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Stepper Motor
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Advantages
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Disadvantages
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Inexpensive relative to other motion control systems.
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Low
efficiency. Motor draws substantial power regardless of load.
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Needs
no feedback. The motor is also the position transducer.
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Torque
drops rapidly with speed (torque is the inverse of speed).
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Stable.
Can drive a wide range of frictional and inertial loads.
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Low
accuracy. 1:200 at full load, 1:2000 at light loads.
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Standardized frame size and performance.
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Prone
to resonance. Requires micro-stepping to move smoothly.
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Plug
and play. Easy to setup and use.
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No
feedback to indicate missed steps.
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Safe.
If anything breaks, the motor stops.
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Low
torque to inertia ratio. Cannot accelerate loads very rapidly.
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Long
life. Bearings are the only wear-out mechanism.
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Motor
gets very hot in high performance configurations.
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Excellent low speed torque. Can drive many loads without
gearing.
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Motor
will not "pick up" after momentary overload.
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Excellent repeatability. Returns to the same location
accurately.
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Motor
is audibly very noisy at moderate to high speeds.
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Overload safe. Motor cannot be damaged by mechanical overload.
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Low
output power for size and weight.
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DC Motor
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Advantages
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Disadvantages
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High
output power relative to motor size and weight.
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Higher
cost.
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Encoder
determines accuracy and resolution.
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Motor
"runs away" when something breaks. Safety circuits required.
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High
efficiency. Can approach 90% at light loads.
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Complex. Requires encoder.
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High
torque to inertia ratio. Can rapidly accelerate loads.
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Brush
wear limits life to 2,000 hrs. Service is then required.
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Has
"reserve" power. 2-3 times continuous power for short periods.
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Peak
torque is limited to a 1% duty cycle.
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Has
"reserve" torque. 5-10 times rated torque for short periods.
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Motor
can be damaged by sustained overload.
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Motor
stays cool. Current draw proportional to load.
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Requires "tuning" to stabilize feedback loop.
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Usable
high speed torque. Maintains rated torque to 90% of NL RPM.
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Power
supply current 10 times average to use peak torque.
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Audibly
quiet at high speeds.
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Motor
develops peak power at higher speeds. Gearing often required.
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Resonance and vibration free operation.
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Poor motor cooling. Ventilated
motors are easily contaminated.
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