Specifying Units in Block Dialogs
Simscape block dialogs have drop-down combo boxes for units
next to a parameter value. For example, in the Constant Volume Chamber
block, 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, 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
dialogs, 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.
Note
Currently, physical units are not propagated through the blocks
in the Physical Signals library, such as PS Add, PS Gain, and so on. |
 | Unit Definitions | | Thermal Unit Conversions |  |
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