INTRODUCTION Increasing environmental and safety concerns, along with rising gasoline prices, are driving a worldwide shift in the automotive industry towards the development of green intelligent transportation systems. Today, electric vehicles (EVs) are seen as the leading contender to displace existing fleets of gasoline-powered cars. EVs allow for the possibility of zero greenhouse-gas and air-pollutant emissions as well as very little noise pollution. Another important advantage of electric vehicles over the conventional internal combustion engines (ICEs) is the very high energy efficiency and relatively low cost of the electric motor. The main concern currently being faced is the low energy and power densities of batteries compared to the liquid fuels. EVs use electric motors to propel the car and use batteries to store electricity. Four in-wheel motors, two independentmotors for the front and rear axles, and a single motor running all four wheels are possible motor configurations for shaping the propel system. The rapid dynamics of the motors provide the opportunity to accurately control the wheel speeds, thereby achieving better handling performance. In addition, this property allows stability and safety controllers such as active cruise control, collision avoidance, and emergency brake assist to apply their commands much faster, resulting in better incident prevention. Motors in EVs also help in stabilizing vehicle motion by generating counter- directional torques between the left and right wheels using control strategies such active software differentials, active brake bias, and brake steer. While applying these controllers on ICEVs requires sophisticated hardware components that add complexity to the vehicle structure, the application of such controllers in EVs can be carried out using only software modification. 2013-01-0674 Published 04/08/2013 Copyright © 2013 SAE International doi:10.4271/2013-01-0674 saecomveh.saejournals.org Optimal Torque Control for an Electric-Drive Vehicle with In- Wheel Motors: Implementation and Experiments Abtin Athari Univ. of Waterloo Saber Fallah Univ. of Surrey Bin Li and Amir Khajepour Univ. of Waterloo Shih-Ken Chen and Baktiar Litkouhi General Motors Company ABSTRACT This paper presents the implementation of an off-line optimized torque vectoring controller on an electric-drive vehicle with four in-wheel motors for driver assistance and handling performance enhancement. The controller takes vehicle longitudinal, lateral, and yaw acceleration signals as feedback using the concept of state-derivative feedback control. The objective of the controller is to optimally control the vehicle motion according to the driver commands. Reference signals are first calculated using a driver command interpreter to accurately interpret what the driver intends for the vehicle motion. The controller then adjusts the braking/throttle outputs based on discrepancy between the vehicle response and the interpreter command. A test vehicle equipped with four in-wheel electric motors, vehicle sensors, communication buses, and dSPACE rapid prototyping hardware is instrumented and the control performance is verified through vehicle handling tests under different driving conditions. CITATION: Athari, A., Fallah, S., Li, B., Khajepour, A. et al., "Optimal Torque Control for an Electric-Drive Vehicle with In-Wheel Motors: Implementation and Experiments," SAE Int. J. Commer. Veh. 6(1):2013, doi:10.4271/2013-01-0674. ____________________________________ 82Downloaded from SAE International by Univ of California, Tuesday, July 31, 2018Substantial research has been carried out on the development of electric vehicles and related control strategies during the last two decades. For example, Ref. [ 1] provides an overview of electric-vehicle technology while Refs. [ 2] and [ 3] report on the application of different stability controllers in electric vehicles. Moreover, a combination of direct yaw-moment and act