Specifications

40 ζ ZETA6104 Installation Guide
Ringing (Transient
Response)
Inside a step motor, the rotor behaves like a mass on a spring, as mentioned above. When
commanded to quickly accelerate to a given velocity, the rotor will “ring” about that velocity,
oscillating back and forth. As shown in the next drawing, the ringing decays—grows smaller
over time—and the rotor eventually settles at the commanded velocity.
Time
Velocity
Ringing
Transients
CommandedActual
Notice that ringing can be caused both by accelerating or decelerating to a commanded
velocity, and decelerating to a stop. In any of these cases, ringing causes error in rotor
position.
Ringing is a transient phenomenon (unlike resonance, which occurs during steady state
operations). It is a response to a sudden change that we impose on the system, such as
“Accelerate to Velocity” or “Stop.”
Several problems are associated with ringing. It can cause audible noise; the motor must have
a margin of extra torque to overcome the ringing; and longer settling times can decrease
throughput.
To eliminate these problems, system designers use damping to force the ringing to decay
quickly. Inertial dampers have been used as components in passive damping methods.
Accelerometers, encoders, and tachometers have been used as components in active damping
methods. These devices can have the unwanted effect of limiting performance, adding
complexity, and increasing cost.
The ZETA6104 has internal electronics that can damp ringing transients, and cause them to
decay quickly. No external devices are necessary.
Damping in the ZETA6104
The ZETA6104 has three different circuits that can damp resonance and ringing.
Anti-Resonance – General-purpose damping circuit. The ZETA6104 ships from the
factory with anti-resonance enabled. No configuration is necessary. Anti-resonance
provides aggressive and effective damping.
Active Damping – Extremely powerful damping circuit. The ZETA6104 ships from the
factory with active damping disabled. You must use the DACTDP command to enable
active damping and optimize it for a specific motor size and load (see procedure on page 26).
Electronic Viscosity – Provides passive damping at lower speeds. The ZETA6104
ships with electronic viscosity disabled. You must use the DELVIS command to enable
electronic viscosity, and optimize it for a specific application (see procedure on page 29).
The first two damping circuits—anti-resonance and active damping—work at speeds greater
than three revolutions per second (rps). Electronic viscosity works at speeds from rest up to
three rps. The ZETA6104 will automatically switch between the damping circuits, based
upon the motor’s speed. The next drawing shows the effective range of each circuit.