Industrial Automation course

Transcription

1 Industrial Automation course Lesson 2 PLC - Introduction Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 1

2 What is a PLC PLC: Programmable Logic Controller Processing unit able to drive the actuator due to variations acquired from the sensors connected to it Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 2

3 What is a PLC PLC: Programmable Logic Controller In order to work, this device needs to execute task at a defined frequency, for this reason it must be real-time What does real-time mean? It means to know the maximum execution time of a code portion Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 3

4 PLC cycle Inputs Acquisition Algorithms execution Outputs Write N.B.: Usually the cycle re-launch time is defined; however, with some PLCs (for example Siemens), is a function block, with a predefined sampling time isn t used, the execution will be in an «infinite loop», then without a known re-launch time Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 4

5 Real-time Each PLC maker personalizes one or more real-time operating systems, in order to allow the integration with its own devices The most used operating systems, used in the field of industrial automation are: VXWorks QNX Windows embedded (or CE) Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 5

6 Real-time How does a real-time operating system work? A real-time operating system is a deterministic system, it means that it is able to guarantee, a priori, the maximum execution time of a program. Definitions: Release time: the time in which the program is available for the execution Deadline: the time by which the execution must be terminated Completion time: the execution finish time Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 6

7 Real-time Considering the PLCs, usually: Release time: the program is available for the next execution when the deadline is reached Deadline: corresponds to the re-launch time of the software Completion time: depends from the CPU load used in the execution of the software Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 7

8 Real-time Execution example Deadline Esecuzione Esecuzione Tempo [s] Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 8

9 Products volumes When a PLC is necessary Embedded electronics Modular PLC PLC Product variability The PLC is useful in very variable systems with a reduced number of pieces (or, even, in one single prototype, as the production lines) when the complexity in terms of interfaces is very high Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 9

10 PLC types μplc Medium PLC Big PLC In Out <= 64 Since some years with Digital / Analogic expansion modules 64 < In Out < 512 In Out >=512 The difference between these two PLC types is loosing importance because of the massive usage of modular PLCs Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 10

11 Structure DIN rail IO modules CPU Power supply module Ethernet interface (programming / connectivity) Powerlink Battery Compact Flash O.S. + Software Interface modules Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 11

12 Hardware architecture The trend, in the last years, is to bring the PLC architecture to that of a normal x86. Generally, the used memory are: EEPROM that contains the O.S and the user software (now installed on removable memory as CF, SD, etc ) RAM that contains the software in execution and holds the variables (in some cases the RAM is kept active with the battery, in case of power supply loss) Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 12

13 Hardware architecture There are a lot of I/O boards, the most important (that can be found on the companies catalogues) are: Analogic In / Out ( 10 V, ma, 4 20 ma) Digital In / Out (5 V-DC, 24 V-DC, 240 V-AC) Motor control In / Out (encoder, PWM) Various In (thermocouples, load cells, etc ) Fieldbus interfaces Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 13

14 Programming All the PLCs can be programmed with a PC (usually with a Windows O.S.) Basically, all the companies use the Ethernet interface on the PLC Almost all use a proprietary programming software, some of them are compatible with third part development environment (for example Codesys) N.B.: For the Lab lectures we use B&R Automation Studio 4.0 Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 14

15 IEC IEC is a no-profit and non governmental organization born with the aim of to define and publish standards related to the electrical / electronic technologies (and those connected to them) It is born on June 26, 1906 from the English IEE and the American AIEE The headquarter was, in the beginning, in London, but since 1948 it was moved to Genève Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 15

16 IEC Relating to the PLC standards, the reference norm is the IEC (that, before the numbering variation of the 1996 was called IEC 1131) Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 16

17 IEC Why this norm is so important? Because it is also a de facto standard in the industry Because the 80% of the PLCs is based on it Because allows to keep a coherent structure with the «rest of the world» Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 17

18 IEC The norm is composed of these parts: 1. General overview, definitions 2. Hardware 3. Programming languages 4. Users guidelines 5. Communication 7. Fuzzy logic programming 8. Implementation guidelines Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 18

19 Application structure Configuration Resource Resource Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 19

20 Application structure Configuration Resource Resource Program Program Program Program FB FB FB FB Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 20

