1. Control Systems With Embedded Implementation (CSEI) Dr. Imtiaz Hussain Assistant Professor email: imtiaz.hussain@faculty.muet.edu.pkimtiaz.hussain@faculty.muet.edu.pk URL :http://imtiazhussainkalwar.weebly.com/ Lab-1 Introduction to Simulink & Stateflow® 1

2. Lecture Outline Introduction Objective 2

3. Introduction Simulink and Stateflow provide: – A powerful environment for modeling real processes... – and are fully integrated with the MATLAB environment. – Instrument Control and Data Acquisition enable verification and validation of models. 3

4. Introduction to Simulink® Block-diagram environment Model, simulate, and analyze multidomain systems Accurately design, implement, and test: – Control systems –Signal processing systems – Communications systems – Other dynamic systems 4

5. Simulink Product Key Features Extensive and expandable libraries of predefined blocks Hierarchical, component-based modeling Open Application Program Interface (API) Hybrid (mixed-signal), multirate and multitasking system simulation Full MATLAB®integration 5

6. Types of Models Continuous-Time Discrete-Time / Multi-Rate Sampled-Data Finite State Machines / Mode Logic Discrete Event Systems Physical Domains 6

7. Stateflow Overview Extend Simulink with a design environment for developing state machines and flow charts. Design systems containing control, supervisory, and mode logic. Describe logic in a natural and understandable form with deterministic execution semantics. 7

8. How does Stateflow work with Simulink? Simulink is used to respond to continuous changes in dynamic systems. Stateflow is used to respond to instantaneous changes in dynamic systems. Real-world systems have to respond to both continuous and instantaneous changes. 8 Use both Simulink and Stateflow so that you can use the right tool for the right job.

9. Key Features Defines functions –Procedurally, using Embedded MATLAB TM –Graphically, using flow diagrams –In tabular form, with truth tables Provides language elements, hierarchy, and parallelism Animates Stateflow®charts Incorporates custom and legacy C code Performs static and run-time checks 9

10. Objective of the Lab In this lab we will cover the basic workflow for building Stateflow charts that are used to model event−driven systems, and how they work with Simulink blocks. We will begin with definitions that are essential in understanding Stateflow and its relation to Simulink and MATLAB. Later with the help of a demo model provided by The MathWorks™, we will develop an example model with step−by−step procedure. 10

11. What is a finite state machine? A finite state machine is a model describing the behavior of a finite number of states, the transitions between those states, and actions. A state represents an operating mode of a machine. – For instance, a typical household portable space heater has four states, off, low, medium, and high. An action describes the activity that is to be performed. An action can be further classified as an entry action which is performed when entering the state, an exit action which is performed when exiting the state, and as a transition action which is performed during a transition. 11

12. What is a finite state machine? A representation of a reactive system that contains a finite number of states. System changes states based on defined conditions. Examples: – Automatic transmission: First, second, third, and fourth gears – Actuator in a fault detection, isolation, and recovery system: Active, standby, off, isolated – Robot arm: Initialization, normal mode, or shutdown 12

13. What is a finite state machine? A finite state machine can be represented either by a state diagram or a state transition table. Thus, a typical household heater can be represented as shown in Figure-1, or as a state transition table shown as in Table-1. 13 Figure-1 Table-1

14. Event Driven System An event is an action that can trigger a variety of activities. For example, in a typical household space heater a switch allows a transition to occur between medium state and high state. Thus, event driven systems allow the transition from one operating mode to another in response to events and conditions. Event−driven systems can be implemented as finite−state machines. 14

15. What Is Stateflow? Stateflow is a graphical design and development tool for control and supervisory logic used in conjunction with Simulink. Stateflow is a product that is part of Simulink. In Simulink, Stateflow blocks are referred to as Stateflow Chart blocks. 15

16. Stateflow Is a Finite State Machine If you double-click the Stateflow block in the preceding Simulink model, its Stateflow diagram appears in the Stateflow diagram editor window. 16

17. Stateflow Is a Finite State Machine The preceding example has two states: Power_on and Power_off. When you first turn the state machine on, this chart is set to execute a special transition called a default transition that points to the initial state, Power_off. This makes the Power_off state active. Later, when you 17

