ADLINK PCI-8102 - Manual (Page 54)

Operations 43
PCI-8102
The following sections describe the motion control modes of this
motion controller could be performed.
4.2.1 Coordinate System
We use Cartesian coordinate and pulses for the unit of length. The
physical length depends on mechanical parts and motor’s resolu-
tion. For example, if users install a motor on a screw ball. The
pitch of screw ball is 10mm and the pulses needed for a round of
motor are 10,000 pulses. We can say that one pulse’s physical
unit is equal to 10mm/10,000p =1 micro-meter.
Just set a command with 15,000 pulses for motion controller if we
want to move 15mm. How about if we want to move 15.0001mmΔ
Don’t worry about that, the motion controller will keep the residue
value less than 1 pulse and add it to next command.
The motion controller sends incremental pulses to motor drivers. It
means that we can only send relative command to motor driver.
But we can solve this problem by calculating the difference
between current position and target position first. Then send the
differences to motor driver. For example, if current position is
1000. We want to move a motor to 9000. User can use an abso-
lute command to set a target position of 9000. Inside the motion
controller, it will get current position 1000 first then calculate the
difference from target position. It gets a result of +8000. So, the
motion controller will send 8000 pulses to motor driver to move the
position of 9000.
Sometimes, users need to install a linear scale or external
encoder to check machine’s position. But how do you to build this
coordinate system Δ If the resolution of external encoder is 10,000
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