Application of the Watanabe-modified Smith predictor control technique in thermoforming

In this paper, the application of the Watanabe-modified Smith predictor control technique in a thermoforming heating process is presented. It has been observed that the temperature rise of a plastic sheet exhibits an input delay-like behavior due to heater lags and other environmental parameters. Therefore, the modified Smith predictor technique is applied to compensate for this delay, allowing for improved tunability, performance, and robustness to parameter variations in the system, compared to the existing controllers. The Watanabe-modified Smith predictor control technique is then included in the control diagram of the system, tuned, and tested on an industrial thermoforming machine simulator. The performance and robustness of the new control technique is then compared to the existing PI controllers in simulation.