Real-Time Normal Measurement and Error Compensation of Curved Aircraft Surface Based on On-line Thickness Measurement

Large aerospace thin-walled workpieces easily give rise to random deformation in clamping and machining processes, in which the real-time monitoring of wall thickness needs a high-quality normal technology. A high-precision on-line surface normal measurement and a real-time compensation strategy are developed in this paper. Firstly, the deviation between the actual normal vector and the spindle direction of curved workpiece surface is calculated from the data measured by four eddy current displacement sensors which are installed at the front end of the spindle; then, the deviation is converted into the compensation of each axis via homogeneous coordinate transformation and post-processing of tools. Meanwhile online compensation results get finished on the move. A simulated and experimental platform is established on an A-C five-axis machine tool in order to measure deviations of sensors at each point position and record the result of compensation. The application of this method in practical engineering can greatly improve the efficiency of measurement and control.