Current estimation of switched reluctance motor based on piecewise model and iteration calculation

To reduce the number of current sensors in the switched reluctance motor (SRM) system, a current estimation method of the SRM is proposed. There is only one current sensor needed to measure the sum of phase currents. Current estimation model consists of two equations, one is equation of the sum of phase currents and another is mechanical equation of the SRM. Torque, a variable in the mechanical equation, has complex nonlinear relation with phase currents. This makes it difficult to solve the current estimation model online. To deal with the problem, a piecewise modeling method is used to establish a simple analytical torque model. Accuracy of the established torque model is better than that of traditional torque models after comparisons. A parameter of speed and acceleration is defined to compensate errors of the torque model and avoid identifications of moment of inertia and friction coefficient. On the basis of features of the current estimation model and phase currents of the SRM, Newton's method is chosen to solve the current estimation model and a practical stop condition of iteration is given. Realization process of online computation is illustrated. Finally, the proposed current estimation method is validated by experiments.