ADLINK PCI-8144 - Manual (Page 44)

34 Operation Theory
pulses per 1mm and the motor will move 1mm if the motion con-
troller send 1,000 pulses, It means that when we want to move 1
mm, we need to send 1,000 pulses to motor driver then we will get
the encoder feedback value of 10,000 pulses. If we want to use an
absolute command to move a motor to 10,000 pulses position and
current position read from encoder is 3500 pulses, how many
pulses will it send to motor driver? The answer is (10000 – 3500 ) /
(10,000 / 1,000)=650 pulses. The motion controller will calculate it
automatically if users set “move ratio” already. The “move ratio”
means the (feedback resolution/command resolution)
Note: The PCI-8144 provides only one dimension motion function.
4.2.2 Absolute and relative position move
In the coordinate system, we have two kinds command for users
to locate the target position. One is absolute and the other is rela-
tive. Absolute command means that user give the motion control-
ler a position, then the motion controller will move a motor to that
position from current position. Relative command means that user
give the motion controller a distance, then the motion controller
will move motor by the distance from current position. During the
movement, users can specify the speed profile. It means user can
define how fast and at what speed to reach the position.
The PCI-8144 provides only relative position move because it
is designed for stepper motor. It is meaningless for a stepper
motor controller to have the encoder feedback interface for abso-
lute motion.