Parker Compumotor ZETA6104, Руководство по установке

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Appendix A Ð Resonance, Ringing & Damping
4 1
Anti-Resonance (AR)
Anti-resonance monitors the ZETA6104Õs motor
terminals, and looks at power exchange between the
ZETA6104 and motor. From this, it extracts information
about error in rotor position caused by resonance or
ringing. It modifies the internal motor current command
to correct for the error.
Anti-resonance is a general-purpose circuit. It corrects
rotor position error, without knowledge about the
systemÑwhether the motor is large or small, or the
system inertia is high or low. You cannot modify the
circuitÕs gains, or customize it for a particular
applicationÑbut, anti-resonance is easy to use. When
enabled via the
DAREN1
command, it works
automatically.
Active Damping (AD)
Active damping monitors the ZETA6104Õs motor
terminals and, like anti-resonance, uses the same current
command modulator to modify motor current.
Active damping uses a different method to extract
information about rotor position error, however. The
circuitÕs gains are adjustableÑyou can configure it for
your particular system. The
DMTIND
and
DMTSTT
commands scale the circuit for motor inductance and static
torque, respectively. The
DACTDP
command scales the
circuit for system inertia.
The active damping circuit uses this information for two
purposes:
1. It determines error in rotor position very accurately.
2. It adjusts the gains of its feedback loop, based upon
how much inertia the system has, and how much
torque the motor can produce.
If the rotor rings or vibrates, the active damping circuit
will detect the corresponding error in rotor position. It
will then modify the motor current command to damp the
ringing.
DIP switches on top of the ZETA6104 set the amount of
motor current during normal operations; this current is
constant. To damp ringing, the active damping circuit can
cause the ZETA6104 to produce up to twice as much
current as is set by the DIP switches. The extra current is
only applied during damping oscillations, and lasts a very
brief time.
Electronic Viscosity (EV)
The ZETA6104 uses closed-loop current control to
develop and maintain precise currents in the motor phases.
When EV is off, the current loops have a bandwidth of
approximately 1000 Hz. Because this bandwidth is well
beyond the knee of step motor speed-torque curves, the
current loop dynamics do not limit the response of the
motor.
EV monitors motor velocity, and turns on below 3 rps. It
ÒdetunesÓ the current loop compensation values and brings
the bandwidth down to 150ÊHz. With this lower
bandwidth, the drive electronics become Òsluggish.Ó
Ordinarily, when the rotor oscillates, it generates current
in the motorÕs coils; but with EVÕs lower bandwidth, the
driveÕs electronics impede the flow of current caused by
oscillations.
The effect on the motor is as if there were a viscous drag
on the rotor. At the end of a move, oscillations are
damped, and the rotor quickly comes to rest. After
accelerating or decelerating to velocities below 3 rps, the
rotor quickly settles at the commanded velocity. During
moves below 3 rps, EV significantly reduces low speed
velocity ripple.
EV is a ÒpassiveÓ circuit. It imposes viscosity on the
system, but has no feedback loop to monitor the effect of
the viscosity. EV keeps the amount of viscosity the
same, regardless of the response of the system.
You can adjust the amount of viscosity by using the
DELVIS
command. This allows you to tailor the circuit
for different motor sizes and system inertias, and adapt it
to your application.
Recommendations
We recommend that you configure active damping and
electronic viscosity. Even if you believe resonance and
ringing will not cause problems in your system, you may
find that the ZETA6104Õs damping circuits provide
increased smoothness, reduced audible noise, and better
performance. Refer to the configuration procedures
beginning on page 26.
If you choose not to use active damping and electronic
viscosity, at least use anti-resonance. The ZETA6104 is
shipped from the factory with anti-resonance enabled
(
DAREN1
).
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