HELLO FRIENDS IN EARLIER POST I GIVE YOU OVER VIEW ABOUT THE ACTUATORS .I DISCUSSED ONLY HYDRAULIC,PNEUMATIC,AND HALF OF ELECTRIC ACTUATORS …..
so in this post I explain about the stepper motor actuators that are also used in robot
STEPPER MOTOR -:
stepper motor basically a DC brush less electric motor which convert the electrical energy to the discrete mechanical torque. here discrete means step wise movement of the rotor according to signal.the stepper motor rotates when electric pulse are applied in proper sequence.sequence of the input pulse which is applied to the motor related to the direction of the rotation of the motor.in this type of motor open loop controller is used.open loop control means control without feedback sensor.it means that it become more inexpensive than the servo motors because it eliminates the use of expensive feedback sensors,and also optical encoders.stepper motor is mainly used when controlling movement of the motor is required .
1. less expensive
2. fast response for starting or stopping the motor at any stepping condition
3.these are brushless ,so the life of the motor is mainly dependent upon the bearing of the motor.
1.due to lack of feedback sensor it creates resonance during the controlling of the motor
2.it is restricted only for normal speed .it does not at extremely high speed
TYPES OF STEPPER MOTOR -:
there are basically three types of stepper motors
this type of stepper can be easily understand by figure which consist of a stator on which winding is done on the stator poles . it also consist of a soft iron rotor with multi touch teeth on it.when the stator windings energized due to application of DC current.they become magnetize.the rotation of the rotor may occur due to attraction of the stator pole which is applied on the pole by DC source .it based on the principle that minimum reluctance occurs with minimum gap.
permanent magnet type stepper motor (electrical actuators)more efficient than variable reluctance type of stepper motor
because in this type of PM motors the rotor shaft does not consist of multi teeth .instead of this it consist of a rotor magnetized with alternating north and south pole parallel to the axis of the rotor.due to magnetized rotor the magnetic flux intensity is increase.due to this it become more efficient than variable reluctance type of motor.PM motors also
known as “tin can”or “canstock”. it is lower in cost .
oil impregnated bushing are use to increase the life of the PM motors .there are three types of PM motors.Nd-Fe-B Bonded Magnet,Ferrite Sintered Magnet,Ferrite Plastic Magnet.main application of the PM motors are printers,scanner,also used in valve operation.
Characteristics of the PM step motor:
- Increase of holding and dynamic torque over conventional products in excess of 15%.
- it used as different-2 application by changing the combination of shaft, front plates and wire harnesses.
- Fully automated coil assembly.
- Reduction of steps required from order to delivery.
HYBRID STEPPER MOTOR