Analysis Of The Hexaglide Parallel Mechanism With Double-end Universal Joints In Kinematics Chains

With the rapid development of economy, requirements of oils, gas and other hazardous chemicals in industry increase significantly, which also attrack more and more attention for the security consideration. In the past, monitoring and control such kinds of flammable, explosive and toxic materials are often performed on a real vehicle in a actual transportation process. Such method is not only costly, high-risk but also unrepeatability, so a Hexaglide parallel simulator is developed in the laboratory which is used to repeat the simulation of hazardous chamicals transportation.The motion simulator used to simulate the tansportation process of hazardous chamicals has been already built up, on which some transporation simulation can be performed. In order to estimate the simulator's capability, different methods are adopted such as theoretical analysis, simulation and experimental validation. The thesis focuses on the analysis of workspace, accuracy and dynamic performances.First of all, with the consideration of hexaglide parallel simulator's structure feature, i.e. double universal joints in a kinematics chain, a branch-fixed modle is established which is used to describe universal joints'range. The range of universal is also calculated when the parallel simulator is at a dedinite pose. Based on that, 12 univesal joints rotation angles are solved combining inverse kinematics of the simulator when the end-platform is located with a specific pose. Combined with inverse kinematics and other structural constraints, a position workspace of the simulator with zero pose is determined.Secondly, to further improve the end-effector's motion repeatability, a calibration process is carried out with a laser tracker as measurement instruments to measure the platforms's pose. By subtracting the nominal links'length from the length that calculated by the measured pose, a calibration model is established. Through a nonlinear least squares method, parameters of the simulator are identified. In the end of the section, a circle trjectory and several arbitrary poses are chose to verify the effectiveness of the calibration.Finally, in order to analyze the simulator's dynamic performance, a kinematic influence coefficient method is utilized to calculate each parts'kinematic information based on the simulator's structural parameters. With the utility of kinematic influence coefficient, the rigid dynamic model of the simulator is built up by the principle of virture work. A comparison with commercial ADAMS is carried out to verify the effectiveness of the proposed model.Through a detailed analysis of the Hexaglide parallel mechanism, such as the workspace, kinematic calibration and dynamic analysis, the simulator's capability is more clear, and the motion of the platform is more accurate. The simulator's trjectory planning process can take full advantages of the analysis results based on this work.