blockRamp

Information

Block that limits the rate of change of the input u by a ramp if the boolean input active is true, otherwise the block outputs y = u.

This block computes a threshold for the rate of change between input u and output y as thr = (u-y)/Td, where Td > 0 is a parameter. The output y is computed as follows:

• If thr < fallingSlewRate, then dy/dt = fallingSlewRate,
• if thr > raisingSlewRate, then dy/dt = raisingSlewRate,
• otherwise, dy/dt = thr.

A smaller time constant Td > 0 means a higher accuracy for the derivative approximation.

Note that the block limits the rate of change of the input u in the same way as Buildings.Controls.OBC.CDL.Reals.LimitSlewRate. However, the Buildings.Controls.OBC.CDL.Reals.LimitSlewRate has a boolean parameter to flag if the rate of change should be limited, while this block has the boolean input activate to enable or disable the functionality. When the input activate switches to false, the output y can have a discontinuity.

Implementation

For the block to work with arbitrary inputs and in order to produce a differentiable output, the input is numerically differentiated with derivative time constant Td.

Parameters

Connectors

Revisions

• September 15, 2025, by Jianjun Hu:
  Updated documentation to clarify the difference with the block Buildings.Controls.OBC.CDL.Reals.LimitSlewRate.
• February 15, 2024, by Michael Wetter:
  Updated documentation.
• November 16, 2022, by Jianjun Hu:
  First implementation.