Jacek Czeczot

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.

Filtering in adaptive control of distributed parameter bioreactors in the presence of noisy measurements

Abstract This paper deals with simulation experiments on the model-based adaptive control of the distributed parameter bioreactor in the presence of the measurement noise. Since in such cases the adaptive controller itself is not able to ensure good control performance, there is a need to propose more sophisticated application. It is based on the first-order digital low-pass filters and allows us to decrease the influence of the measurement noise on the control performance. In order to decrease this influence it is possible to adjust three parameters of the application: controller tuning parameter, forgetting factor for the estimation of the substrate consumption rate and time constant of the low-pass filters. Simulation results, presented in this paper, have been obtained for different values of these parameters and, based on these results, it is possible to propose a robust application for the adaptive control of the bioreactor with optimally chosen values of the adjustable parameters. This application can be suggested to be applied in the adaptive control of a real industrial distributed parameter bioreactor with noisy measurement data.

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.

New boundary conditions and adaptive control of fixed-bed bioreactors

Modelling, simulation, state estimation and feedback control of a distributed parameter fixed-bed bioreactor are studied in reference to two different types of boundary conditions. The bioreactor is described by two nonlinear and coupled partial differential equations including a single space variable. Classical Danckwerts boundary conditions and so-called Salmi and Romanainen boundary conditions are the two alternatives applied. For process model simulation the method of orthogonal collocation is used in the spatial discretisation. The idea of linearising state-feedback control is applied in the controller design. For control law calculation, two estimation procedures are used: one for estimating the state variables and the specific growth rate, and the other for obtaining the substrate consumption rate of the micro-organisms in the reactor. The state estimator is based on asymptotic observer design. Estimation of the substrate consumption rate is based on temporal discretisation and on the recursive exponentially weighted least-squares procedure resulting in adaptive nature of the final control law.

Balance-based adaptive control of a neutralisation process

This paper deals with the application of the general Balance-Based Adaptive Control (B-BAC) methodology to the control of the nonlinear neutralization process. Since usually in the practice only the flow rates and the pH values are measurable on-line, it is very difficult to derive any model-based control strategy on the basis of the complete nonlinear model, partially because there is always a large uncertainty both on the form and on the values of the parameters of this model and partially because even if this model was known, the resulting control law would have very complex form. Thus, in the paper, the quasi-phenomenological and simplified model of the process is suggested. This input–output model describes the relationship between the measurable parameters, such as flow rates and inlet and outlet pH values, and all the nonlinearities of the process are represented by the only one time-varying parameter. Its value can be easily estimated on-line by the recursive least-squares procedure, which ensures the adaptability of the control law. On the basis of this model, the final explicit form of the B-BAController is derived and it is evaluated by simulation and compared with the conventional PI controller in the application to the example complete nonlinear model of the neutralization process. The simulation results demonstrate very good control performance of the suggested control law in the presence of the disturbances changes. Moreover, the robustness to the large uncertainty on the measurement data of the disturbing parameters included in the control law as the feedforward action is also proved.

Flexible function block for PLC-based implementation of the Balance-Based Adaptive Controller

This paper presents the flexible and ready-to-use function block for the implementation of the Balance-Based Adaptive Controller (B-BAC) embedded in the Siemens S7 PLCs. It is written according to the IEC-61131-3 programming standard using the SIMATIC software package STEP 7. The basic design principles are discussed in terms of ensuring the functionality similar to a PID function block and this functionality allows for direct B-BAC implementation to control a wide variety of different industrial SISO processes. Laboratory experimental tests were carried out in the laboratory water pumping system and the implementation aspects and control results are discussed in the paper.

Simulation Validation of Three Nonlinear Model-Based Controllers in the Adaptive Cruise Control System

In this paper, the simulation validation of the hierarchical two-loop Adaptive Cruise Control (ACC) system is considered as a candidate for the application in the Advanced Driver Assistance Systems (ADAS), which aims to ensure driving safety and comfort as well as to improve fuel efficiency. Three different nonlinear model-based approaches for the inner-loop controllers are investigated for this system: the conventional Proportional-Integral Gain Scheduling controller (PI + GS) and two other strategies based on the simplified modelling of the vehicle dynamics: Balance-Based Adaptive Controller (B-BAC) and Nonlinear Model Predictive Controller (NMPC). The performance of each considered ACC system is tested by simulation under the same realistic scenarios for distance tracking mode and switching mode. The comparative criteria include driving safety, comfort of the driver and passengers and the fuel-economy aspect defined as BSFC (Brake Specific Fuel Consumption) index. The simulation results demonstrate that all the considered control algorithms meet the safety and car-following requirements while they provide slightly different level of driving comfort and fuel consumption, depending on the traffic situation and operating mode.

Modelling for the effective control of the electric flow heaters – Simulation validation

Abstract This paper suggests the possibility of improving the performance of the control system for electric flow heaters by applying the balance-based adaptive control (B-BAC) methodology, in which the synthesis of the control law is always preceded by the nonstationary balance-based modelling according to the general but also strictly defined rules. The resulting simplified model of a heater is derived assuming a large uncertainty on the process nonlinearities and it has the form of the first-order dynamic equation with the only one time-varying parameter that represents the unknown nonlinearities and modelling inaccuracies. The value of this parameter is unknown so we suggest its on-line estimation by the weighted recursive least-squares (WRLS) method. The modelling accuracy is investigated by the simulation in the application to the example nonlinear electric flow heater. It is also shown how to derive the B-BAController on the basis of the suggested model. The generality of the simplified model ensures that the B-BAC methodology can be applied to control a wide variety of electric flow heaters and its application results in more effective control system, which is also verified by simulation in the comparison to the conventional PI controller.

Virtual commissioning for the control of the continuous industrial processes — Case study

This paper concentrates on the possibilities of the application of the virtual commissioning procedure for the design and verification of the control systems for the continuous industrial processes. After short review and defining the motivation and recognizing the bottlenecks, the case study is presented. It is based on the laboratory pneumatic setup representing the nonlinear continuous process of the higher relative degree. The stages of its modeling are presented and the potential possibilities of the application of the virtual commissioning for its control are discussed, based on the practical results.

Simplified modeling of plate heat exchangers

In this paper, the simplified modeling of the counter-flow plate heat exchanger is presented. The aim of the work is to propose a relatively simple model useful for the controller design. Dynamical behavior of the plate heat exchanger is modeled by simple double pipe model. Two different methods are used to approximate the partial differential equations. The first one is the finite difference method. The second one is the orthogonal collocation method. Both methods are compared in terms of the modeling accuracy and model complexity.