Research On A Circular Soft Robot Actuated By SMA Springs

Most of the current soft robot's researches focus on achieving bionic movement only,but the actuating mechanism of the deforming locomotion is usually lack of research.As with controlling aspect,since it is difficult to allocate a built-in sensor,researchers use simple open-loop control systems in normal conditions.The current situations as have been noted limit the further development of soft robots.This paper studies circular soft robot driven by shape memory alloy springs.It focuses on researching the deformation mechanism of shape memory alloy spring driver,the deformation principles in circular soft robot,the dynamic analysis of the robot movement,the robot's motion control strategy and so on.The main contents of the paper are as follows:(1)Modeling and experiment in shape memory alloy deformation.Based on Clausius-Clapeyron equation and the Taylor expansion method,the shape memory alloy springs' deformation model is built with undetermined parameters approach.Thus,we get the non-linear relationship among the deformation,load and temperature of shape memory alloy spring.Then,according to the heat balance equation,the temperature change model of the shape memory alloy spring under the condition of electric heating is established,and the relationship between the heating time and the spring temperature is obtained.Based on the above two models,the relationship between the heating time and the shape memory alloy spring is obtained.Lastly,the electric drive model of the shape memory alloy spring is established and verified experimentally to provide support for the driving control of the circular soft robot.(2)Development and deformation analysis of circular soft robot.We develop a circular soft robot driven by shape memory alloy spring,and according to micro-element hypothesis and beam bending theory,we study the deformation principle of the flexible circle of the robot.The load during shape memory alloy's deforming serves as driving force.Thus the robot's locomotion model is built and could be base of locomotion strategy and controlling system designing.(3)Dynamic modeling and simulation of ring-shaped soft robot.The process of circular soft robot's deforming locomotion is divided into two parts: the deformation of flexible circle driven by the SMA springs and the rotation around the contacting point with ground.Then according to the dynamic characters,Lagrange equation and Newton-Euler method are applied respectively to the dynamic analysis of the two parts.The analysis of the flexible circle's deforming process is based on micro-element assumption and involved with a great number of DOFs.Therefore it is simple to perform the analysis with Lagrange method.While the robot is considered as a whole part in the rotation and only one DOF is involved.Thus Newton-Euler method is a better choice in this part.Finally,the rolling process is simulated in ADAMS.(4)Hardware and software design of the robot's control system.We analyze the requirements of the control system,and on this basis,we design the hardware modules,including microprocessor module,power supply module,signal processing module,driver heating switch circuit module,wireless communication module and so on.At last,the slave computer's control program and the principle computer's interaction interface are also designed.Based on the independently designed hardware and software system,the closed-loop control system is built with four flexible sensors.Thus the circular sort robot could be controlled automatically and serves as a platform in experiment on control algorithm.(5)Control strategy and experiment of the robot.The open loop control strategy and closed loop control strategy are experimented respectively,and the experimental results are analyzed.