Design and Modeling of a Spiral Pneumatic Soft Actuator
ZHANG Zhiyuan1, WANG Songtao2, WANG Xueqian1, MENG Deshan1, LIANG Bin2,3
1. Shenzhen Key Laboratory of Artificial Intelligence and Robotics, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China; 2. Research Institute of Tsinghua University at Shenzhen, Shenzhen 518057, China; 3. Department of Automation, Tsinghua University, Beijing 100084, China
Abstract：In order to explore the unwinding ability of the seahorse tail, a pneumatic soft actuator (PSA) with the spiral configuration is proposed based on the biological inspiration. Different from the bending motion of common soft actuators, the spiral pneumatic soft actuator (spiral PSA) can realize the unwinding motion in both directions of the positive and the negative curvature as the input air pressure increases. Firstly, 3 types of structures of the spiral PSAs are designed based on the mathematical expression of 3 different spirals, the circular spiral, the Archimedes spiral, and the logarithmic spiral, keeping the length of the outside arc of the actuator bodies the same. Secondly, the general statics model of the spiral PSA is established and modified based on the superelastic material model, the geometric relationship and the virtual work principle, to describe the relationship between the input pressure and the unwinding angle. Thirdly, the 3 types of structures of the spiral PSAs are prototyped, and their actual unwinding performances are tested. Finally, the data calculated by statics model is compared with the data from prototype experiments, and the maximum average unwinding angle error is 10.0166°, which proves the accuracy of the model. In addition, the actuator theoretical unwinding shapes under different unwinding states are reconstructed according to the configuration parameters converted from experimental data of shape scale lines, and the feasibility of the method for obtaining the configuration parameters is verified.
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