1. Unit 3b Industrial Control Systems
Sections:
Basic Elements of an Automated System
Levels of Automation
Process Industries vs. Discrete Manufacturing Industries
Continuous Control
Discrete Control
Computer Process Control
Supervisory Control
Enterprise Control

2. Process vs. Discrete Industries
Process industries
Production operations are performed on amounts of materials
Liquids, gases, powders, etc.
Discrete manufacturing industries
Production operations are performed on quantities of materials
Parts, product units

3. Discrete Control Systems
Process parameters and variables are discrete
Process parameters and variables are changed at discrete moments in time
The changes are defined in advance by the program of instructions
Combinational logic control
The state of the system has changed (event-driven changes)
Sequential control
A certain amount of time has elapsed (time driven changes)

4. Event-Driven Changes
Executed by the controller in response to some event that has altered the state of the system
Examples:
A robot loads a workpart into a fixture, and the part is sensed by a limit switch in the fixture
The diminishing level of plastic in the hopper of an injection molding machine triggers a low-level switch, which opens a valve to start the flow of more plastic into the hopper
Counting parts moving along a conveyor past an optical sensor

5. Time-Driven Events
Executed by the controller either at a specific point in time or after a certain time lapse
Examples:
The factory “shop clock” sounds a bell at specific times to indicate start of shift, break start and stop times, and end of shift
Heat treating operations must be carried out for a certain length of time
In a washing machine, the agitation cycle is set to operate for a certain length of time
By contrast, filling the tub is event-driven

6. Controller Requirements
Process-initiated interrupts
Timer-initiated actions
Computer commands to process actuators
System- and program-initiated events
Operator-initiated events
Capabilities
Polling (data sampling)
Interlocks
Interrupt system
Exception handling

7. Polling (Data Sampling)
Periodic sampling of data
Polling frequency – reciprocal of time interval between data samples
Polling order – sequence in which data collection points are sampled
Polling format – alternative sampling procedures:
All sensors polled every cycle
Update only data that has changed this cycle
High-level and low-level scanning

8. Interlocks Preventing one device from interfering with the other(s)
Input interlocks
Proceed to execute work cycle program
Interrupt execution of work cycle program
Output interlocks

9. Interrupt System
Suspend program and execute another program requiring a higher priority event
Internal interrupt – generated by the computer itself
Examples: timer-initiated events, polling, system- and program initiated interrupts
External interrupts – generated external to the computer
Examples: process-initiated interrupts, operator inputs

10. Interrupt Systems
Single-Level Interrupt
Multi Level Interrupt

11. Exception Handling Event outside of normal or desired operation
Examples:
Product quality problem
Process variable outside normal operating range
Shortage of raw materials
Hazardous conditions, e.g., fire
Controller malfunction
Exception handling is a form of error detection and recovery

12. Forms of Discrete Control
Computer process monitoring
Direct digital control (DDC)
Numerical control and robotics
Programmable logic control
Supervisory control
Distributed control systems and personal computers

13. Computer Process Monitoring
Computer observes process and associated equipment, collects and records data from the operation
The computer does not directly control the process
Types of data collected:
Process data – input parameters and output variables
Equipment data – machine utilization, tool change scheduling, diagnosis of malfunctions
Product data – to satisfy government requirements, e.g., pharmaceutical and medical

14. Direct Digital Control (DDC)
Components in a conventional analog control system are replaced by the digital computer
Multiplexer
ADC
Multiplexer
DAC

15. Numerical Control and Robotics
Computer numerical control (CNC) – computer directs a machine 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

16. Programmable Logic Controller (PLC)
Implement logic, sequencing, counting, and arithmetic functions to control industrial machines and processes.
Both discrete and continuous control functionality

17. NXT Controller

18. Transformation Processes
Supervisory Control
Supervisory control, controls a number of integrated unit operations in a cell:
Machines
Robots
Conveyors
Supervisory
Control
Conveyor
Control
Machine
Control
Robot
Control
Transformation Processes

19. Distributed Control System
Materials
Planning
Production
Planning
Design
Quality
Control
Shop Floor
Control
Financial
Planning
Enterprise Network
Supervisory
Control
Supervisory
Control
Shop Floor Network
Machine
Control
Storage
Control
Conveyor
Control
Machine
Control
Robot
Control
Assembly
Control
Transformation Processes

20. Control Architecture Level 4 Business Information (Business Office)
Enterprise Control
Plant Control
(Production, Quality, …)
Cell Controller
(Supervisory Control)
Machine Controller
(Automatic Control)
Device Control
(Sensors/Actuators)
Level 4
Business Information
(Business Office)
Level 3
Level 2
Level 1
Industrial Automation
(Shop Floor)
Level 0

21. Computer Integrated Manufacturing
Business functions - sales and marketing, order entry, cost accounting, customer billing
Product design - research and development, design engineering, prototype shop
Manufacturing planning - process planning, production planning, MRP, capacity planning
Manufacturing control
shop floor control,
inventory control, quality control

22. Customer Relationship Management/ Enterprise Resource Planning

23. YouTube Industrial Control Programmable Logic Controller
Distributed Control
CAD/CAM
Computer Integrated Manufacturing
Customer Relationship Management
Enterprise Resource Management