INDUSTRIAL CONTROL SYSTEMS & COMPUTER PROCESS CONTROL

Transcription

1 1 INDUSTRIAL CONTROL SYSTEMS & COMPUTER PROCESS CONTROL

2 INDUSTRIAL CONTROL - DEFINED The automatic regulation of unit operations and their associated equipment as well as the integration and coordination of the unit operations into the larger production system Usually refers to a manufacturing operation Can also apply to material handling or other equipment 2

3 INDUSTRIAL CONTROL SYSTEMS Process Industries vs. Discrete Manufacturing Industries Continuous vs. Discrete Control Computer Process Control 3

4 CONTINUOUS AND DISCRETE VARIABLES AND PARAMETERS 4

5 DISCRETE VARIABLES AND PARAMETERS Categories: Binary -they can take on either of two possible values, ON or OFF, 1 or 0, etc. Discrete other than binary - they can take on more than two possible values but less than an infinite number of possible values Pulse data -a train of pulses that can be counted 5

6 CONTINUOUS CONTROL Usual objective is to maintain the value of an output variable at a desired level Parameters and variables are usually continuous Similar to operation of a feedback control system Most continuous industrial processes have multiple feedback loops Examples of continuous processes: Control of the output of a chemical reaction that depends on temperature, pressure, etc. Control of the position of a cutting tool relative to workpartinacnc machinetool 6

7 TYPES OF CONTINUOUS PROCESS CONTROL Regulatory control Feed forward control Steady-State optimization Adaptive control 7

8 REGULATORY CONTROL 8

9 FEEDFORWARD CONTROL COMBINED WITH FEEDBACK CONTROL 9

10 STEADY STATE (OPEN-LOOP) OPTIMAL CONTROL 10

11 ADAPTIVE CONTROL OPERATES IN A TIME-VARYING ENVIRONMENT The environment changes over time and the changes have a potential effect on system performance Example: Supersonic aircraft operates differently in subsonic flight than in supersonic flight If the control algorithm is fixed, the system may perform quite differently in one environment than in another An adaptive control system is designed to compensate for its changing environment by altering some aspect of its control algorithm to achieve optimal performance 11

12 ADAPTIVE CONTROL SYSTEM 12

13 TWO BASIC REQUIREMENTS FOR REAL-TIME PROCESS CONTROL 1. Process-initiated interrupts Controller must respond to incoming signals from the process (event-driven changes) Depending on relative priority, controller may have to interrupt current program to respond 2. Timer-initiated actions Controller must be able to execute certain actions at specified points in time (time-driven changes) Examples: (1) scanning sensor values, (2) turning switches on and off, (3) re-computing optimal parameter values 13

14 OTHER COMPUTER CONTROL REQUIREMENTS 3. Computer commands to process To drive process actuators System initiated events -communications between computer and peripherals Program initiated events - non-process-related actions, such as printing reports 4. System- and program-initiated events 5. Operator-initiated events to accept input from personnel Example: emergency stop 14

15 FORMS OF COMPUTER PROCESS CONTROL 1. Computer process monitoring 2. Direct digital control (DDC) 3. Distributed control systems 4. Numerical control and robotics 5. Programmable logic control 6. Supervisory control 15

16 APPLICATION Continuous or semi-continuous production operations involving materials such as chemicals, petroleum, foods, and certain basic metals. In these operations the products are typically processed in gas, liquid, or powder form to facilitate flow of the material through the various steps of the production cycle. 16

17 Measurement of important process variables such as temperature, flow rate, and pressure, Execution of optimizing strategy. Actuation of devices as valves, switches, and furnaces that enable the process to implement the optimal strategy 17

18 COMPUTER PROCESS MONITORING 18

19 Batch Furnace Nominal temperature: up to 900 C commissioned by Bickley Inc., USA 19

20 (A) PROCESS MONITORING, (B) OPEN-LOOP CONTROL, AND (C) CLOSED-LOOP CONTROL (a) (b) (c) 20

21 COMPONENTS OF A DIRECT DIGITAL CONTROL SYSTEM 21

22 DISTRIBUTED CONTROL SYSTEMS (DCS) Multiple microcomputers connected together to share and distribute the process control workload Features: Multiple process control stations to control individual loops and devices Central control room where supervisory control is accomplished Local operator stations for redundancy Communications network(data highway) 22

23 DISTRIBUTED CONTROL SYSTEM 23

24 DCS ADVANTAGES Can be installed in a very basic configuration, then expanded and enhanced as needed in the future Multiple computers facilitate parallel multitasking Redundancy due to multiple computers Control cabling is reduced compared to central controller configuration Networking provides process information throughout the enterprise for more efficient plant and process management 24

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26 Computerized Process Control improves Sugar Refinery Production

27 NUMERICAL CONTROL AND ROBOTICS Computer numerical control (CNC) computer directs a machine tool through a sequence of processing steps defined by a program of instructions Distinctive feature of NC control of the position of a tool relative to the object being processed Computations required to determine tool trajectory Industrial robotics manipulator joints are controlled to move and orient end-of-arm through a sequence of positions in the work cycle 27

