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Nonlinear Control and Synchronization of Multiple Lagrangian Systems with Application to Tethered Formation Flight Spacecraft

by cfynanon 9 June 2015in Technology Development & Demonstration No comment

This dissertation focuses on the synchronization of multiple dynamical systems using contraction theory, with applications to cooperative control of multi-agent systems and synchronization of interconnected dynamics such as tethered formation flight. Inspired by stable combinations of biological systems, contraction nonlinear stability theory provides a systematic method to reduce arbitrarily complex systems into simpler elements. One application of oscillation synchronization is a fully decentralized nonlinear control law, which eliminates the need for any inter-satellite communications. We use contraction theory to prove that a nonlinear control law stabilizing a single-tethered spacecraft can also stabilize arbitrarily large circular arrays of tethered spacecraft, as well as a threespacecraft inline configuration. The convergence result is global and exponential due to the nature of contraction analysis. The proposed decentralized control strategy is further extended to robust adaptive control in order to account for model uncertainties. Numerical simulations and experimental results validate the exponential stability of the tethered formation arrays by implementing a tracking control law derived from the reduced dynamics. This thesis also presents a new synchronization framework that can be directly applied to cooperative control of autonomous aerospace vehicles and oscillation synchronization in robotic manipulation and locomotion. We construct a dynamical network of multiple Lagrangian systems by adding diffusive couplings to otherwise freely moving or flying vehicles. The proposed tracking control law synchronizes an arbitrary number of robots into a common trajectory with global exponential convergence. The proposed control law is much simpler than earlier work in terms of both the computational load and the required signals. Furthermore, in contrast with earlier work which used simple double integrator models, the proposed method permits highly nonlinear systems and is further extended to adaptive synchronization, partial-joint coupling, and concurrent synchronization. Another contribution of the dissertation is a novel nonlinear control approach for underactuated tethered formation flight spacecraft. This is motivated by a controllability analysis that indicates that both array resizing and spin-up are fully controllable by the reaction wheels and the tether motor. This work reports the first propellant-free underactuated control results for tethered formation flight. We also fulfill the potential of the proposed strategy by providing a new momentum dumping method. This dissertation work has evolved based on the research philosophy of balancing theoretical work with practicality, aiming at physically intuitive algorithms that can be directly implemented in real systems. In order to validate the effectiveness of the decentralized control and estimation framework, a new suite of hardware has been designed and added to the SPHERES (Synchronize Position Hold Engage and Reorient Experimental Satellite) testbed. Such recent improvements described in this dissertation include a new tether reel mechanism, a force-torque sensor and an air-bearing carriage with a reaction wheel. This thesis also introduces a novel relative attitude estimator, in which a series of Kalman filters incorporate the gyro, force-torque sensor and ultrasound ranging measurements. The closed-loop control experiments can be viewed at http://ssl.mit.edu/spheres/videos.html.

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

by cfynanon 9 June 2015in Technology Development & Demonstration No comment

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 six-degree-of-freedom force-torque sensors and rate gyroscopes is introduced and validated in the closed-loop control experiments.

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On-Orbit Measurements of the ISS Atmosphere by the Vehicle Cabin Atmosphere Monitor

by cfynanon 9 June 2015in Technology Development & Demonstration No comment

We report on trace gas and major atmospheric constituents results obtained by the Vehicle Cabin Atmosphere Monitor (VCAM) during operations aboard the International Space Station (ISS). VCAM is an autonomous environmental monitor based on a miniature gas chromatograph/mass spectrometer. It was flown to the ISS on shuttle mission STS-131 and commenced operations on 6/10/10. VCAM provides measurements of ppb-to-ppm levels of volatile trace-gas constituents, and of the atmospheric major constituents (nitrogen, oxygen, argon, and carbon dioxide) in a space vehicle or station. It is designed to operate autonomously and maintenance-free, approximately once per day, with a self-contained gas supply sufficient for a one-year lifetime. VCAM is designed to detect and identify 90% of the target compounds at their 180-day Spacecraft Maximum Allowable Concentration levels.

Related URLs:
http://dx.doi.org/10.2514/6.2011-5214

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SPHERES Tethered Formation Flight Testbed: Application to NASA's SPECS Mission

by cfynanon 9 June 2015in Technology Development & Demonstration No comment

This paper elaborates on theory and experiment of the formation flight control for the future space-borne tethered interferometers. The nonlinear equations of multi-vehicle tethered spacecraft system are derived by Lagrange equations and decoupling method. The preliminary analysis predicts unstable dynamics depending on the direction of the tether motor. The controllability analysis indicates that both array resizing and spin-up are fully controllable only by the reaction wheels and the tether motor, thereby eliminating the need for thrusters. Linear and nonlinear decentralized control techniques have been implemented into the tethered SPHERES testbed, and tested at the NASA MSFC's flat floor facility using two and three SPHERES configurations. The nonlinear control using feedback linearization technique performed successfully in both two SPHERES in-line configuration and three triangular configuration while varying the tether length. The relative metrology system, using the ultra sound metrology system and the inertial sensors as well as the decentralized nonlinear estimator, is developed to provide necessary state information.

