Variable Mass
Time-varying mass
Library
Inertias & Loads
Description
The Variable Mass block represents the effects of a time-varying mass. A physical signal input port provides the instantaneous mass at each time step. To minimize solver errors, avoid discontinuities and abrupt changes in the input signal.
As the component mass changes, so does the inertial force acting on that component.
where:
FI is the inertial force.
m is the variable mass.
v is the velocity of the mass.
The physical signal input saturates at the value of the Minimum mass parameter. When the input falls below this value, the block performs calculations on the minimum mass and inertial force becomes
where mMin is the minimum mass allowed.
The linear momentum of the variable mass is conserved. In the absence of external forces, a decrease in mass leads to a proportional increase in linear velocity. The linear momentum remains constant until a net external force causes it to change.
Variables
To set the priority and initial target values for the block variables prior to simulation, use the Initial Targets section in the block dialog box or Property Inspector. For more information, see Set Priority and Initial Target for Block Variables.
Nominal values provide a way to specify the expected magnitude of a variable in a model. Using system scaling based on nominal values increases the simulation robustness. Nominal values can come from different sources, one of which is the Nominal Values section in the block dialog box or Property Inspector. For more information, see Modify Nominal Values for a Block Variable.
