To define planetary motion in ABAQUS CAE, particularly for modeling the motion of three rollers around a central axis with passive rotation about their own axes, you can follow these steps:

### Step-by-Step Guide

1. **Create the Geometry**:

- Define the geometry of the central axis and the three rollers in the Part module.

- Create a central shaft and three rollers as separate parts.

2. **Assembly**:

- Assemble the parts to position the rollers around the central shaft in the Assembly module.

3. **Define Reference Points and Coordinate Systems**:

- Create reference points at the center of each roller and the central axis.

- Define local coordinate systems at these reference points to facilitate the definition of motion constraints.

4. **Define Constraints**:

- **Central Axis Rotation**: Apply a rotational boundary condition to the central axis reference point.

- Go to the Load module, create a new boundary condition, and select the rotational DOF for the central axis reference point.

- **Planetary Motion**:

- Use a *KINEMATIC COUPLING* to define the motion of the rollers around the central axis.

- Create a coupling constraint that connects each roller reference point to the central axis reference point with the appropriate kinematic constraints.

- **Passive Rotation**:

- Define a second kinematic coupling for each roller to allow rotation around their own axes.

- This can be done by coupling the rotational degree of freedom of the roller's local coordinate system to allow free rotation.

5. **Apply Loads and Boundary Conditions**:

- Define the necessary loads and boundary conditions for the central shaft to impart the desired rotational motion.

- Ensure that the rollers are free to rotate about their own axes by not constraining their local rotational DOF excessively.

6. **Mesh the Model**:

- Mesh the parts appropriately, ensuring that the mesh is fine enough to capture the interactions between the rollers and the central shaft.

7. **Define Interaction Properties**:

- Define contact properties between the rollers and the central shaft if they are in contact.

- Ensure that the contact interactions allow for realistic rolling behavior.

8. **Run the Simulation**:

- Set up the analysis steps to capture the motion.

- Submit the job and analyze the results.

### Example of Applying Kinematic Coupling

1. **Create Reference Points**:

- Create a reference point at the center of the central shaft.

- Create reference points at the center of each roller.

2. **Define Kinematic Coupling for Central Rotation**:

- In the Interaction module, create a kinematic coupling constraint.

- Select the reference point of the central shaft as the control point.

- Select the nodes or surfaces on the rollers that should follow the central rotation.

3. **Allow Passive Rotation**:

- Define another kinematic coupling for each roller to allow for passive rotation.

- Use the local coordinate systems defined earlier to ensure the correct rotational DOF is free.

### Considerations

- **Material Properties**: Ensure that the material properties of the rollers and the central shaft are defined correctly.

- **Friction**: If the rollers are in contact with the central shaft, define the friction properties appropriately to simulate rolling friction.

- **Validation**: Validate your model by checking if the rollers exhibit the expected planetary motion and passive rotation.

### References

- **ABAQUS Documentation**: Always refer to the latest ABAQUS documentation for detailed commands and options. The documentation can provide specific details on kinematic couplings, boundary conditions, and contact interactions.

- **ABAQUS Tutorials**: Online tutorials and forums can provide practical examples and community support.

These steps should help you set up and define the planetary motion and passive rotation of the rollers in ABAQUS CAE.