第4章-COMPUTER-CONTROL-SYSTEMSppt课件(全)

1、CHAPTER 4COMPUTER CONTROL SYSTEMSCHAPTER 4 COMPUTER CONTROL SYSTEMS4.1 Fundamentals of Computer Control Consider the level control system shown in schematic form in Figure 4.1.1. CHAPTER 4 COMPUTER CONTROL SYSTEMS4.1 Fundamentals of Computer Control Figure 4.1.2 Block diagram of level control system

2、.CHAPTER 4 COMPUTER CONTROL SYSTEMS4.1 Fundamentals of Computer Control Figure 4.1.3 Block diagram for realisation of analogue control loop.CHAPTER 4 COMPUTER CONTROL SYSTEMS4.1 Fundamentals of Computer ControlAssume that the dp cells output is one of a number of 420 mA channels handled by the card,

3、 the circuit for which is as depicted in Figure 4.1.4.4.1.1 Input InterfaceCHAPTER 4 COMPUTER CONTROL SYSTEMS4.1 Fundamentals of Computer ControlThe following equation is used universally for linear scaling. For brevity, a 10-bit A/D converter is assumed:4.1.2 Input ScalingCHAPTER 4 COMPUTER CONTROL

4、 SYSTEMS4.1 Fundamentals of Computer ControlA typical algorithm, written in structured text, for implementing it would be:4.1.2 Input ScalingCHAPTER 4 COMPUTER CONTROL SYSTEMS4.1 Fundamentals of Computer ControlThe most common type of filter is the simple first order lag, which is of the form:4.1.3

5、FilteringCHAPTER 4 COMPUTER CONTROL SYSTEMS4.1 Fundamentals of Computer ControlUsing Eulers first order explicit method of numerical integration:4.1.3 FilteringCHAPTER 4 COMPUTER CONTROL SYSTEMS4.1 Fundamentals of Computer ControlA typical algorithm for implementing the filter would be4.1.3 Filterin

6、gCHAPTER 4 COMPUTER CONTROL SYSTEMS4.1 Fundamentals of Computer ControlThe PID function block of Figure 4.1.3 represents the routine for a 3-term controller. It operates on the output of the FIL function block. In particular, a discretised version of the absolute form of the classical PID controller

7、 with derivative feedback was developed. Typical algorithms, written in structured text, for implementing this controller would be4.1.4 PID ControlCHAPTER 4 COMPUTER CONTROL SYSTEMS4.1 Fundamentals of Computer ControlThe following equation is used extensively for output scaling. The range of the con

8、troller output is normally 0100% and, for brevity, an 8-bit A/D converter is assumed:4.1.5 Output ScalingCHAPTER 4 COMPUTER CONTROL SYSTEMS4.1 Fundamentals of Computer ControlThe output q0 is stored in the database as a bit pattern. The algorithm used for the output scaling is typically4.1.5 Output

9、ScalingCHAPTER 4 COMPUTER CONTROL SYSTEMS4.1 Fundamentals of Computer ControlFigure 4.1.5 Analogue output channel.4.1.6 Output InterfaceCHAPTER 4 COMPUTER CONTROL SYSTEMS4.1 Fundamentals of Computer ControlFigure 4.1.6 depicts the construction of the quasi analogue signal.4.1.6 Output InterfaceCHAPT

10、ER 4 COMPUTER CONTROL SYSTEMS4.1 Fundamentals of Computer ControlFigure 4.1.6 depicts the construction of the quasi analogue signal.4.1.6 Output InterfaceCHAPTER 4 COMPUTER CONTROL SYSTEMS4.1 Fundamentals of Computer ControlFigure 4.1.6 depicts the construction of the quasi analogue signal.4.1.6 Out

11、put InterfaceCHAPTER 4 COMPUTER CONTROL SYSTEMS4.2 Computer Control System ArchitectureFigure 4.2.1 Advisory control system.4.2.1 Advisory ControlCHAPTER 4 COMPUTER CONTROL SYSTEMS4.2 Computer Control System ArchitectureFigure 4.2.2 Supervisory control system.4.2.2 Supervisory ControlCHAPTER 4 COMPU

12、TER CONTROL SYSTEMS4.2 Computer Control System ArchitectureFigure 4.2.3 Direct digital control (DDC) system.4.2.3 Direct Digital ControlCHAPTER 4 COMPUTER CONTROL SYSTEMS4.2 Computer Control System ArchitectureFigure 4.2.4 Integrated control system (ICS).4.2.4 Integrated ControlCHAPTER 4 COMPUTER CO

13、NTROL SYSTEMS4.2 Computer Control System ArchitectureFigure 4.2.5 Dual integrated control system.4.2.4 Integrated ControlCHAPTER 4 COMPUTER CONTROL SYSTEMS4.2 Computer Control System ArchitectureFigure 4.2.6 Multi-drop type of distributed control system (DCS).4.2.5 Distributed ControlCHAPTER 4 COMPU

