Galil DMC-4040, User Manual

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reset of the controller. If no Hall sensors are used, the controller will not be able to make this estimate and
the commutation phase must be set before enabling the motor.
To initialize the commutation without Hall effect sensor use the command, BZ. This function drives the
motor to a position where the commutation phase is zero, and sets the phase to zero.
The BZ command is followed by real numbers in the fields corresponding to the driven axes. The number
represents the voltage to be applied to the amplifier during the initialization. When the voltage is specified
by a positive number, the initialization process ends up in the motor off (MO) state. A negative number
causes the process to end in the Servo Here (SH) state.
WARNING: This command must move the motor to find the zero commutation phase. This
movement is instantaneous and will cause the system to jerk. Larger applied voltages will cause
more severe motor jerk. The applied voltage will typically be sufficient for proper operation of the BZ
command. For systems with significant friction, this voltage may need to be increased and for
systems with very small motors, this value should be decreased. For example:
BZ –2, 0,1
will drive both A and C axes to zero, will apply 2V and 1V respectively to A and C and will end up with
A in SH and C in MO.
Step F - part 2 (Systems with Hall Sensors Only). Set Zero Commutation Phase
With Hall sensors, the estimated value of the commutation phase is good to within 30
°
. This estimate can
be used to drive the motor but a more accurate estimate is needed for efficient motor operation. There are
3 possible methods for commutation phase initialization:
Method 1. Use the BZ command as described above.
Method 2. Drive the motor close to commutation phase of zero and then use BZ command. This method
decreases the amount of system jerk by moving the motor close to zero commutation phase before
executing the BZ command. The controller makes an estimate for the number of encoder counts between
the current position and the position of zero commutation phase. This value is stored in the operand _BZn.
Using this operand the controller can be commanded to move the motor. The BZ command is then issued
as described above. For example, to initialize the A axis motor upon power or reset, the following
commands may be given:
SHA ;Enable A axis motor
PRA=-1*(_BZA) ;Move A motor close to zero commutation phase
BGA
;Begin motion on A axis
AMA ;Wait for motion to complete on A axis
BZA=-1 ;Drive motor to commutation phase zero and leave motor on
Method 3. Use the command, BC. This command uses the Hall transitions to determine the commutation
phase. Ideally, the Hall sensor transitions will be separated by exactly 60
°
and any deviation from 60
°
will
affect the accuracy of this method. If the Hall sensors are accurate, this method is recommended. The BC
command monitors the Hall sensors during a move and monitors the Hall sensors for a transition point.
When that occurs, the controller computes the commutation phase and sets it. For example, to initialize the
A axis motor upon power or reset, the following commands may be given:
SHA ;Enable A axis motor
BCA ;Enable the brushless calibration command
PRA=50000 ;Command a relative position movement on A axis
BGA ;Begin motion on A axis. When the Hall sensors detect a
;phase transition, the commutation phase is reset
Chapter 2 Getting Started
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23 DMC-40x0 User Manual