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1

Reduced gain pi/pid controllers for foptd/soptd processes under load disturbance

Bożek Andrzej, Trybus Leszek

Acta Mechanica et Automatica

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2024

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Vol. 18, no. 2

212--222

EN

In practical applications, an engineer is sometimes expected to execute the step test for tuning the controller without waiting much for the steady-state or a low level of disturbances. Hence, knowing that the initial settings may not be quite reliable, he/she detunes the controller by reducing its gain as a precaution against possible poor behaviour of the closed-loop system. It is up to their experience to choose by how much to detune. Therefore, the development of a practically oriented approach that would assist the engineer to choose the degree of gain reduction is the goal of this paper. The approach assumes that process parameters are determined by the least-squares approximation of the step response. Accuracy of the approximation is evaluated by a relative approximation error involving integrals of the error and the process response itself. The SIMC tuning rules are applied to choose the initial controller settings. The approach relies on detecting by simulation the worst case that may happen when the step response is triggered at any time. Detuning nomograms specify by how much to reduce the initial gain for PI-FOPTD and PID-SOPTD designs, given the relative approximation error. Two long-lasting lab experiments involving temperature control identify a plant, verify the load disturbance model through multiple step tests and demonstrate usage of the approach in the closed-loop system.

2

Jednolite projektowanie regulatorów kursu i ścieżki dla autopilota statku

Stec Andrzej, Świder Zbigniew, Trybus Leszek

Pomiary Automatyka Robotyka

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2023

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R. 27, nr 1

45--50

PL

Przedstawiono jednolity sposób doboru nastaw PID dla regulatora kursu i regulatora śledzenia ścieżki, które występują w kaskadowym układzie autopilota statku. Jednolitość projektowania jest możliwa dzięki temu, że w odniesieniu do każdego regulatora sterowany przez niego obiekt wygląda jak integrator ze stałą czasową. W przypadku regulatora kursu jest to znany model Nomoto. Dzięki eliminacji przez regulator stałej czasowej obiektu, układ zamknięty staje się układem 2-go rzędu. Założono, że układ ten ma mieć podwójną stałą czasową różniącą się w zadanym stosunku od stałej czasowej obiektu. Pokazano, że tak zaprojektowany regulator kursu lepiej tłumi zakłócenia środowiskowe niż regulator z wzorcowymi nastawami.

EN

Uniform approach to selection of PID settings for heading and path tracking controllers that create a cascade control system for ship autopilot is presented. Uniformity of the design follows from observation that for each of the controllers the controlled plant looks like an integrator with time constant. In case of the heading controller, the plant is represented by the known Nomoto model. Due to elimination of the plant time constant by the controller, each of the closed loop systems becomes of 2nd order. One assumes that such system should have a double time constant, different in a prescribed ratio from time constant of the controlled plant. It is shown that the heading controller designed in this way suppresses disturbances better than the controller with standard settings.

3

Consistent design of PID controllers for an autopilot

Świder Zbigniew, Trybus Leszek, Stec Andrzej

Polish Maritime Research

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2023

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nr 1

78--85

EN

A consistent approach to the development of tuning rules for course-keeping and path-tracking PID controllers for a ship autopilot are presented. The consistency comes from the observation that for each of the controllers the controlled plant can be modelled by an integrator with inertia. In the case of the course controller, it is the well-known Nomoto model. The PID controller may be implemented in series or parallel form, the consequence of which is a 2nd or 3rd order of the system, specified by a double or triple closed-loop time constant. The new tuning rules may be an alternative to the standard ones given in [1,2]. It is shown that, whereas the reference responses for the standard and new rules are almost the same, the new rules provide better suppression of disturbances such as wind, waves or current. The parallel controller is particularly advantageous. The path-tracking PID controller can provide better tracking accuracy than the conventional PI. Simulated path-tracking trajectories generated by a cascade control system are presented. The novelty of this research is in the theory, specifically in the development of new tuning rules for the two PID autopilot controllers that improve disturbance suppression.

4

Krok dyskretyzacji i nastawy PID w dyskretnym serwomechanizmie napięciowym

Bożek Andrzej, Trybus Leszek

Pomiary Automatyka Robotyka

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2022

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R. 26, nr 1

5--10

PL

Przedstawiono metodę doboru kroku dyskretyzacji i nastaw dyskretnego regulatora PID dla modelu serwomechanizmu z silnikiem sterowanym napięciowo, opisanym jako integrator ze stałą czasową. Założeniem metody jest lokalizacja potrójnego bieguna układu zamkniętego, aby zapewnić gładkie przebiegi regulacyjne. Daną projektową stanowi czas regulacji. Zbadano, w jakim stopniu filtracja składowej różniczkującej regulatora skraca wymagany krok dyskretyzacji. Rozważono także rozszerzony problem projektowy z zadanym dodatkowo stopniem filtracji.

