Qiu Zurong

A study on dynamic error of the measurement machine with low stiffness

The higher measuring accuracy and velocity of the coordinate measuring machine are required for shorter cycle time for modern manufacturing industry. However, the increments in measuring accuracy and velocity of CMM applications are limited by the low stiffness components which cause the complicated deformation and dynamic errors. According to the structural characteristics of a special structure coordinate measuring machine, a non-rigid body model is established and the error compensation formula is derived. Further more the dynamic model of this CMM is established by Lagrange energy theory. Based on the models of this CMM, the systematic analysis method of the measurement error is proposed. In this paper, the measurement errors of CMM are studied in an integrated theoretical and an experimental approach. We use a laser interferometer to measure the measurement errors of this CMM under static deformation, and the dynamic errors are measured by different motion parameters of CMM. The experiment results show that the measuring errors caused by the limited stiffness of the components of the measuring machine can not be neglected. By software compensation, the measurement error can be reduced from 8.9μm to 2μm. The outcome of the dynamic errors experiment reflects the influence of dynamic errors under different motion parameters. Hence, the result is useful to study the measurement for decreasing and restraining the dynamic errors and to present a clearer and deeper knowledge of compensation for dynamic errors.

A precision robotic system for 3-D Micro-Assembly

A type of robotic system for 3-D precision Micro-assembly was described, which can be used to assemble the micro Inertial confinement fusion (ICF) target which was made up of two Half-hohlraum (diameter:800μm∼1000μm, length:1mm) and a capsule (diameter:200μm∼500μm). The system structure and composing were described, and the key technology was introduced too. A new kinds of piezoelectric micro-gripper was developed in this robotic system. The assembly experimental results verify the position accuracy of capsule in the hohlraum is less than 10 μ m.

Measurement error caused by bearing runout in laser tracking system and the selection of bearings

Bearing runout is one of the main error sources of laser tracking system. This paper tried to analyze the relationship between the measurement errors and the bearing runouts through establishing an error model. According to the model, the error distribution diagram has been drawn. It is pointed out that the measurement errors change as the pitch angle changes, the maximum errors distribute on a plane whose pitch angle equals π/2. With regard to the measurement, it is better to avoid placing the measured points on this plane. The errors are irrelevant to the distance between the measured point and the tracking head. When bearings with P2 precision grade are used, the measurement error is as high as 9.8091µm. The error model can effectively guide bearing selection, shorten selection time and improve production efficiency.

Thread probe measuring angle calculation of flexible calibration

Large tubular serrated thread detection method uses a new type of threaded probe, the Cone anvil of the probe is selected by the thread teeth type. The angle between the axis of thread and cone is 60 °, the calibration device in this paper is designed to flexible to the angle of calibration, and the measuring range of flexible calibration for anvil is theoretical analyzed and calculated.

Application of particle filter in high accuracy geometry measurement

In order to enhance the adaptability of visual inspection systems to different environmental illuminations and backgrounds in projects, to eliminate the interference owing to various disturbances, such as the noises of inside circuits, the ideal model and the actual situation with the disturbances of noise of a gray transition region of a target edge was investigated and a new self-adaptive method for noise elimination and image segmentation based on a particle filter was proposed. First, the noise particle set of the pixels in the gray transition region of the target edge at the initial time was established, posterior probability density of noise particle was acquired through the recursive Bayesian estimation method, and disturbances on pixels of the gray transition region of the target edge was eliminated. Then, the iterate result of the precise edge position was estimated for the instability of the grey value of pixels in the gray transition region of the target edge. Finally, the geometrical parameters of the target concerned were solved with the computation of the data of the complete contour extracted. Using the method, the angle measurement accuracy is less than 0.0068 degrees, and the standard deviation is 0.00123; the diameter ratio measurement accuracy is less than 0.00057 degrees, and the standard deviation is 8.67215E-5. In conclusion, the proposed algorithm can quickly and precisely achieve the noise elimination and image segmentation.