# Documentation

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## Essential Steps to Build a Driveline Model

The example model of Run Example Model illustrates a typical drivetrain system you can model with Simscape™ Driveline™ software. It also illustrates the key rules for connecting driveline blocks to each other and the dual roles of driveline connection lines: transferring torque and enforcing angular velocity constraints. You should review these rules before building and running the tutorial models of this chapter.

• Driveline blocks, in general, feature both driveline connector ports and regular Simulink® inports and outports `>`. You connect connector ports to one another and Simulink ports to one another. But you cannot connect a driveline port to a Simulink port.

• The driveline connection lines interconnecting driveline connector ports represent driveline axes and enforce physical relationships. Unlike Simulink lines, they do not represent signals or mathematical operations, and they have no inherent directionality.

• A driveline connection line represents an idealized massless and perfectly rigid spinning shaft. A driveline connection line between two ports enforces the constraint that the two driveline components so connected rotate at the same angular velocity. The connection line also transfers any torque applied to a driveline component at one end to the component at the other end.

• You can branch driveline connection lines. You must connect the end of any branch of a driveline connection line to a driveline connector port .

• Branching a driveline connection line modifies the physical constraints that it represents. All driveline components connected to the ends of a set of branched lines rotate at the same angular velocity. The torque transferred along the input driveline axis is split up among the branches. How the torque is split depends on the dynamical details of the system that you are modeling.

• Driveline connection lines satisfying the angular velocity constraint must have the same initial angular velocities.

Branching Driveline Connection Lines

The Driveline Environment block does not use any torque. It does share the angular velocity constraint from the branch point.

Symbolically, the branching conditions on driveline connection lines are

ω = ω1 = ω2= ω3 ...

τ = τ1 + τ2 + τ3 ...

The driveline axes have an implicit directionality. Torque and motion are transferred "down" the driveline from input or drive shafts to output or driven shafts. Certain Simscape Driveline blocks require explicit directionality and represent it by designating one driveline connector port as the input base (B) and the other as the output follower (F). Relative motion of driveline axes or shafts, when needed, is measured as follower relative to base.

 Caution:   All motion in Simscape Driveline models, except when relative motion is explicitly required, is measured in implicit absolute coordinates. An absolute orientation defines zero angle, and an absolute reference frame defines zero angular velocity. The Housing block implements the absolute zero angular velocity and, if connected to a driveline axis, enforces this zero-motion state on that axis.