Simplified Estimation of Stator Flux of Induction Motor for Direct Torque Control using SPLINE

Direct torque control (DTC) allows having a speed and torque control with good dynamic response. However, DTC uses a square root function to get the motor stator flux. This function is difficult to implement in microcontrollers or FPGAs. Hence, this paper proposes the use of SPLINE interpolation to implement the square root function with low computational cost, in order to get the magnitude of the stator flux. In SPLINE, the function is divided in intervals, and each interval is approximated using polynomial function. Besides, different discretization techniques to implement the integrator used in flux estimation will be tested in order to show their effects in flux and torque estimation. Simulations show that the proposed approach gives good estimations of torque and flux.