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DMC-1700/1800 Chapter 6 Programming Motion • 89
VELOCITY
(COUNTS/SEC)
20000
10000
5000
15000
20
40 60
80
TIME (ms)
100
X axis velocity profile
Y axis velocity profile
Z axis velocity profile
0
Figure 6.1 - Velocity Profiles of XYZ
Notes on fig 6.1: The X and Y axis have a ‘trapezoidal’ velocity profile, while the Z axis has a ‘triangular’ velocity
profile. The X and Y axes accelerate to the specified speed, move at this constant speed, and then decelerate such
that the final position agrees with the command position, PR. The Z axis accelerates, but before the specified speed
is achieved, must begin deceleration such that the axis will stop at the commanded position. All 3 axes have the
same acceleration and deceleration rate, hence, the slope of the rising and falling edges of all 3 velocity profiles are
the same.
Independent Jogging
The jog mode of motion is very flexible because speed, direction and acceleration can be changed during motion.
The user specifies the jog speed (JG), acceleration (AC), and the deceleration (DC) rate for each axis. The direction
of motion is specified by the sign of the JG parameters. When the begin command is given (BG), the motor
accelerates up to speed and continues to jog at that speed until a new speed or stop (ST) command is issued. If the
jog speed is changed during motion, the controller will make a accelerated (or decelerated) change to the new speed.
An instant change to the motor position can be made with the use of the IP command. Upon receiving this
command, the controller commands the motor to a position which is equal to the specified increment plus the current
position. This command is useful when trying to synchronize the position of two motors while they are moving.
Note that the controller operates as a closed-loop position controller while in the jog mode. The DMC-1700/1800
converts the velocity profile into a position trajectory and a new position target is generated every sample period.
This method of control results in precise speed regulation with phase lock accuracy.
Command Summary - Jogging
COMMAND DESCRIPTION
AC x,y,z,w Specifies acceleration rate
BG XYZW Begins motion
DC x,y,z,w Specifies deceleration rate
IP x,y,z,w Increments position instantly
IT x,y,z,w Time constant for independent motion smoothing
JG +/-x,y,z,w Specifies jog speed and direction
ST XYZW Stops motion