A
ppend
ix
Moog Animatics SmartMotor™ Developer's Guide, Rev. L
Page 872 of 909
Stiffness
The ability to resist movement induced by an applied torque. Stiffness is often specified as a
torque displacement curve, indicating the amount a motor shaft will rotate upon application of
a known external force when stopped.
Torque
A measure of angular force which produces rotational motion. This force is defined by a linear
force multiplied by a radius, e.g., lb-in. The formula is:
Torque (lb-ft.) = 5,250 x HP/RPM
Torque Constant (KT = lb-ft./A)
An expression of the relationship between input current and output torque. For each ampere
of current, a fixed amount of torque is produced.
NOTE:
Torque constants
are not
linear over the operating range of a motor. They
apply best at approximately 75% of no-load maximum speed or where the peak
and continuous torque curves meet.
Torque-to-Inertia Ratio
Defined as the motor’s holding torque divided by the inertia of its rotor. The higher the ratio,
the higher a motor’s maximum acceleration capability will be.
Trapezoidal Move Profile (TMP)
The motion profile defined by an ascend (ramp up) part, a slew part and descend (ramp down)
part, which are associated with follow or cam modes. Also, referred to in whole as "ramp",
and as "ramp up" and "ramp down" for the ascend and descend parts, respectively. See the
diagram Trapezoidal Move Profile (TMP) and Output Position Diagrams on page 141.
Velocity
The change in position as a function of time. Velocity has both a magnitude and sign.
Voltage Constant (KE) (V/kRPM peak, line-to-line)
May also be termed Back-EMF constant. When a motor is operated, it generates a voltage
proportional to speed but opposing the applied voltage. The shape of the voltage waveform
depends on the specific motor design. For example, in a brushless motor, the wave shape
may be trapezoidal or sinusoidal.
Appendix: Glossary
