A Method for Measuring the Inclination of Forgings Based on an Improved Optimization Algorithm for Fitting Ellipses

Abstract

During a piercing or punching process, the center axis of a forging stock is required to be parallel to the direction of movement of the upsetting rod or piercing needle because any small tilt of the stock will cause uneven upsetting or uneven punching wall thickness. In order to detect the inclination of a stock during forging, a method for measuring the inclination of forgings based on an improved optimization algorithm for fitting ellipses is proposed in the work. Specifically, a laser rangefinder is used to measure the distances to the surface of the workpiece, which are converted into Section profile coordinates through coordinate transformation. Next, the randomly divided area and random sampling are presented for screening data points, making it possible to effectively eliminate the influence of abnormal values in the measurement points. Then, taking the point-to-ellipse orthogonal distance as the geometric model, we propose an improved particle swarm optimization (PSO) algorithm to solve the target ellipse parameters. Subsequently, we compare the fitting effect with four other contemporary advanced methods to verify the superiority of the algorithm in ellipse fitting. Finally, the three-dimensional linear equation of the center axis of the forging stock is obtained according to the center point of the long axis of the ellipse in the vertical direction, and the inclination angle of the forging stock is calculated according to the linear equation. The experimental measurement reveals that the error that occurred using the method is less than 0.05°.