MultiFlex PCI 1000 Series User's Manual
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Glossary
Accuracy - A measure of the difference between the expected position and actual position of a motion
system.
Actuator - Device that creates mechanical motion by converting energy to mechanical energy.
Axis Phasing - An axis is properly phased when a commanded move in the positive direction causes the
encoder decode circuitry of the controller to increment the reported position of the axis.
Back EMF - The voltage generated when a permanent magnet motor is rotated. This voltage is
proportional to motor speed and is present regardless of whether the motor windings are energized or de-
energized.
Closed Loop - A broadly applied term, relating to any system in which the output is measured and
compared to the input. The output is then adjusted to reach the desired condition. In motion control, the
term typically describes a system utilizing a velocity and/or position transducer to generate correction
signals in relation to desired parameters.
Command Set – Defines the operations that can be executed by the motion controller
Commutation - The action of applying currents or voltages to the proper motor phases in order to produce
optimum motor torque.
Critical Damping - A system is critically damped when the response to a step change in desired velocity
or position is achieved in the minimum possible time with little or no overshoot.
DAC - The digital-to-analog converter (DAC) is the electrical interface between the motion controller and
the motor amplifier. It converts the digital voltage value computed by the motion controller into an analog
voltage. The more DAC bits, the finer the analog voltage resolution. DACs are available in three common
sizes: 8, 12, and 16 bit. The bit count partitions the total peak-to-peak output voltage swing into 256,
4096, or 65536 DAC steps, respectively.
Dead Band - A range of input signals for which there is no system response.
Driver - Electronics that convert step and direction inputs to high power currents and voltages to drive a
step motor. The step motor driver is analogous to the servo motor amplifier.
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