Study On Driving System Of Passive Flexible Variable Stiffness Joint

Flexible variable stiffness joints,which are capable of changing the apparent output stiffness independently of the output position,have a strong ability to adapt to the environment as well as advantages in establishing a safe human–robot interaction,increasing energy efficiency and reducing the effects of impacts.Passive flexible variable stiffness joint is a flexible variable stiffness joint with property of physical adjustable stiffness.It is an important research direction of robot driving technology that the structural stiffness of the flexible variable stiffness joints are adjusted by changing the structural properties of the internal variable stiffness elastic element of the joint.This paper is devoted to the study of a new safe and controllable passive flexible variable stiffness joint and the independent control of stiffness and position so as to achieve the balance of actuator accuracy and safety requirements under different environmental conditions.The following studies are conducted:Firstly,the variable stiffness scheme and configuration scheme are proposed and the system mechanical model is established.Based on the mechanical model,the variable stiffness characteristics of the passive flexible stiffness joints are analyzed.Joint physical prototype is designed according to the theoretical analysis results,and finite element analysis of the key components in prototype is carried out.Secondly,architecture of the independent stiffness adjustment system and the position control system is established.The half-closed-loop control of the stiffness system is realized by the speed / position double-loop PI controller.The parameters of the controller are adjusted by the particle swarm optimization algorithm and the stiffness step tracking simulation experiment is carried out.The Driving system dynamic model of flexible variable stiffness joint with single link is established.The open-loop control on the position of the link was realized by the sliding mode method while the system status was effectively observed by the robust observer,and position sine tracking simulation experiment is carried out.Then the stiffness / position linkage control law of the flexible joint stiffness system with single link is designed to establish the linkage mechanism of the link speed and joint stiffness.Next,hardware of the driving system is configured according to the control characteristics of flexible variable stiffness joint and the interface circuit is designed.Then,host computer of the driving system is designed according to the hardware system and the function modules of the software control system are briefly introduced.Finally,the experimental test platform of flexible variable stiffness joint is set up.Then,the characteristic analysis experiments of flexible variable stiffness joint are carried out.The experimental data are analyzed and the ability of variable stiffness of passive flexible stiffness joint is verified by experiments.