Measurement and on-line estimation approaches to parameter variation in vector controllers

A compromise exists in a drive based around a vector-controlled induction motor between the need to obtain reliable control information (for both feedback and parameter identification) and the need to maintain the mechanical ruggedness and cost advantage of the motor. Voltage and current sensors within the power converter are acceptable whereas sensors fixed to the motor are to be avoided. Rotor currents and voltages will be unavailable for cage rotors. Two approaches to this problem are considered. The first is to obtain the maximum information from the sensors available by injecting known, small-amplitude voltages and processing the resulting currents. The second is to use on-line parameter estimation with particular attention to the rotor resistance parameter needed to calculate the magnitude and position of the rotor flux