Design and development of an earth based experimental setup for testing algorithms on space robots
TL;DR: The development of one such system that replicates zero gravity conditions for planar robots is described and the planar dual-arm space robot built is distinctive by being relatively lightweight, compact and modular.
Abstract: In space robots, coupling between the base and the arms causes the floating base to translate and rotate when the arms execute a maneuver, which is typically not seen in earth based robots. Since it is difficult to test developments in space robotics primarily due to the high cost and lack of access to robots in space, it is necessary to have physical systems that can mimic space conditions for experimental validation on earth. Among several options, the use of air bearings to build floating-base robots is one of the most effective. We describe the development of one such system that replicates zero gravity conditions for planar robots. Although similar systems exist elsewhere, the planar dual-arm space robot we have built is distinctive by being relatively lightweight, compact and modular. The setup can be used to test a wide range of experiments such as visual servoing, reactionless maneuvering and object grasping in space. In this paper, the approach taken during the development of both the hardware and software for the experimental setup are discussed. A few results obtained by numerical simulations as well as experimentation are also presented.
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TL;DR: A unified framework is provided for modeling impact dynamics, post-capture stabilization and target maneuvering of a multi-arm robotic system mounted on a servicing satellite while capturing orbiting objects.
Abstract: Autonomous on-orbit servicing, such as capture, refuel, repair and refurbishment of on-orbit satellites using a robotic arm mounted on servicing satellite is one of the important components of future’s space missions. Space robots increase reliability, safety, and ease of execution of space operations, but pose a novel challenge due to micro-gravity and space environments. While capturing high speed orbiting objects, robotic arms undergo impact and require appropriate modeling of the system. In this paper, a unified framework is provided for modeling impact dynamics, post-capture stabilization and target maneuvering of a multi-arm robotic system mounted on a servicing satellite while capturing orbiting objects. The dynamic model of multi-arm space robot is obtained using the Decoupled Natural Orthogonal Complement (DeNOC) based formulation and closed-loop constraint equations. All three phases of the capturing operation, namely, approach, impact, and post-impact are modeled using Impulse-momentum approach and conservation of momentum. In the approach phase, robot arms are planned to move from its initial configuration to the desired capture configuration. In the impact phase, a framework is developed to estimate the impulse forces and changes in the generalized velocities caused by the impact. In post-impact phase, these velocities are used as initial conditions for the post-impact dynamics simulations. The uncontrolled dynamics during post-impact will result in an undesirable motion, thus post-impact reactionless control (minimum base disturbance) strategy is used to maneuver the space robot’s arms and target object. As such, the robotic arms can be used to maneuver an astronaut for repair of satellite. Most of the times the parameters of target object are not known. Hence, an adaptive reactionless control strategy has been devised for capturing object with unknown parameters. The effectiveness of the framework is shown using a dual-arm robot mounted on a servicing satellite performing capturing operation for multiple objects. The effects of relative velocity and angle of approach on the impact forces are also investigated.
11 citations
TL;DR: In this paper, a rudimentary estimate of the inertial parameters of a space robot is provided. But this estimate is limited to motion planning and control of a single robot, and it cannot be used to estimate the motion of the entire robot.
Abstract: Accurate information of inertial parameters is critical to motion planning and control of space robots. Before the launch, only a rudimentary estimate of the inertial parameters is available from e...
10 citations
TL;DR: A new momentum model-based method for identifying the minimal parameters of a space robot while on orbit, and a novel joint trajectory planning and optimization technique based on direction combinations of joints' velocity is proposed.
Abstract: Accurate information of inertial parameters is critical to motion planning and control of space robots. Before the launch, only a rudimentary estimate of the inertial parameters is available from experiments and computer-aided design (CAD) models. After the launch, on-orbit operations substantially alter the value of inertial parameters. In this work, we propose a new momentum model-based method for identifying the minimal parameters of a space robot while on orbit. Minimal parameters are combinations of the inertial parameters of the links and uniquely define the momentum and dynamic models. Consequently, they are sufficient for motion planning and control of both the satellite and robotic arms mounted on it. The key to the proposed framework is the unique formulation of momentum model in the linear form of minimal parameters. Further, to estimate the minimal parameters, we propose a novel joint trajectory planning and optimization technique based on direction combinations of joints' velocity. The efficacy of the identification framework is demonstrated on a 12 degrees-of-freedom, spatial, dual-arm space robot. The methodology is developed for tree-type space robots, requires just the pose and twist data, and scalable with increasing number of joints.
