An optimized module-type hybrid stepper motor for spacecraft solar array drive

The paper presents the computer-aided design and development of an optimized module-type 200 steps hybrid stepper motor used as the drive motor of a solar array of the Indian National Satellite (INSAT) in geostationary orbit. The motor is of size 23 having coil redundancy and the step angle is 1.8°. It is designed with an optimized tooth-geometry and module-geometry, using finite element (FE) analysis technique which makes it very compact. The motor delivers a holding torque of 0.5 Nm against a varying supply voltage of 28 to 42 V DC and in an operating temperature range of -55 to +75°C, by taking advantage of the torque saturation phenomenon available in a hybrid stepper motor. Results of the 2-D and 3-D FE analysis on tooth-geometry and module-geometry respectively are also discussed. Apart from the design procedure, relevant details regarding fabrication and testing are also provided. The test results of the developed motor match fairly well with the design goal