EN

A method for selection of discretization step and discrete PID controller settings is presented for a model of servo with voltage controlled motor, described by an integrator with time constant. The method assumes a triple pole location of the closed-loop system to provide smooth control transients. Settling time is a design data. Influence of filtering degree in controller derivative component on reduction of discretization step is examined. Extended design problem with the filtering degree being an additional requirement is also considered.

5

Tuning PID and PI-PI servo controllers by multiple pole placement

Bożek Andrzej, Trybus Leszek

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2022

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Vol. 70, nr 1

art. no. e139957

EN

Tuning rules for PID and PI-PI servo controllers are developed using a pole placement approach with a multiple pole, i.e. a triple one in the case of PID and a quadruple for PI-PI. The controllers involve complex roots in the numerators of the transfer functions. This is not possible in the classical P-PI structure which admits real roots only. The settling time of the servos determined by the multiple time constant is the only design parameter. Nomograms to read out discrete controller settings in terms of the time constant and control cycle are given. As compared to the classical structures, the upper limit on the control cycle is now twice longer in the case of PID, and four times in the case of PI-PI. This implies that the settling times can be shortened by the same ratios. Responses of a PLC-controlled servo confirm the validity of the design.

6

Implementacja środowiska inżynierskiego na przykładzie pakietu CPDev

Rzońca Dariusz, Sadolewski Jan, Stec Andrzej, Świder Zbigniew, Trybus Bartosz, Trybus Leszek

Pomiary Automatyka Robotyka

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2020

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R. 24, nr 1

21--28

PL

Norma IEC 61131-3 definiuje pięć języków programowania sterowników przemysłowych. Norma ta jest powszechnie stosowana, wiele środowisk inżynierskich jest z nią całkowicie, bądź częściowo zgodnych. W literaturze opisano kilka akademickich rozwiązań, jednak zazwyczaj implementują one jedynie wybrane elementy normy (np. tylko jeden lub dwa języki). Komercyjne środowiska inżynierskie zwykle obsługują wszystkie języki, ale ich dokumentacja skupia się na korzystaniu ze środowiska, natomiast rzadko ujawniane są szczegóły dotyczące wewnętrznej architektury i implementacji. W artykule przedstawiono takie rozwiązania dla pakietu inżynierskiego CPDev. Architektura bazująca na maszynie wirtualnej sprawia, że środowisko jest przenośne, co ułatwia wdrożenie na różnych platformach sprzętowych. W artykule przedstawiono kilka wdrożeń przemysłowych środowiska CPDev.

EN

The IEC 61131-3 standard defines five languages, dedicated for programming industrial controllers. The standard is commonly used, there are numerous engineering environments fully or partially compatible with it. Several academic solutions have been described in the literature, but they typically implement only selected parts of the IEC 61131-3 standard (e.g. only one or two languages). On the other hand, commercial engineering environments usually implement all languages, but their documentation focuses on the application of the environment, whereas details about internal architecture and implementation are rarely disclosed. The paper describes such internal details of the CPDev engineering environment. The architecture based on the virtual machine makes the environment portable, thus facilitate implementation on diverse hardware platforms. Several industrial implementations of CPDev are also mentioned.

7

Developing a multiplatform control environment

Rzońca Dariusz, Sadolewski Jan, Stec Andrzej, Świder Zbigniew, Trybus Bartosz, Trybus Leszek

Journal of Automation Mobile Robotics and Intelligent Systems

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2019

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Vol. 13, No. 4

73--84

EN

IEC 61131‐3 control environment is called multiplatform if source programs can be executed by various processors, beginning from 8‐bit microcontrollers up to 32/64‐ bit efficient CPUs. This implies that virtual machine (VM), i.e. a software implemented processor, is used as runtime by the host CPU. The VM executes certain intermediate code into which IEC 61131‐3 programs are compiled. En‐ vironment of this type called CPDev has been gradually developed by the authors over the last decade, beginning with initial report in this journal in 2008 [47]. However, technical implementations of its functionalities have not been described so far. This involves such matters as intermediate language, parametrization of the compiler and VM, multiproject runtime, translators of graphical languages, device‐independent HMI, target platform and communication interfacing, which are presented in compact form in this paper. Some characteristic industrial implementations are indicated.