The Research On Modular Humanoid Stiffness Joint

In recent years,the developing of robot technology broadens the scope of application of the robot greatly.The traditional industrial robots are used in a fixed situation which is unable to meet the new needs of the new era.People wish the robots of the next generation with the ability of higher flexibility,enhancing the ability of man-machine collaboration,deepening the degree of human-machine interaction,and replacing human beings to complete varieties of complex tasks in an unknown environment.In the process of cooperative working of robots and humans,the robot is completely exposed to the human environment completely,which is complex and unknown to the robot.How to ensure the safety of human beings in this environment is the core problem which determine the application scope of the robot in the future.And replacing humans to complete varieties of complex missions better for the next generation robots is the other problem which must to be solved in the developing process of the of robots.Aiming at solving the above problems which restrict the development of robots,this paper designs a kind of flexible joint with variable stiffness based on the idea of impedance control.The introduction of flexible element into the joints has the advantage of improving the flexibility of the joints,buffering the load,and reducing the contact force in the collision.All of the advantage can ensure the safety of human and the robot.The simple mapping relationships between the sEMG signal and the human arm stiffness are established,and the research that how the joint flexible be able to accomplish the specific complex tasks better from the perspective of the stiffness changing is taken off.In the first part of the paper,it analyzes the current research situation of flexible joints home and abroad and summarizes the advantages and disadvantages of the different design principles of the flexible joints.Then,the methods of changing the stiffness of the robot joint are researched,and the necessity of stiffness changing is analyzed.A reasonable joint designing principle is chosen based on the research.The principle of variable stiffness and the way to change stiffness are modeled,and the stiffness curve and torque curve are deduced theoretically.After several optimization,the ideal joint characteristic curve is obtained.Finally,the theoretical model is transformed into concrete mechanical objects.In order to carry out the related experiments,it is necessary to control the joints.In this paper,the electrical hardware system and the basic control system are built,the data transmission channel and the drives among different hardware are also built.The data transfers from the host computer to the lower computer,and then converts into the motion of the motor.After completing the above work,experiments are designed to demonstrate the characteristics of the joint.In order to introduce the control strategy of stiffness of human central nervous system,this paper presents three mapping relationship between the sEMG signals and human upper limb joint stiffness.The sEMG signal acquisition device is used to collect the sEMG signal in the process of human changing its stiffness.And the signal is transformed into the stiffness information of the variable stiffness joint by the mapping relationship to realize the control of the flexible joint with the central nervous system.In the end of this paper,some experiments are designed to simulate the changes of the stiffness of the human arm during the corresponding actions.The experiments demonstrate the effect of stiffness changing and the effect of variable stiffness on the output of the joint,by comparing the joint action effect under variable stiffness and the action effect of the joints under the three kinds of stiffness.