Design And Control Of Flexible Drive Module Based On Shape Memory Alloy Spring

As the earliest multicellular animals on the earth,mollusks have evolved all over the world through billions years of evolution.They have evolved various physiological structures to adapt to the complex and changeing natural environment.Inspired by the diverse body structures of molluscs,soft robot has gradually become a hot topic in the field of robotics research.Compared with rigid robots,soft robots are more flexible and compact to adapt to the changing unstructured environment,and their safety in the process of interacting with humans is better than rigid robots.As the field of human exploration continues to expand,flexible robots will play a greater role.After years of development,the design of software robots has made great progress from simple to complex.It is continuing to move toward flexibility and multi-degree of freedom,but current drives and sensors are derived from traditional rigid robots,which are bulky and cumbersome due to their lack of flexibility.These are not in line with the development requirements of flexible,compact and highly integrated soft robots.Finding a way that is different from traditional driving methods,sensing and control methods has become the focus of soft robots.On the other hand,soft robots are designed for specific tasks,lacking versatility and costly.If the soft robot can be modularized,a universal flexible drive module that can be precisely controlled can be designed,and then the flexible robot can be assembled using a flexible module for a specific task.This modular design of soft robots can greatly increase production efficiency,reduce costs and save design time.This thesis focuses on the flexible drive module,shape memory alloy spring,closed-loop control,compression compensation,bionic dexterous hand and other concepts.By studying the octopus wrist,design a flexible drive module that can be precisely controlled,and the flexible module is moved by geometric analysis.Learning modeling.Based on this,the flexible module is optimized.Through the research on the structure of the human hand,the idea and method of designing the flexible module are applied to design and manufacture a flexible bionic dexterous hand.The main research contents and results of the thesis are as follows:(1)Firstly,the bionics structure of the octopus wrist and foot was studied.According to the structure and movement mechanism of the brachiopod muscle,and the idea of modularization was applied,a flexible drive module was designed.Silicone is used as the support material,and the SMA spring acts as an actuator,using linear Hall sensors and magnetic steel to feed back the shape of the flexible module.Explain in detail the flexible module construction and pouring process.After studying the motion mechanism of the SMA spring,PWM waves were used to control the shrinkage and stretching of the SMA spring.The flexible module control system and the basic control scheme are established.The linear Hall sensor is used to feedback the bending variation in a specific three directions,and the incremental PID is used to control the motion of the flexible module in a closed loop.The SMA spring is heated by controlling the heating actuator to cause a contraction,stretching or holding motion to cause the flexible module to flex and rotate.(2)Apply kinematic analysis to kinematics modeling of flexible modules.There are four assumptions:The deformation of the flexible module is only produced by the SMA spring actuator;the flexible module is incompressible in the axial direction;the flexible module is curved with equal curvature;the deformation of the flexible module is only affected by statics.The forward and inverse kinematic relations of the flexible module from the operating space to the joint space are established by the DH coordinate system transformation matrix.Because the flexible module moves according to its own deformation,the joint space and the driving space are not the same,so it is necessary to establish a mapping relationship between the joint space and the driving space..The flexible module has axial compression during the actual motion,so this thesis also analyzes the compression deformation of the flexible module,and establishes a mathematical model of compression compensation to compensate for the error caused by axial compression.Finally,the static force analysis of the bending motion of the flexible module is carried out.(3)By loading the transverse load on the curved flexible module,it is proved that the bending of the flexible module no longer conforms to the constant curvature under the loaded state,and the sensing and measurement of the flexible module needs to be improved.The curvature of the first and last arcs of the flexible module is measured by adding three sets of sensors to the upper,middle and lower positions of the central axis of the flexible module.The Lagrange interpolation method is used to find the curvature of the arc of the unknown segment,and the arcs of each segment are accumulated to find the bending angle and rotation angle of the whole flexible module.By using the visual measurement method to compare the central axis bending curve and the constant curvature bending curve obtained by Lagrangian interpolation method,it is verified that the improvement measures and the interpolation algorithm can effectively determine the true bending state of the flexible module under load.According to the space environment requirements,this thesis also designs the lightweight module,and adds the connection structure at the beginning and the end of the module to facilitate the end-to-end connection of the flexible modules.The flexible robotic arm is assembled using a lightweight module.Simulate the space-free environment in the pool,let the flexible manipulator move and grab various objects,and verify that the assembled arm of the module has good flexibility and coordinated control.(4)By studying the structure and movement of the bones,muscles and tendons of human hands,this thesis designs a bionic dexterous hand.In order to maximize the imitative structure of the human hand,this article uses 3d printing to design and make the bone structure of the bionic hand.The SMA spring is used to simulate the action of the muscle,and the linear Hall sensor is used to feed back the movement of the finger joint.In order to make the bionic hand closer to the human hand from the appearance and feel,this article also adds a layer of silicone skin to the bone of the bionic hand,and designs the process of casting the skin and pouring the process.Establish a bionic dexterous hand control system and control strategy to achieve coordinated movement between each finger joint and multiple fingers of the bionic hand.Finally,by controlling the bionic dexterous hand to make the fist and the gestures representing the number,it is verified that the dexterous hand not only highly imitates the human hand in the shape,but also simulates the human hand very well in the movement mode.(5)By studying the structure and movement of the bones,muscles and tendons of human hands,this thesis designs a bionic dexterous hand.In order to imitate the structure of the human hand,this article uses 3d printing to design and make the bone structure of the bionic hand.Use SMA springs as the drive.The motion of the finger joint is fed back using a linear Hall sensor.In order to make the bionic hand closer to the human hand from the appearance and feel,this article also adds a layer of silicone skin to the bone of the bionic hand,and designs the process of casting the skin and pouring the process.Establish a bionic dexterous hand control system and control strategy to achieve coordinated movement between each finger joint and multiple fingers of the bionic hand.Finally,by controlling the bionic dexterous hand to make the fist and the gestures representing the number,it is verified that the dexterous hand not only highly imitates the human hand in the shape,but also simulates the human hand very well in the movement mode.