An Adaptive Dimming System of High-Power LED Based on Fuzzy PID Control Algorithm for Machine Vision Lighting

High-power LED is one of the important lighting sources of machine vision in industrial on-line detection system. However, the image quality of the detected object collected by the image sensor will change with the illumination intensity of lighting sources. It is necessary to ensure the stability of the detection ambient illumination so as to improve detection efficiency and quality. For this purpose, an adaptive dimming system of High-power LED based on Fuzzy PID algorithm for machine vision lighting is designed to maintain constant detection ambient illumination. The proposed system is consisted of hardware design and software design. The hardware which uses DSP as the core control device includes constant current drive circuit for High-power LED, temperature of LED measurement circuit, and ambient illumination intensity of detection circuit. If the detection ambient illumination is not equal to the given ambient illumination, the fuzzy PID algorithm is started to adjust automatically the PID parameter according to the error and error rate in DSP chip. The duty cycle of PWM pulse generated by DSP is regulated with fuzzy PID algorithm. The experimental result shows that the adaptive constant of the measured ambient illumination can be achieved. The application of this system has certain reference value for energy-saving lighting and automatic dimming control of industrial on-line detection.