4 citations
Cites background from "Design and development of an earth ..."
...Moreover, an inaccurate estimate of the inertial parameters adversely affects the motion planning and control [9]....
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01 Jan 2019
TL;DR: An attempt has been made to develop a framework for closed-loop impact modeling of a multi-arm robotic system mounted on a servicing satellite while capturing a tumbling orbiting object.
Abstract: In this paper, an attempt has been made to develop a framework for closed-loop impact modeling of a multi-arm robotic system mounted on a servicing satellite while capturing a tumbling orbiting object. When the satellite is in broken state or does not have provision for grapple and tumbling, the interception is very difficult. In such cases, interception using multi-arm robotic system can be appealing as this will certainly increase the probability of grasp in comparison to a single-arm robot. When multiple arms of a robot will capture only one target object from different points of contact, then it is termed as closed-loop impact. In this paper, first, the dynamic models of a multi-arm robot and a tumbling orbiting object are obtained. The target dynamics has been modeled considering it to be a rigid body. Then, the three phases of the capturing operation, namely, approach, impact, and postimpact have been modeled. Efficacy of the framework is shown using a dual-arm robot mounted on a servicing satellite performing capturing operation when both arms of robot capture a single target object. The effects of relative velocity and angle of approach on the impact forces would also be investigated.
2 citations
TL;DR: In this paper , the attitude stabilization problem of post-capture flexible spacecraft with non-cooperative target in the presence of input fault and saturation was investigated, and a static output feedback controller was applied to convert the closed-loop attitude control system to a stable negative imaginary system with H ∞ performance constraints according to negative imaginary theory.
Abstract: This paper investigates the attitude stabilization problem of post-capture flexible spacecraft with non-cooperative target in the presence of input fault and saturation. In modeling, these non-cooperative characteristics are often manifested in uncertain and unknown inertia, model parameter uncertainty, input faults, etc. In this paper, aiming at the attitude stabilization problem of such post-capture flexible spacecraft, the attitude dynamics modeling is completed by introducing the nominal inertia to construct the comprehensive disturbance term including external disturbance, inertia uncertainty and actuator failure. Then, a static output feedback controller is applied to convert the closed-loop attitude control system to a stable negative imaginary system with H ∞ performance constraints according to negative imaginary theory. As long as the optimization variables approach zero, the iterative algorithm can find such a static output feedback controller to achieve attitude stabilization of post-capture flexible spacecraft. It is worth mentioning that an event-triggered mechanism is introduced into the control scheme to reduce the communication pressure. Finally, the numerical simulation is performed in the presence of model parameter uncertainty and controller gain perturbations. Simulation results demonstrate the effectiveness, robustness and non-fragility of the control method.
2 citations
References
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01 Jun 1989
TL;DR: The authors develop a control method for space manipulators based on the resolved motion control concept that is widely applicable in solving not only free-flying manipulation problems but also attitude-control problems.
Abstract: The authors establish a control method for space manipulators taking dynamical interaction between the manipulator arm and the base satellite into account. The kinematics of free-flying multibody systems is investigated by introducing the momentum conservation law into the formulation and a novel Jacobian matrix in generalized form for space robotic arms is derived. The authors develop a control method for space manipulators based on the resolved motion control concept. The proposed method is widely applicable in solving not only free-flying manipulation problems but also attitude-control problems. The validity of the method is demonstrated by computer simulations with a realistic model of a robot satellite. >
568 citations
"Design and development of an earth ..." refers methods in this paper
...The end-effector motion can be mapped to the joint motion while accounting for translations and rotations of the base using the Generalised Jacobian Matrix (GJM), given by [18]...
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TL;DR: An overview of air-bearing spacecraft simulators is provided in this article, where the authors consider the history of this technology, how early systems were first devised and what diverse capabilities current systems provide.
Abstract: An overview of air-bearing spacecraft simulators is provided. Air bearings have been used for satellite attitude determination and control hardware verie cation and software development for nearly 45 years. It is interesting to consider the history of this technology: how early systems were e rst devised and what diverse capabilities current systems provide. First a survey is given of planar systems that give a payload freedom to translate and spin. Then several classes of rotational air bearings are discussed: those which simulate three-axis satellite attitude dynamics. The subsequent section discusses perhaps the most interesting facilities: those that provide both translational and three-dimensional rotational freedom. Thediverse capabilities each styleofair-bearing testbed provides, themany settings they can be found in, and ways to improve facility performance are described.
