Propellant-Free Control of Tethered Formation Flight, Part 2: Nonlinear Underactuated Control

Abstract

This is the second in a series of papers that exploit the physical coupling of tethered spacecraft to derive a propellant-free spin-up and attitude control strategy. We take a nonlinear control approach to underactuated tethered formation flying spacecraft, whose lack of full state feedback linearizability, along with their complex nonholonomic behavior, characterizes the difficult nonlinear control problem. We introduce several nonlinear control laws that are more efficient in tracking time-varying trajectories than linear control. We also extend our decentralized control approach to underactuated tethered systems, thereby eliminating the need for any inter-satellite communication. To our knowledge, this work reports the first nonlinear control results for underactuated tethered formation flying spacecraft. This article further illustrates the potential of the proposed strategy by providing a new momentum dumping method that does not use torque-generating thrusters.

On Development of 100-Gram-Class Spacecraft for Swarm Applications

“…A capability of synchronized rotation [30], [29] can integrate attitude control with control of the orbital dynamics on concentric PROs. Also, due to the modest actuation capability of a femtosat, control of coupled underactuated spacecraft [31], [32], [33] can be exploited.…”

Propellant-Free Control of Tethered Formation Flight, Part 1: Linear Control and Experimentation

“…V, for simplicity, we emphasize that the linearization-based control would only provide a local stability result, as opposed to global convergence of the nonlinear control strategies introduced in the second paper [29] of this series. Again, the controllability analysis in Section II states that the spinning underactuated tethered system is fully controllable around the relative equilibrium manifold ( _ !, 0, and _ 0).…”

Dynamics of variable-length tethers with application to tethered satellite deployment

“…Steiner et al [7] and Williams [8,9] used a spring model to study the deployment and retrieval processes of satellites. In addition, Kim and Hall [10,11], Kumar and Yasaka [12], Chung and Miller [13], and Chung et al [14] studied the dynamics and control of tethered satellite systems with self-spinning configurations. Some other works on the dynamics of tethered satellite systems can be found in the comprehensive review articles by Kumar [15] and Cartmell and McKenzie [1].…”