Learning Constrained Corner Node Trajectories of a Tether Net System for Space Debris Capture

The earth's orbit is becoming increasingly crowded with debris that poses significant safety risks to the operation of existing and new spacecraft and satellites. The active tether-net system, which consists of a flexible net with maneuverable corner nodes launched from a small autonomous spacecraft, is a promising solution for capturing and disposing of such space debris. The requirement of autonomous operation and the need to generalize over scenarios with debris scenarios in different rotational rates makes the capture process significantly challenging. The space debris could rotate about multiple axes, which, along with sensing/estimation and actuation uncertainties, calls for a robust, generalizable approach to guiding the net launch and flight - one that can guarantee robust capture. This paper proposes a decentralized actuation system combined with reinforcement learning for planning and controlling this tether-net system. In this new system, four microsatellites with cold gas type thrusters act as the corner nodes of the net and can thus help control or correct the flight of the net after launch. The microsatellites pull the net to complete the task of approaching and capturing the space debris. The proposed method uses a RL framework that integrates a proximal policy optimization to find the optimal solution based on the dynamics simulation of the net and the microsatellites performed in Vortex Studio. The RL framework finds the optimal trajectory that is both fuel-efficient and ensures a desired level of capture quality.Comment: This paper was presented at AIAA Aviation 2023 Foru

Control of a compact, tetherless ROV for in-contact inspection of complex underwater structures

In this paper we present the dynamic modeling and control of EVIE (Ellipsoidal Vehicle for Inspection and Exploration), an underwater surface contact ROV (Remotely Operated Vehicle) for inspection and exploration. Underwater surface inspection is a challenging and hazardous task that demands sophisticated automation – as in boiling water nuclear reactors, water pipeline, submarine hull and oil pipelines inspection. EVIE is inspired by its predecessor, the Omni Submersible, in its ellipsoidal, streamlined, and appendage free shape. The objective for the robot is to carry inspection sensors – magnetic, acoustics or visual – to determine cracks on submerged surfaces. Unlike a robot moving in a practically boundless fluid, contact forces complicate the dynamics by bringing in normal and frictional forces, both of which are highly non linear in nature. This makes the modeling much more challenging and the development of an integrated controller more difficult. In this paper we will discuss the preliminary design and hydrodynamic modeling of such a robot. We analyze in detail the controls for one of the many transitional states of this robot. Eventually all transitional states need to be integrated to develop a hybrid dynamical system which shall use a controller that can adapt to its different states.Electric Power Research Institut

HiMAT flight program: Test results and program assessment overview

The Highly Manueverable Aircraft Technology (HiMAT) program consisted of design, fabrication of two subscale remotely piloted research vehicles (RPRVs), and flight test. This technical memorandum describes the vehicles and test approach. An overview of the flight test results and comparisons with the design predictions are presented. These comparisons are made on a single-discipline basis, so that aerodynamics, structures, flight controls, and propulsion controls are examined one by one. The interactions between the disciplines are then examined, with the conclusions that the integration of the various technologies contributed to total vehicle performance gains. An assessment is made of the subscale RPRV approach from the standpoint of research data quality and quantity, unmanned effects as compared with manned vehicles, complexity, and cost. It is concluded that the RPRV technique, as adopted in this program, resulted in a more complex and costly vehicle than expected but is reasonable when compared with alternate ways of obtaining comparable results

Learning to Plan Near-Optimal Collision-Free Paths

A new approach to find a near-optimal collision-free path is presented. The path planner is an implementation of the adaptive error back-propagation algorithm which learns to plan “good”, if not optimal, collision-free paths from human-supervised training samples. Path planning is formulated as a classification problem in which class labels are uniquely mapped onto the set of maneuverable actions of a robot or vehicle. A multi-scale representational scheme maps physical problem domains onto an arbitrarily chosen fixed size input layer of an error back-propagation network. The mapping does not only reduce the size of the computation domain, but also ensures applicability of a trained network over a wide range of problem sizes. Parallel implementation of the neural network path planner on hypercubes or Transputers based on Parasoft EXPRESS is simple and efficient, Simulation results of binary terrain navigation indicate that the planner performs effectively in unknown environment in the test cases

