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