322 citations
"Design and development of an earth ..." refers background in this paper
...Magnetic suspension systems offer a smaller range of motion than air bearings [10], making air bearings the best choice among the two....
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TL;DR: A new sensitivity study on using ADR to stabilize the future LEO debris environment is described, using the NASA long-term orbital debris evolutionary model, LEGEND, to quantify the effects of several key parameters, including target selection criteria/constraints and the starting epoch of ADR implementation.
Abstract: Recent analyses on the instability of the orbital debris population in the low Earth orbit (LEO) region and the collision between Iridium 33 and Cosmos 2251 have reignited interest in using active debris removal (ADR) to remediate the environment. There are, however, monumental technical, resource, operational, legal, and political challenges in making economically viable ADR a reality. Before a consensus on the need for ADR can be reached, a careful analysis of its effectiveness must be conducted. The goal is to demonstrate the need and feasibility of using ADR to better preserve the future environment and to explore different operational options to maximize the benefit-to-cost ratio. This paper describes a new sensitivity study on using ADR to stabilize the future LEO debris environment. The NASA long-term orbital debris evolutionary model, LEGEND, is used to quantify the effects of several key parameters, including target selection criteria/constraints and the starting epoch of ADR implementation. Additional analyses on potential ADR targets among the existing satellites and the benefits of collision avoidance maneuvers are also included.
320 citations
"Design and development of an earth ..." refers background in this paper
...Robots in space can be used to perform several operations such as debris removal, refueling, inspection and other onorbit services [1] [2] [3]....
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TL;DR: In this article, a micro-satellite system for active space debris removal was proposed, and the applicability of electro-dynamic tether technology as its high efficiency orbital transfer system was examined.
Abstract: Since the number of satellites in Earth orbit is steadily increasing, space debris will eventually pose a serious problem to near-Earth space activities if left unchecked, and so effective measures to mitigate it are becoming urgent. Equipping new satellites with an end-of-life de-orbit or orbital lifetime reduction capability could be an effective means of reducing the amount of debris by reducing the probability of the collisions between objects. On the other hand, the active removal of space debris and the retrieval of failed satellites by spacecraft are other possible measures. The Institute of Aerospace Technology, Japan Aerospace Exploration Agency (JAXA), is studying a micro-satellite system for active space debris removal, and is examining the applicability of electro-dynamic tether (EDT) technology as its high efficiency orbital transfer system. A small EDT package provides a possible means for lowering the orbits of objects without the need for propellant. Capture is indispensable for the retrieval of large space debris objects, and we propose a flexible robot arm for this purpose. This paper discusses a space debris removal satellite system and describes the development status of prototypes of the EDT package and a new robot arm for capturing non-cooperative targets.
202 citations
"Design and development of an earth ..." refers background in this paper
...Robots in space can be used to perform several operations such as debris removal, refueling, inspection and other onorbit services [1] [2] [3]....
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21 May 2001
TL;DR: The existence of the ZRM is very limited for a 6 DOF manipulator arm mounted on a free-flying base, but it is discussed how more operational freedom is obtained with a kinematically redundant arm.
Abstract: Presents the experimental results and post-flight analysis of reaction null-space based reactionless manipulation, or zero reaction maneuver (ZRM). The concept has been developed with an insight into the motion dynamics of free-flying multibody systems and its practical availability is clearly demonstrated with ETS-VII, a Japanese space robot. The ZRM is proven particularly useful for removing the velocity limit of manipulation due to the reaction constraint and the time loss due to waiting for the attitude recovery. The existence of the ZRM is very limited for a 6 DOF manipulator arm mounted on a free-flying base, but it is discussed how more operational freedom is obtained with a kinematically redundant arm.
154 citations
"Design and development of an earth ..." refers background or methods in this paper
...For an n-Degrees-Of-Freedom (n-DOF) robotic system mounted on a floating-base, linear and angular momenta (p and l respectively) are given by [6] [ p l ] = Ibtb + Ibmθ̇ + [ 0 r0 × p ]...
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...It is necessary to have methods and algorithms that take this coupling into consideration, especially for robots such as Dextre [4] and ETS-VII [5] [6] where it is significant....
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...Several studies on reactionless manipulation [6], dynamic singularity avoidance [7] and visual servoing [8] have been performed for space robots in the past....
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