Using P7000Tools
04/06
Danaher Motion
4.4.8.1.
Anti-Resonance
Step motors are highly resonant, which results in vibration and ringing. The
ringing utilizes a large fraction of the motor's available torque – thereby
wasting performance. Furthermore, at mid-range velocities, the resonance
can become so severe that the motor looses synchronism and stalls. The
P7000 drives provide robust anti-resonance control to stop the vibrations
and maintain equilibrium. This feature requires that the drive be configured
with respect to the total inertia in the system. The rotor inertia and the Load-
to-Rotor inertia ratio are set in the Mechanical screen. If set improperly, the
effectiveness of the feature may be diminished.
The anti-resonance check box is used to invoke or disable the feature. It
should be enabled unless the system configuration either does not need it
or cannot tolerate it. A system with lossy couplings or viscous loading
generally does not need this feature. If a system has compliant (springy)
coupling and is absent appreciably viscosity, it may not respond well to the
active, anti-resonant loop in the drive. The anti-resonant feature is not
designed to damp such a 4
th
order system. If the application of anti-
resonance results in degradation or instability, it should be disabled
(unchecked).
Frequency
Break frequency of anti-resonance tuning filter. Typically set to
1/10 the resonant frequency of the motor.
2
m
kg
Rotor
M
N
max
100
ToothCount
Frequency
ARes
⋅
⋅
•
•
=
J
T
Amplitude
Set to 6500 nominal. Do not alter this value unless advised by
technical support.
4.4.8.2.
Current Reduction
Unlike a servo system, the step motor is left energized – even at rest. This
leaves full torque available to oppose external disturbing influences and
hold position precisely. However, many applications encounter vanishingly
small load effects at rest and may benefit from the reduction of current when
not moving. The reduced level is programmed as a percent of full current
and the time delay is entered in milliseconds (ms). The drive will gently
reduce the current to the programmed value after the motor has been at rest
for a specified time. If the box is left unchecked, the numeric entries have no
effect and full current is maintained at rest.
Motor heating is proportional to the square of the current. Thus, a reduction
of 70% current represents a reduction to 50% power. Current reduction has
little effect as long as the resting motor is not opposing a continuous torque
as in lifting applications. If a disturbing torque is present, the current
reduction will result in a small amount of movement. The current vector is
restored to full value the instant an incoming step is received or the move
engine begins a move.
34 Rev
D
M-SD-7AC-01