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    • Instructions
      • PID_Compact
        • New features of PID_Compact
        • Compatibility with CPU and FW
        • CPU processing time and memory requirement PID_Compact V2.x
        • PID_Compact V2
          • Description of PID_Compact V2
          • Mode of operation of PID_Compact V2
          • Input parameters of PID_Compact V2
          • Output parameters of PID_Compact V2
          • In/out parameters of PID_Compact V2
          • Static tags of PID_Compact V2
          • Changing the PID_Compact V2 interface
          • Parameters State and Mode V2
          • Parameter ErrorBits V2
          • Tag ActivateRecoverMode V2
          • Tag Warning V2
          • IntegralResetMode V2 tag
          • Sample program for PID_Compact
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    Entry type: Manual, Entry ID: 108210036, Entry date: 12/04/2019

    SIMATIC S7-1200, S7-1500 PID control

    Document: PID control (11/2019, English)
    Type of topic: Fact

    IntegralResetMode V2 tag

    The IntegralResetMode tag determines how the integral action PIDCtrl.IntegralSum is pre-assigned:

    • When switching from "Inactive" operating mode to "Automatic mode"
    • With edge TRUE -> FALSE at parameter Reset and parameter Mode = 3

    This setting only works for one cycle and is only effective if the integral action is activated (Retain.CtrlParams.Ti > 0.0 tag).

    IntegralResetMode

    Description

    0

    Smooth

    The value of PIDCtrl.IntegralSum is pre-assigned so that the switchover is bumpless, which means "Automatic mode" starts with the output value = 0.0 (parameter Output) and there is no jump of the output value regardless of the control deviation (setpoint – actual value).

    1

    Delete

    We recommend setting the weighting of the proportional action (Retain.CtrlParams.PWeighting) to 1.0 if this option is used.

    The value of PIDCtrl.IntegralSum is deleted. Any control deviation will cause a jump change of the output value. The direction of the output value jump depends on the configured weighting of the proportional action (Retain.CtrlParams.PWeighting tag) and the control deviation:

    • Proportional action weighting = 1.0:

      Output value jump and control deviation have identical signs.
      Example: If the actual value value is smaller than the setpoint (positive control deviation), the output value jumps to a positive value.

    • Proportional action weighting < 1.0:

      For large control deviations, the output value jump and control deviation have identical signs.
      Example: If the actual value is much smaller than the setpoint (positive control deviation), the output value jumps to a positive value.

      For small control deviations, the output value jump and control deviation have different signs.
      Example: If the actual value value is just below the setpoint (positive control deviation), the output value jumps to a negative value. This is usually not desirable, because it results in a temporary increase in the control deviation.

      The smaller the configured weighting of the proportional action, the greater the control deviation must be to receive an output value jump with identical sign.

    We recommend setting the weighting of the proportional action (Retain.CtrlParams.PWeighting) to 1.0 when this option is used. Otherwise, you may experience the undesirable behavior described for small control deviations. Alternatively, you can also use IntegralResetMode = 4. This option guarantees identical signs of the output value jump and control deviation independent of the configured weighting of the proportional action and the control deviation.

    2

    Hold

    The value of PIDCtrl.IntegralSum is not changed. You can define a new value using the user program.

    3

    Pre-assign

    The value of PIDCtrl.IntegralSum is automatically pre-assigned as if Output = OverwriteInitialOutputValue in the last cycle.

    4

    Like setpoint change (only for PID_Compact with version ≥ 2.3)

    The value of PIDCtrl.IntegralSum is automatically pre-assigned so that a similar output value jump results as for a PI controller in automatic mode in case of a setpoint change from the current actual value to the current setpoint.

    Any control deviation will cause a jump of the output value. Output value jump and control deviation have identical signs.
    Example: If the actual value value is smaller than the setpoint (positive control deviation), the output value jumps to a positive value. This is independent of the configured weighting of the proportional action and the control deviation.

    If IntegralResetMode is assigned a value outside the valid value range, PID_Compact behaves as with the pre-assignment of IntegralResetMode:

    • PID_Compact up to V2.2: IntegralResetMode = 1
    • PID_Compact V2.3 and higher: IntegralResetMode = 4

    All statements made above regarding the sign of the output value jump are based on a normal control logic (Config.InvertControl = FALSE tag). With an inverted control logic (Config.InvertControl = TRUE), the output value jump will have a reverse sign.