7. Scenario
●Engineer forms a model on the software
●Our software: PCS (Process Control
Studio)
●Model analogous to real-process
●Associate model parts to I/O channels
on controller
●Load .pcs file to laptop or PDA
12. PCS Features
●Attractive user interface
●Support two mode
Design time mode
Run time mode
●Designing & Monitoring more than one
process at the same time
●Save and load Design process
●Failure notification
●Authentication
16. PCS Data Base
●Simple to use
●It improves the capabilities of the overall the system
●Able to trace the shortage in any component in the
system & notify for making order
●It holds useful data about each component
●Store any alarm accrues In run time
51. Why “ Data Acquisition ” is needed ?
●The Data Acquisition does:
Sampling of the process data
Any Digital or Analog
conversions
52. What is “ Data Acquisition “ ?
●It consists of 2 sub-modules:
1) Analog-to-Digital (ADC)
2) Digital-to-Analog (DAC)
●The ADC and DAC are controlled by the
microcontroller
Data
Preparation
53. Interfacing the Process with the
Data Acquisition
●Process Input and Output
●Input is Control Action
( Manipulated Variable)
●Output is Controlled
Variable
54. Hardware Choices
●Freescale DEMO9S12NE64 based on
MC9S12NE64 MCU
- Main Features:
oAnalog-to-Digital converter (ADC)
oTimer module (TIM )
oSerial interfaces
- One Serial Peripheral Interface (SPI)
55. Analog-to-Digital converter (ADC)
●ADC is a built in module in the MCU
- 8 channel module
- 10 Bit Resolution
●8-Bits was used (1-byte)
- To ease the calculations
- Compromise data storage
62. Digital Control
●There are differences between digital
control and analog control
●Analysis in z-domain rather than s-domain
●We need to consider:
oSampling Time
oResolution
63. Microcontroller Capabilities
●8 Analog Input Channels
●8 Analog Output Channels
●8 Digital Input Channels
●8 Digital Output Channels
●8 On/Off Controllers
●8 PID Controllers
●Implemented in C-code using structures
64. On/Off Control
●Analog Input & Digital Output
●Simply implemented using IF-ELSE
statement
●Only valid for first-order processes
●Parameters: Set Point and On-Off
65. PID Control
●Analog Input & Analog Output
●Implemented using mathematical
expressions
●Valid for any order process
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Editor's Notes
Why we need local controller ? Local controller is essential when we need to do process monitoring and control
Later we will know how this two tasks will be achieved.
- Sampling the process data variables of interest every specified period of time and keeps it ready for any monitoring requests.
-
Data Acquisition Controller do all the control actions and specify the ranges and the channel numbers … Communication sub-module is used to send/receive data to/from the Software application
One 8-channel module with 10-bit resolution
- Different types of addressing
- Sampling time: too high? Too low?
- resolution: why use double if it will change back to integer
