Actuator Selection

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Actuator Selection
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Basic Forms

• Linear Actuation
• Hydraulic cylinder
• Pneumatic cylinder
• Solenoid
• Power screw

• Rotary Actuation
• Electric motor
• Pneumatic motor
• Hydraulic motor
• Internal combustion engine

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Electric Motors
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DC Electric MotorsPM
Torque/Speed Characteristics
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DC Electric MotorsPM

• Stationary field from permanent magnets
• Advantages
• Smaller size
• Easier to manufacture than other DC mtrs
• Good starting torque
• Disadvantages
• Speed is load sensitive

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DC Electric MotorsField Coils
Torque/Speed Characteristics
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DC Electric MotorsShunt Wound

• Field coils in parallel with armature coils
• Advantages
• Lower speed/load sensativity
• Disavantages
• Poor characteristics for overload torque

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DC Electric MotorsSeries Wound

• Field coils in series with armature coils
• Advantages
• High starting torque capacity
• Speed is very load sensitive (limits accel in
  sys)
• Disadvantages
• Speed can run-away under no-load cond.

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DC Electric MotorsCompound Wound

• Field and armature coils connected in combination
  of series and parallel
• Compromise between series and parallel
• Advantages
• Will not run-away under no-load
• Good starting capabilities
• Disadvantages
• More expensive

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AC Motors

• Speed is determined by the number of poles in
  the motor
• Less expensive than comparable DC motors
• Single phase
• Easier to build and install
• 3-phase.
• More expensive, but more capable

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AC Motors
Torque/Speed Characteristics
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Modified Motors

• Stepper Motor
• Good for positioning and intermittent motion
• Gear Motors
• Motor with an integral gearbox
• Servo Motor
• Closed loop controlled motor
• Controlled for position, velocity and accel.