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Trajectory Optimization for Velocity Jumps Reduction Considering the Unexpectedness Characteristics of Space Manipulator Joint-Locked Failure


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1 School of Automation, Beijing University of Posts and Telecommunications, Beijing 100876, China
 

Aiming at reducing joint velocity jumps caused by an unexpected joint-locked failure during space manipulator on-orbit operations without shutting downmanipulator, trajectory optimization strategy considering the unexpectedness characteristics of joint-locked failure is proposed in the paper, which can achieve velocity jumps reduction in both operation space and joint space simultaneously. In the strategy, velocity in operation space concerning task completion directly is treated as equality constraints, and velocity in joint space concerning motion performance is treated as objective function. Global compensation vector which consists of coefficient, gradient of manipulability, and orthogonal matrix of null space is constructed to minimize the objective function. For each particular failure time, unique optimal coefficient can be obtainedwhen the objective function is minimal. As a basis, amethod for optimal coefficient function fitting is proposed based on a priori failure information (possible failure time and the corresponding optimal coefficient) to guarantee the unexpectedness characteristics of joint-locked failure. Simulations are implemented to validate the efficiency of trajectory optimization strategy in reducing velocity jumps in both joint space and operation space. And the feasibility of coefficient function is also verified in reducing velocity jump no matter when joint-locked failure occurs.
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  • Trajectory Optimization for Velocity Jumps Reduction Considering the Unexpectedness Characteristics of Space Manipulator Joint-Locked Failure

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Authors

Qingxuan Jia
School of Automation, Beijing University of Posts and Telecommunications, Beijing 100876, China
Tong Li
School of Automation, Beijing University of Posts and Telecommunications, Beijing 100876, China
Gang Chen
School of Automation, Beijing University of Posts and Telecommunications, Beijing 100876, China
Hanxu Sun
School of Automation, Beijing University of Posts and Telecommunications, Beijing 100876, China
Jian Zhang
School of Automation, Beijing University of Posts and Telecommunications, Beijing 100876, China

Abstract


Aiming at reducing joint velocity jumps caused by an unexpected joint-locked failure during space manipulator on-orbit operations without shutting downmanipulator, trajectory optimization strategy considering the unexpectedness characteristics of joint-locked failure is proposed in the paper, which can achieve velocity jumps reduction in both operation space and joint space simultaneously. In the strategy, velocity in operation space concerning task completion directly is treated as equality constraints, and velocity in joint space concerning motion performance is treated as objective function. Global compensation vector which consists of coefficient, gradient of manipulability, and orthogonal matrix of null space is constructed to minimize the objective function. For each particular failure time, unique optimal coefficient can be obtainedwhen the objective function is minimal. As a basis, amethod for optimal coefficient function fitting is proposed based on a priori failure information (possible failure time and the corresponding optimal coefficient) to guarantee the unexpectedness characteristics of joint-locked failure. Simulations are implemented to validate the efficiency of trajectory optimization strategy in reducing velocity jumps in both joint space and operation space. And the feasibility of coefficient function is also verified in reducing velocity jump no matter when joint-locked failure occurs.