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Adaptive Robot Detumbling of a Non-Rigid Satellite

Longsen Gao, Claus Danielson, Rafael Fierro

TL;DR

The paper tackles on-orbit detumbling of non-rigid client satellites with uncertain post-capture dynamics. It models the tumbling satellite as a two-link serial chain with unknown stiffness, damping, mass, and inertia, and uses two space tugs to apply wrenches to each link in a decentralized adaptive controller. A regressor-based adaptive control framework with Lyapunov guarantees drives the composite velocity error $\mathbf{s}$ to zero while updating parameter estimates $\boldsymbol{\hat{\varphi}}$ and grasping misalignment $\boldsymbol{\hat{d}}$, and a Lyapunov function $V(t)$ ensures $\dot{V}(t) \le 0$. Simulation in MuJoCo demonstrates convergence of angular and linear velocities to zero, reduction of contact wrenches to zero, and convergence of parameter estimates, validating the approach for robust on-orbit servicing of non-rigid satellites.

Abstract

The challenge of satellite stabilization, particularly those with uncertain flexible dynamics, has become a pressing concern in control and robotics. These uncertainties, especially the dynamics of a third-party client satellite, significantly complicate the stabilization task. This paper introduces a novel adaptive detumbling method to handle non-rigid satellites with unknown motion dynamics (translation and rotation). The distinctive feature of our approach is that we model the non-rigid tumbling satellite as a two-link serial chain with unknown stiffness and damping in contrast to previous detumbling research works which consider the satellite a rigid body. We develop a novel adaptive robotics approach to detumble the satellite by using two space tugs as servicer despite the uncertain dynamics in the post-capture case. Notably, the stiffness properties and other physical parameters, including the mass and inertia of the two links, remain unknown to the servicer. Our proposed method addresses the challenges in detumbling tasks and paves the way for advanced manipulation of non-rigid satellites with uncertain dynamics.

Adaptive Robot Detumbling of a Non-Rigid Satellite

TL;DR

The paper tackles on-orbit detumbling of non-rigid client satellites with uncertain post-capture dynamics. It models the tumbling satellite as a two-link serial chain with unknown stiffness, damping, mass, and inertia, and uses two space tugs to apply wrenches to each link in a decentralized adaptive controller. A regressor-based adaptive control framework with Lyapunov guarantees drives the composite velocity error to zero while updating parameter estimates and grasping misalignment , and a Lyapunov function ensures . Simulation in MuJoCo demonstrates convergence of angular and linear velocities to zero, reduction of contact wrenches to zero, and convergence of parameter estimates, validating the approach for robust on-orbit servicing of non-rigid satellites.

Abstract

The challenge of satellite stabilization, particularly those with uncertain flexible dynamics, has become a pressing concern in control and robotics. These uncertainties, especially the dynamics of a third-party client satellite, significantly complicate the stabilization task. This paper introduces a novel adaptive detumbling method to handle non-rigid satellites with unknown motion dynamics (translation and rotation). The distinctive feature of our approach is that we model the non-rigid tumbling satellite as a two-link serial chain with unknown stiffness and damping in contrast to previous detumbling research works which consider the satellite a rigid body. We develop a novel adaptive robotics approach to detumble the satellite by using two space tugs as servicer despite the uncertain dynamics in the post-capture case. Notably, the stiffness properties and other physical parameters, including the mass and inertia of the two links, remain unknown to the servicer. Our proposed method addresses the challenges in detumbling tasks and paves the way for advanced manipulation of non-rigid satellites with uncertain dynamics.
Paper Structure (13 sections, 1 theorem, 37 equations, 11 figures, 1 table)

This paper contains 13 sections, 1 theorem, 37 equations, 11 figures, 1 table.

Table of Contents

  1. Introduction
  2. On-Orbit Detumbling Problem
  3. Agents and Reference Frames
  4. Dynamics of Link-1
  5. Dynamics of Link-2
  6. Grasping Dynamics of Manipulator System
  7. Satellite Stabilization Problem
  8. Decentralized Adaptive Stabilization
  9. Simulation Results
  10. Conclusions
  11. Appendix
  12. Detail of Regressor Matrix $\boldsymbol{Y}_{\varphi}^\nu$
  13. Proof of Matrix $\boldsymbol{M}_\nu$ Positive Definiteness

Key Result

Lemma 2.1

$\boldsymbol{M}_\nu$ as given in (eq:all_wrench) is symmetric and positive definite.

Figures (11)

  • Figure 1: Two space tugs collaboratively detumble a non-rigid satellite together in Space environment.
  • Figure 2: Two free-flying space tugs de-tumble a client satellite. One space tug holds the base of the satellite; another space tug the solar panel, which is connected to the base by a hybrid stiffness system.
  • Figure 3: Simplified diagram of the detumbling process. The base and a fully functional solar panel connected to the base by a fixed joint together as a combined "module" as Link-1(orange ellipse); another nonfunctional solar panel as Link-2(blue ellipse). The hybrid stiffness system can be treated as a specific revolute joint(yellow rectangle).
  • Figure 4: Two Space tugs attaching on different locations of a satellite to apply wrenches on the Link-1 (yellow part) and Link-2 (blue part) in zero-gravity simulation environment. We import the hybrid hinge system from real and integrate the friction, spring and damper properties on the rotor. Supplemental video: http://tiny.cc/stabglsfinal
  • Figure 5: Force(a) and Torque(b) applied by space tug-1.
  • ...and 6 more figures

Theorems & Definitions (3)

  • proof
  • Lemma 2.1
  • proof