The manual command is continuously updated: it tracks the command output. On Auto / Manual switching, the first manual value given is the last value calculated by the loop controller; which prevents bumps.
Manual / Auto switching (for any loop controller other than ON OFF) is bumpless on the output command, on condition that the BUMPLESS option is selected on configuration. For the PID, two scenarios can be distinguished:
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Scenario: PID with integral action (Ti <> 0):
The PID algorithm in incremental form guarantees there will be no bumps during the transition from Manual to Auto. In this case, the PID algorithm always tracks the applied actual output.
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Scenario: PID without integral action (Ti = 0):
It is possible to obtain a bumpless Manual/Auto transition if the mode is configured as bumpless in the PID function parameters (if the PID has an integral action, this configuration has no object).
The OUTBIAS manual integral parameter is calculated during the switch so that deviation between the actual output and the output calculated by the PID algorithm in absolute format is accepted.
If bumpless mode is not selected, OUTBIAS is not recalculated on switch.
