Deadtime is a common issue in the process industry, affecting loop performance significantly. In an article from a partner publication of Automation World,
Control discuss how adding deadtime to the reset feedback signal enhances loop performance in processes characterized by deadtime and lag.
There are several misconceptions surrounding deadtime compensation, such as the belief that it can eliminate the effect of deadtime or that it's only useful for deadtime-dominant processes.
Instead, Control argues that deadtime compensation, particularly through external reset feedback (ERFB), can improve the robustness and performance of control loops, especially in lag-dominant and integrating processes. For automation engineers, the ability to update ERFB deadtime based on production rates and observed setpoint changes is a valuable feature for maintaining optimal control.
The article presents experimental results demonstrating the effectiveness of ERFB deadtime compensation. For lag-dominant processes, adding deadtime to the ERFB signal initially increases the integrated absolute error (IAE), but re-optimizing controller tuning parameters significantly reduces IAE and improves performance.
In contrast, for deadtime-dominant processes, the improvement is less pronounced but still notable when tuning parameters are adjusted. The study also explores the impact of process gain and deadtime variability, suggesting that deadtime compensation via ERFB can enhance stability in unpredictable conditions.
