Abstract
The output and input coupling characteristics of the compliant parallel mechanism (CPM) bring difficulty in the motion control and challenge its high performance and operational safety. This paper presents a systematic design method for a 2-degrees-of-freedom (DOFs) CPM with excellent decoupling performance. A symmetric kinematic structure can guarantee a CPM with a complete output decoupling characteristic; input coupling is reduced by resorting to a flexure-based decoupler. This work discusses the stiffness design requirement of the decoupler and proposes a compound flexure hinge as its basic structure. Analytical methods have been derived to assess the mechanical performances of the CPM in terms of input and output stiffness, motion stroke, input coupling degree, and natural frequency. The CPM’s geometric parameters were optimized to minimize the input coupling while ensuring key performance indicators at the same time. The optimized CPM’s performances were then evaluated by using a finite element analysis. Finally, a prototype was constructed and experimental validations were carried out to test the performance of the CPM and verify the effectiveness of the design method. The design procedure proposed in this paper is systematic and can be extended to design the CPMs with other types of motion.
Highlights
Manipulators with ultrahigh precision and resolution are urgently needed and play more and more important roles in modern technology, such as atomic force microscopy, ultra precision machining, biological cell manipulation, and chip assembly in the semiconductor industry [1,2,3]
The stiffness model of the 2-DOF compliant parallel mechanism (CPM) is given in Figure 8a, and the input and output stiffness matrices will be derived first
The motion strokes along the x- and y-axes of the 2-DOF CPM are the same
Summary
Manipulators with ultrahigh precision and resolution are urgently needed and play more and more important roles in modern technology, such as atomic force microscopy, ultra precision machining, biological cell manipulation, and chip assembly in the semiconductor industry [1,2,3]. Compliant mechanisms, which are composed of rigid links and flexure hinges, transmit motion solely through the deformation of materials They can provide high accuracy and resolution in micro-scale motion, benefitting from no friction, no backlash, no wear, and monolithic structure, while being easy to manufacture and assemble [4,5]. Output coupling refers to any motion along one axis is affected by the actuation/input force along another axis It results in a complicated kinematic model and additional calibration should be performed in the absence of terminal feedback. A novel method was proposed within the tests, in order to evaluate the input coupling of the 2-DOF CPM by detecting the variations of axial forces at each actuation point instead of measuring their transverse deformations, which is difficult to achieve experimentally. The results demonstrated the decoupled CPM’s excellent performances and verified the effectiveness of the design method
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