functionexponentialDamper
Damper opening characteristics for an exponential damper
Extends from Modelica.Icons.Function (Icon for functions).
Information
This function computes the opening characteristics of an exponential damper.
The function is used by the model IDEAS.Fluid.Actuators.Dampers.Exponential.
For yL < y < yU, the damper characteristics is
kd(y) = exp(a+b (1-y)).
Outside this range, the damper characteristic is defined by a quadratic polynomial.
Note that this implementation returns sqrt(kd(y)) instead of kd(y). This is done for numerical reason since otherwise kd(y) may be an iteration variable, which may cause a lot of warnings and slower convergence if the solver attempts kd(y) < 0 during the iterative solution procedure.
Inputs
| Type | Name | Default | Description |
|---|---|---|---|
| Real | y | Control signal, y=0 is closed, y=1 is open | |
| Real | a | Coefficient a for damper characteristics | |
| Real | b | Coefficient b for damper characteristics | |
| Real | cL | Polynomial coefficients for curve fit for y < yl | |
| Real | cU | Polynomial coefficients for curve fit for y > yu | |
| Real | yL | Lower value for damper curve | |
| Real | yU | Upper value for damper curve |
Outputs
| Type | Name | Default | Description |
|---|---|---|---|
| Real | kThetaSqRt | Square root of loss coefficient, sqrt(pressure drop/dynamic pressure) |
Revisions
-
April 14, 2014 by Michael Wetter:
Improved documentation. -
July 1, 2011 by Michael Wetter:
Added constraint to control input to avoid using a number outside0and1in case that the control input has a numerical integration error. -
April 4, 2010 by Michael Wetter:
Reformulated implementation. The new implementation computessqrt(kTheta). This avoid havingkThetain the iteration variables, which caused warnings when the solver attemptedkTheta < 0. -
June 22, 2008 by Michael Wetter:
First implementation.