User manual

PMAC User Manual
Getting Started with PMAC 15
Velocity-Loop (Motor) Feedback Address
It is possible to have separate motor and load feedback encoders (this can allow good control even with
poor coupling). In this case, the sensor on the load is used to close the position loop; it is addressed by
Ix03 above. The sensor on the motor is used to close the velocity loop; it is addressed by Ix04. The vast
majority uses only one feedback encoder, whether it is on the motor, or on the load. For these, Ix04 will be
set to the same value as Ix03, addressing the same encoder. If only using one feedback encoder (ENC1) for
the Motor #1 in the example, make sure I104 is set to 1824, just as I103 is (this is the default).
Flag Address
Now, make sure the card knows where to look for its limit and home flag inputs, which is controlled by
I125 (remember that this is essential to command a move). To use +LIM1, -LIM1, and HMFL1, I125
should be set to ($C000) 49152. This should be the value set at the factory. If not using overtravel limit
switches and the limit pins have not been wired to ground, set I125 to $2C000 instead.
If the amplifier is expecting sign (direction) and magnitude command, disable the use of AENAn/DIRn as
an amplifier-enable line so it can be used for direction. For motor 1, set I125 to $1C000. If the limits
should be disabled, set I125 to $3C000.
Reading Position
Now start checking on some basic motor functions. First, try to read motor position. With the Executive
program in terminal mode, type #1<CR> to address motor 1. Next, type P<CR>, and PMAC should return
a position value to the terminal screen. Now turn the motor shaft by hand and type P<CR> again. The
reported position should have changed. (Alternately, use the F7 position reporting window of the PMAC
Executive program, which automatically polls position repeatedly.)
Repeat this as often as needed to verify that the position counting is working properly in both directions. If
it is not, check the following:
• Is the encoder receiving power (+5V and GND)?
• Are both quadrature channels connected properly?
• If single-ended, are the complementary lines floating?
• If single-ended, is E27 (or equiv.) in default setting?
• If differential, has E27 been changed?
• Is the motor activated (I100=1)?
• Is I103 set to the proper encoder input?
• Is I900 set for proper decode of the signal?
• Can a signal be detected with a scope or voltmeter?
Changing Position Direction
If getting position feedback, but want to change the positive and negative directions, use I900 (for ENC 1)
to change the direction sense (or exchange the Channel A and Channel B inputs). For example, if I900 is 7,
changing it to 3 will change the direction sense.
Setting DAC Output Range
Check the output range by looking at I169. This is the maximum value that can be written to the DAC,
whose full range is -32,768 to +32,767 (16 bits for +/- 10V). The default value of I169 is 20,480, which is
about +/-6.25V. If the amplifier is expecting +/-10V and the full range is being used, set I169 to 32,767. If
the amplifier is expecting a differential signal with up to +/- 10V between the lines (each line is +/-5V), set
I169 to 16,384 or less.