To limit the maximum voltage signal to your amplifier, the DMC-1600 controller has
a torque limit command, TL. This command sets the maximum voltage output of the
controller and can be used to avoid excessive torque or speed when initially setting
up a servo system.
When operating an amplifier in torque mode, the v
voltage output of the controller will be directly related to the torque output of the
motor. The user is responsible for determining this relationship using the
documentation of the motor and amplifier. The torque limit can be set to a value that
will limit the motors output torque.
When operating an amplifier in velocity or voltage mode, the voltage output of the
controller will be directly related to the velocity of the motor. The user is
responsible for determining this relationship using the documentation of the motor
and amplifier. The torque limit can be set to a value that will limit the speed of the
motor.
For example, the following command will limit the output of the controller to 1 volt
on the X axis:
TL 1 <CR>
Note:
Once the correct polarity of the feedback loop has been determined, the torque
limit should, in general, be increased to the default value of 9.99. The servo will not
operate properly if the torque limit is below the normal operating range. See
description of TL in the command reference.
Step C.
Enable Off-On-Error as a safety precaution. To limit the maximum distance the
motor will move from the commanded position, enable the Off-On-Error function
using the command , OE 1. If the motor runs away due to positive feedback or
another systematic problem the controller will disable the amplifier when the
position error exceeds the value set by the command, ER.
Step D.
Disable motor with the command MO (Motor off).
Step E.
Connect the Motor and issue SH
Once the parameters have been set, connect the analog motor command signal
(ACMD) to the amplifier input.
To test the polarity of the feedback, command a move with the instruction:
PR 1000 <CR> Position relative 1000 counts
BGX <CR>
Begin motion on X axis
When the polarity of the feedback is wrong, the motor will attempt to run away. The
controller should disable the motor when the position error exceeds 2000 counts. If
the motor runs away, the polarity of the loop must be inverted.
Inverting the Loop Polarity
When the polarity of the feedback is incorrect, the user must invert the loop polarity and this may
be accomplished by several methods. If you are driving a brush-type DC motor, the simplest way
is to invert the two motor wires (typically red and black). For example, switch the M1 and M2
connections going from your amplifier to the motor. When driving a brushless motor, the polarity
reversal may be done with the encoder. If you are using a single-ended encoder, interchange the
signal CHA and CHB. If, on the other hand, you are using a differential encoder, interchange only
CHA+ and CHA-. The loop polarity and encoder polarity can also be affected through software
with the MT, and CE commands. For more details on the MT command or the CE command, see
the Command Reference section.
16
•
Chapter 2 Getting Started
DMC-1600
