Transcript PID control in Vision

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UNITRONICS
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P
I
D
roportional
ntegral
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erivative
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PID – What's our goal?
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The PID function uses system feedback to
continuously control a dynamic process.
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The purpose of PID control is to keep a process
running as close as possible to a Second
desired Setlevel
Point.
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ON – OFF control
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Switches the power ON and OFF (0% - 100%)
Pros:
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edittoMaster
Easy to understand,
perform. text styles
Cons:
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Not precise. In some systems "waves" of over and
undershoots can reach 10-20% of PV.Third level
In some fast systems is impossible of all.
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What's PID?
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Mathematical process, which is calculating in
each moment the energy need by the system
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to achieve Click
the goaltoin edit
the best
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What's PID?
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PID means:
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ProportionalClick
+ Integral
+ Derivative
CV = CV (P) + CV(I) + CV(D)
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What's PID?
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Proportional control is leading.
The control can be:

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P control only
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PI control
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PD control
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Full PID control
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Proportional control
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A band around SP is defined – in percents of
PV range.
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Out of proportional
is alwaystext
100%
and no calculations are done.
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Proportional error is 100% on the border of PB.
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Proportional error is 0% at SP.
P-control outputs CV(P) value that Fourth
is in:
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Direct linear proportion to the size of the
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Error value.
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Proportional control
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Simple – easy to understand, easy to program
even in ladder
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Cons:
Never reach Set point!
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Integral control
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The integral time you set is the amount of time, as
calculated by the controller, required to bring the
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process to Set
Point.
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According to the delay, Integral action adds value to
this, calculated by Proportional action.Third level •
Integral value is accumulated with the time.
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Integral action
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CV = CV(P) + CV(I)
On set point – CV(P) = 0  CV = CV(I)
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Derivative action
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Derivative action responds to the rate and
direction of change in the Error.
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This meansClick
that a to
fastedit
change
in errortext
causes
a
strong response from the controller.
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PID control in Vision
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Functional block.
Many PID loops can be controlled simultaneously.
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Fully independent
loops.
Large scale of inputs and outputs.Second level
Integrated in full system logic.
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PID control in Vision
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Advanced control functions:
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 Ramp and
soak.to
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 Full step programmer.
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Bumpless control.
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 Cascade control.
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PID control in Vision
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Configurating FB PID:
With one scan condition (mostly Power up SB2)
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On subroutine,
which
is always
scanned
(recommended Main routine!)
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PID parameters
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Let's open configuration block:
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Why Autotune?
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Each system has its own set of P, I, D and St
values.
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editparameters
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Finding "manually"
needsstyles
experience and time.
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Autotune learns the system and calculates
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the optimal parameters for it.
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Autotune – how it works?
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Autotune runs ON-Off cycles
According to the "wave" of overshoot, the base
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tocalculated
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PID parameters
.
Number of cycles 1 ~ 3 is set in Autotune
module.
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More cycles – more precise result, but longer process.
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Autotune – how it works?
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FB PID –
Advanced functions
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 Pause Integral and Derivative action
 Read & Force
Error
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 Read Control components
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PID Server
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PID server is ideal tool for understanding, learning
and debug PID process!
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You can use
it:
 To view process.
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 To Log it.
 To Autotune it – up op to 8 cycles. Third level
It's part of VisiLogic or independent tool.
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Thank You
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