Simscape™ block dialogs have drop-down combo
boxes for units next to a parameter value. For
example, in the Constant Volume Chamber block
dialog box, the drop-down list for the
Chamber volume parameter
contains l,
gal, in^3,
ft^3, mm^3,
cm^3, m^3,
and km^3, and the drop-down
list for the Initial pressure
parameter contains Pa,
bar, psi,
and atm.
You can either select a unit from the
drop-down list, or type a commensurate unit name
(or a mathematical expression with unit names)
directly into the unit combo box of the block
dialog. You can use the abbreviations for the
units defined in your registry, or any valid
mathematical expressions with these abbreviations.
For example, you can specify torque in
newton-meters (N*m) or
pound-feet (lbf*ft). To specify
velocity, you can use one of the defined unit
abbreviations (mph,
fpm, fps),
or an expression based on any combination of the
defined units of length and time, such as
meters/second (m/s),
millimeters/second (mm/s),
inches/minute (in/min), and so
on.
Note
Affine units (such as Celsius or Fahrenheit) are not allowed in unit expressions. For more information, see About Affine Units.
The following operators are supported in the unit mathematical expressions:
* | Multiplication |
/ | Division |
^ | Power |
+ | Plus — for exponents only |
- | Minus — for exponents only |
() | Brackets to specify evaluation order |
Metric unit prefixes, such as kilo, milli, or micro, are not supported. For example, if you want to use milliliter as a unit of volume, you have to add it to the unit registry:
pm_addunit('ml', 0.001, 'l');
The drop-down lists next to parameter names are automatically populated by those units that are commensurate with the unit of the parameter. If you specify the units by typing, it is your responsibility to enter units that are commensurate with the unit of the parameter. The unit manager performs error checking when you click Apply or OK in the block dialog box, and issues an error if you type an incorrect unit.
In the Simulink-PS Converter and the PS-Simulink Converter block dialog boxes, the drop-down lists are prepopulated with some common input and output units, and it is your responsibility to select or type a unit expression commensurate with the expected input or output units. The error checking for the converter blocks is performed at the time of simulation. See Model Validation for details.