| Surface shape error is the deviation between the actual shape and the desired one of the surface. The main work in measurement of surface shape is to measure the deviation. The surface mentioned here usually refers to flat, cylindrical surface (conical surface) and spherical surface. The surface of work pieces with these shapes need to be measured before and after processing, in order to determine whether they meet the processing standard and whether they can be applied to the actual production. In large-scale equipment manufacturing industry, such as aircraft, ships and other industries, some large devices often need to be measured for their surface shape error. The traditional measurement method uses offline measurement, which means the measurement is separated from the processing, while the method is time-consuming, laborious and inefficient. In recent years, the method of the integration of process and measurement is increasingly popular, which means during the artifacts processing, people can complete the course of online and real-time measurement. At present, people usually use the two successive least squares method based on time domain, however, this method has some drawbacks, such as less sampling points, complex matrix operations, which cannot meet the requirements of real-time processing.To solve this problem, this paper studied a method to measuring surface shape error by frequency-domain measurement of surface partitioned. The whole devices’ surface is separated online in this method first, and then each part needs to be measured using4-point irregular frequency domain method in digital signal processor.To validate this approach, we designed a corresponding measurement system, and by measuring shape error to validate the feasibility of this method. We used a linear displacement sensor as a data collection tool, a digital signal processor as the core chip to design the hardware, which contents data acquisition, data processing and other functions. The system analyzed and assessed the final data of planar shape in the industrial computer, and then transmitted the results to the inspector through wireless transmission technology synchronous. The hardware circuit includes a sensor array acquisition circuit, A/D conversion circuit, data signal processing module and the serial/wireless transmission circuit. Through simulation testing, we use the data processing system to process the simulation plane data. The results show that the accuracy and efficiency of the measurement system basically meet the design requirements, which proves that such measurement technology is feasible. |
