Design And Experimental Research Of Flexible Joint Of Lightweight Manipulator

Currently, due to the high load/weight ratio and low power consumption, etc.,flexible joints are widely used in many fields, including lots of workplace whoseworking position changes continually, such as space, the battlefield and the family,and some other dangerous workplace. In addition, as a force output drive, SEA has alow output impedance, which means it can greatly increase flexibility of the jointsand better withstand the impact. In consideration of the broader applicationprospects of flexible joints, the flexible joint based on SEA has been developed, andthis paper will be divided into the following aspects.This paper designs the mechanical systems, drive systems and sensor systemsof the flexible joint. Firstly, we design the transmission system, and describes indetail the process of the optimized design of SEA.By Workbench DOE experimentaldesign method, several shapes frequently used for the SEAs are optimized separately,and ultimately the three-dimensional model is determined. Then the stiffnessanalysis on the SEA is done. Through the relationship between flexible angle-loadtorque and load torque-stiffness, we get the SEA model with fixed stiffness andwith variable stiffness separately. Then the sensor system is designed, the suitablejoint position sensors are selected, and the torque sensors is designed on which thesimulation analysis and stiffness analysis are done.Considering the SEA model with fixed stiffness and with variable stiffnessrespectively, we establish the appropriate dynamic model of the flexible joint. Firstly,simplifying the flexible joint and adopting the assumptions proposed by Spong, thedynamic model is simplified to be undamped linear torsion with fixed stiffness.Then, the dynamic model is simplified to be undamped linear torsion with variablestiffness. Meanwhile, in order to simplify the control model, we adopt the dynamicmodel with fixed SEA’s stiffness. And we present the control model of the torquefeedback with the inner position loop to overcome the impact of the nonlinearfactors of flexible joints. And we get open-loop transfer function and closed-looptransfer function of the position loop and torque loop from the control model.The performance test of the flexible joint is divided into the stiffness analysisexperiment, torque sensor calibration load-following experiments. Firstly, weestablish the experimental platform of the flexible joint, conduct the stiffnessanalysis experiment, compare the deviation between the experimental results andthe theoretical value, and analyze the its main reason the SEA after heat treatmentcan not meet the design requirement. Then we conduct torque sensor calibration experiments, do the hysteresis and linearity analysis and check the designspecifications of the torque sensor. At last, we carry out the load-followingexperiment of the flexible joint, including the position-following experiment andtorque-following experiment, and conclude that the control model for the flexiblejoint is appropriate.