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Configuring Active Damping (DACTDP)
1.
2.
3.
4.
Configuring Stall Detect Settings
You can use the Gemini drive's encoderless stall detect function to detect motor
stalls. A stall occurs when the motor's rotor loses synchronism with the stator. An
external feedback device is not required to detect stalls.
Some machine safety regulations require that external hardware feedback be used.
Do not use the Gemini's stall detect function as a replacement for external
feedback in such cases.
In order for the drive to detect a stall, the duration of the stall must be greater than
50 milliseconds. NOTE: if you use high values of active damping, extremely
aggressive accelerations are possible during which the motor may skip poles (lose
position). This loss of position can be less than 50 milliseconds; if so, it will not be
recognized as a stall.
Because the command velocity must be in the 3 – 37 rps range for stall detect to be
active, the drive will not recognize static loss of position as a stall. Therefore, do
not use this function to detect loss of holding torque in vertical applications.
Settings are summarized below.
Stall Detect Settings:
Command:
Default:
Velocity Range:
Required Parameter: LJRAT
Stall detect performance is based on motor parameters that you set up with the
configuration utility in Motion Planner or Pocket Motion Planner. For optimum
performance, accurate motor parameters are required.
If you select a Compumotor motor with the configuration utility, the motor
parameters are set automatically, according to the motor you have chosen. If you
use other motors, see Appendix B Using Non-Compumotor Motors.
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Using motor and load parameters, the drive calculates the optimum damping setting
for your system, and scales this value to a setting of DACTDP20. However, the
default setting is DACTDP4.
Enter an accurate value for the load parameter, using the following command:
Command:
Parameter:
LJRAT
system load-to-rotor inertia ratio
If you use a Parker motor, the following parameters are automatically set when you
use the configuration utilities (Motion Planner or Pocket Motion Planner) to select a
motor. You do not need to enter values for them now.
If you use a non-Parker motor, use the following commands to enter accurate
values for the specified motor parameters:
Command:
Motor Parameter:
DMTJ
rotor inertia
DMTSTT
static torque
DMTIND
inductance
Begin configuration with low values of DACTDP. Low values yield less aggressive
damping.
Increase DACTDP until the system performs as you require. The optimum setting is
DACTDP20. Note that higher values tend to cause overly aggressive damping, and
generate jerk impulses that may result in machine vibration.
DSTALL
Disabled (DSTALL0)
3 to 37 rps
Chapter 3 – Configuration
29
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