Axial Flux Topology Based Control Moment Gyroscope for Integrated Speed and Tilt Control

Abstract

This paper presents a control moment gyroscope (CMG) for small satellites, driven and controlled based on axial flux motor principle. The presented structure is coreless with Halbach array rotor and a stator to control the rotational speed/torque and effective gimbal rate/ angle. This topology allows a relatively simple mechanical structure with an equivalent dual gimbal control for limited angle. There are two sets of windings for torque generation along three orthogonal axes, one is 8 pole and other is 6 pole. The winding structure is novel in the sense of accommodating different number of poles <formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex>$ (&gt;4)$</tex></formula> using the same stator slots. Two 3 phase inverters are used to accurately control the torques by energising two sets of windings. Analytical formulation is provided to understand various torque generation mechanisms and 3D FEM simulations are performed to verify the operation and to get better quantitative torque generation capabilities of the CMG along different axes. Finally, a quick experiment prototype is developed to verify the operation with open loop speed control and closed loop tilt position control more qualitatively with off the shelf available components. Independent control of torque in 3 axes was achieved experimentally and the results are explained.