Step Response 1Ch

Step Response 1Ch identifies parameters of the step response of a PT2 track. These include the delay time T_e, the compensation time T_b, the settling time T_cs, and the time of maximum t_m.

To detect whether the track is steady, a local minimum or maximum is searched for. If this is within the tolerance band (marked in gray), it is assumed that the track is steady. Only then is the settling time set.

The algorithm starts when a new setpoint is outside the previously stored tolerance band.

Optionally, a Boolean signal can be selected for the Enable Execution input so that the algorithm is only active if the value of the selected signal is TRUE.

Configuration options

• Threshold Reversal: threshold for identifying reversals. Reversals are only detected if their difference from the next reversal exceeds the value of Threshold Reversal.
  Below are three examples of peak identification using the parameter Threshold Reversal.
  (a) The value y₃ is identified as a peak immediately after processing the value y₄ because the difference between y₃ and y₄ is greater than Threshold Reversal.
  (b) The value y₃ is not identified as a peak because the difference between y₃ and y₄ is smaller than Threshold Reversal and the curve starts rising again after y₄.
  (c) The value y₂ is identified as a peak after processing the value y₅ because the difference between y₂ and y₅ exceeds Threshold Reversal. The value y₂ cannot be identified as a peak beforehand because the difference between y₂ and y₃ (y₄) is less than/equal to Threshold Reversal and it is not known whether the values will continue to decrease.

• Relative Tolerance: Boolean flag. If this flag is True, the parameter Error Tolerance refers to the setpoint at the input as a percentage. Otherwise, an absolute tolerance band is taken into account.
• Error Tolerance: Specifies the size of the tolerance band in relation to the parameter Relative Tolerance. The tolerance band is updated when parameter identification is restarted.

Output values

• Executing: True if parameter identification is active.
• Equivalent Dead Time: Delay time of the track. Timespan between the start of the step response and the intersection of the inflectional tangents with the start value.
• Equivalent Time Constant: Compensation time of the track. Timespan between the intersection point of the inflectional tangents with the start value and the intersection point of the inflectional tangents with the setpoint.
• Settling Time: Settling time of the track.
• Time Max: Time of the maximum overshoot.
• Error: Difference between input value and setpoint.

Standard HMI Controls

For the Step Response 1Ch algorithm, the following HMI controls are available for generating an Analytics Dashboard:

1. The Table Control and Multivalue Control visualize all output values.

Alternatively, customer-specific HMI controls can be mapped using the Mapping Wizard.