Step 7. Setting Safety Features
Step A. Setting Amplifier Gains
A transconductance (current) amplifier takes a ±10V command signal and produces a current in the motor
proportional to that signal. This ratio is the amplifier gain (amps/volts) and can be set via the Amplifier Gain (AG)
command when using Galil's internal amplifiers. See the AG command in the Command Reference for proper
current gain settings for Galil's internal amplifiers.
The Current Loop Gain (AU) command sets the current loop gain for the amplifier and is set based on the bus
voltage powering the amplifier as well as the inductance of the motor. Consult the amplifier appendix section or
command reference for more details.
Step B. Setting Torque Limits
The Torque Limit (TL) command will limit the output voltage of ±10V motor command line. This command should
be used to avoid excessive torque and speed when initially setting up a servo system. The Peak Torque Limit (TK)
command sets the peak torque limit of the motor output allowing the command line to momentarily exceed TL.
See the TL and TK settings in the Command Reference for more information. Amplifier gain needs to be taken into
account when setting both TL and TK. For example, if a particular motor has a continuous current rating of 2.0 A
and a peak current rating of 5.0 A and the amplifier gain is 0.8A/V, TL and TK can be calculated as follows:
TL setting = (2.0A)/(0.8A/V) = 2.5V (TL n=2.5)
TK setting = (5.0A)/(0.8A/V) = 6.25V (TK n=6.25)
The user is responsible for determining the relationship between the motor command line and the amplifier
torque/velocity using the documentation of the motor and/or amplifier.
Step C. Setting Error Limits
When an Error Limit (ER) and Off-on-Error (OE) is set, the controller will automatically shut down the motors when
excess error (|TE| > ER) has occurred.
OE requires the amplifier enable signal to be connected from the controller to the amplifier. When using Galil's
internal amplifiers, the amplifier enable is already configured. See Step 2b. Connecting External Amplifiers and
Motors, pg 15 when using external amplifiers.
Step D. Other Safety Features
This section only provides a brief list of safety features that the DMC can provide. Other features include Encoder
Failure Detection (OA, OT, OV), Automatic Subroutines to create an automated response to events such as limit
switches toggling (#LIMSWI), large following error (#POSERR), amplifier errors (TA, #AMPERR), and more. For a full
list of features and how to program each see Chapter 8 Hardware & Software Protection, pg 145.
Chapter 2 Getting Started ▫ 18 DMC-41x3 User Manual
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