Control of induction machines on an electric vehicle with maximum torque and efficiency via the optimal slip factor

The indirect rotor field-oriented control with the optimal slip factor adjustment is exploited for the a 0.75kW induction machine (IM) control and it has been successfully implemented on an electric vehicle (EV) to provide satisfactory acceleration and efficiency. To achieve dynamic control of the flux and torque, precise synchronous angle estimation based on the rotor time constant is crucial for stator current decoupling, and thus control performance is highly dependent on the accuracy of parameter identification. Since traditional identification approaches are suffered from difficulty of implementation, a simple and accurate identification process by applying experiments to obtain the rotor time constant corresponding to the maximum acceleration is proposed in this paper. As a low-power IM implemented on EVs is usually overloaded during the acceleration period, the maximum torque per amperage (MTPA) control is thus desirable. A novel control approach by which the optimal slip factor is obtained through experiments for the maximum acceleration and efficient is proposed. Experimental results show that the proposed slip factor adjustment is more suitable to traction control of the EV because of its smooth operating performance.