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

Abstract

We introduce a decentralized attitude control strategy that can dramatically reduce the usage of propellant, by taking full advantage of the physical coupling of the tether. Motivated by a controllability analysis, indicating that both array resizing and spin-up are fully controllable by the reaction wheels and the tether motor, we report the first propellant-free underactuated control results for tethered formation flying spacecraft. This paper also describes the hardware development and experimental validation of the proposed method using the Synchronized Position Hold, Engage, and Reorient Experimental Satellites test bed. In particular, a new relative sensing mechanism that uses sixdegree-of-freedom force-torque sensors and rate gyroscopes is introduced and validated in the closed-loop control experiments.

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

“…The proposed underactuated method is most effective for a compact configuration with short baselines. 1 This article also fulfills the potential of the proposed strategy by providing a new momentum dumping method without the need for torquegenerating thrusters; the compound pendulum mode and array spin rate are stabilized using only the linear thruster and translational actuator on the tether during the operation of momentum dumping. Control of underactuated mechanical systems is an active area of research.…”

“…We exploit partial feedback linearization, feedback linearization via momentum decoupling, and backstepping, and compare the performance of nonlinear control laws with that of gain-scheduling linear control. 1 We shall consider only the case of the fixed tether length, focusing on the spin-up attitude control problem on the assumption that the tether length is controllable separately. This paper investigates the feasibility of controlling the array spin rate and relative attitude without the use of thrusters.…”

“…This paper investigates the feasibility of controlling the array spin rate and relative attitude without the use of thrusters. As stated in the first paper of this series, 1 we can dramatically increase the life span of the mission by using reaction wheels instead of thrusters for controlling the array spin-rate. Also, the optics will not risk contamination by exhaust from the 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.…”

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].…”