Measurable Disturbances Compensation: Analysis and Tuning of Feedforward Techniques for Dead-Time Processes

Andrzej Pawlowski,José Guzmán,Sebastián Dormido,Carlos Rodríguez,Manuel Berenguel

doi:10.3390/pr4020012

Andrzej Pawlowski, José Guzmán + Show 3 more

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https://doi.org/10.3390/pr4020012

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Abstract

In this paper, measurable disturbance compensation techniques are analyzed, focusing the problem on the input-output and disturbance-output time delays. The feedforward compensation method is evaluated for the common structures that appear between the disturbance and process dynamics. Due to the presence of time delays, the study includes causality and instability phenomena that can arise when a classical approach for disturbance compensation is used. Different feedforward configurations are analyzed for two feedback control techniques, PID (Proportional-Integral-Derivative) and MPC (Model Predictive Control) that are widely used for industrial process-control applications. The specific tuning methodology for the analyzed process structure is used to obtain improved disturbance rejection performance regarding classical approaches. The evaluation of the introduced disturbance rejection schemes is performed through simulation, considering process constraints in order to highlight the advantages and drawbacks in common scenarios. The performance of the analyzed structure is expressed with different indexes that allow us direct comparisons. The obtained results show that the proper design and tuning of the feedforward action helps to significantly improve the overall control performance in process control tasks.

Highlights

The vast majority of industrial processes require a tailored control architecture to fulfill the system requirements
Taking into account the importance of the disturbance compensation problem and previous aspects, in this work, we focus on the processes, the dynamics of which involves the time delays
The process configuration with the realizable feedforward compensator is introduced. This example is used to show the classical approach and to highlight the limitations of the Generalized Predictive Control (GPC) implicit feedforward action based on the classic scheme

Summary

Introduction

The vast majority of industrial processes require a tailored control architecture to fulfill the system requirements. In such a scheme, the control system should keep the controlled variable as close as possible to its desired value acting against external phenomena (disturbances) that affect process variables. Disturbances should be considered in the control problem design [1]. Due to their origin, disturbances can be classified as measurable and unmeasurable. The measurable disturbances are an important issue that must be considered in control schemes, especially for process control [2]. It is usual that the control system only focuses on one of the listed

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Results

Conclusion