ADLINK Technology PCI-8174, Руководство пользователя

Страница: 50 / 170

40 Operation Theory
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
and we want to move a motor to 9000, you can use an absolute
command to set a target position of 9000. Inside the motion con-
troller, it will get current position 1000 first then calculate the differ-
ence from target position. The result is +8000. So, the motion
controller will send 8000 pulses to motor driver to move the posi-
tion 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? 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
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).
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