21 Application structure Configuration Resource Resource Task Task Task Task Program Program Program Program Inputs acquisition FB FB FB FB Algorithms execution Outputs Write Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 21

22 Application structure Configuration Resource Resource Task Task Task Task Program Program FB FB Program Program FB FB Variabile Access path Global and directly represented variables Access paths Communication function Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 22

23 Application structure The communication between the programs can be Inside the same configuration Direct if between two function blocks of the same program Using global variables if between two programs Between two configurations Direct, using communication function blocks Access to a shared access path Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 23

24 Programming languages In the third part of the norm (as already mentioned) five possible programming languages are defined: Ladder Diagram SFC Sequential Function Chart FBD Function Block Diagram Graphical languages Instruction List ST Structured Text Textual languages N.B.: In order to guarantee the real-time execution, these languages are usually converted in low-level instructions Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 24

25 Programming languages Common elements of the 5 IEC languages: Identifiers The first character can t be a number It isn t possible to use two consecutives _ Without spaces Keywords PROGRAM, FUNCTION, VAR, END_, etc BOOL, BYTE, WORD, INT, REAL, TIME, STRING, prefix S, D, L, U, etc RETAIN, CONSTANT, etc Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 25

26 Programming languages Common elements of the 5 IEC languages: Functions ADD, SQRT, SIN, COS, GT, MIN, MAX, AND, OR, etc Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 26

27 Programming languages Ladder Diagram It is the oldest programming languages of the IEC norm It is based on symbols that come from the electric field: Power rails, Contacts, Coils, etc It is called Ladder because of the graphical structure that the programs implemented in this language have Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 27

28 Programming languages Ladder Diagram Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 28

29 Programming languages SFC Sequential Function Chart Language derived from the IEC 848 standard It is a sequencing oriented language, for this reason it is suitable for a top-down programming approach It is based on: Step, Transitions, Actions, Oriented arcs Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 29

30 Programming languages SFC Sequential Function Chart Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 30

31 Programming languages FBD Function Block Diagram Language derived from the IEC 167 standard The FBD graphical representation is similar to that of the block diagram (will be explained in the Prof. Corno s course) Usually isn t used a lot for the logical control The execution depends from the position of the blocks Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 31

32 Programming languages FBD Function Block Diagram Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 32

33 Programming languages Instruction List It is the lowest level language of the IEC norm It is very similar to the assembly code that,maybe, you already saw The level is too low to be used in the real scope, even if the Siemens «dialect» (called AWL) is used in a lot of cases Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 33

34 Programming languages Instruction List Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 34

35 Programming languages ST Structured Text It s a language born from the old Pascal and Visual Basic It must be considered as a high level languages, compared to the Instruction List There are some tools that allow to generate Structured Text starting from high level implementation (con example Mathworks PLC Coder) Each PLC producer has its own ST «dialect» Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 35

36 Programming languages ST Structured Text Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 36

37 Programming languages In the context of the course we focus on: Graphical languages Ladder Diagram Sequential Function Chart Textual languages Structured Text Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 37

38 Tool-chain As already mentioned, in the course we will use the B&R Automation Studio 4.0 programming environment Before enter in the IEC languages details, let s look at how the software is structured and how it works Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 38

39 Automation Studio During the lecture, I can save on your external hard-drives the software installer (it s 4.7 GB), we have 30 days of real use. Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 39

40 Automation Studio Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 40

41 Automation Studio Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 41

42 Automation Studio Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 42

43 Automation Studio Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 43

44 Automation Studio Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 44

45 Automation Studio In this screen it is possible to assemble via «software» the hardware configuration installed on the real PLC. In the case of this software this activity can be done with a simple drag and drop of the modules Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 45

46 Automation Studio Let s try to install a two analog inputs module (0 20 ma) With a right click it is possible to configure the single module N.B.: these settings are part of the Configuration Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 46

47 Automation Studio Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 47

48 Automation Studio Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 48

49 Automation Studio Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 49

50 Automation Studio Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 50

51 Automation Studio Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 51

52 Automation Studio Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 52

53 Automation Studio In this window the PLC scheduler is shown, as it is possible to notice the new Task is installed on a 100 ms cyclic. It is possible to change the position or the frequency of the task using the right click on the cyclic Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 53

54 Automation Studio Variables viewer Variables logger Politecnico di Milano Universidad de Monterrey, July 2015, A. L. Cologni 54