Moog Animatics SmartMotor™ Developer's Guide,Rev. L
Page 497 of 909
KD=formula
Constant, Derivative Coefficient
APPLICATION: Motion control
DESCRIPTION: Derivative coefficient
EXECUTION: Value of buffered derivative gain
CONDITIONAL TO: Buffered until an F command is issued
LIMITATIONS: Must be positive
READ/REPORT: RKD
WRITE: Read/write
LANGUAGE ACCESS: Assignment, formulas and conditional testing
UNITS: N/A
RANGE OF VALUES: 0 to 65535
TYPICAL VALUES: 400 to 2000
DEFAULT VALUE: Motor-size dependent
FIRMWARE VERSION: 5.x and later
COMBITRONIC: KD:3=1234
where ":3" is the motor address — use the actual address or a
variable
DETAILED DESCRIPTION:
KD sets the value of the PID filter's derivative gain. If the PID filter gives stable performance,
KD is usually the vibration absorbing or damping term.
NOTE: The motion or servo modifications from this command must be applied by
the F function. For details, see F on page 446.
For any stable KP value, there is an optimum KD value, and any KD value outside of that
causes the motor to be unstable. Therefore, an effective way to tune the filter is to
repetitively raise the KP value, and then run the KD term up and down to find the optimum
setting. The point at which the KD term cannot stabilize the servo is the point where KP has
gone too far.
To test each setting, twist the shaft of the motor and let it go while looking for an abrupt and
firm response. Typically, a KD value of approximately ten times KP is a good starting point
when KP<300. The SMI software Tuner tool can be useful in finding the optimum setting.
EXAMPLE:
KD=2000 'Set buffered derivative gain
F 'Update PID filter
Part 2: Commands: KD=formula
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