Structure Optimization Of Coordinate Measuring Machine With3-PUU Parallel Mechanism

Over the past decade parallel mechanism has been in-depth researched and extensiveapplied in the fields of robotics and machine tools with its high stiffness, small motioninertia, average error effects and other unique advantages, and some of them hasachieved commercialization, but relatively few applied and developed in the fields oftesting and measuring. A bran-new style coordinate measuring system with3-PUUparallel mechanism and its advantages as well as the lack of traditional coordinatemeasuring machine (CMM) was proposed which could realize3D measurement withonly one linear grating and two precision guides.Firstly, the theories of parallel CMM are described:6-bar measurement model wasachieved based on the theory of parallel kinematic mechanism, and the workspace of theparallel CMM was worked out by the limit boundary searching method. Thenmeasuring space with a0.05mm error of structure parameter as target was exploredbased on workspace and error model, and then the principle of maximum measuringspace was presented to elaborate the relationship between measuring space and lengthof bar. In order to enlarge the scale of measuring space of CMM, improve the measuringaccuracy and flexibility, the key dimensions and positional parameters of CMM wereoptimization designed, and the deformation of key components was processed by FiniteElement Method (FEM) according to the motion characteristics and parameters of thenew CMM prototype, so that the affect of deformation to measuring accuracy can becontrolled and decreased. Finally the hardware of control system of parallel CMM wasdesigned to achieve active measuring and the2ndgeneration prototype is developed. Thenew design will generally enlarge101%measuring space in x axis,134%in y axis,113%in z axis compared with the old one.