Actuators

This chapter is dedicated to briefly present all the major actuator typologies for spacecraft guidance, navigation, and control (GNC) applications, to discuss their operating principles, to highlight their peculiarities, strengths, and weaknesses, to categorize the available components according to their performances, and to discuss the most relevant modeling techniques and rules. The actuator modeling techniques are presented, discussing the main implementation principles of the most common numerical models to include the actuators behavior in the GNC design, analysis, verification, and validation phases. The principles of errors modeling and the most common actuator faults are also introduced. Dedicated sections on thrusters, reaction wheels, control moment gyros, and magnetorquers are present, discussing their primary operating principles, outlining the fundamental characteristics and comparing the available performance.