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Zero Propellant Maneuver Flight Results for 180deg ISS Rotation

by cfynanon 9 June 2015in Technology Development & Demonstration No comment

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

by cfynanon 9 June 2015in Technology Development & Demonstration No comment

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 intersatellite 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.

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Perspectives of Bar Telemetric Means Utilization for Leakage Detection and Monitoring of the ISS Construction Conditions

by cfynanon 9 June 2015in Technology Development & Demonstration No comment

The set of telemetric means for prompt leakage detection on the ISS modules in the orbit was developed in course of preparation of BAR space experiment on the Russian Segment of the ISS. The set of instruments to be accommodated in pressurized volume is aimed at leakage points detection as well as solving some fundamental problem such as: - early detection and preventing leakage from habitable modules of the ISS resulting from biological degradation of construction elements; - analysis of ultrasonic atmospheric oscillation intensity in the modules’ pressurized volume as a source of adverse crew effect. That pressurized equipment set for leakage detection in the ISS modules can be used together with SSRMS manipulator that gives the following opportunities: - to detect promptly air leakage from the ISS modules; - to monitor results of unknown factors and objects impact on the modules for contingency prediction; - to monitor the ISS outer surface elements conditions. The most important task is to support the manipulator control and image obtaining by the operators of the Mission Control Center.

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Space radiation damage to HDTV camera CCDs onboard the international space station

by cfynanon 9 June 2015in Technology Development & Demonstration No comment

The image quality of high-definition television (HDTV) cameras and camcorders for space activity is degraded by the presence of permanent bright pixels (so-called “white defects”) due to space radiation. We studied the space radiation damage to HDTV charge-coupled devices (CCDs; 2 × 106 pixels per chip) loaded in the Russian service module (SM) of the International Space Station (ISS) for 71 days, 256 days and 446 days. We used the “Passive Dosimeter for Lifescience Experiments in Space” (PADLES), which consists of CR-39 plastic nuclear track detectors (PNTDs) and thermoluminescent dosimeters, to measure space radiation doses received by the HDTV CCDs in the SM during loading periods. The average production rates of white defects for output voltage greater than 0.5 mV were 2.366 ± 0.055 pixels/day in Si and 5.213 ± 0.071 pixels/mGy in Si. We also investigated the correlation between the position of the white defects and tracks of high-energy particles with LET∞,Si of approximately 300 keV/μm or more using stacks of CR-39 PNTDs and the HDTV CCD chips. We found that approximately 30% of these high-energy high-LET particles coincided with the position of white defects on the HDTV CCDs in the SM.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S135044871000380X

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First Ever Flight Demonstration of Zero Propellant Maneuver(TM) Attitude Control Concept

by cfynanon 9 June 2015in Technology Development & Demonstration No comment

This paper presents the results for the first ever flight demonstration of the Zero Propellant Maneuver (ZPM) TM attitude control concept. On November 5, 2006, the ZPMTM was used to reorient the International Space Station by 90 degrees without using any propellant. By maneuvering along a pre-planned trajectory which was optimized to take advantage of naturally occurring environmental torques, the Space Station CMGs were maintained within operational limits. The trajectory was obtained from a PseudoSpectral solution to a new optima attitude control problem. With the flight test, the breakthrough capability to simultaneously perform large angle attitude maneuver and momentum desaturation without the need to use thruster was established. The flight implementation did not require any modification to flight software. The approach is applicable to any spacecraft that are controlled by momentum storage devices.

Related URLs:
http://dx.doi.org/10.2514/6.2007-6734

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Autonomous docking algorithm development and experimentation using the SPHERES testbed

by cfynanon 9 June 2015in Technology Development & Demonstration No comment

The MIT Space Systems Laboratory (SSL) has developed a testbed for the testing of formation flight and autonomous docking algorithms in both 1-g and microgravity environments. The SPHERES testbed consists of multiple micro-satellites, or Spheres, which can autonomously control their position and attitude. The testbed can be operated on an air table in a 1-g laboratory environment, in NASA"s KC-135 reduced gravity research aircraft and inside the International Space Station (ISS). SPHERES launch to the ISS is currently manifested for May 19 2004 on Progress 14P. Various types of docking maneuvers, ranging from docking with a cooperative target to docking with a tumbling target, have been developed. The ultimate objective of this research is to integrate the different algorithms into one program that can assess the health status of the target vehicle, plan an optimal docking maneuver while accounting for the existing constraints and finally, execute that maneuver even in the presence of simulated failures. In this paper, results obtained to date on the ground based air table using the initial version of the program will be presented, as well as results obtained from microgravity experiments onboard the KC-135.

Related URLs:
http://dx.doi.org/10.1117/12.547430

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