Joint Control Technology Of Bionic Variable Stiffness Robot

The deep development of robotics technology has led to the application of robotics in all aspects of daily life,especially in the medical and logistics industries,where robots have become an important force for industrial reform,while the safety and flexibility of human-robot collaboration has become a pressing issue needing to be solved.Based on the principle of human upper limb flexibility,this paper designs a two-degree-of-freedom robotic arm with variable elbow joint stiffness,while taking the surface electromechanical signals as the human elbow joint stiffness information carrier,so as to propose a humanrobot stiffness matching control method and improve the flexibility during human-robot interaction.The main works accomplished in the paper are as follows:First of all,the prototype design and processing of SoftJoint ? was completed based on the biological parameters of human upper limbs.Improved design of SoftJoint ? was carried out for laboratory variable stiffness flexure joints: the shoulder joint pitch freedom was increased,the variable stiffness adjustment structure was designed,light weight was achieved by selecting suitable materials and 3D printing,kinematic forward and inverse solution calculations were performed to analyze the robot arm workspace.Secondly,based on the static analysis,the relationship between the stiffness of elbow joint of the robotic arm and the adjustment amount of elastic band,the angular displacement of elbow joint and the deformation angle of elbow joint was derived,while the mathematical model of the stiffness of elbow joint was also established;the human stiffness determination method taking the electromyographic signal as the characterization quantity was proposed.The sEMG signal was collected through the MYO hand loop,while the sEMG signal was rapidly amplitude enveloped and normalized to map the sEMG signal segmentally based on the upper limb muscle activity level as the human elbow joint stiffness.Then,the control system of robot arm was constructed,and the human-robot collaborative stiffness matching algorithm was designed to complete the hardware selection and software program writing of the control system.It realized the robot arm joint motion control,stiffness adjustment and human-robot collaborative stiffness matching function.Finally,the experiment of linear trajectory following,variable stiffness joint stiffness step,and human-robot stiffness matching static collaborative lifting of heavy objects were completed,which demonstrated that the robot arm has faster variable stiffness response and better human-robot collaborative effect.