Dexterity optimization of kinematically redundant manipulators in the presence of joint failures

Lewis, Christopher L.; Maciejewski, Anthony A.

doi:10.1016/0045-7906(94)90021-3

Cited by 75 publications

(57 citation statements)

References 9 publications

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“…The algorithm consists of three main parts. In the first part, the inverse kinematics equation of single redundancy manipulator based on selfmotion variable and null-space velocity array of Jacobian 02015-p. 4 are analyzed and the group of joint space configurations which satisfies the request of end-effector trajectory tracking can be obtained by choosing different selfmotion variables. In the second part the mathematical description of fault tolerance criteria of the configuration for redundant manipulator is established and considering the joint limits and minimum the energy consumption the secondary optimization target is established in the third part.…”

Section: Resultsmentioning

confidence: 99%

“…The redundancy feature of manipulators makes its joint configuration move free in a certain rules without changing the posture of end-effector and this process is called self-motion, which provides the possibility for the global trajectory optimization [3] This idea was first proposed in [4], where the null-space component of a redundant manipulator was used to locally minimize the kinematic fault tolerance measure. However, due to the local nature of the fault tolerance measure, fault tolerance could not be guaranteed globally.…”

Section: Introductionmentioning

confidence: 99%

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The optimization of global fault tolerant trajectory for redundant manipulator based on self-motion

Zhang

Jia

Chen

et al. 2015

MATEC Web of Conferences

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Abstract. The redundancy feature of manipulators provides the possibility for the fault tolerant trajectory planning. Aiming at the completion of the specific task, an algorithm of global fault tolerant trajectory optimization for redundant manipulator based on the self-motion is proposed in this paper. Firstly, inverse kinematics equation of single redundancy manipulator based on self-motion variable and null-space velocity array of Jacobian are analyzed. Secondly, the mathematical description of fault tolerance criteria of the configuration of manipulator is established and the fault tolerance configuration group of manipulator is obtained by using iteration traversal under the fault tolerance criteria. Then, considering the joint limits and minimum the energy consumption as the optimization target, the global fault tolerant joint trajectory is achieved. Finally, simulation for 7 degree of freedom (DOF) manipulator is performed, by which the effectiveness of the algorithm is validated.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The optimization of global fault tolerant trajectory for redundant manipulator based on self-motion

Zhang

Jia

Chen

et al. 2015

MATEC Web of Conferences

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“…Consider a manipulator at a nonsingular configuration, driven by a generalized inverse control (10) where G=w-1f(Jw-1JT)-1 for some symmetric W>O.5 Let S be the set of the indices of the k locked joints, and let ji and Wi denote the ith columns ofJand W, respectively. Then, 1. Only the failed joints are commanded motion if and only if the commanded end-effector velocity vector Xc lies in the space spanned by the columns corresponding to the failed joints of the Jacobian, i.e., for some a; E IR, i E S, where e, represents a natural basis vector.…”

Section: Characterizing Convergencementioning

confidence: 99%

Analyzing unidentified locked-joint failures in kinematically redundant manipulators

2004

Self Cite

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Robots are frequently used for operations in hostile environments. The very nature of these environments, however, increases the likelihood of robot failures. Common failuretolerance techniques rely on effective failure detection and identification. Since a failure may not always be successfully identified, or, even if identified, may not be identified soon enough, it becomes important to consider the behavior of manipulators with unidentified failures. This work investigates the behavior of robots experiencing unidentified locked-joint failures in a general class of tasks characterized by point-to-point motion. Based on the analysis, a procedure for workspace evaluation is developed that allows for the identification of regions in the manipulator's workspace in which tasks may be completed even with such failures. where xe R" is the position of the end effector, q eRn is the vector of joint variables, and m and n the dimensions of the task space and joint space, teepeetively. Manipulators that have more degrees of freedom (DOFs) than required for a task, i.e., n>m, are said to be redundant. 'The end-effector velocity is expressed in terms of the joint rates as where] E H m X n is the manipulator Jacobian, xis the end-effector velocity, and it is the joint velocity.If perfect servo control of the joints is assumed, then in a healthy manipulator the actual joint velodfailed, the ability of manipulators to converge to desired end-effector positions even with imperfect/ approximated lacobtana/Iacobian-inverses has been addressed in refs. 26 and 27. Therefore, we focus on the other case where a joint has actually locked, but the controller continues to command motion of that joint as though it were healthy. For a general class of tasks characterized by point-to-point motion, we examine convergence issues such as whether the manipulator comes to rest and, if so, what is the terminal position and orientation of the end-effector. The convergence analysis is restricted to purely kinematic effects, due to the fact that the dynamic effects of a failure are essentially transient in nature and do not significantly affect the convergence behavior. 18.28 -3 0 Conditions under which the manipulator converges are explicitly defined and the anomalies in behavior due to the faults explained and illustrated with examples. These conditions are used to evaluate the convergence behavior of the manipulator over the postfailure workspace. This allows for the identification of workspace regions for which task completion may be possible even with unidentified failures.The position and orientation-of the end effector of a manipulator can be expressed in terms of its joint variables by the kinematic equation "nus assumes a typical commercial robot where duplicate sensing and/or analytical redundancy does not exist.

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“…The failure tolerant control scheme would then try to optimize this value to maximize a robot's tolerance to a failure at a given manipulator configuration. Types of failure modes considered include both lockedjoint [31], [16], [32] and free-swinging joint failures [33]. A real-time implementation of kinematic failure tolerant control is demonstrated in [31].…”

Section: Introductionmentioning

confidence: 99%

A path planning strategy for kinematically redundant manipulators anticipating joint failures in the presence of obstacles

Jamisola

Maciejewski

Roberts³

Proceedings 2003 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2003) (Cat. No.03CH37453)

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Abstract-This work considers the failure tolerant operation of a kinematically redundant manipulator in an environment containing obstacles. In particular, the article addresses the problem of planning a collision-free path for a manipulator operating in a static environment such that the manipulator can reach its desired goal despite a single locked-joint failure and the presence of obstacles in the environment. A method is presented that searches for a continuous obstacle-free space between the starting configuration and the desired final end-effector position which is characterized in the joint space by the goal selfmotion manifold. This method guarantees completion of critical tasks in the event of a single locked-joint failure in the presence of obstacles.

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Dexterity optimization of kinematically redundant manipulators in the presence of joint failures

Cited by 75 publications

References 9 publications

The optimization of global fault tolerant trajectory for redundant manipulator based on self-motion

The optimization of global fault tolerant trajectory for redundant manipulator based on self-motion

Analyzing unidentified locked-joint failures in kinematically redundant manipulators

A path planning strategy for kinematically redundant manipulators anticipating joint failures in the presence of obstacles

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