Plasma Torch Height Tracking Based on Rolling Grey Prediction

Among the parameters influencing plasma arc cutting, arc current, cutting speed, and plasma torch height act as the main factors. Among them, the plasma torch height plays an important role in improving the kerf width and cut quality, and the automatic control of the plasma torch height is essential due to the deformation of the workpiece during the cutting process. Therefore, according to the surface condition of the workpiece during plasma cutting, it is required to have automatic control so that the gap between the plasma nozzle and the cut workpiece remains constant. The plasma torch height control system in this paper consists of the sensing, controller, prediction, and stepper motor control system of the plasma torch height. Here, the rolling mode grey prediction algorithm is applied to predict the next state for the cutting forward direction and to control the previous data continuously updating. It is shown by the Simulink results of Matlab that the plasma torch height tracking with rolling grey prediction has better tracking accuracy than the general PID control method. In addition, the comparison between the plasma torch height tracking experimental results using the rolling grey prediction based method and the tracking experimental results using the general PID control method in the cutting test showed that the variation of the arc voltage is less, the cutting width is smaller, and the tracking performance is improved.