Gear set with parallel-axis rotation and variable meshing efficiency
The block represents a simple gear train with variable meshing efficiency. The gear train transmits torque at a specified ratio between base and follower shafts arranged in a parallel configuration. Shaft rotation can occur in equal or opposite directions. Gear losses are optional. They include meshing and viscous bearing losses. To specify the variable meshing efficiency, the block contains a physical signal port that you can use to input a general time-varying signal. Inertia and compliance effects are ignored.
You can model the effects of heat flow and temperature change through an optional thermal conserving port. By default, the thermal port is hidden. To expose the thermal port, right-click the block in your model and, from the context menu, select Simscape > Block choices. Specify the associated thermal parameters for the component.
Enter the gear ratio. This is the fraction of follower over
base gear teeth numbers, NF/NB. The ratio must be positive. The default
Select the relative rotation between shafts. This is the rotation
direction of the output shaft with respect to the input shaft. Options
include equal or opposite directions. The default setting is
opposite direction to input shaft.
Enter the smallest efficiency value allowed for the gear. The
efficiency is the power ratio between output and input shafts. The
physical signal input saturates for values below the minimum efficiency
or above 1. The minimum efficiency must be positive. The default value
Enter the follower shaft power above which full efficiency factor
is in effect. A hyperbolic tangent function smooths the efficiency
factor between zero when at rest and the value provided by the temperature-efficiency
lookup table when at the power threshold. The default value is
Enter a two-element vector with the viscous friction coefficients
of the base and follower gears. Coefficients must be positive. The
default vector is
[0 0]. The default unit is
Thermal energy required to change the component temperature
by a single degree. The greater the thermal mass, the more resistant
the component is to temperature change. The default value is
Component temperature at the start of simulation. The initial
temperature alters the component efficiency according to an efficiency
vector that you specify, affecting the starting meshing or friction
losses. The default value is
Simple Gear imposes one kinematic constraint on the two connected axes:
rFωF = rBωB .
The follower-base gear ratio gFB = rF/rB = NF/NB. N is the number of teeth on each gear. The two degrees of freedom reduce to one independent degree of freedom.
The torque transfer is:
gFBτB + τF – τloss = 0 ,
with τloss = 0 in the ideal case.
In the nonideal case, τloss ≠ 0. For general considerations on nonideal gear modeling, see Model Gears with Losses.
Gear inertia is assumed negligible.
Gears are treated as rigid components.
Coulomb friction slows down simulation. See Adjust Model Fidelity.
|B||Rotational conserving port representing the base shaft|
|F||Rotational conserving port representing the follower shaft|
|H||Thermal conserving port for thermal modeling|