Aerotech UNIDEX 600 Series, User Manual

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U600 User’s Guide Getting Started
Version 1.4
Aerotech, Inc.
2-9
2.3.2.3. Digital-to-Analog Conversion (Output to the Amplifier)
Eight 16-bit DAC’s are available per each UNIDEX 600 or encoder expansion card. Two
of the channels are used per axis to provide commutation for brushless motors. The DAC
channels have 16 bits of resolution on the UNIDEX 600\650 Series. The DACs provide a
maximum output of
±
10 volts.
2.3.3. Configuring a Spindle (Open-Loop Velocity Mode)
A special condition exists when configuring an open-loop axis that requires a velocity
command (as opposed to a torque command), such as a spindle axis. Configuring the axis
for a D/A channel, but utilizing NULL feedback for the feedback device does this. In
addition, the lines per revolution of the feedback device should be set to 100,000 lines per
revolution. The Type machine parameter (see section 2.4.1.) should be set to 1 or 2
defining the axis as a rotary axis. If the spindle requires a unipolar velocity command (0
to 10 not -10 to +10) the ICMDPOLARITY axis parameter should be set to -1. The
CntsPerDeg machine parameter (see 2.4.2.) should be set 277.777778 (100,000 lines per
rev. / 360 degrees). The servo loop gains (axis parameters) should be set as follows; KI =
0, PGAIN = 0, KP = 1. If required, the DACOFFSET axis parameter may be used to null
any offset from the D/A. The IMAX axis parameter defaults to 32,767 producing a 10 volt
peak velocity command output. This value may be changed as required for the drive (for
example a value of 16,384 will produce a 5 volt peak). For velocity command systems,
IAVGLIMIT should be set to zero.
Now that all the parameters have been configured for the axis, it must be properly scaled
to the desired maximum velocity. First, enable the spindle axis and command it to rotate
at its maximum velocity. After it accelerates to its maximum velocity, increase the value
of the KP axis parameter until the velocity command output from the D/A is at 10 volts.
The D/A command may be monitored with a voltmeter, oscilloscope or by using the
AerDebug utility program to monitor the Torque (the ICMD axis parameter) command for
the spindle axis. AerDebug will display 32,767 when the velocity command is at 10 volts.
If the KP axis parameter cannot be adjusted so that the velocity command is at 10 volts
for the maximum velocity, the user may increase/decrease the lines per revolution of the
NULL feedback device to achieve the desired scaling. After completing this, save all the
parameters in an INI file, since the spindle is properly configured.
If the user desires to control the spindle in a CNC program with the standard M-codes, the
user needs to setup two additional task parameters. The S1_Index (Spindle #1) task
parameter should be set to the desired task-axis index and the S1_RPM can be set to
specify a default feedrate for the S-Word. The UNIDEX 600 supports up to four spindles
per task, to use more than one spindle, configure the axes as above and specify the proper
task-axis indexes. For more information, see the description for the M-codes in the
UNIDEX 600 Series CNC Programming WIN95/NT Manual, P/N EDU158.