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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TL;DR: In this paper, the existence and location of dynamic singularities cannot be predicted solely from the manipulator kinematic structure because they are functions of the dynamic properties of the system, unlike the singularities for fixed-base manipulators.
Abstract: Dynamic Singularities are shown for free-floating space manipulator systems where the spacecraft moves in response to manipulator motions without compensation from its attitude control system. At a dynamic singularity the manipulator is unable to move its end-effector in some inertial direction; thus dynamic singularities must be considered in the design, planning, and control of free-floating space manipulator systems. The existence and location of dynamic singularities cannot be predicted solely from the manipulator kinematic structure because they are functions of the dynamic properties of the system, unlike the singularities for fixed-base manipulators. Also analyzed are the implications of dynamic singularities to the nature of the system’s workspace.
146 citations
"Real-time dynamic singularity avoid..." refers background in this paper
...is formulated taking dynamic effects into consideration, dynamic singularity is more prominent [8]....
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01 Jan 2010
TL;DR: In this article, a manipulator system accommodated on a servicing satellite (Servicer) operated semi-autonomously and from Earth is used to serve and lift malfunctioning satellites from their operational orbit to avoid large scale damage caused by uncontrollable satellites.
Abstract: There are many concepts how to serve and lift malfunctioning satellites from their operational orbit to avoid large scale damage caused by uncontrollable satellites. For many years now Germany has been developing robotic techniques especially to handle its spacecraft to the very end of life – just until their disposal. The German approach is based on berthing techniques using a manipulator system accommodated on a servicing satellite (Servicer) operated semi-autonomously and from Earth.
87 citations
07 Aug 2002
TL;DR: An online trajectory control scheme that uses the manipulability measure as a distance criteria to avoid manipulator singularities is described and a method for limiting the minimum value of the distance criteria is proposed.
Abstract: In autonomous system, it is important to establish a control scheme that works with stability even near singularity configurations. We describe an online trajectory control scheme that uses the manipulability measure as a distance criteria to avoid manipulator singularities. The proposed approach consists in a method for limiting the minimum value of the distance criteria. The performance is simply affected by the choice of the lower limit. Based on a real-time evaluation of the measure of manipulability, this method does not require a preliminary knowledge of the singular configurations. The proposed algorithm is validated by experimental results.
80 citations
"Real-time dynamic singularity avoid..." refers background or methods in this paper
...In this paper, we attempt to solve the problem of dynamic singularity of the system stated in [7] by adopting framework of real-time singularity avoidance methods from [14] and applying them for visual servoing of a free-floating dual-arm space robot....
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...In [14], it is shown using singular value decomposition of the Jacobian matrix that the mom can be regarded as the distance from the singularity....
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...The proposed methodology incorporates methods of [14] into GJM based visual servoing and results are verified by numerical experiments....
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...The unit vector normal to the surface [14] is given by...
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...In [14], a real-time singularity avoidance approach, however, for earth-based robots was proposed in which robot’s motion is projected on to a surface of constant mom when in vicinity of singular configurations preventing the index from dropping any further....
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04 Nov 1996
TL;DR: A control scheme based on the task function approach that combines the regulation of the selected vision based task with the minimization of a secondary cost function, which reflects the manipulability of the robot in the vicinity of internal or external singularities.
Abstract: We propose in this paper solutions to avoid robot joint limits and kinematic singularities in visual servoing. We use a control scheme based on the task function approach. It combines the regulation of the selected vision based task with the minimization of a secondary cost function, which reflects the manipulability of the robot in the vicinity of internal or external singularities. Several methods are proposed to avoid joint limits and a comparison between them is presented. We have demonstrated on various experiments the validity of our approach.
80 citations
"Real-time dynamic singularity avoid..." refers background in this paper
...where C is the combination matrix [16], and assumed to be an identity matrix in this work....
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09 May 2011
TL;DR: An image-based visual servoing for controlling the position and orientation of a quadrotor using a fixed downward camera observing landmarks on the level ground using the negative feedback to the image moments is presented.
Abstract: This paper presents an image-based visual servoing for controlling the position and orientation of a quadrotor using a fixed downward camera observing landmarks on the level ground. In the proposed method, the negative feedback to the image moments is used to control the vertical motion and rotation around the roll axis. On the other hand, the negative feedback cannot be used to control the horizontal motion due to under-actuation of a quadrotor. Thus, a novel control method is introduced to control the horizontal motion. Simulations are presented to validate the proposed method.
66 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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