and inspected in the paper, with digital model of a modified SUV simulated for validation, and the vehicle responses with and without such controller are compared to elaborate its strengths. Such controlling method has more safety margin under close-to-limits driving conditions with presence of tire slippage. The controlling method along with drive-by-wire features also enhance driving safety by correcting excessive inputs by human drivers. Additionally, a comprehensive index reflecting the stability and maneuverability of the vehicle is also introduced and based on which a model-based controller is designed and compared.