National Instruments NI-Motion - Manual (Page 97)

© National Instruments Corporation 7-1 NI-Motion User Manual
7
Contoured Moves
A contoured move moves an axis or a coordinate space of axes in a pattern
that you define. The trajectory generator on the motion controller is not
used during a contoured move. The controller takes position data in the
form of an array, and splines the data before outputting it to the DACs or
stepper outputs, as shown in Figure 7-1.
Figure 7-1. Contoured Move Data Path
Overview
All positions in a contouring buffer are relative to the current position when
starting. There is an assumed 0 point that the firmware adds to the front of
the buffer of points. For example, if the contour buffer is [10, 20, 30, 40],
the positions are [0, 10, 20, 30, 40] in the firmware.
When a contour move starts it takes a snap shot of the current position
according to the following equation:
StartPosition = currentPosition.
The start position is added to each point in the buffer to get the actual
position to move through according to the following equation:
Point = StartPosition + bufferPosition[n].
If the current position is 100, and the buffer is [10, 20, 30, 40], the contour
move follows these points: [100, 110, 120, 130, 140].
Cubic Spine
User-Defined
Points
Output to DACs or
Stepper Output