Design and Control of a Lever-Bridge Differential Displacement Reducer With Sub-Nanometer Resolution

Piezoelectric actuators and giant magnetostrictive actuators are widely used in micropositioning and micromanipulation devices. To achieve sub-nanometer resolution with these actuators, a compact flexure-based displacement reducer, which shows the capability of obtaining a very large reduction ratio so as to achieve motion resolution of sub-nanometer, is proposed. It incorporates both bridge-type and lever-type mechanisms, arranged such that the reducer’s output equals the differential displacement between the two mechanisms. Additionally, a kinetostatic model for the reducer is developed. The parameters of the reducer are optimized to minimize the variation of the reduction ratio. The optimization results are validated by those of a finite element model, proving the effectiveness and correctness of the proposed reducer and the kinetostatic model. A prototype is fabricated and valuated by open-loop control and closed-loop control. The average reduction ratio can reach 206.4. By adopting a neural network-based H_∞ robust controller, the reducer achieves satisfactory tracking performance. This comprehensive study affirms the reducer’s potential in enhancing the precision of micropositioning and micromanipulation devices.