Dynamic Modeling And Control Of A Wire-driven Parallel Robot In Low-speed Wind Tunnels

In order to realize the control of5kinds of single degree-of-freedom forcedoscillatory motions of the vehicle model in low-speed wind tunnels, the methodscombined with theoretical analysis and experimental research are adopted forinvestigations about dynamics as well as the trajectory control of a wire-drivenparallel robot, some beneficial results and conclusions are obtained, as follows:Firstly, the working principle of the wire-driven parallel mechanism for forcedoscillation experiment in low-speed wind tunnels is introduced, and the mathematicalconfigurations of the mechanism are built by local coordinates and global coordinates;the kinematic problems of the mechanism of the system is analyzed on the basis ofthe mathematical model for dynamic analysis. Since the elasticity of wire can not beignored with the consideration that the elasticity will affect the driving force ofactuators and the pose of vehicle, an approach for modeling of wire dynamics ispresented in which the wires are regarded as linear springs. In order to meet thefrequency requirements of the forced oscillation experiments, vibration characteristicsis analyzed and the natural frequencies of the mechanism is obtained which can avoidthe resonance, a series of appropriate spring parameters are set by normal modeanalysis which provides a theoretical basis for the selection of wire parameters for theexperimental prototype of the robot.Secondly, the dynamics problem of the mechanism for the wire-driven parallelrobot is analyzed, but it is difficult to solve the dynamics equations for which are agroup of complicated, coupling and nonlinear ordinary differential equations. Hencethe dynamics model of the mechanism is built in the professional dynamics analysissoftware ADAMS. It is the fist time to build cable dynamic model based on the linearspring theory using ADAMS software, and the rigid-flexible coupled multi-bodydynamic modeling of the mechanism is given. The dynamic simulation results haveindicated that the vehicle model can realize the desired forced oscillatory motions inthe whole, but there is an obvious fluctuation and delay in the comparison of the realtrajectories with the desired ones. Thirdly, in order to realize the accurate control of the forced oscillatory motionsof the vechile mode in low-speed wind tunnels, the control system model of thewire-driven parallel robot is established with the consideration of the the influencesby the actuator dynamics. A Proportional Integra (PI for short) control strategy basedon vector control of permanent magnet synchronous motor is presented. Because thedynamics of the wire-driven parallel robot is a highly coupled and inherentlynonlinear system, an electromechanical coupling system consisting of a mechanicalsystem dynamics model built by ADAMS software and an actuator dynamics modelbuilt in the environment of MATLAB/Simulink is used as the robot dynamics model,and a PI controller is designed for conotroling the robot dynamics in the environmentof MATLAB/Simulink. The control simulations results have indicated that the realrotation angles of the winches can well follow the desired ones, and the realtrajectories of the vehicle models are close to the desired ones.Finally, the experimental prototype of the wire-driven parallel robot is built. Thekinematic control of the robot is only implemented because of the limitedexperimental conditions. The experimental results have shown that there is a certainerror between the real trajectories of the vehicle model and the desired ones. Then theerror analysis is given for the further improvement which is of practical significance.