Performance prediction of a wide-angle limited-motion rotary actuator

A doubly excited, doubly salient, concentrated winding type of rotary actuator structure is examined. Neglect of iron-member reluctances predicts a flat torque characteristic over the normal limited range of movement. In practice, a flat characteristic is not achieved. The reason for this is shown, by analysis and measurement, to be due to the significance of the iron reluctances both before and after the onset of magnetic saturation in the iron. A lumped magnetic circuit approach is used in conjunction with the rate-of-change-of-coenergy method to predict the torque characteristic under linear conditions. Beyond saturation, an iterative method is used to find the fluxes and hence the torque characteristic. Correlation between predicted and measured torque/angle curves is reasonably good.