Driver-Assistance Lateral Motion Control for In-Wheel-Motor-Driven Electric Ground Vehicles Subject to Small Torque Variation

Electric ground vehicles driven by in-wheel-motors (IWMs) have control flexibility of easily generating external yaw moment, which is effective for vehicle lateral motion control without interfering driver steering maneuvers. However, IWMs small torque variationmay introduce undesired yaw moment that causes vehicle trajectory drifts and affects lateralmotion. This paper proposes a driver-assistance lateralmotion control method specifically considering IWMs small torque variation. In driving conditions where a driver steering maneuver is not expected, the controller compensates for small torque variation to reduce the driver workload. However, for driving conditions that require steering input from the driver, the controller assists the driver to maintain the path when there is a tendency of lane departure. A gain-scheduling robust controller is designed to deal with a time-varying parameter and system uncertainty. The weighted H-infinity performance and eigenvalue placement technique are employed to derive a suitable feedback gain. CarSim simulations are conducted to illustrate the control effectiveness for compensating small torque variation and prevent lane departure. Furthermore, human-in-the-loop tests are conducted to verify the effectiveness of the designed controller for human drivers. Both simulation results and human driving simulator tests show that the proposed controller can assist drivers with vehicle lateral motion control under different driving conditions subject to IWMs small torque variation.