Advanced Techniques and Technology of Computer-Aided Feedback Control

By Jean Mbihi

This book covers various modern theoretical, technical, practical and technological aspects of computerized numerical control and control systems of deterministic and stochastic dynamical processes.

• Language: English
• Publisher: Wiley
• Release date: May 24, 2018
• ISBN: 9781119528326

Book preview

Preface

This book presents an in-depth study of advanced design techniques and modern technology for the implementation of computer-aided feedback control systems for deterministic and stochastic dynamic processes.

It is addressed to stakeholders (students, teachers and researchers) in engineering schools, teacher training schools for technical education, PhD schools and applied science research centers.

This book will provide readers with:

– techniques for building canonical discrete state models of dynamic processes, as well as methods for the design of discrete state feedback digital controllers;

– a detailed case study of the creation and effective implementation of a new computer-aided multimedia test bench for servomechanisms, based on virtual toolboxes of PIDF (proportional, integral and derivative with filter) controllers, state feedback controllers (with or without observer) and virtual instruments;

– detailed algorithmic schemes of deterministic or stochastic optimal control, with finite or infinite optimization time;

– secrets of the creation and prototyping of a new remote virtual Matlab®/GUI platform, the rapid design of systems for deterministic and stochastic optimal control;

– infrastructural topologies of real-time remote feedback control systems;

– a detailed case study of the creation and effective implementation of a new remotely operated automation laboratory (REOPAULAB) via the Internet;

– Matlab programs for teaching purposes, allowing the replication, if needed, of the numerical and graphic results presented in this book;

– corrected exercises at the end of each chapter, aimed at consolidating the acquired technical knowledge.

The content of this book is the outcome of the experiences gathered by the author throughout the last 15 years with ENSET (École Normale Supérieure d’Enseignement Technique) and UFD (Unité de Formation Doctorale) in Engineering Sciences at the University of Douala, which involved multiple activities:

– lectures on deterministic and stochastic optimal control and Matlab-aided advanced programming;

– scientific research of new flexible teaching platforms;

– support for the development of computer-aided control technology in modern automated process engineering.

The author wishes to commend the state of Cameroon for the scientific research grant awarded via the Ministry of Higher Education, which allowed him to cover a part of the costs involved for preparing and editing this book.

The author wishes to sincerely thank:

– Prof. Womonou Robert, director and promoter of ESSET at the University of Douala and Nkongsamba, for his motivational support in completing this book.

– Prof. Nneme Nneme Léandre, director of ENSET at the University of Douala, who participated in the study of the remotely operated automation laboratory, which is presented in Chapter 8.

– Pauné Félix, PhD lecturer in the Computer Science Engineering department of ENSET at the University of Douala, who is the main author and the system administrator of the above-mentioned remotely operated automation laboratory, a subject that he has studied and implemented in his PhD thesis, conducted under the author’s supervision.

– Lonlac Konlac Karvin Jerry PhD lecturer and head of the department of Computer Science Engineering of ENSET at the University of Douala. While abroad, during his post-doctoral studies at Lens, in France, he was the first remote test operator without online assistance of the above-mentioned remote automation laboratory.

– The ISTE editorial team, for their excellent collaboration throughout all the editing phases of this book.

– His wife, Mrs. Mbihi, born Tsafack Pélagie Marthe, who offered her close assistance, and all those who have substantially contributed to the production of this book.

Jean MBIHI

March 2018

Introduction

I.1. Architecture of computer-aided control systems

The general architecture of a complete computer-aided control system is represented in Figure I.1, where the main constitutive subsystems are designated as follows:

– real dynamic process to be controlled;

– multifunction data acquisition (MDAQ) interface;

– multimedia PC for closed digital control;

– stations for the remote control of the real process via the Internet.

The next sections of this book offer a detailed study of these constituent subsystems.

