Research On Hybrid Equipment Suitable For Processing Large Marine Propeller And Crucial Technology Of Parallel Machine Tool

The traditional serial machine tool is overstretched in machining the complexsurface parts such as propellers or impellers, parallel machine tool is its beneficialsupplement, and the hybrid machine tool is a further development of the parallelmachine tool. The hybrid machine tool combines the main advantages of the parallelmachine tool and serial machine tool. It has a number of advantages, such as highstiffness, high load capacity, large workspace, strong reconfigurability and othercharacteristics. It is a promising form of multi-axis CNC machine tools. In this paper,a hybrid equipment that suitable for machining large marine propellers is designed byusing the branched chain constitution form of the BJ-04-02(A) type crossbar parallelmachine tool and some serial machine tools being applied widely and successful forreference.Then, positional forward solution and inverse kinematics, velocity,acceleration, singularity, workspace, dexterity and structural parameter optimizationof the crossbar parallel machine tool have been studied. Furthermore, the kinematicsand dynamics simulation of the machine tool are analyzed by using the virtualprototype technology.Firstly, for the deficiencies of the serial and parallel machine tools, drawing onthe advantages of both, a hybrid device used for processing large-scale marinepropellers is designed through a comprehensive configuration. This device cancomplete the processing of the entire propeller by a single fixture, avoidingduplication positioning, improve the machining accuracy and efficiency.Secondly, the research on positional forward solution of the6-UPS type crossbarparallel machine tool has been carried out by using quaternion and the generalizedinverse. In addition, the solution of forward position analysis of the general6-UPStype parallel mechanism is also studied through constructing12identical equationsand using elimination method of reducing order.Thirdly, the new Jacobian matrix which is a velocity mapping from three pointsof the moving platform to drive rods with consistent dimensionless of the BJ-04-02(A)type machine tool is derived by means of three-points method proposed by Gosselin.On the basis of the inverse kinematics, the degree of freedom, velocity, acceleration,and singular configuration of the machine tool are studied based on screw theory. Then, on the basis of inverse kinematics, workspace of the crossbar parallelmachine tool with constraints is obtained via three-dimensional search method and theinfluences of the hinge angle on workspace is discussed. Dexterity distribution of themachine tool is obtained based on the new Jacobian matrix. The influence rules of themachine structural parameters on workspace and global dexterity index are analyzed.Structural optimization is carried out by treating workspace volume and globaldexterity indexes as the global optimization goals. Compared with the initial data,optimized results are respectively increased by0.40and0.26times, achieved thedesired goal.Finally, the corresponding virtual prototype was established in UG based on thereal machine tool. After that, it was imported into ADAMS to do some kinematicssimulation analysis by modifying processing, adding kinematic pair constraints,increasing driving influence and function. Forward kinematics and inverse kinematics,driving functions of the motors, angular variation range of the hinges, the mappingbetween driven joint velocities and the end effector velocities, force analysis of thedriving joints and passive joints, etc are obtained through measuring tools in thesimulation process.