Moog Animatics SmartMotor™ Developer's Guide,Rev. L
Page 868 of 909
Electrical Time Constant (te) (Seconds)
The time required for current to reach 63.2% of its final value for a fixed voltage level. It can
be calculated from the relationship
te=L/R
Where L is inductance (henries) and R is resistance (ohms).
Encoder
A feedback device that converts mechanical motion into electronic signals. The most
commonly used rotary encoders output digital pulses corresponding to incremental angular
motion. For example, a 1000-line encoder produces 1000 pulses every mechanical revolution.
The encoder consists of a glass or metal wheel with alternating transparent and opaque
stripes, detected by optical sensors to produce the digital outputs.
Feedback
A signal which is transferred from the output back to the input for use in a closed loop system.
Form Factor
The ratio of RMS current to average current. This number is a measure of the current ripple in
a SCR or other switch-mode type of drive. Because motor heating is a function of RMS current
while motor torque is a function of average current, a form factor greater than 1.00 means
some fraction of motor current is producing heat but not torque.
Four Quadrant
Refers to a motion system which can operate in all four quadrants, i.e., velocity in either
direction and torque in either direction. This means that the motor can accelerate, run and
decelerate in either direction.
Friction
A resistance to motion caused by contact with a surface. Friction can be constant with varying
speed (Coulomb friction) or proportional to speed (viscous friction).
Hall Sensor
A feedback device which is used in a brushless servo system to provide information for the
amplifier to electronically commutate the motor. The device uses a magnetized wheel and
Hall effect sensors to generate the commutation signals.
Holding Torque
Holding torque (sometimes called static torque) specifies the maximum external torque that
can be applied to a stopped, energized motor without causing the rotor to move. Typically
used as a feature specification when comparing motors.
Appendix: Glossary
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