Translation and Rotation

Translations and rotations are introduced to model a displacement between connected components in the turbine assembly. These can be understood as rigid links without mass or degrees of freedom.

Instances where a translation or rotation may be used include:

1. A rotation object used to apply a constant yaw offset between the tower top and the drivetrain to represent a constant yaw angle.
2. A translation that moves the tower component beneath the ground to allow the user to represent the foundations of the turbine explicitly as part of the tower component.

Translation

A translation object adds a displacement between two connected components in the turbine assembly. The displacement occurs in the distal frame of the parent component in the assembly tree. This results in an offset between the distal frame of the parent component and body-fixed frame of the child component. The body-fixed component in the assembly tree is connected to the ground for onshore towers (global origin). The definition of a translation consists of the three distances of X,Y and Z shift, respectively.

An example of a translation component defined at the root of the turbine assembly that shifts the tower from the ground level down by 5 metres is provided below.

"Assembly": {
    "Translation_1": {
    "ComponentReference": "#/ComponentDefinitions/Translation",
        "Tower_1": {
        "ComponentReference": "#/ComponentDefinitions/Tower"
...
            }
        }
    },
"ComponentDefinitions": {
"Translation_1": {
    "X": 0.0,
    "Y": 0.0,
    "Z": -5.0,
    "ComponentType": "Translation"
    }
    ...
}

Note

The soil line is always the origin for the assembled structure, even on offshore-turbines. The water line is not relevant for the definition of a tower.

Rotation

A rotation object is often used to prescribe a tilt to the tower. This is done by proving the axis-angle representation of the rotation in a right-hand coordinate system.

The following example shows a rotation object that is used to introduce a constant yaw angle of 0.05 radians between the tower top and the drivetrain.

"Assembly": {
    "Tower_1": {
        "ComponentReference": "#/ComponentDefinitions/Tower",
            "Rotation_1": {
            "ComponentReference": "#/ComponentDefinitions/Rotation",
                "DrivetrainAndNacelle_1": {
                "ComponentReference": "#/ComponentDefinitions/DrivetrainAndNacelle",
...
                    }
                }
            }
        },
"ComponentDefinitions": {
"Rotation_1": {
    "AxisOfRotation":{
        "X": 0.0, 
        "Y": 0.0, 
        "Z": 1.0
    }, 
    "AngleOfRotation": 0.05,
    "ComponentType": "Rotation"
    }
...
}