Research on SMA wires actuator of flower robot

摘要

Shape memory alloy (SMA) is a smart material that can remembers its geometry. After a sample of SMA has been deformed from its original atomic configuration, it regains its original geometry by itself during heating. SMA actuator has been applied in practice work extensively. Based on its smart characteristic, the mechanical properties of structures can be improved. The devices developed using SMA can sufficiently resolve the problems that are present in various fields. In this study, a new type of actuator based on silica gel rod with embedded off-axis SMA wires was presented. After the structure of flower robot was designed, the 3D formulation of flexible stem of flower robot with embedded SMA wires was derived. Using the 3D formulation and continuity theory of rod-wire interface, the equilibrium equations for both the rod and SMA wires are obtained. By this equation, the forces and moments in stem structure of flower robot can be yielded in theoretical predictions. To verify these formulations, we first use the finite element method to simulate and analyze. And then, a SMA test stand was established and property experiments were conducted. All results show these equations are correct. For the stem structure of flower robot with embedded a certain SMA wires, we conduct some experiment and get the relationship between input voltage and deflection of stem. Combine above relationship and equilibrium equations, we also present a nonlinear control scheme for deflection control of the flexible rod. Based on this method, a control system was designed and used to flower robot. The control effect is better.