Variable Inertia
Variable inertia.
Description
The Variable Inertia block models variable inertia. This block can be used when modelling the opening of a spacecraft’s solar panels. The input port receives the instantaneous inertia value at each time step throughout the simulation. To minimise solver errors, avoid discontinuities and abrupt changes in the input signal.
When the inertia of a component changes, the torque acting on that component also changes:
where
-
- torque;
-
- variable inertia;
-
- angular velocity.
If the input inertia value is lower than the minimum inertia value specified in the Minimum inertia parameter, the block performs its calculations for the minimum inertia. The torque of the inertia force is calculated as:
where is the minimum inertia.
The angular momentum at variable inertia is conserved. In the absence of external torque, a decrease in the moment of inertia results in a proportional increase in angular velocity. The angular momentum remains constant until an external torque forces it to change.
Ports
Conserving
#
Flange
—
port connecting the unit to the network
`rotational mechanics
Details
A mechanical rotational port that connects a block to a physical network.
| Program usage name |
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Input
#
I
—
variable inertia, kg/m2
scalar
Details
The input port that receives the value of the variable inertia.
| Data types |
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| Complex numbers support |
No |
Parameters
Parameters
#
Minimum inertia —
minimum inertia
g*cm^2 | kg*m^2 | lbm*ft^2 | lbm*in^2 | slug*ft^2 | slug*in^2
Details
The minimum value that the inertia variable can take during simulation.
If the input inertia value is lower than the minimum inertia value, it is set equal to the minimum inertia value.
| Values |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |