Study On Dynamics And Terminal Trajectory Control Of DOF Gantry

In order to improve the lifting efficiency, the semi-automatic operating mode ofcrane robots, known as various of cable guiding material handling systems, is worthyof being adopted, in which the materials are handled automatically under thesupervision of the operators. In most of the previous studies, the related theoreticaland technological problems about the rigid-flexible coupled time-varying multi-bodydynamics as well as the trajectory tracking control of the end-effectors in the cranerobots, so the end-effectors are unable to track the desired trajectories accurately withgood dynamic characteristics. However, the mechanism system of2-DOF(2-degree-of-freedom) gantry crane robots is differentially flat if the distributed massof the cable are not taken into account, thereafter, it is expected that the problemsmentioned above is simplified.In order to prove whether the dynamic modeling of the mechanism of2-DOFgantry crane robots without considering the cable mass as well as the feedbacktrajectory control based on the property of differential flatness is suitable or not, themethods combined with theoretical analysis and experimental research are adoptedfor investigations about the mechanism dynamics as well as the trajectory control ofthe end-effectors of2-DOF gantry crane robots, some beneficial results andconclusions are obtained, as follows:The rigid-flexible coupled multi-body dynamic modeling and analysis of directdynamic problem of the manipulator are given are given using the ADAMS software,and it is found that the effectors brought by the cable mass can not be neglected,which will make the problem about real-time trajectory control of the end-effectorsmore difficult.In order to tackle it, the feasibility of the solution is further studied, in which thetheory and technology about trajectory tracking control of the end-effectors based onthe differential flatness are adopted, as follows:The various open-loop control experiments of the end-effectors are finishedbased on three different control modes including torque control, position control and velocity control in the test bed built, then it is found that the test trajectories are a bitdifferent from the desired trajectory, and they are closer to the simulated trajectoryusing the ADAMS software but there still exists some differences. Thereafter, it ispointed out the necessary to adopt a kind of trajectory tracking feedback controlscheme of the end-effectors.The various closed-loop control experiments of the end-effectors are finishedbased on three control modes, including torque control, position control and velocitycontrol, in which the trajectory tracking control scheme of the end-effectors based ondifferential flatness is used, then it is found that the control precision of the testtrajectories in the closed-loop experiments are improved a bit compared with those inthe open-loop experiments are experiments, also the test trajectories based on positionand velocity control modes are closer to the desired trajectory. So the feasibility of theproposed solution scheme is proven on the basis of theoretical analysis andexperimental research. If the technology of variable frequency about cranes are alsoused together, the use of2-DOF gantry crane robot in the industry practice ispromising, in spite of handling tasks for big loads.However, some useful measures should be taken to reduce the trajectory trackingcontrol error of the end-effectors, such as, to better eliminate the effects on trajectorycontrol precision brought by the mass and the flexibility of cables by optimizing thecontrol programming, to use high precision mechanical structures especially jointswith little friction should be used, to improve the measurement precision of the cableinclination angles, to use a high-performance and real-time motion control system andso on.