Disturbance invariant speed controlled servo drive with Tesla's induction motor

From the late nineteenth century to the present, Tesla's motor has been advantageously used in many applications where the torque capabilities, acceleration characteristics, power density, and high degree of reliability are indispensable. Nevertheless, in the design of high performance electrical drives, the choice of DC motor was preferable, since its torque and flux are controlled independently through two separate terminals. To match this suitable feature of a DC motor in servo applications, the concept of vector control was developed to enable decoupled control of the flux and torque of the induction motor; thus, Tesla's motor may enable control characteristics of a DC motor. In this paper, it is shown how Tesla's induction motor can be applied in the design of digitally controlled speed servo drive in the presence of immeasurable arbitrary torque disturbances. For rejection of effects of torque disturbance on the steady-state value of motor speed the principle of absorption is applied in the design of a disturbance estimator within the control portion of the system controlling structure.