Real-time dynamic singularity avoidance while visual servoing of a dual-arm space robot
TL;DR: This paper presents a real-time dynamic singularity avoidance approach for such autonomous free-floating space robots where visual servoing is used as feedback in the control loop and uses manipulability measure as distance criteria and does not require any prior knowledge of singular configurations.
Abstract: Singularity of robotic manipulators is an important issue in the stability and control of autonomous robotic systems. This paper presents a real-time dynamic singularity avoidance approach for such autonomous free-floating space robots where visual servoing is used as feedback in the control loop. The proposed method uses manipulability measure as distance criteria and does not require any prior knowledge of singular configurations. Velocities in task space are projected on a surface of constant manipulability measure to avoid singular configurations. Numerical experiments are carried out, to validate the proposed method, on a 6-Degrees-of-Freedom dual-arm space robot mounted on a service satellite.
Citations
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TL;DR: The field of space robotics regarding the kinematics, dynamics and control of manipulators mounted onto spacecraft is explored, concluding that space robotics is well-developed and sufficiently mature to tackling tasks such as active debris removal.
Abstract: Space-based manipulators have traditionally been tasked with robotic on-orbit servicing or assembly functions, but active debris removal has become a more urgent application. We present a much-needed tutorial review of many of the robotics aspects of active debris removal informed by activities in on-orbit servicing. We begin with a cursory review of on-orbit servicing manipulators followed by a short review on the space debris problem. Following brief consideration of the time delay problems in teleoperation, the meat of the paper explores the field of space robotics regarding the kinematics, dynamics and control of manipulators mounted onto spacecraft. The core of the issue concerns the spacecraft mounting which reacts in response to the motion of the manipulator. We favour the implementation of spacecraft attitude stabilisation to ease some of the computational issues that will become critical as increasing level of autonomy are implemented. We review issues concerned with physical manipulation and the problem of multiple arm operations. We conclude that space robotics is well-developed and sufficiently mature to tackling tasks such as active debris removal.
31 citations
Cites background from "Real-time dynamic singularity avoid..."
...Nevertheless, dual arms introduce greater challenges in avoiding dynamic singularities [258]....
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TL;DR: A method named off-line optimizing visual servoing algorithm is innovatively proposed to minimize the base disturbance during the visual Servoing process where the degrees-of-freedom of the manipulator is not enough for a zero-reaction control.
Abstract: During visual servoing space activities, the attitude of free-floating space robot may be disturbed due to dynamics coupling between the satellite base and the manipulator. And the disturbance may cause communication interruption between space robot and control center on earth. However, it often happens that the redundancy of manipulator is not enough to fully eliminate this disturbance. In this paper, a method named off-line optimizing visual servoing algorithm is innovatively proposed to minimize the base disturbance during the visual servoing process where the degrees-of-freedom of the manipulator is not enough for a zero-reaction control. Based on the characteristic of visual servoing process and the robot system modeling, the optimal control method is applied to achieve the optimization, and a pose planning method is presented to achieve a second-order continuity of quaternion getting rid of the interruption caused by ambiguity. Then simulations are carried out to verify the method, and the results show that the robot is controlled with optimized results during visual servoing process and the joint trajectories are smooth.
9 citations
Additional excerpts
...σ̇ = ⎛ ⎝σ̇(1) σ̇2 σ̇3 ⎞ ⎠= Jbσ θ̇ = ⎡ ⎣0 − sin(σ1) cos(σ1) cos(σ2) 0 cos(σ1) sin(σ1) cos(σ2) 1 0 − sin(σ2) ⎤ ⎦ Jbωθ̇ (29)...
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29 Mar 2018
TL;DR: Neural networks are constructed under the proposed torque control design as to approximate the unknown dynamics and achieve small tracking errors in the operation-space to cope with the unknown and unstructured dynamic nonlinearities of the robot model.
Abstract: In this paper, adaptive operation-space control with joint limits avoidance is proposed for a redundant robot manipulator. Utilizing redundant properties of the robotic manipulator, joint limits avoidance is achieved without interfering the main-task objective in the operation-space. Two control objectives are unified under one common control framework. To cope with the unknown and unstructured dynamic nonlinearities of the robot model, neural networks (NNs) are constructed under the proposed torque control design as to approximate the unknown dynamics and achieve small tracking errors. Simulation studies are carried out to verify the effectiveness of the proposed framework.
3 citations
References
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07 Jul 1992
TL;DR: A Cartesian space planning method that permits the effective use of a system’s reachable workspace by planning paths that avoid dynamically singular configurations is proposed and demonstrated by an example.
Abstract: Nonholonomic behavior is observed in free-floating manipulator systems, and is due to the nonintegrability of the angular momentum. Free-floating manipulators exhibit dynamic singularities which cannot be predicted by the kinematic properties of the system and whose location in the workspace is path dependent. Trouble-free Path Independent Workspaces are defined. A joint space planning technique used to control the orientation of the spacecraft by using joint manipulator motions is reviewed, and its limitations are discussed. Finally, a Cartesian space planning method that permits the effective use of a system’s reachable workspace by planning paths that avoid dynamically singular configurations is proposed and demonstrated by an example.
59 citations
"Real-time dynamic singularity avoid..." refers methods in this paper
...[12] Kostas Nanos and Evangelos Papadopoulos....
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...Nanos and Papadopoulos have proposed a methodology to avoid dynamically singular con.gurations during the motion by yielding the appropriate initial system con.gurations for the prede.ned path [12]....
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...[10] Evangelos G Papadopoulos....
