📄 picontroller.htm
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<p align="left" style="margin-top: 1; margin-bottom: 1">w(t) - DesiredValue in continuous time domain<br>
y(t) - MeasuredValue (feedback) in continuous time domain<br>
e(t) - input error in continuous time domain<br>
u(t) - controller output in continuous time domain</p>
<p align="left" style="margin-top: 1; margin-bottom: 1"> </p>
<p align="left" style="margin-top: 1; margin-bottom: 1">w(k) - DesiredValue in step k - discrete time domain<br>
y(k) - MeasuredValue (feedback) in step k - discrete time domain<br>
e(k) - input error in step k - discrete time domain<br>
u(k) - controller output in step k - discrete time domain</p>
<p align="left" style="margin-top: 1; margin-bottom: 1"> </p>
<p align="left" style="margin-top: 1; margin-bottom: 1">u_max - u(k) range max <br>
w_max - w(k) range max<br>
y_max - y(k) range max<br>
e_max - e(k) range max</p>
<p align="left" style="margin-top: 1; margin-bottom: 1"> </p>
<p align="left" style="margin-top: 1; margin-bottom: 1">The PI controller algorithm in continuous time domain:</p>
<p align="left" style="margin-top: 1; margin-bottom: 1"> </p>
<p align="left" style="margin-top: 1; margin-bottom: 1">
/t<br>
u(t) = K[e(t) + 1/Ti * | e(t)*dt]
(1)<br>
/0 <br>
</p>
<p align="left" style="margin-top: 1; margin-bottom: 1">
K - controller gain<br>
Ti - integral time constant</p>
<p align="left" style="margin-top: 1; margin-bottom: 1"> </p>
<p align="left" style="margin-top: 1; margin-bottom: 1">
e(t) = w(t) - y(t)
(2)</p>
<p align="left" style="margin-top: 1; margin-bottom: 1"> </p>
<p align="left" style="margin-top: 1; margin-bottom: 1">
PI controller expressed in fractional arithmetic:<br>
</p>
<p align="left" style="margin-top: 1; margin-bottom: 1">
u_f(k) = K_sc * e_f(k) + ui_f(k - 1) + Ki_sc * e_f(k)
(3)</p>
<p align="left" style="margin-top: 1; margin-bottom: 1"> </p>
<p align="left" style="margin-top: 1; margin-bottom: 1">
e(k) = w(k) - y(k)
(4)</p>
<p align="left" style="margin-top: 1; margin-bottom: 1"> </p>
<p align="left" style="margin-top: 1; margin-bottom: 1">
when:<br>
w_max = y_max = e_max
(5)<br>
equation (4) can be expressed in fractional
arithmetic as follows:</p>
<p align="left" style="margin-top: 1; margin-bottom: 1"> </p>
<p align="left" style="margin-top: 1; margin-bottom: 1">
e_f(k) = w_f(k) - y_f(k)
(6)<br>
u_f(k) = u(k) / u_max<br>
w_f(k) = w(k) / w_max<br>
y_f(k) = y(k) / y_max<br>
e_f(k) = e(k) / e_max</p>
<p align="left" style="margin-top: 1; margin-bottom: 1"> </p>
<p align="left" style="margin-top: 1; margin-bottom: 1">
K_sc = K * e_max / u_max
(7) <br>
Ki_sc = K * T / Ti * e_max / u_max
(8)</p>
<p align="left" style="margin-top: 1; margin-bottom: 1"> </p>
<p align="left" style="margin-top: 1; margin-bottom: 1">
T - sampling time</p>
<p align="left" style="margin-top: 1; margin-bottom: 1"> </p>
<p align="left" style="margin-top: 1; margin-bottom: 1">
0.5 < ProportionalGain < 1
(9)<br>
ProportionalGain = K_sc * 2 ^
ProportionalGainScale
(10)<br>
</p>
<p align="left" style="margin-top: 1; margin-bottom: 1">
0.5 < IntegralGain < 1
(11) <br>
IntegralGain = Ki_sc * 2 ^ IntegralGainScale
(12) </p>
<p align="left" style="margin-top: 1; margin-bottom: 1"> </p>
<p align="left" style="margin-top: 1; margin-bottom: 1">
[log(0.5) - log(ProportionalGain)] / log(2) < ProportionalGainScale
(13)<br>
[log(1) - log(ProportionalGain)] / log(2) > ProportionalGainScale
(14)<br>
</p>
<p align="left" style="margin-top: 1; margin-bottom: 1">
[log(0.5) - log(IntegralGain)] / log(2) < IntegralGainScale
(15)<br>
[log(1) - log(IntegralGain)] / log(2) > IntegralGainScale
(16)</p>
<p align="left" style="margin-top: 1; margin-bottom: 1"> </p>
<p align="left" style="margin-top: 1; margin-bottom: 1">
-14 < ProportionalGainScale < 14
(17)<br>
14 < IntegralGainScale < 14
(18)</p>
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