Research On Flexible Joint With Adjustable Stiffness For Legged Robot

The legged robot was caught the researchers’ attention due to its strongadoptive capability under complex environment. As an important component of thelegged robot, joint plays a vital role. The robot would work more effectively if thejoint stiffness is adjustable as the animals’ joint. Therefore, the stiffness variationmust be considered during the design of the legged robotic joint. In this paper, therotational joint with adjustable stiffness was designed based on the analysis of thelever transmission mechanism.Firstly, the adjustable joint designed in this study was based on the changeablepivot lever mechanism. The structural parameters and important components andtorque sensor of the joint was analyzed and optimized by finite element analysis inorder to compact the structure as much as possible. The joint design was aimed toreduce its weight and size without weakening the joint structure which couldpotentially improve the joint output capability.Secondly, the kinematics principles are applied to analyze the joint partrelations and further realized the motion of the joint and stiffness control. Then theoutput characteristics of torque and angular displacement were theatricallycalculated and the proper actuator component was chosen based on the overallanalysis. The mathematical models identification of the torque and angulardisplacement relation under static load was studied and the output characteristics ofthe joint were analyzed to realize its stiffness changeable feature.Finally, the present study designed and assembled the platform for testing thestiffness-changing feature of the joint and further build the xPC Target environmentbased Hardware in the loop testing system. The torque sensor of the outputcomponent was calibrated, and thereafter the performance of the prototype joint wastested. The experiment results verified the validity of the joint design.