Not a Siemens head, but have an application where we are using TIA Portal V11 SP2. Need to add a very simple PID loop to control a fan speed which regulates the negative pressure in a glovebox. Have done this many times before using Allen-Bradley but having a problem in TIA Portal.
Created OB35 in the code and added 'CONT_C' into this block as a PI controller. Set the PID cycle to 100ms to equal OB35. Scaled 'PV_IN' and 'SP_INT' to 0-100% and added nominal values for the P and I settings. Attached tags for the 'MAN_ON' i.e. Auto/Manual and the 'MAN' i.e. Manual Out.
With the Setpoint at 50% and the PV reading low (i.e. 20%) the controller output i.e. 'LMN_PER' begins to rise until it eventually reaches 100% even though the PV approaches and rises above the Setpoint. If we organise for the PV to read high say 70% the opposite happens, that is the output continues to drop until it reaches 0% even though the PV has dropped below the setpoint. It appears as if the PID loop is only active by altering the setpoint between 49% and 51% to make the output go from 0% to 100% and vice versa.
No change by altering the action of the controller from direct to reverse (i.e. negative gain value). It appears to function correctly when switched to manual and a manual value input.
Have we left something out when setting this up or are we missing anything obvious?? Would appreciate any help or guidance on this.
Best Regards
Created OB35 in the code and added 'CONT_C' into this block as a PI controller. Set the PID cycle to 100ms to equal OB35. Scaled 'PV_IN' and 'SP_INT' to 0-100% and added nominal values for the P and I settings. Attached tags for the 'MAN_ON' i.e. Auto/Manual and the 'MAN' i.e. Manual Out.
With the Setpoint at 50% and the PV reading low (i.e. 20%) the controller output i.e. 'LMN_PER' begins to rise until it eventually reaches 100% even though the PV approaches and rises above the Setpoint. If we organise for the PV to read high say 70% the opposite happens, that is the output continues to drop until it reaches 0% even though the PV has dropped below the setpoint. It appears as if the PID loop is only active by altering the setpoint between 49% and 51% to make the output go from 0% to 100% and vice versa.
No change by altering the action of the controller from direct to reverse (i.e. negative gain value). It appears to function correctly when switched to manual and a manual value input.
Have we left something out when setting this up or are we missing anything obvious?? Would appreciate any help or guidance on this.
Best Regards