18. Stateflow Is a Finite State Machine Later, when you change the manual switch in Simulink from Off to On, the model sends an event (on_switch) that makes the Off state transition to the On state. This makes the Off state inactive and On state active. 18

19. Stateflow Adds Flow Diagrams to the State Machine Stateflow also adds the feature of flow diagrams that provide decision points in transitions. Stateflow implements flow diagrams with junctions, round objects that provide an alternative path for transitions. 19

20. Exercise 20

21. Stateflow Simulates its State Machine Once you finish a Simulink model with Stateflow charts, you can simulate it. This allows you to see an animated Stateflow chart while it responds to events and changes states. In the animated chart, active states are highlighted. 21

22. Build a Stateflow Model At the MATLAB prompt enter sfnew. Label the Stateflow block in the new untitled model by clicking in the text area and replacing the text Untitled with the text On_Off. 22

23. Creating States Double-click the Stateflow block in the Simulink model window to invoke the Stateflow diagram editor. 23

24. Construction of Finite−State Machines with Stateflow Stateflow provides us the necessary graphical objects to construct finite−state machines. Like Simulink, we can drag and drop objects to create state−transition charts in which a series of transitions directs a flow of logic from one state to another. 24

25. Procedure for Creating a Stateflow Chart To understand the basic steps for creating a Stateflow Chart let us start with an example. We will follow the procedure recommended by The MathWorks illustrated in the functional block diagram. 25

26. Example#1 Let us design a Counter that counts 0-3. 26 0 1 2 3 Clock Pulse Start

27. Example#1 Step 1: We define the Interface to Simulink – Open new model window in Simulink and drag Pulse Generator block from sources. – Drag chart block from stateflow blockset 27

28. Example#1 Step 1: We define the Interface to Simulink – To define the input of the Stateflow Chart block in we double−click this block, and we observe that the Stateflow Editor window appears. – From the Chart drop menu we select Add Inputs & Outputs>Event Input from Simulink, and this opens the event window. 28

29. Example#1 Step 1: We define the Interface to Simulink – To define the output of the Stateflow Chart block From the Chart drop menu we select Add Inputs & Outputs>Data Output to Simulink, and this opens the event window. 29

30. Example#1 Step 2: We define the States for each Mode of Operation – From the object palette on the left side of the Stateflow Editor window we click the State tool 30 State tool

31. Example#1 Step 3: We define State Actions and Variables – We click inside the 0 state after the last letter of its name to cause a blinking text cursor to appear. We press the Enter key and we type entry: COUNT=0; 31

32. Example#1 Step 4: We define Transitions Between States – We need to add a transition from the 0 to the 1 state. – To do this, we move the cursor over the top edge of 0 and we observe that the cursor shape changes to crosshairs. – We hold down the left mouse button, we drag the cursor to the bottom edge of the 1 state, we release the mouse, and a transition pointing from the 0 to the 1 state is formed. 32

33. Example#1 Step 4: We define Transitions Between States – click the Default Transition tool, we move the cursor into the drawing area, and we observe that it changes to a diagonal arrow. 33 Default Transition

34. Example#1 Step 6: Simulation of the Stateflow Chart When a Simulink model that contains a Stateflow Chart block is simulated, we can animate the Stateflow Chart to highlight the states and the transitions as they occur, and this feature provides visual verification that our chart behaves as expected. Animation is enabled by default but we need to specify the speed. 34

35. Example#1 35

36. Example#1 36

37. Example#2 Design a Counter that counts 0-7 with asynchronous reset input. 37

38. Example-3 ABC Company maintains checking and savings accounts with a local bank. The initial deposit in the checking account is $10,000 and the fixed amount of $10,000 is deposited in the savings account. The company has also established an overdraft protection for up to $50,000, and has made an agreement with the bank that if payments by the bank exceed the overdraft protection, the bank will deduct the excess amount from the savings account. There will be no fees imposed as long as payments do not exceed present checking account balance and interest at 0.5% will be earned. A fee of 5% will be imposed for overdrafts, and 1% fee will be charged if it becomes necessary to draw monies from the savings account. 38

39. END OF LAB-1 To download this lecture visit http://imtiazhussainkalwar.weebly.com/ 39