Figure I.1. Architecture of a complete system for computer-aided control

I.2. Dynamic processes to be controlled

The real dynamic process to be controlled corresponds to the power and operative part (POP) of an open-loop regulation system. In the POP, u, x and y notations designate direct control, state and output physical quantities, respectively. These quantities are obviously continuous time variables.

I.3. Multifunction data acquisition (MDAQ) interface

An MDAQ interface is in reality a macrocontroller (unified microcontroller system). It acts as a communication protocol interpreter between the dynamic analog process and a digital computer.

The detailed study of modern MDAQ interfaces is a broad, topical subject in industrial computing [MBI 12]. Here, the focus will be on reviewing the elements of strategic knowledge, allowing the mastery of selection criteria and real-time programming operational scheme of an MDAQ interface in industrial automation and computing.

I.3.1. Input/output buses

An MDAQ interface used in computer-aided feedback control technology has an input/output bus-specific system. Table I.1 summarizes the types of buses used in computer-aided instrumentation.

Table I.1. Buses used in computer-aided instrumentation

(*) D (bits): data per packet; C (bit): control per packet

In practice, RS232 and LPT buses are no longer relevant. On the contrary, multimedia PC motherboards support PCI, PCI-X, PCI-E and WiFi buses.

I.3.2. Unified software structure

In micro-computer science, the software structure of a microsystem designates a simplified descriptive scheme of internal programmable components that are accessible in real time through an application program. Figure I.2 presents the software structure of an MDAQ interface viewed from the computer side and from the POP (power and operative part) side of the dynamic process.

Figure I.2. Software structure unified by an MDAQ interface

In other words, the physical chain comprises the computer motherboard, the connector and the MDAQ interface bus controller can be modeled by a lossless communication macromedia between the computer software environment and the programmable instrumentation resources of the MDAQ interface.

The main types of programmable instrumentation resources that are present in the software structure of modern MDAQ interfaces are the following:

– analog-to-digital converter (ADC);

– digital-to-analog converter (DAC);

– specialized input module (for thermocouple, optical encoders, etc.);

– specialized PWM (pulse width modulation) output module;

– timer for the management of periodic tasks;

– on/off input/output ports, Bluetooth, WiFi, etc.

Each programmable resource of an MDAQ interface is accessible in real time on the software side of a Windows application by relative addressing via a computer memory area allocated to hardware input/output targets. This area starts at a base installation address Ard0 that is automatically assigned after the detection of an MDAQ interface by the operating system.

Thus, the control, state and output quantities of a dynamic process, designated by u(t), x(t) and y(t) are expressed on the computer side as discrete quantities u(kT), x(kT) and y(kT), respectively, where T is the sampling period.

I.3.3. Real-time programming operational diagram

The historical operational diagram of real-time programming of an MDAQ interface is presented in Figure I.3, which illustrates the compatibility between generations of software development tools and computer operating systems.

Figure I.3. Operational diagram of real-time programming of an MDAQ interface

Indeed, the history of real-time programming of an MDAQ interface reveals:

– two generations of software development tools, which are distinguishable by the resources for accessing hardware input/output ports. Thus, Turbo C++ and Borland C++ are examples of historical development tools equipped with functions for addressing hardware input/output ports, which is not the case for Dev C++ and Visual Basic;

– two generations of operating systems, which are distinguishable by the security conditions for effective access to hardware input/output ports addressing the kernel. Thus, DOS and Windows 9.x/Me are examples of historical operating systems equipped with a kernel whose access conditions are not secure, which is not the case for Windows NT, Windows 2000, Windows XP, etc.

Based on this historical information, the following four cases of association between development tools and operating systems can be considered:

– Case 1 → 1: technically interesting, but no longer topical;

– Case 1 → 2: problematic in terms of the direct addressing of ports;

– Case 2 → 1: more problematic than the previous one;

– Case 2 → 2: unrealistic.

In practice, problems related to real-time addressing of hardware ports can be solved by using a software driver provided by the producer of the MDAQ interface to be