Ni 73 xx – National Instruments NI-Motion User Manual

Page 53

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Chapter 4

What You Need to Know about Moves

NI-Motion User Manual

4-12

ni.com

Note

If the distance of the move is too small, it may not be possible to reach the

commanded maximum move constraints. In such instances, NI-Motion adjusts the move
constraints lower to reach the commanded position.

NI 73xx

Arc Angles in Degrees

The Load Circular Arc, Load Helical Arc, and Load Spherical Arc
functions take angle parameters in degrees as double-precision
floating-point values. These values are converted to an internal
16.16 fixed-point representation where the integer part corresponds to
multiples of 45° (for example, 360° is represented as 0x0008 0000).

Use the following formula to convert from floating-point to fixed point:

where

Q = quotient, the integer multiple of 45°

R = remainder

For example, 94.7° is represented in 16.16 format as follows:

The minimum angular increment is

Note

The conversion from floating-point to fixed-point is performed on the host

computer, not on the motion controller. To load arc functions from onboard variables,
you must use the 16.16 fixed-point representation for all angles.

Angle in degrees

45

°

----------------------------------------

Q R

+

=

Angle in 16.16 format

Q.

·

R

45

°

--------

65,536

×

=

Angle in 16.16 format

2.

4.7

°

45

°

----------

65,536

×

0x0002.1ABD

=

=

1

65.536

----------------

 45°

Ч

0.000687

°

=

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