A Research On The Control Strategy Of A Cable Driving Joint And Its Parameter Optimization

In present research of humanoid robot,there is a gap between humanoid robot and human in the aspect of driving flexibility.Cable driving is a way to increase the flexibility,with which the impact can be absorbed well during the movement and robot can act more smoothly with less energy consumption.A particular problem in cable driving is that the cables can only resist traction but not compression,so it is necessary to use at least two cables to control a complete degree of freedom(DOF)of a robot joint.The control of the two cable traction influences not only the articular position of the joint but also the resistance to torque about the joint,so it is necessary to design joint control strategy for position control and force control.In this thesis,the physical model of an antagonistic cable driving joint is constructed,and the relationship between the cable contraction and the joint drive torque is established.A joint control strategy is designed which consists of position control and force control.As the flexible control model is highly nonlinear,the improved ADRC[2] is used in position control to obtain required joint driving torque under the current position error,and cable tensions are arranged in tension arrangement section besed on the torque.The parameters' influences on the controller's performance are determined.By setting the relative independent searching parameters,the multi-dimension parallel searching ability of AFSA is improved and the searching parameters are adjusted according to different stages so the searching speed and precision of the algorithm can be improved.The backward artificial fishes are encouraged in the early stage and re-thrown in the late stage.The objective function is set up for control system optimization,and the ADRC parameter is optimized by artificial fish swarm algorithm.The ADRC control system is built in MATLAB.Using united simulation of ADAMS and MATLAB,a joint angle tracking to human motion is conducted.This thesis studied the problem with cable driving of robot joint,designed an active control strategy for cable contraction.It realizes the control of joint torque and the unflactuating adjustment of joint angle to a specified articular position,through the control of cable contraction.The control strategy should be of great significance in the research of cable driving control and the improvement of humanoid robot performance.