Abstract
Both Natural Coordinate Formulation describing rigid bodies and Absolute Nodal Coordinate Formulation describing flexible bodies are used to model a flexible manipulator with flexible joint and flexible link. The torsional stiffness of flexible joint is tested using a specialized stiffness test equipment, and then the nonlinear torsional stiffness is determined by fitting the experimental data. A new trajectory planning function called the cosine-based function is proposed to design the joint trajectory, which is smoother than the fifth-polynomial and cycloidal motion functions. Finally, a one-link manipulator with flexible joint and flexible link is used to compare the performance of the three trajectory planning functions. Results show that residual vibration can be remarkably reduced by the proposed cosine-based function, which exhibits a significantly better performance than the fifth-polynomial and cycloidal motion functions.
Highlights
A space manipulator undertakes tasks of cabin translocation, transfer, and installation of equipment, as well as serves as an astronaut auxiliary in a station system
Due to the above deficiencies in the previous work, both Natural Coordinate Formulation (NCF) [8] describing rigid bodies and Absolute Nodal Coordinate Formulation (ANCF) [9, 10] especially suitable for flexible bodies with large deformation are applied to model the flexible manipulator in this paper
The above analysis shows that, whether with joint flexibility considered or with both joint flexibility and link flexibility considered, the tracking errors caused by the three planning functions are similar in the course of motion, but the residual vibration caused by the cosine-based function proposed in this paper is significantly less than that caused by the fifthpolynomial and cycloidal motion functions after motion
Summary
A space manipulator undertakes tasks of cabin translocation, transfer, and installation of equipment, as well as serves as an astronaut auxiliary in a station system. The greatest disadvantage of the space manipulator is the vibration problem due to the flexibility of the joint and link. Joint flexibility and link flexibility are basic reasons of manipulator vibration, which cannot be neglected in the dynamic modeling. In the dynamic modeling of flexible link, the assumed mode method is typically used by most researchers. Due to the above deficiencies in the previous work, both Natural Coordinate Formulation (NCF) [8] describing rigid bodies and Absolute Nodal Coordinate Formulation (ANCF) [9, 10] especially suitable for flexible bodies with large deformation are applied to model the flexible manipulator in this paper. To suppress the residual vibration, a new planning function called the cosine-based function is proposed to design the joint trajectory.
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