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...[8] Evangelos Papadopoulos and Steven Dubowsky....
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...A point-topoint Cartesian space planning method that permits the effective use of a systems reachable workspace avoiding dynamic singularities has presented by Papadopoulos [10]....
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19 Aug 2013
TL;DR: Three point-to-point path planning strategies are presented, which improve the reactionless operation of the dual-arm robot for capture of tumbling orbiting objects, such as out-ofcommission satellites and space debris.
Abstract: This paper presents strategies for point-to-point reactionless manipulation of a satellite mounted dual-arm robotic system for capture of tumbling orbiting objects, such as out-ofcommission satellites and space debris. Use of the dual-arm robot could be more effective than the single arm when there is no provision for a grapple fixture or the object is tumbling. The dual arms can also provide dexterous manipulation. As the main objective in capture of orbital objects is to move the end-effector from initial position to the grapple point with desired velocity, the task-level reactionless constraints in terms of end-effector velocities are derived. The trajectory planned using these constraints, however, results in several singular points within the robot’s workspace. In order to overcome this shortcoming, three point-to-point path planning strategies are presented, which improve the reactionless operation of the dual-arm robot. The strategies are illustrated by carrying out simulations for a 6-degree-of-freedom (DOF) dual-arm robotic system mounted on a satellite.
46 citations
"Real-time dynamic singularity avoid..." refers background or methods in this paper
...Such an expression can be obtained from the total momentum equation [13] which is stated as [ p l ] = Ibtb + Ibm1θ̇1 + Ibm2θ̇2 + [ 0 c0 × p ]...
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...More recently, a method for singularity avoidance while performing reactionless manipulation was presented in [13]....
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TL;DR: An autonomous trajectory planning method is proposed, directly using the 2D image features of hand–eye camera, that predicts the target motion, plans the end-effector's velocities and solves the inverse kinematic equations using practical approach to avoid the dynamic singularities.
Abstract: Space robotic systems are expected to play an increasingly important role in the future Unlike on the earth, space operations require the ability to work in the unstructured environment Some autonomous behaviors are necessary to perform complex and difficult tasks in space This level of autonomy relies not only on vision, force, torque, and tactile sensors, but also the advanced planning and decision capabilities In this paper, the authors study the autonomous target capturing from the issues of theory and experiments Firstly, we deduce the kinematic and dynamic equations of space robotic system Secondly, the visual measurement model of hand–eye camera is created, and the image processing algorithms to extract the target features are introduced Thirdly, we propose an autonomous trajectory planning method, directly using the 2D image features The method predicts the target motion, plans the end-effector's velocities and solves the inverse kinematic equations using practical approach to avoid the dynamic singularities At last, numeric simulation and experiment results are given The ground experiment system is set up based on the concept of dynamic simulation and kinematic equivalence With the system, the experiments of autonomous capturing a target by a free-floating space robot, composed of a 6-DOF manipulator and a satellite as its base, are conducted, and the results validate the proposed algorithm
40 citations
"Real-time dynamic singularity avoid..." refers methods in this paper
...Xu et al.[11] have proposed a trajectory planning method that uses damped least squares to avoid dynamic singularity....
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10 Apr 2007
TL;DR: Simulation results show that these two methods provide an efficient solution to the camera retreat and features visibility problems and Gradient decent and Gauss-Newton as a second order approximation are considered in this paper.
Abstract: In this paper, we present a new hybrid visual servoing algorithm for robot arm positioning task. Hybrid methods in visual servoing partially combine the 2D and 3D visual information to improve the performance of the traditional image-based and position-based visual servoing. Our algorithm is superior to the state of the art hybrid methods. The objective function has been designed to include the full 2D and 3D information available either from the CAD model or from the partial reconstruction process by decomposing the homography matrix between two views. Here, each of 2D and 3D error functions is used to control the six degrees of freedom. We call this method 5D visual servoing. The positioning task has been formulated as a minimization problem. Gradient decent as a first order approximation and Gauss-Newton as a second order approximation are considered in this paper. Simulation results show that these two methods provide an efficient solution to the camera retreat and features visibility problems. The camera trajectory in the Cartesian space is also shown to be satisfactory.
36 citations
"Real-time dynamic singularity avoid..." refers methods in this paper
...Whereas the GJM is commonly used to control the end-effectors of such a free-floating system, visual servoing as a feedback control system has been proven to be reliable [5, 6] in carrying out autonomous operations....
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01 Jun 1996
TL;DR: It is shown that if the end-effector motion is the only concern, as desired in kinematic control, it should be selected as the primary body, and this leads to the most efficient algorithms.
Abstract: An essential step in deriving kinematic models of free-flying space robots, consisting of a free-base and a manipulator mounted on it, is to write the total momenta of the system at hand. The momenta are, usually, expressed as the functions of the velocities of a preselected body that belongs to the robot, e.g., the free-base. In this paper, no preselection is recommended. On the contrary, the total momenta are expressed as the functions of the velocities of an arbitrary body of the space robot, namely, the primary body (PB). The identity of the PB, unlike the conventional approaches, need not be known at this stage. Therefore, the generalized expressions for the total momenta are obtained. The resulting expressions can explain the existing kinematic models and how they affect the efficiencies of the associated control algorithms. Based on the proposed approach, it is shown that if the end-effector motion is the only concern, as desired in kinematic control, it should be selected as the PB. This leads to the most efficient algorithms.
33 citations
"Real-time dynamic singularity avoid..." refers methods in this paper
...Later, a unified framework for space robot kinematice was given in [4] by using the GJM....
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