Research On Design Of SMA Actuated Humanoid Wrist And The Control System

The bionic robot,refers to the robots that employ biological-structure-like mechanism and engage in the biological work.Bionic robot technology is a combination technique of multidisciplines.The concept of intelligent materials originates from the bionic purpose,shape memory alloys(SMA)as a kind of smart material,its most important feature is the Shape Memory Effect(SME).The main function of SMA is used as an actuator.It has been widely used in robots of humanoid,biomedical,aerospace and automobile,etc.The main work of this thesis is arranged as follows:First of all,this thesis introduces the research background,introduces the development and research status of shape memory alloy at domestic and foreign;then,it introduces the present situation of application and development of SMA driven bionic robot at home and abroad;and then it describes the research significance of this project and the main research contents of this thesis.According to the characteristics of the humanoid wrist movement in this work,the drive structure of the bias two-way SMA actuator was selected.Then the structure of the SMA actuator is designed,and manufacturing process is conducted and its installation was finished.At the same time,this thesis designed the SMA driven humanoid wrist,analyzed the forward and inverse kinematics,statics and dynamics of the wrist of humanoid,and the finite element analysis of universal joint was carried out.The feasibility of the designed 2-DOF SMA driven wrist was verified.Third,the overall control system design for the wrist was conducted,including the SMA heating unit circuit design,the hardware and software of control system feedback signal data acquisition selection,include:Arduino Mega 2560,Matlab and Arduino IDE,and the displacement sensor,the angle sensor and the temperature sensor selection.Finally,based on Matlab platform and the Arduino IDE integrated development environment,this thesis programmed the direct PWM signal control algorithm,PID control algorithm and model free adaptive control(MFAC)algorithm to compare and complete the motion control tasks of the SMA actuator driven wrist.Via experiments,the results show that the control system can realize accurate displacement control of bias two-way SMA actuator,can drive the SMA actuator to achieve the required functions;the experimental results can also verify that the wrist of humanoid is able to achieve the performance specifications mentioned in this thesis.