14、TER CONTROL SYSTEMS4.2 Computer Control System ArchitectureFigure 4.2.7 Programmable logic controller (PIC) system.4.2.6 Programmable Logic ControllersCHAPTER 4 COMPUTER CONTROL SYSTEMS4.3 Programmable ControllersThe first programmable controller,introduced in 1970, was developed in response to a de

15、mand from General Motors for a solid-state system that had the flexibility of a computer, yet could be programmed and maintained by plant engineers and technicians. These early programmable controllers took up less space than the relays, counters, timers, and other control components they replaced,

16、and they offered much greater flexibility in terms of their re-programming capability (Figure 4.3.1).4.3.1 Programmable Controllers DefinedCHAPTER 4 COMPUTER CONTROL SYSTEMS4.3 Programmable ControllersFigure 4.3.1 Basic PLC components.4.3.1 Programmable Controllers DefinedCHAPTER 4 COMPUTER CONTROL

17、SYSTEMS4.3 Programmable ControllersThe initial programming language, based on the ladder diagrams and electrical symbols commonly used by electricians, was key to industry acceptance of the programmable controller (Figure 4.3.2).4.3.1 Programmable Controllers DefinedCHAPTER 4 COMPUTER CONTROL SYSTEM

18、S4.3 Programmable ControllersThe success of the programmable controller has spurred innovation in a number of competing technologies. Below is a brief review of these technologies, which may in some cases be successfully applied as an alternative to programmable controllers.4.3.2 Alternatives to Pro

19、grammable ControllersCHAPTER 4 COMPUTER CONTROL SYSTEMS4.3 Programmable ControllersPC-Based ControlDistributed Control SystemRelay-Based ControlSingle-Board Controllers4.3.2 Alternatives to Programmable ControllersCHAPTER 4 COMPUTER CONTROL SYSTEMS4.3 Programmable ControllersFigure 4.3.3 Relay logic

20、 control4.3.2 Alternatives to Programmable ControllersCHAPTER 4 COMPUTER CONTROL SYSTEMS4.3 Programmable ControllersTable 4.3.1 Evaluation of control methods for the application.4.3.2 Alternatives to Programmable ControllersCHAPTER 4 COMPUTER CONTROL SYSTEMS4.4 Distributed Control System (DCS)Figure

21、 4.4.1 Multi-drop type of distributed control system (DCS).4.4.1 Introduction and Architecture of DCSCHAPTER 4 COMPUTER CONTROL SYSTEMS4.4 Distributed Control System (DCS)The operators control station (OCS) is a term which refers to the hardware used by an operator. It typically consists of a colour

22、 graphics VDU, a keyboard, and some processor capacity for handling the operators control program (OCP). In essence the OCP is the software with which the operator interacts. It enables access to the systems database and handles the various displays.4.4.2 Operator StationCHAPTER 4 COMPUTER CONTROL S

23、YSTEMS4.4 Distributed Control System (DCS)Figure 4.4.2 Typical card, rack and frame structure. 4.4.3 Physical StructureCHAPTER 4 COMPUTER CONTROL SYSTEMS4.4 Distributed Control System (DCS)Figure 4.4.3 Connections between cards and back plane.4.4.3 Physical StructureCHAPTER 4 COMPUTER CONTROL SYSTEM

24、S4.4 Distributed Control System (DCS)4.4.4 Card TypesI/O cards1System cards2Coms cards3CHAPTER 4 COMPUTER CONTROL SYSTEMS4.5 Computer Control System Communications(1)4.5.1 MessagesFigure. 4.5.1 IEEE802 type of frame.CHAPTER 4 COMPUTER CONTROL SYSTEMS4.5 Computer Control System Communications(1)4.5.2

25、 Local Area NetworksThe most commonly used type of communications system is the local area network (LAN). The IEEE has developed standards for LANs which are generally adhered to by systems suppliers. The three LANs of particular interest for process control purposes are Ethernet, token bus and toke

26、n ring. The essential difference between them is the method by which messages on the LAN, known as traffic, are controlled.CHAPTER 4 COMPUTER CONTROL SYSTEMS4.5 Computer Control System Communications(1)4.5.3 Token SystemsThe token bus is a LAN, often referred to as a highway, to which the IEEE 802.4

27、 standard applies. Token bus topology, which is essentially the same as for Ethernet, has an open structure as depicted in Figure 4.5.2. CHAPTER 4 COMPUTER CONTROL SYSTEMS4.5 Computer Control System Communications(1)4.5.3 Token SystemsToken ring is another type of LAN to which the IEEE 802.5 standar

28、d applies. It is essentially the same as token bus, except that the ends of the bus are physically connected to form a ring, as depicted in Figure 4.5.3.CHAPTER 4 COMPUTER CONTROL SYSTEMS4.5 Computer Control System Communications(1)4.5.4 ProtocolsThe open systems interconnection (OSI) protocol, known as the OSI model, published in ISO 7498-1 (1995) for reference purposes, has seven layers whose functionality is as summarised in Table 4.5.1.CHAPTER 4 COMPUTER CONTROL SYSTEMS4.5 Computer Control System Communications(1)4.5.5 Netw