Induction motor drive for electric vehicles without speed- and position sensors

A novel induction motor control is presented which works without mechanical sensors and hence yields cheaper and more robust drive solutions. However, the drive is able to produce full torque even at standstill without tachos and position encoders. This is achieved by using the new INFORM (indirect flux detection by online reactance measurement) flux model. The basic idea is to evaluate saturation effects in the motor in real-time, yielding speed-independent information about the flux axis. The INFORM algorithm is coupled with well-known EMF-based flux models, providing optimal flux information for field oriented control over the full operating range. In the paper, the algorithms for flux and torque control in the base speed and field weakening range are given. At very high speed, the pull-out torque of the motor is taken into account by a special control strategy. The whole drive control including fast current control is realised by software using a digital signal processor, generating directly inverter firing commands. Measurements and practical experiences verify the applicability of the proposed method to electrical traction drives