Design And Experimental Analysis Of Robot Active Variable Stiffness Joint

As the core components of robot body,joints are not only the power source for the robot to complete various movements,but also the key to ensure the flexibility and safety of multi-robot cooperation and human-robot interaction.Traditional rigid robot joints can meet the requirements of position accuracy control,but they are not flexible and safe enough.Therefore,relevant scholars have proposed a solution based on flexible arm with compliant joints.In this scheme,a variable stiffness joint has become a research focus and hotspot.The difference between active and passive variable stiffness joints is that a variable stiffness device is added between load and drive.Up to now,the key technical problems of active variable stiffness joint mainly focus on the breakthrough of mechanism,light modularization and engineering application.Using mature material and meehanism teehnology to solve new problems,a new variable stiffness joint based on leaf spring flexible element and crank slider stiffness adjusting mechanism is designed.Its advantage is that it has the flexibility of passive variable stiffness joint at the same time,and can overcome the shortcomings of passive variable stiffness joint stiffness which is not adjustable.In this paper,the joint is modeled and simulated mathematically for stiffness control.The simulation results show that the joint stiffness can be effectively and actively adjusted by controlling the input angle of the rigid-adjusting mechanism.The transfer function and PID position control block diagram of the system are established.By simulating the external collision interference of the system.The simulation results show that the system can respond to the external impact load effectively and protect the electrical system and main structure.In this paper,a single-degree-of-freedom experimental platform for variable stifl&iess joints is built,and the program is designed for three basic functional units of variable stiffness joints:transfer motion,adjusting stiffness and collision protection.Through the analysis of the invariance and variability of joint stiffness,the feasibility of the principle of joint variable stiffness is verified,which shows that the active variable stifiness joint has both flexibility and can actively change its stiffness.The designed variable stiffness joint has certain engineering application value.