## 4 Prediction Performance Analysis
From the residual curves and residual breakdowns in Figures 19-24, it can be seen that at a spindle rate of 1000 r/min, the POA-CNN-LSTMNN model demonstrated the highest residual of 0.797 \(\upmu\)m, the lowest residual of \(-\)0.589 \(\upmu\)m, and an absolute residual fluctuation of 1.386 \(\upmu\)m; in the CSOA-CNN-LSTMNN model, the highest residual was 1.369 \(\upmu\)m, the lowest residual was \(-\)1.628 \(\upmu\)m, and the absolute residual fluctuation was 2.997 \(\upmu\)m; for the CNN-LSTMNN model, the highest residual was 1.561 \(\upmu\)m, the lowest residual was \(-\)1.272 \(\upmu\)m, and the absolute residual fluctuation was 2.833 \(\upmu\)m; and in the LSTMNN model, the highest residual was 2.369 \(\upmu\)m, the lowest residual was \(-\)1.418 \(\upmu\)m, and the absolute residual fluctuation was 3.787 \(\upmu\)m. From the residual curve graph, the blue color represents the residual curve of the POA-CNN-LSTMNN model, the green color represents the residual curve of the CSOA  
represents the residual curve of the CNN-LSTMNN model, and the red color represents the residual curve of the LSTMNN model. The range of residual curves in red covers all other curves, and the residual curves in blue had the least amount of fluctuation. At a spindle speed of 2500 r/min, the maximum residual observed for the POA-CNN-LSTMNN model was 1.212 um, whereas the minimum residual was \(-\)1.043 um, resulting in an absolute residual fluctuation of 2.255 um; in the case of the CSOA-CNN-LSTMNN model, the maximum residual was found to be 1.592 um, whereas the minimum residual was \(-\)1.294 um and the absolute residual fluctuation measured at 2.886 um; regarding the CNN-LSTMNN model, the maximum residual was recorded at 1.876 um, the minimum residual was observed at \(-\)1.388 um, and the absolute fluctuation in residual values amounted to 3.264 um; and the LSTMNN model showed a maximum residual of 2.045 um and a minimum residual of \(-\)2.005 um, resulting in an absolute residual fluctuation of 4.05 um. The graphs of residuals were still blue for the POA-CNN-LSTMNN residual curve, which was closest to the X-axis when the vertical coordinate was zero. At a spindle rate of 4000 r/min, the residual fluctuation ranges of the POA-CNN-LSTMNN, CSOA-CNN-LSTMNN, CNN-LSTMNN, and LSTMNN models were 3.162 um, 3.642 um, 4.538 um, and 6.433 um, respectively, the residual maxima were 1.515 um, 2.517 um, 2.652 um, and 2.973 um, respectively; and their residual minimums were \(-\)1.647 um, \(-\)1.125 um, \(-\)1.886 um, and \(-\)3.46 um, respectively. From the residual curve graphs, it can also be clearly seen that the residual curves of the LSTMNN model had the largest coverage and those of the POA-CNN-LSTMNN model had the has the smallest coverage. When the spindle rate was 7000 r/min, the peak values of the residuals for the POA-CNN-LSTMNN, CSOA-CNN-LSTMNN, CNN-LSTMNN, and LSTMNN models were 1.241 um, 2.233 um, 2.943 um, and 4.016 um, respectively; the minimum values of the residuals were \(-\)2.601 um, \(-\)3.862 um, \(-\)1.761 um, and \(-\)6.353 um, respectively; and the absolute values of the residuals were 3.842 um, 6.095 um, 4.704 um, and 10.369 um, respectively. The blue residual curves of the POA-CNN-LSTMNN model had the smallest fluctuation range. When the spindle rate was 8500 r/min, the maximum, minimum, and absolute residual values of the LSTMNN model were 4.056 um, \(-\)4.76 um, and 8.816 um respectively. The maximum residual value, minimum residual value, and absolute residual value of the CNN-LSTMNN model were 3.188 um, \(-\)3.435 um, and 6.623 um respectively. The maximum, minimum, and absolute residual values of the CSOA-CNN-LSTMNN model were 2.458 um, \(-\)4.558 um, and 7.016 um respectively. The maximum, minimum, and absolute residual values of the POA-CNN-LSTMNN model were 1.895 um, \(-\)3.068 um, and 4.963 um, respectively. The prediction residual curve of the POA-CNN-LSTMNN model was closest to the 0 axis.