Small-Satellite Attitude Control Using Sinusoidal Actuator Motion: Experiments on the International Space Station

In this work, we design, build, and test two 1.25U CubeSats. These small satellites were deployed on the International Space Station to perform attitude control experiments in microgravity. These CubeSats use an oscillating-mass actuation system for attitude control as opposed to traditional flywheels. Each CubeSat uses 3 pairs of servomotors to oscillate masses about 3 orthogonal axes. The servomotors have strict rotational stroke limits. Thus, they cannot spin continually. To oscillate each pair of masses, the angle of each servomotor is commanded using signals that are continuous and piecewise sinusoidal with amplitudes that do not violate the servomotor stroke constraints. We present the open-loop and closed-loop attitude control results from experiments in microgravity onboard the International Space Station. The open-loop results demonstrate that this oscillating-mass actuation system can be used for attitude manipulation in microgravity. The closed-loop results demonstrate successful setpoint tracking