Zhonghua Gao

Error analysis and modeling for the time grating length measurement system

Through analyzing errors of the length measurement system in which a linear time grating was the principal measuring component, we found that the study on the error law was very important to reduce system errors and optimize the system structure. Mainly error sources in the length measuring system, including the time grating sensor, slide way, and cantilever, were studied; and therefore total errors were obtained. Meanwhile we erected the mathematic model of errors of the length measurement system. Using the error model, we calibrated system errors being in the length measurement system. Also, we developed a set of experimental devices in which a laser interferometer was used to calibrate the length measurement system errors. After error calibrating, the accuracy of the measurement system was improved from original 36um/m to 14um/m. The fact that experiment results are consistent with the simulation results shows that the error mathematic model is suitable for the length measuring system.

Research on a novel method of real-time detection and dynamic calibration for angular displacement sensor

Aiming to improve the measurement accuracy of angular displacement sensor effectively and greatly reduce the production costs under an ordinary machining accuracy. A new method of error correction called harmonic calibration based on the closure property of circle was presented. Using this method, real-time and dynamic error separation and correction can be realized when error curve of angular displacement sensor is uncertain. In addition, a method of “spatial sampling” is presented to solve the problem of asynchrony for dynamic sampling. Furthermore, another method which adopts software assist to accomplish adaptive filter is presented to eliminate the influence of random error in the dynamic measurement. As a result a system of full-automatic real-time detection and dynamic calibration for angular displacement sensor with intelligent functions was developed. Experiment results prove that the accuracy of time grating can reach up to ±1” in this way. This effective dynamic method can provide a qualitative and quantitative analysis for calibration of angular displacement sensor.