28 PLASTIC INJECTION MOLDING MACHINE BLD 280 CNC USE FOR A) MULTIPLE HYDRAULIC CORE PULLING B) CYLINDER TRANSDUCER CONTROL C) MULTIPLE OPTIONS OF... 28

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30 ROBOTS 30

31 PROGRAMMABLE LOGIC CONTROLLER (PLC) Microprocessor-based controller that executes a program of instructions to implement logic, sequencing, counting, and arithmetic functions to control industrial machines and processes Introduced around 1970 to replace electromechanical relay controllers in discrete product manufacturing Today s PLCs perform both discrete and continuous control in both process industries and discrete product industries 31

32 PLC 32

33 BLOW MOLDING MACHINE 33

34 PONGRASS MODEL32H 32MM CAPACITY MANDREL TUBE BENDING MACHINE PLC CONTROLUSE FOR RISING CLAMP & LENGTH STOPBAR 34

35 SUPERVISORY CONTROL In the process industries, supervisory control denotes a control system that manages the activities of a number of integrated unit operations to achieve certain economic objectives In discrete manufacturing, supervisory control is the control system that directs and coordinates the activities of several interacting pieces of equipment in a manufacturing system Functions: efficient scheduling of production, tracking tool lives, optimize operating parameters Most closely associated with the process industries 35

36 SUPERVISORY CONTROL SUPERIMPOSED ON PROCESS LEVEL CONTROL SYSTEM 36

37 Introduction to SCADA A subset of PCS systems that manage systems over very large geographic areas are typically referred to as Supervisory Control and Data Acquisition systems or SCADA systems. SCADA systems make up the critical infrastructure associated with electric utilities, water and sewage treatment plants, and large-scale transportation systems like interstate rail. Supervisory Control and Data Acquisition systems are basically Process Control Systems (PCS), specifically designed to automate systems such as traffic control, power grid management, waste processing etc. 37

38 Aspects of SCADA Most often, a SCADA system will monitor and make slight changes to function optimally SCADA systems are considered closed loop systems and run with relatively little human intervention One of key processes of SCADA is the ability to monitor an entire system in real time 38

39 SCADA systems in INDIA SCADA systems are still to come into widespread infrastructural use in India Now, they are being used primarily for automation in industrial production, and to some extent for specialized process control Ranbaxy Labs and Voltas are two of the companies in India using SCADA systems for controlling a variety of processes Other examples of pseudo-scada usage also observed 39

40 Components of SCADA The basic structure of PCS systems is made up of a wide range of components and several different communication protocols. The operation of such a large and diverse infrastructure requires an extensive network of electronic devices, communications, and control and monitoring systems, such as: Field Devices Remote Terminal Units (RTU) Programmable Logic Controllers (PLC) Intelligent Electronic Devices (IED) Programmable Automation Controller (PAC) 40

41 Components of SCADA Management systems to monitor and control field equipment Human Machine Interface (HMI) SCADA Controller or Real Time Processor Historian Communications Ethernet, Wireless, Serial Modbus, DNP3 ICCP, OCP 41

42 Construction of SCADA SCADA systems are primarily control systems. A typical control system consists of one or more remote terminal units (RTU) connected to a variety of sensors and actuators, and relaying information to a master station. 42

43 A typical 3-tiered approach to SCADA systems 43

44 Sensors & Actuators Sensors perform measurement, and actuators perform control. Sensors get the data (supervision and data acquisition) Actuators perform actions dependent on this data (control). The processing and determination of what action to take, is done by the master control system (i.e. SCADA). 44

45 RTU/ PLC Remote Terminal Units (RTUs) connect to sensors Convert sensor signals to digital data and sending digital data to the supervisory system Operate actuators as per control signals received/ generated Provide local processing capability Applications that had previously been programmed at the central master station can now be programmed at the RTU. 45

46 Master Station Master stations have two main functions: Periodically obtain data from RTUs/PLCs (and other master or submaster stations) Control remote devices through the operator station Other duties include trending, alarm handling, logging and archiving, report generation, and facilitation of automation. These duties may be distributed across multiple PCs, either standalone or networked. 46

47 Segregation of functions of a SCADA system into a functional representation 47

48 Data Flow Data acquisition begins at the RTU or PLC level and includes meter readings and equipment status reports that are communicated to SCADA as required Data is then compiled and formatted in such a way that a control room operator using the HMI can make supervisory decisions to adjust or override normal RTU (PLC) controls Data may also be fed to a Historian, often built on a commodity Database Management System, to allow trending and other analytical auditing. 48

49 SCADA of Cooling System 49

50 Applications of SCADA Electric power generation, transmission & distribution (USA) Water supply, sewage & drainage (UK & Netherlands) Buildings, facilities & environment Manufacturing (Robots-Toyota, Porsche, VW) Traffic Signals (USA) Mass transit (Rail crossing gates, USA) Suburban Railway system (Mumbai, Western Railway) 50

51 Bibliography SCADA-IBM whitepaper Whitepaper on SCADA systems security-arjun Venkatraman SACAD-A. Daneels-CERN, Geneva 51

52 Thank You 52