The IMC function is identical to the IMC single loop controller.
The PID function is identical to the PID single loop controller.
The only differences are:
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the absence of autotuning,
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the limiting of OUT_MAN between 0 and 100,
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the value of OUT_BIAS is fixed at 0 and cannot be parameterized.
The OUT_MAN command is recalibrated according to the limitations which are applied (as with a single PID), in order to avoid problems with overflow of the integral action and with the operation of the Split Range or Heat/Cool function.
Each output of the Split Range or Heat/Cool function has its own limitations with regard to level and gradient.
The operating mode acts on the output of the OUT_MAN loop controller.
Block Diagram of the Split Range or Heat/Cool Loop Controller
Block diagram of the Split Range or Heat/Cool loop controller (PID or IMC).
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There is a consistency check on the configuration selected. If there is a problem with the configuration:
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On cold start-up, the parameters and input values PV, SP, etc. associated with this branch are first updated before the launch of the first loop controller process.
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It is possible to select the initial loop controller operating modes, by creating parameters in the configuration screen or by sending commands in a sequential program. The loop can thus start in manual or automatic mode.
Runtime Control Operation
Setpoint processing checks for two types of errors: parameter errors (not written in floating point format) and internal calculation errors (division by zero, overflow, etc.). Should such an error occur:
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Loop controller processing goes into a fallback position:
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The state returns to normal as soon as the fault disappears. The loop then starts off again on the outputs without bumps.
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The input and output scale values are checked.
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In case of inconsistency on a cold start, the loop switches to serious error mode.
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Warnings are generated in the status words.
