3442 industrial instruments 2 chapter 8 discrete-state process control dr. bassam kahhaleh princess...

34423442Industrial Instruments 2Industrial Instruments 2

Chapter 8Chapter 8Discrete-State Process ControlDiscrete-State Process Control

Dr. Bassam KahhalehDr. Bassam Kahhaleh

Princess Sumaya Univ.Princess Sumaya Univ.Electronic Engineering Dept.Electronic Engineering Dept.

Princess Sumaya UniversityPrincess Sumaya University 3442 - Industrial Instruments 23442 - Industrial Instruments 2 22 / 32 / 32

8: Discrete-State Process Control8: Discrete-State Process ControlDefinitionsDefinitions

The The discrete statediscrete state of the process at any of the process at any moment is the set of all input and output moment is the set of all input and output values.values.

An An eventevent in the system is defined by a in the system is defined by a particular state of the system, i.e. particular particular state of the system, i.e. particular values of inputs and outputs.values of inputs and outputs.

A A discrete-state process controldiscrete-state process control is a is a particular particular sequence ofsequence of eventsevents through which through which the process the process accomplishesaccomplishes some objective some objective


8: Discrete-State Process Control8: Discrete-State Process ControlExampleExample

Frost-free refrigerator/freezerFrost-free refrigerator/freezer

Discrete-state I/PDiscrete-state I/P Door open/closedDoor open/closed Cooler temp. high/lowCooler temp. high/low Freezer temp. high/lowFreezer temp. high/low Power switch on/offPower switch on/off Frost detector on/offFrost detector on/off Frost eliminator timer out/not outFrost eliminator timer out/not out


8: Discrete-State Process Control8: Discrete-State Process ControlExampleExample

Frost-free refrigerator/freezerFrost-free refrigerator/freezer

Discrete-state O/PDiscrete-state O/P Light on/offLight on/off Compressor on/offCompressor on/off Timer on/offTimer on/off Heater on/offHeater on/off Baffle open/closedBaffle open/closed


8: Discrete-State Process Control8: Discrete-State Process ControlDiscrete-State VariablesDiscrete-State Variables Continuous ControlContinuous Control


8: Discrete-State Process Control8: Discrete-State Process ControlDiscrete-State VariablesDiscrete-State Variables Continuous ControlContinuous Control Discrete ControlDiscrete Control


8: Discrete-State Process Control8: Discrete-State Process ControlDiscrete-State VariablesDiscrete-State Variables Continuous ControlContinuous Control Discrete ControlDiscrete Control Composite Composite

Discrete/Continuous Discrete/Continuous ControlControl


8: Discrete-State Process Control8: Discrete-State Process ControlProcess SpecificationsProcess Specifications Process ObjectivesProcess Objectives Process HardwareProcess Hardware

Input DevicesInput Devices• Limit SwitchesLimit Switches• ComparatorsComparators• Push ButtonsPush Buttons

Output DevicesOutput Devices• LightsLights• MotorsMotors• SolenoidsSolenoids


8: Discrete-State Process Control8: Discrete-State Process ControlEvent Sequence DescriptionEvent Sequence Description Narrative StatementsNarrative Statements FlowchartsFlowcharts Binary-StateBinary-State

00

011X

X / 0

1 / 1

0 / 0

X / 1


8: Discrete-State Process Control8: Discrete-State Process ControlEvent Sequence DescriptionEvent Sequence DescriptionFlowchart ExampleFlowchart Example


8: Discrete-State Process Control8: Discrete-State Process ControlEvent Sequence DescriptionEvent Sequence DescriptionBinary-State ExampleBinary-State Example

1.1. Fill the tank to level A Fill the tank to level A from valve A.from valve A.

2.2. Fill the tank to level B Fill the tank to level B from valve B.from valve B.

3.3. Start the timer, heat, and Start the timer, heat, and stir for 5 minutes.stir for 5 minutes.

4.4. Open output valve C Open output valve C until the empty switch until the empty switch engages.engages.



I/P VariablesI/P Variables LALA LBLB LELE TUTU

O/P VariablesO/P Variables VAVA VBVB VCVC TMTM SS HH



State: LA LB LE TU VA VB VC TM S H


8: Discrete-State Process Control8: Discrete-State Process ControlRelay Controllers & Ladder DiagramsRelay Controllers & Ladder Diagrams Control Relays (Relay Sequencer)Control Relays (Relay Sequencer)


8: Discrete-State Process Control8: Discrete-State Process ControlRelay Controllers & Ladder DiagramsRelay Controllers & Ladder Diagrams Ladder DiagramLadder Diagram


8: Discrete-State Process Control8: Discrete-State Process ControlRelay Controllers & Ladder DiagramsRelay Controllers & Ladder DiagramsLadder Diagram ExampleLadder Diagram Example



1. When the START button is pushed, the platform is driven to the down position.

2. When the STOP button is pushed, the platform is halted at whatever position it occupies at that time.

3. When the UP button is pushed, the platform, if it is not in downward motion, is driven to the up position.

4. When the DOWN button is pushed, the platform, if it is not in upward motion, is driven to the down position.



Start

Stop



START

STOP

Power



START

STOP

Power

↓ Motor



PowerDown

STOP

START

↑ Motor

↓ MotorUP



CR

CR


8: Discrete-State Process Control8: Discrete-State Process ControlHardwired ProgrammingHardwired Programming Relay SequencersRelay Sequencers

Programmable Logic Controllers (PLCs)Programmable Logic Controllers (PLCs) ProcessorProcessor Input ModulesInput Modules Output ModulesOutput Modules


8: Discrete-State Process Control8: Discrete-State Process ControlProgrammable Logic Controllers (PLCs)Programmable Logic Controllers (PLCs) Input ModuleInput Module


8: Discrete-State Process Control8: Discrete-State Process ControlProgrammable Logic Controllers (PLCs)Programmable Logic Controllers (PLCs) Output ModuleOutput Module


8: Discrete-State Process Control8: Discrete-State Process ControlProgrammable Logic Controllers (PLCs)Programmable Logic Controllers (PLCs) Logic ProgrammingLogic Programming

Using a NC switch to turn off a light with relay logic and with PLC programming:

a) The button turns the light OFF.

b) With relay logic the button turns the light ON.

c) With a PLC program the button turns the light ON


8: Discrete-State Process Control8: Discrete-State Process ControlProgrammable Logic Controllers (PLCs)Programmable Logic Controllers (PLCs) Logic ProgrammingLogic Programming

NO switches are considered INACTIVE when they are read as open circuit, and ACTIVE when they are read as closed circuit.

In the ladder diagram, 01 must be ACTIVE while 03 must be INACTIVE to turn 08 ON.


8: Discrete-State Process Control8: Discrete-State Process Control

End of Chapter 8End of Chapter 8

3442 industrial instruments 2 chapter 8 discrete-state process control dr. bassam kahhaleh princess...

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