Research On Passive Flexible Variable Stiffness Joint Based On Temperature Controlled Shape Memory Alloy

Flexible variable stiffness refers to an adaptability that can flexibly change the system stiffness outside the output end of the system to change the system environment.Flexible variable stiffness has huge advantages in the research and establishment of safe human-computer interaction.Passive flexible variable stiffness joint refers to a kind of joint that changes the structural characteristics of the passive elastic element inside the joint to change the joint stiffness characteristics.This is an important trend in the research of robot drive technology.This paper is devoted to exploring the feasibility of the application of temperature-controlled shape memory alloy in passive flexible variable stiffness system.Based on the series elastic actuator SEA to improve the linear passive flexible variable stiffness joint,the angle of the temperature-controlled shape memory alloy elastomer in the connection system is improved.,Temperature and other parameter control for stiffness control to achieve a balance between the differences in actuator accuracy and safety requirements under different environmental conditions.Mainly conducted the following research:First,the functional requirements of passive flexible variable stiffness joints are analyzed,a design plan for variable stiffness joints is proposed,physical prototypes of joints are made,joint component parts are designed and selected,and the range of joint stiffness adjustment is variable and variable stiffness Elaborated.Secondly,a position control system designed independently of stiffness adjustment was designed.From the perspective of dynamics,a flexible and variable-stiffness joint system model is established.And the transfer function of the variable stiffness joint system is measured and calculated.Based on the transfer function of the joint system,the fuzzy-PID control simulation was carried out through Matlab/Simulink.Then,with reference to the requirements of the controllers related to flexible variable stiffness joints,the hardware of the drive system is configured.An experimental platform of hardware drive system based on BECKHOFF/TwinCAT real-time control system was built.The control program of the host computer based on the experimental platform of the drive system is designed,and the position control of the passive variable stiffness joint is completed.Finally,a static stiffness experiment was carried out on the temperature-controlled shape memory alloy elastomer,which confirmed the variable stiffness capability of the elastomer used in the passive flexible variable stiffness joint.And the tracking experiments of position step signal and sinusoidal trajectory signal were carried out on the joint systems in different stiffness states.The experimental results and data were analyzed and processed.The feasibility of the application of temperature-controlled shape memory alloy in passive flexible variable stiffness system was verified.