actuators used in robot

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 -:

200px-StepperMotor actuators used in robot 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 .

ADVANTAGE  -:
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.

DISADVANTAGE-: 
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
1.permanent magnet 
2.Hybrid
3.variable reluctance

variable reluctance

www.twovolt actuators used in robot 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 

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article-2011october-an56551-fig4 actuators used in robot

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

 

 

stepper-motor-8-638 actuators used in robotAS name denotes that hybrid motor is the combination of the permanent and variable reluctance stepper motors.it is also a type of electrical actuators.it is more expensive and so complicated.it may rotates full,half and micro stepped.  these  electrical actuators are widely used in industrial areas. these motors are more precise and reliable  than other motors.due to this these are used widely.the working process is similar as other  motors.the electric pulse is provided to the stator and due to this application ,teeth that are present on the rotors attracted due to development of magnetic field in the winding (these are present on the stator).it consist of open loop control system. a schematic gives a understanding about that it used for very small stepped angle at very high torque.application of these motors in many areas like medical,lab automation,and also in agriculture field.

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