Unit Scaling - Danfoss iC7 Motion Series Application Manual

Application Guide | iC7 Series Motion
Rotary example:
Min position = 0°
Max position = 360°
270°
Figure 7: Rotary Example

Unit Scaling

2.12.1.6
Position values for settings and readouts can be scaled to any physical value relevant for the application. The scaling is done relative
to 1 motor rotation and the default is 360° per motor rotation. To avoid rounding errors, the scaling factor is set as a fraction with 2
parameters, 5.13.4.4 Position Unit Numeratorand 5.13.4.5 Position Unit Denominator.
The scaling factors are found by calculating or measuring how far the machine part is moving per motor rotation in the required
unit. Measuring is typically not 100% accurate. It is often an advantage for readout resolution to scale the position units with a higher
resolution than what is required for positioning accuracy. For example, scaling to 10th of a millimeter when an accuracy of 1 mm is
required.
The following examples show how to calculate the scaling factors:
Example 1
A linear belt drive with pulley wheel is directly connected to the motor. The pulley wheel has 32 teeth, and the timing belt pitch is 10
mm.
Linear movement per motor revolution is 32 x 10 = 320 mm.
For position values in millimeters, set parameter 5.13.4.4 Position Unit Numerator to 320 and parameter 5.13.4.5 Position Unit
Denominator to 1.
Example 2
A linear belt drive using a VLT® OneGearDrive (OGD) with a gear ratio of 14.13 is driving the pulley wheel. The pulley wheel has 32 teeth
and the timing belt pitch is 10 mm. 14.13 is a rounded value, the actual gear ratio of this 2-stage gear is 43/7 for stage 1 and 46/20 for
stage 2. Without making rounding errors, the resulting ratio is (43*46) : (7*20) = 1978 : 140 = 989 : 70.
The linear movement is 70*32*10 = 22400 mm per 989 motor rotations.
For position values in millimeters, set parameter 5.13.4.4 Position Unit Numerator to 22400 and parameter 5.13.4.5 Position Unit
Denominator to 989.
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0° = 360°
90°
180°
AB318753549016en-000301 / 136R0284