Vibration suppression of induction-motor-driven vehicle using wheel torque observer

The vibration phenomenon occurring under indirect field oriented control or vector control when induction motors drive an inertia load through a spring under overload conditions at high speed is described. The vibration mechanism is clarified, and a suppression method is proposed. The subject of this study is a hybrid vehicle consisting of a front engine-driven system and two rear motor-driven systems, which are designed to improve the driving stability. A stability analysis of the total system, including a vector control system and a mechanical system, reveals that the vector control system is essentially unstable under extreme overload and demagnetization conditions, even if the motor is perfectly controlled. Therefore, suppression of vibrations was attempted using an observer for estimating wheel torque and a regulator for state feedback from the outside of the vector control system. These methods perfectly suppressed the vibration, realizing a compact, light motor-driven system with rapid, stable performance.<>