New Electromagnetic Actuator for On-Orbit Inspection

Abstract

Induction couplers are a new technology for actively controlling the relative position and orientation between an inspection spacecraft and a target without mechanical contact. To the authors’ knowledge, no other contactless actuators exploit eddy-current effects to produce force and torque relative to a conductive target. Instead, other actuators rely on magnetic dipole interactions or cooperation from the target. A model for dynamic induction-coupler systems based on previous fast eddy-current force models is presented; design requirements through a case study of an inspection mission relevant to the International Space Station are outlined; and the feasibility of flight applications is established. This model has two restrictions; it assumes the gap between the inspector and the surface is already fixed, and it holds only near locally planar surfaces. Experiments show that induction couplers in normal operating conditions can generate forces of 5 mN with a specific force of $3.33\mathrm{mN}/\mathrm{W}$ for spacecraft actuation. Using these experimental values, a simulation shows that an inspection vehicle could traverse a flat surface the size of the Destiny International Space Station module in 2 h.