Piotr Laszczyk

General tuning procedure for the nonlinear balance-based adaptive controller

Abstract This paper presents the intuitive and ready-to-use, general procedure for tuning the balance-based adaptive controller (B-BAC) based on its equivalence to the controller with PI term and with additional improvements shown for the linearised approximation of the dynamics of the nonlinear controlled process. The simple formulas are suggested to calculate the B-BAC tunings based on the PI tunings determined by any PI tuning procedure chosen accordingly to the desired closed-loop performance. This methodology is verified by comparing the closed-loop performance of the equivalently tuned B-BAC and PI/PI+feedforward controllers under the same scenario, both by the simulation and practical experiments.

Flexible function block implementation of the balance-based adaptive controller as the potential alternative for PID-based industrial applications

This paper deals with the practical aspects of the implementation of the balance-based adaptive control (B-BAC) technique. It gives the simple mathematical background of this methodology, shows the case-independent implementation concept as the ready-to-use flexible function block that results from the B-BAC generality, discusses how to embed the additional functionalities required in professional industrial control applications and finally presents three implementation examples for three different programming and hardware platforms. The control performance of each B-BAC function block is validated experimentally and compared with the performance of the corresponding platform-related standard PID function blocks. The comparative results and the potential accessibility of both the flexible function block and the simple tuning method put forward B-BAC methodology as a strong alternative for PID-based industrial control applications.

Comparison of DMC and PFC control for heating process

The paper presents comparison between two popular predictive control algorithms DMC and PFC. General description of both algorithms are presented in details for FOPDT (First Order Plus Dead Time) dynamics. Heating process with heat source and heat exchanger was used as an example control plant for testing both algorithms. Design of controllers and tuning procedures are presented. Results of control and performance tests are included as well as conclusion remarks on practical aspects of implementation of the algorithms.

Function block practical implementation of Balance-Based Adaptive Control for pH process

This paper deals with the Balance-Based Adaptive Control (B-BAC) of the pH process. The implementation is in the form of the general, flexible and ready-to-use function block written for Allen Bradley® PLC family according to IEC-61131-3 standard. Additionally, the very important aspects of practical implementation are addressed: signal conditioning, bumpless switching, anti-windup action, etc. Experimental results show the functionality of this function block and the superiority of the B-BAC methodology over the conventional PI control in the application to the laboratory pH process.

Practical verification of the control strategies for the counter-current heat exchanger

This paper shows the experimental results of the control of the heat exchanger working as a part of the laboratory heat exchange and distribution pilot plant. Two control strategies are considered: PI + gain scheduling (PI+GS) technique and Balance-Based Adaptive Control (B-BAC) methodology. In both cases, simplified modeling of different type is required and the results of the comparative tests show the control performance of both strategies when the flow rate of the heating medium is the manipulated variable.

LabView-based implementation of Balance-Based Adaptive Control technique

This paper presents the flexible function block for the implementation of the Balance-Based Adaptive Controller (B-BAC) designed in the form of the ready-to-use virtual controller in the LabView programming environment. The functionality of this block is very similar to the functionality of the PID function block embedded in various PLC devices. It allows for direct B-BAC implementation to control a wide variety of different industrial SISO processes. Laboratory experimental tests were carried out for the control of the electric flow heater and the performance of the B-BAC function block is compared with the gain-scheduling PI controller. The results show the functionality and generality of the presented B-BAC function block.

Agent-based approach to model-based dynamically reconfigurable control algorithm

There is a class of control algorithms, which are based on models of the controlled processes. The common feature of these algorithms is the fact that at the design stage the algorithm can be modified to take into account multiple sensors available in the controlled plant. Each additional independent measurement increases the accuracy of the simulation carried on by the model embedded in the algorithm. In this work the authors propose to improve this established static approach and implement the control system which dynamically derives the control law during its operation, depending on the availability of individual sensors. Availability may be reduced in the event of sensor failure, or increased after new sensors are connected. It is proposed to employ the agent-based programming paradigm as it has the dynamic reconfiguration capabilities which are crucial for the proposed technique. The presented idea is still a work on progress, so no experimental results are available, but this paper focuses on the details of the proposed technique in order to collect the opinions and conclusions of the research and engineering community.

Probe dynamics influence on determination of volumetric oxygen transfer coefficient

This paper deals with practical aspects of volumetric oxygen transfer coefficient determination. The attention was paid to influence of dissolved oxygen probe dynamics on measurements. A new identification method of volumetric oxygen transfer coefficient was developed. This method involves numerical integral calculation. The new method and three other methods (graphical, logarithmic and regression) of determining volumetric oxygen transfer coefficient value were applied. The comparative simulation research was done using dissolved oxygen concentration model. All four methods were finally aplied to real biotechnological wastewater process with the activated sludge.

Cooperative Engineering of Agent-Based Process Control Algorithm

Process control algorithms constitute a specific software model, as they have well-defined and constant sets of inputs and outputs, and perform calculations cyclically in real time. Therefore, the algorithms rarely are implemented otherwise than embedded in the low level control instrumentation. This paper proposes a departure from this well-known approach in order to apply multi-agent system directly in the control layer. While this novel approach creates few issues requiring resolving, such as the need to develop an agent-based software operating in real time, it also provides the crucial benefit i.e. the possibility of developing the modules of the control algorithm by experts from different fields, which allows for cooperative dynamic engineering of a control algorithm. The resulting methodology allows to include more modern and advanced solutions from various fields of control science than it is possible in the case of the classical approach.

Practical Implementation of the Nonlinear Control of the Liquid Level in the Tank of Irregular Shape

In this paper, the control of the liquid level in the tank of irregular (partially conical) shape is considered. The process nonlinearities must be incorporated in the control law to ensure good tracking properties and disturbances rejection despite of the variations of the operating point defined by the desired liquid level. For this purpose, two control strategies are considered: PI+GS (gain scheduling) controller with scheduling function based on the preliminary process identification and B-BAController (Balance-Based Adaptive Controller), which is derived from the nonlinear but significantly simplified model of the process, without any preliminary identification. The control performance of both techniques is verified experimentally and the results show superiority of the latter.