Research On The Control Strategy Of Vibration Suppresion For The Flexible-joint Manipulator

Because of their unique properties and good performance, some elasticcomponents, such as the harmonic reducers and the torque sensors, are widely usedin the joints of the robots and manipulators, in order to obtain high reduction ratio,detect the joint torque and realize the modularization of the joint system. Howeverthese elastic components bring joint flexibility into the system at the same time,which makes its stability control more complex. The robots will vibrate duringoperation due to the existence of the parameter uncertainties and externaldisturbances. Also the joint flexibility makes it inevitable that there remains someresidual vibration when the robots stop. These phenomena will not onlysignificantly reduce the efficiency of the system, but also make it impossible thatthe end-effector stays in the desired position quickly and accurately, if so thehigh-precision position control would be meaningless. Therefore it’s necessary totake measures to suppress vibration. This paper will study the strategy andalgorithm of high-precision position control and vibration suppression control,simulate the control system designed for the flexible joint manipulator with th esimulation software Simulink, and carry out some experiments to verify theeffectiveness of the controller in the7-DOF humanoid manipulator.Firstly, the dynamic model of the7-DOF humanoid manipulator withconsideration of joint flexibility is built based on the Newton-Euler method.Strategy of high-precision position control is brought out. Based on the LuGredynamic friction model, the adaptive identification and online compensation offriction is realized. Backstepping approach is used to design position controller formulti-joint manipulator, but the traditional backstepping approach is much sensitiveto the accuracy of the model parameters, parameter uncertainties and externaldisturbances will significantly reduce the controller’s performance. So a series offuzzy adaptive disturbance observers are designed to identify the disturbances in themotor side and the joint side respectively. At the same time, first-order low-passfilters based on the Dynamic Surface Control are introduced in the controller toeliminate the dependence of the acceleration and jerk signals. The simulation of thecontroller designed for the2-link flexible joint manipulator verified theeffectiveness of algorithm for the stability and submissiveness control.In order to make up for the shortcomings of the open-loop control in residualvibration suppression and anti-jamming performance, a hybrid controller, whoseopen-loop control is based on input shaping technique and closed-loop control is based on PD-type fuzzy logic algorithm, is designed. Through the introduction ofnegative-amplitude pulses and the rational design for time delay and amplitude, thedelay is greatly shortened compared with the ZVDD input shaper. Simulation resultshave showed that the hybrid controller can achieve the expected goals, fuzzy logiccontrol, compared with conventional PD control with gravity compensation, caneliminate the dependence of model parameters and the gain limitation brought in byhardware’s performance. Finally some related experiments are carried out to verifythe viability of the control algorithm studied in this dissertation.