Synthetic Jet Propulsion for Small Underwater Vehicles

This paper proposes a new synthetic jet actuation concept for small, low speed, highly maneuverable AUVs. Synthetic jet thrusters, which produce jets of vortex rings, are inspired by the pulsatile jet propulsion of salps, jellyfish, and squid. To assess the potential utility of this scheme, we developed synthetic jet actuator prototypes, and verified their function via both force measurement and flow visualization experiments. We used a genetic-algorithm based technique for optimizing the actuation profile of the thrusters. Also presented is an initial discussion of vehicle design. Our conclusion is that synthetic jet thrusters are a viable propulsion method for small underwater vehicles

MAD-STORM:Maneuverable Autonomous Drone with Sensing Technologies for Observing Rainfall and Meteorology in Northern Ireland

The Maneuverable Autonomous Drone with Sensing Technologies for Observing Rainfall and Meteorology (MAD-STORM) is an in-house Internet of Things (IoT)-driven Unmanned Aerial Vehicle (UAV) targeting wide array of applications, encompassing search and rescue, surveillance, crowd monitoring, and environmental sensing. This paper focuses on the design and implementation of MAD-STORM, highlighting its environmental sensing for temperature, humidity, and rain detection. Leveraging internet connectivity, MAD-STORM facilitates real-time data streaming and analysis from a ground station, while also aligning with IoT principles to establish cloud connectivity. The inclusion of global positioning system modules aids in determining navigation coordinates, ensuring the precise execution of MAD-STORM activities. This paper offers a comprehensive overview of MAD-STORM's development stages, system design, hardware, software components, intelligent capabilities and challenges. The real-time demonstration video and detals for this work is available at https://www.ulster.ac.uk/research/topic/engineering/afmm/projects/madni.</p

A framework to account for flexibility in modeling the value of on-orbit servicing for space systems

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2001.Includes bibliographical references (p. 195-197).by Elisabeth Sylvie Lamassoure.S.M

Operationally Responsive Spacecraft Using Electric Propulsion

A desirable space asset is responsive and flexible to mission requirements, low-cost, and easy to acquire. Highly-efficient electric thrusters have been considered a viable technology to provide these characteristics; however, it has been plagued by limitations and challenges such that operational implementation has been severely limited. The technology is constantly improving, but even with current electric propulsion, a spacecraft is capable of maneuvering consistently and repeatedly in low-Earth orbit to provide a responsive and flexible system. This research develops the necessary algorithm and tools to demonstrate that EP systems can maneuver significantly in a timely fashion to overfly any target within the satellite’s coverage area. An in-depth analysis of a reconnaissance mission reveals the potential the proposed spacecraft holds in today’s competitive, congested, and contested environment. Using Space Mission Analysis and Design concepts along with the developed algorithm, an observation mission is designed for three conventional methods and compared to the proposed responsive system. Analysis strongly supports that such a spacecraft is capable of reliable target overflight at the same cost as non-maneuvering ones, while it is three times as responsive in terms of time-to-overflight by sacrificing one third of its mission life. An electric versus a chemical system can maneuver 5.3 times more. Its responsiveness and mission life are slightly inferior to that of a Walker constellation, but cuts total system cost by almost 70%

Soft phototactic swimmer based on self-sustained hydrogel oscillator.

Oscillations are widely found in living organisms to generate propulsion-based locomotion often driven by constant ambient conditions, such as phototactic movements. Such environment-powered and environment-directed locomotions may advance fully autonomous remotely steered robots. However, most man-made oscillations require nonconstant energy input and cannot perform environment-dictated movement. Here, we report a self-sustained soft oscillator that exhibits perpetual and untethered locomotion as a phototactic soft swimming robot, remotely fueled and steered by constant visible light. This particular out-of-equilibrium actuation arises from a self-shadowing-enabled negative feedback loop inherent in the dynamic light-material interactions, promoted by the fast and substantial volume change of the photoresponsive hydrogel. Our analytical model and governing equation unveil the oscillation mechanism and design principle with key parameters identified to tune the dynamics. On this autonomous oscillator platform, we establish a broadly applicable principle for converting a continuous input into a discontinuous output. The modular design can be customized to accommodate various forms of input energy and to generate diverse oscillatory behaviors. The hydrogel oscillator showcases agile life-like omnidirectional motion in the entire three-dimensional space with near-infinite degrees of freedom. The large force generated by the powerful and long-lasting oscillation can sufficiently overcome water damping and effectively self-propel away from a light source. Such a hydrogel oscillator-based all-soft swimming robot, named OsciBot, demonstrated high-speed and controllable phototactic locomotion. This autonomous robot is battery free, deployable, scalable, and integratable. Artificial phototaxis opens broad opportunities in maneuverable marine automated systems, miniaturized transportation, and solar sails