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Set Initial Conditions of Driveline Motion

When driveline simulation starts, the complete driveline determines the initial motion of all driveshafts by a combination of constraints, motion sources, and initial condition settings. You set the initial conditions for the rotational and translational motion of inertias and masses in their respective Inertia and Mass blocks. The block default for initial velocities is zero (no initial motion).

For more information about constraints and degrees of freedom, see Driveline Degrees of Freedom.


Ensure that the initial conditions that you impose on the Inertia and Mass blocks in your driveline are consistent with all of the constraints and motion sources for the driveline. If an inconsistency occurs, Simscape™ Driveline™ simulation stops with an error at model initialization.

Resolving Undetermined Motions in Complex Gears

A simple gear has two ports and imposes one constraint between them, leaving one independent DoF. Once one port is connected to a driveshaft, the motion of the driveshaft of the other port is determined.

A complex gear has three or more ports and imposes one or more constraints among them. A complex gear can have any number of independent DoFs, including none.

If a simulation apportions the initial motions of a complex gear in an unsatisfactory way, enforce your preferred division by setting initial conditions on the connected Inertia and Mass blocks.

However you divide the initial motion among the gear shafts, ensure that this division is consistent with all constraints in your driveline, and with any motion sources.

For more information about complex gears, see Basic Motion, Torque, and Force Modeling.