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24 • Chapter 2 Getting Started DMC-3425
generated by the controller. The first signal is the main controller motor output,
ACMD. The second signal utilizes the second DAC on the controller and is brought
out on the ICM-1460 at pin 38 (ACMD2).
It is not necessary to be concerned with cross-wiring the 1
st
and 2
nd
signals. If this
wiring is incorrect, the setup procedure will alert the user (Step D).
Step C. Specify the Size of the Magnetic Cycle.
Use the command, BM, to specify the size of the brushless motors magnetic cycle in
encoder counts. For example, if you are using a linear motor where the magnetic
cycle length is 62 mm, and the encoder resolution is 1 micron, the cycle equals
62,000 counts. This can be commanded with the command:
BM 62000 <CR>
On the other hand, if you are using a rotary motor with 4000 counts per revolution
and 3 magnetic cycles per revolution (three pole pairs) the command is:
BM 1333.333 <CR>
Step D. Test the Polarity of the DACs and Hall Sensor Configuration.
Use the brushless motor setup command, BS, to test the polarity of the output DACs.
This command applies a certain voltage, V, to each phase for some time T, and
checks to see if the motion is in the correct direction.
The user must specify the value for V and T. For example, the command:
BS 2,700 <CR>
will test the brushless axis with a voltage of 2 volts, applying it for 700 milliseconds
for each phase. In response, this test indicates whether the DAC wiring is correct and
will indicate an approximate value of BM. If the wiring is correct, the approximate
value for BM will agree with the value used in the previous step.
Note: In order to properly conduct the brushless setup, the motor must be allowed to
move a minimum of one magnetic cycle in both directions.
Note: When using Galil Windows software, the timeout must be set to a minimum of
10 seconds (time-out = 10000) when executing the BS command. This allows the
software to retrieve all messages returned from the controller.
If Hall Sensors are Available:
Since the Hall sensors are connected randomly, it is very likely that they are wired in
the incorrect order. The brushless setup command indicates the correct wiring of the
Hall sensors. The hall sensor wires should be re-configured to reflect the results of
this test.
The setup command also reports the position offset of the hall transition point and the
zero phase of the motor commutation. The zero transition of the Hall sensors
typically occurs at 0°, 30° or 90° of the phase commutation. It is necessary to
inform the controller about the offset of the Hall sensor and this is done with the
instruction, BB.
Step E. Save Brushless Motor Configuration
It is very important to save the brushless motor configuration in non-volatile
memory. After the motor wiring and setup parameters have been properly
configured, the burn command, BN, should be given.