Actuators

Question 1

What is a brushed DC motor

Answer 1

It had two sets of windings in the armature that generate the magnetic field. The commutator provides the current to the sets of winding in the armature. Depending on which brush contracts which commutator.. the direction of current changes and the magnetic field polarity changes in the armature coils. The magnetic fields in the coils interact with the permenant magnets, generating force

Question 2

What is a brushless DC motor

Answer 2

It’s a brushed motor inside out.
It’s usually used for computer cooling fan
It does not have a brush, the rotating part is lighter than the brushed motor and can rotate at higher speeds.on the other hand, it needs a circuit o control the direction of the current as it does not have a commutator

Question 3

What is a stepper motor

Answer 3

A type of brushless motor. The stepper motor rotates a fixed amount of angle per step input voltage. Two types: bipolar, and unipolar

Question 4

What is a bipolar stepper motor

Answer 4

It’s a stepper motor in which the whole coil is magnetised. The direction of supplied current determines the the poles. It needs a switching polarity mechanism or two power sources

Question 5

What’s a unipolar stepping motor

Answer 5

It only uses half of the coil at each time therefore produces less torque than the bipolar

Question 6

Name 8 questions you’d consider in motor selection

Answer 6

• what is the moment of inertia of the object connected to the motor?
• what is the angular acceleration requirement ?
• what is the peak power?
• what is the cost limitation?
• what are the size and weight limitations?
• us a gearbox required?
• what control precision requirement is for angle and angular velocity control?