Control System by Laser Positioning Based on Free Pendulum

Abstract

The system is designed on the basis of Question B from 2011 National Undergraduate Electronic Design Contest-plate control system based on free pendulum. The system measures the angle change of the pendulum using the rotary encoder to control the motor mounted on the end of the pendulum in order to make the plate fixed on the motor shaft stable, ensuring that coins on the plate are stable. According to the trigonometric relation among the angle and direction of pendulum, the angle of the plate, and the distance between the pendulum and the light point from the laser pen fixed on the plate, the system controls the angle of the plate and makes the laser pen irradiate on the central line. When the pendulum swings freely, the system uses the PID algorithm to control the angle of the plate, so that the laser pen always irradiates on the central line. The experimental data show that the angle error is less than 5° during the rotation of the plate, and eight coins on the plate can keep in the stacked state when the pendulum swings freely within the range of ±60°, and the offset between the light point and the target is less than 3 cm during the free swing of the pendulum. The system won the national first prize in National Undergraduate Electronic Design Contest of China.