Design, Manufacturing, and Ground Testing of a Control-Moment Gyro for Agile Microsatellites

A recently emerged driving requirement for microsatellites is a precise and fast attitude maneuvering capability. Agility enhances the operational efficiency of missions requiring a high level of retargeting ability, such as space station and satellite on-orbit servicing, formation flying, Earth monitoring, and space-based space debris observation and tracking. Three-axis stabilized microsatellites are mainly equipped with momentum wheels, barely meeting agility requirements. In this paper, the design and manufacturing of a cluster of four single-gimbal variable-speed control-moment gyros (SGCMGs), suitable for attitude control with high-agility capability of a 10–30 kg class microsatellite, is presented. The flywheel design is based on a brushless motor out-runner configuration, in which the motor magnets, embedded in the rotor, provide for the wheel inertia. This configuration has the advantage of providing a high inertia while minimizing cogging torque at low speed. The elimination of the wheel dummy mass provides a significant improvement in the system mass efficiency. In addition, this configuration allows using commercial off-the-shelf parts, eliminating the wheel-balancing procedure with evident jitter limitation and economic and development time benefits. A relevant feature is the electronics architecture based on a field-programmable gate array (FPGA) integrated circuit, chosen to improve power efficiency and provide a high level of reliability for the system. This can be assured by proper time and space redundancy for each low-level logic block of the design. The system performance in terms of provided torque and power consumption has been experimentally measured by using a ground-testing prototype mounted on a test bed, and the results are reported. The results confirm the effectiveness of the proposed actuator as an efficient solution for the attitude control of microsatellites, in terms of mass, volume, and power constraints.