This paper presents a novel nested, compliant, constant-force mechanism (CFM) that generates millimeter-scale manipulation stroke. The nested structure is utilized to improve the overall compactness of the CFM. A combination strategy of positive and negative stiffness is induced to generate constant force with a millimeter-level range. In particular, bi-stable beams are used as the negative stiffness part, and V-shaped beams are selected as the positive stiffness part, and they are constructed into the nested structures. With this, a design concept of the CFM is first proposed. From this, an analytical model of the CFM was developed based on the pseudo-rigid body method (PRBM) and chain beam constraint model (CBCM), which was verified by conducting a simulation study with nonlinear finite-element analysis (FEA). Meanwhile, a parametric study was conducted to investigate the influence of the dominant design variable on the CFM performance. To demonstrate the performance of the CFM, a prototype was fabricated by wire cutting. The experimental results revealed that the proposed CFM owns a good constant-force property. This configuration of CFM provides new ideas for the design of millimeter-scale, constant-force, micro/nano, and hard-surface manipulation systems.
This paper presents a novel beam flexure-based X–Y–θ micro-stage integrated with a laser interferometric type displacement measurement approach for reducing the measurement error induced by the rotational motion and cross-axis load effect. Aiming at achieving high-precision real-time control of the proposed system, an active disturbance rejection controller is developed such that the inevitable parasitic and coupling errors can be treated as disturbances and actively compensated by using the extended state observer. Finally, the verification experiments are deployed on the fabricated prototype, where the results indicate that the proposed approach achieves excellent performance in terms of motion accuracy and disturbance rejections.
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