Slide 1
Touch your nose while your eyes are closed.
Can you?Control means absolute precision
Introduction
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MotorWhat does motor do?
Power Conversion
How simple dc motor differs from a stepper motor?
The main difference between them is the way they revolve. Unlike other motors, stepper motors does not continuously rotate. Instead, they rotate in steps.Each step is a fraction of a full circle. This fraction depends mostly from the mechanical parts of the motor, and from the driving method.The stepper motors also differs in the way they are powered. Instead of an AC or a DC voltage, they are driven (usually) with pulses.
For example, an 1.8ostepper motor, will revolve its shaft 1.8oon every pulse that arrives. Often, due to this characteristic, stepper motors are called also digital motors.
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Stepper MotorAstepper motor(orstep motor) is abrushless DC electric motorthat divides a fullrotation into a number of equal steps. The motor's position can then be commandedto move and hold at one of these steps without any feedback sensor (anopen-loop controller), as long as the motor is carefully sized to the application.
Prctical stepper motor operation:
Frame 1:The top electromagnet (1) is turned on, attracting the nearest teeth of the gear-shaped iron rotor. With the teeth aligned to electromagnet 1, they will be slightly offset from right electromagnet (2).
Frame 2:The top electromagnet (1) is turned off, and the right electromagnet (2) is energized, pulling the teeth into alignment with it. This results in a rotation of 3.6 in this example.
Frame 3:The bottom electromagnet (3) is energized; another 3.6 rotation occurs.
Frame 4:The left electromagnet (4) is energized, rotating again by 3.6. When the top electromagnet (1) is again enabled, the rotor will have rotated by one tooth position; since there are 25 teeth, it will take 100 steps to make a full rotation in this example.
The top electromagnet (1) is turned on, attracting the nearest teeth of the gear-shaped iron rotor. With the teeth aligned to electromagnet 1, they will be slightly offset from right electromagnet (2).
The top electromagnet (1) is turned off, and the right electromagnet (2) is energized, pulling the nearest teeth slightly to the right. This results in a rotation of 3.6 in this example.
The left electromagnet (4) is enabled, rotating again by 3.6. When the top electromagnet (1) is again enabled, the teeth in the sprocket will have rotated by one tooth position; since there are 25 teeth, it will take 100 steps to make a full rotation in this example.The bottom electromagnet (3) is energized; another 3.6 rotation occurs.
Types of Stepper MotorPermanent Magnet MotorVariable Reluctance MotorHybrid Motor
Driving Modes Wave drive or Single-Coil ExcitationFull step driveHalf steppingMicrostepping
Application of Stepper motor
Steppper motor to move read right head
Paper feeder on printersCNC lathesStepper motors
CNC stepper motor
Advantages:-Low cost for control achievedRuggednessSimplicity of constructionCan operate in an open loop control systemLow maintenanceLess likely to stall or slipWill work in any environmentDisadvantages:-Require a dedicated control circuitUse more current than D.C. motorsHigh torque output achieved at low speeds
Advantages and disadvantages
