Motor types

Servo motor is a electromechanical mechanical actuator with feedback allowing precision closed loop motion control and monitoring.

Construction

Servo motor consists two main parts:

• Motor part - typically electromagnetic device that produces torque or force when driven with current
• Feedback device - typically electronic device that outputs measurement information such as shaft angle or velocity

Shapes

Servo motors and feedback devices come mainly in two shapes:

• Rotary
• Linear

Shape of motor doesn't change their electromechanical princible so both types of motors can be driven with same drives.

Motor technologies

List of electromagnetic motor part types.

AC

Typical AC (alternating current) servo motor is a 3 phase permanent magnet syncronous machine. This type of motors are driven by 3 wires each driving one phase coil. In ideal case 3 phase AC servo is driven by sinusoidal current waveforms that are synchronized to the permanent magnet rotor.

BLDC

BLDC (brushless DC) is very similar to AC motor with only expection that it is desgined to be driven by trapezoidal current waveforms instead of sinusoidal. BLDC motors can always be driven with same drives regardless of current waveform matching.

Brush DC

Brush DC (direct current) motors typically have permanent magnet stator and rotor with mechanical commutator with brushes.

Comparison

Comparison of motor technologies

	Stepping motor	DC servo	BLDC servo	AC servo
Closed loop	No	Yes	Yes	Yes
Torque control	No, inpractical	Yes	Yes	Yes
Velocity control	Yes	Yes	Yes	Yes
Position control	Yes	Yes	Yes	Yes
Available speed range	Low, Medium	Medium	High	Highest
Rated torque vs size	High	Low	Medium	Medium
Dynamic performance	Low, Medium	Medium	High	Highest
Motion smoothness	Very low to high	Medium	Medium	High
Endurance	High	Medium	High	High

Feedback device types

Hall sensors

In no event the Product Information or parts hereof shall be regarded as guarantee of conditions or characteristics. The Product Information or any part thereof may also not be regarded as a warranty of any kind. No liability of any kind shall be assumed by Author with respect to Product Information or any use made by you thereof, nor shall Author indemnify you against or be liable for any third party claims with respect to such information or any use thereof.

As content of this Wiki may be edited by user community, Granite Devices Oy or it's affiliates do not take any responsibility of the contents of this Wiki. Use information at your own risk. However, Granite Devices staff attempts to review all changes made to this Wiki and keep information trustworthy.

Without written consent, Granite Devices' Products or Intellectual Property shall not be used in situations or installations where living beings, material property, or immaterial property could be harmed by the operation, features or failures of Product. Products may only be used in a way where hazards like moving parts, electric shock, laser radiation, or fire can't be realized even if the content of this Wiki would suggest otherwise.