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Automating Manufacturing Systems - Process Control and ...

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plc pid - 25.20<br />

BT9:0/DN<br />

BT9:2/EN<br />

BT9:1/DN<br />

SUB<br />

SourceA N7:80<br />

SourceB N7:42<br />

Dest N7:81<br />

DIV<br />

SourceA N7:81<br />

SourceB 2<br />

Dest N7:60<br />

Block Transfer Write<br />

Module Type Generic Block Transfer<br />

Rack 000<br />

Group 1<br />

Module 0<br />

<strong>Control</strong> Block BT9:2<br />

Data File N9:60<br />

Length 13<br />

Continuous No<br />

Figure 25.21<br />

A Water Tank Level <strong>Control</strong> Program<br />

25.4.3 Position Measurement<br />

- A touch sensor combined with a servo mechanism to measure a dimension<br />

- the sensor must be compliant. The servo axis speed must be slow enough so that<br />

the motion can stop within the compliance of the sensor<br />

- move until the sensor touches then stop <strong>and</strong> backup slowly until it releases<br />

- used for CMMs<br />

25.5 SUMMARY<br />

• Negative feedback controllers make a continuous system stable.<br />

• When controlling a continuous system with a logical actuator set points can be<br />

used.<br />

www.PA<strong>Control</strong>.com

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