Fast Detection Using PID Pre-Interpolation Algorithm for Magnetic Particle Testing

The current tracing scheme is based on a silicon-controlled rectifier (SCR) with phase shift triggering, which is utilized in traditional magnetic particle testing. In industrial applications, the popularization and implementation of magnetic particle flaw detection technology could be degraded by various problems such as poor real-time performance of current tracing, the significant error of current tracing, and low precision of flaw detection. In this work, the magnetization current waveforms under different control angles of the SCR are studied to obtain a real-time magnetization current tracking in less than 0.5 s and a current tracking error smaller than 5%. A fast three-phase electric zero detection circuit is designed in which the current tracking method is optimized by combining a high-speed analog to digital (AD) converter with a true root-mean-square (true-rms) device. Moreover, a Newton interpolation-based fast proportional integral derivative (PID) algorithm is proposed to achieve a precise real-time current tracking. The experimental results show that the real-time magnetic particle flaw detection for current tracking is performed in less than 0.2 s with a current tracking error below 2%, which meets the technical requirements of magnetic particle flaw detection. The fast three-phase electric zero detection method using the PID algorithm can improve the real-time performance and accuracy of current tracking in magnetic particle flaw detection.