Locating Upper and Lower Envelopes on Applied Surface Roughness Curves

When identifying upper and lower envelopes on applied surface roughness curves, the following procedures should be implemented. First, it is essential to detect local maxima and minima along the curve, which can be achieved programmatically using peak detection algorithms like find_peaks() in Python or findpeaks() in MATLAB. These functions typically analyze slope changes and threshold values to identify extreme points accurately. Subsequently, these extreme points are connected using linear interpolation or spline fitting methods to construct the envelope lines. When determining extreme points, factors such as curve slope and rate of change must be considered, often implemented through derivative calculations or gradient analysis in code. Furthermore, the position and shape of the envelopes can be optimized by adjusting parameters like search window size, prominence threshold, and interpolation method to achieve better fitting results. Therefore, during surface roughness analysis, appropriate envelope methods and parameters should be carefully selected, typically involving comparative testing of different algorithms (e.g., Hilbert transform-based methods vs. peak detection approaches) to ensure result accuracy and reliability.