Design of high-precision restrained pressure-driven microgripper based on folded rectangular hinge

The four-bar parallelogram mechanism is widely used in microgrippers due to its parallel clamping characteristics. However, the rotation process of the four-bar parallelogram mechanism will produce parasitic displacement in the vertical direction. According to this, a high-precision restrained amplification mechanism with folding rectangular hinges is introduced, and the research is to reduce the parasitic movement through the structural design of the microgripper. Compared with the traditional four-bar parallelogram mechanism, the relative parasitic displacement of the restrained four-bar parallelogram mechanism is reduced by 80%. However, folding rectangular hinges will reduce the output displacement of the mechanism while improving the clamping accuracy. To solve the problem, the driving method adopts the pneumatic drive, and its large output force and high output displacement characteristics are in line with this kind of microgripper. Based on the Castigliano second theorem, the relationship between the input pressure and the input/output displacement of the mechanism is obtained. Experimental results show that the microgripper can realize the opening and closing of the movable jaw, as well as parallel clamping. When the movable jaw is closed, the error is 2.0% compared with the FEA (finite element analysis) result. The presentation of the folded rectangular hinge is of great significance to improve the clamping accuracy of microgrippers.