Galil Motion Control DMC-18 2 Series, User Manual

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DMC-18x2 Chapter 6 Programming Motion • 91
Additional Commands
The command, WC, is used as a trippoint "When Complete" or “Wait for Contour Data”. This allows
the DMC-18x2 to use the next increment only when it is finished with the previous one. Zero
parameters for DT followed by zero parameters for CD exit the contour mode.
If no new data record is found and the controller is still in the contour mode, the controller waits for
new data. No new motion commands are generated while waiting. If bad data is received, the
controller responds with a ?.
Command Summary - Contour Mode
COMMAND DESCRIPTION
CM XYZW Specifies which axes for contouring mode. Any non-contouring axes may be operated in
other modes.
CD x,y,z,w Specifies position increment over time interval. Range is +/-32,000. Zero ends contour
mode.
DT n Specifies time interval 2
n
msec for position increment, where n is an integer between 1 and
8. Zero ends contour mode. If n does not change, it does not need to be specified with each
CD.
WC Waits for previous time interval to be complete before next data record is processed.
General Velocity Profiles
The Contour Mode is ideal for generating an arbitrary velocity profile. The velocity profile can be
specified as a mathematical function or as a collection of points.
The design includes two parts: Generating an array with data points and running the program.
Generating an Array - An Example
Consider the velocity and position profiles shown in Fig. 6.6. The objective is to rotate a motor a
distance of 6000 counts in 120 ms. The velocity profile is sinusoidal to reduce the jerk and the system
vibration. If we describe the position displacement in terms of A counts in B milliseconds, we can
describe the motion in the following manner:
ω
= (A/B) [1 - cos (2
πΤ
/B)]
X
= (AT/B) - (A/2
π)
sin (2
πΤ
/B)
Note:
ω
is the angular velocity;
X
is the position; and T is the variable, time, in milliseconds.
In the given example, A=6000 and B=120, the position and velocity profiles are:
X
= 50T - (6000/2
π
) sin (2
π
T/120)
Note that the velocity,
ω
, in count/ms, is
ω
= 50 [1 - cos 2
π
T/120]
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