97.315 Basic EM and Power Engineering

ELEC 3105 Basic EM and Power EngineeringStepping Motors1

Context: Lorentz Force2Please visit YouTube

Context: DC Motors3YouTube video

Context: Motor and Generator4Link here

Context: Electromagnetic Wave5Link here

Context: Brushless Motors6Link here

Here is another link to the brushless motor.Gives more detail on motor concept and design.

ELEC 3105 Basic EM and Power EngineeringStepping Motors7

Stepping Motor8Step motors (SMs) are electric motors that have no rotating windings, mechanical commutators, brushes or slip-rings. All the windings are part of the stator, and the rotor is usually a permanent magnet. Unlike traditional motors, all the commutation is done externally by a (digital) controller. The SM and its controller are designed so that the shaft can be set to a specific angular orientation, or driven quasi-continuously forwards or backwards as desired.

Stepping Motor9Step motors (SMs) are electric motors that have no rotating windings, mechanical commutators, brushes or slip-rings. All the windings are part of the stator, and the rotor is usually a permanent magnet. Unlike traditional motors, all the commutation is done externally by a (digital) controller. The SM and its controller are designed so that the shaft can be set to a specific angular orientation, or driven quasi-continuously forwards or backwards as desired.

Variable ReluctanceMotors

Unipolar Motors

Bipolar Motors

Stepping Motor10The idea is to produce a discrete quantum of angular rotation in response to an applied pulse. To produce quasi-continuous rotation, you need to apply a coded pulse train to the stator windings (using digital electronics) that will create an incrementally rotating magnetic pattern. Winding 1 1001001001001001001001001Winding 2 0100100100100100100100100Winding 3 0010010010010010010010010

Variable ReluctanceMotorsStepping Motor11Advantages Low cost Ruggedness Simplicity of construction High reliability No maintenance Wide acceptance No tweaking to stabilize No feedback components are needed Inherently more fail-safe than other types of motors.

Disadvantages Resonance effects and long settling times Rough performance at slow speeds unless micro-stepping is used Position loss Run hot due to current required in drive for all load conditions Noisy

Stepping Motor12Types Permanent magnet (PM) step motors Contain a permanent magnet in the rotor. Sequenced stator coil energizing provides rotation

Variable reluctance (VR) step motors Have no permanent magnets Rotor is a unmagnetized soft magnetic material Special drive circuits a re required

Hybrid step motors Combined PM and VR step motor They are the most common design They usually operate in 2-phase mode 5-phase versions also available.

Stepping Motor13In use, the central taps of the windings are typically wired to the positive supply, and the two ends of each winding are alternately grounded to reverse the direction of the field provided by that winding.

Single-Coil Excitation Each successive coil is energized in turn. Step Coil 4 Coil 3 Coil 2 Coil 1 ==== ====== ====== ====== ====== a1 on off off offa2 off on off offa3 off off on offa4 off off off on This sequence produces the smoothest movement and consumes least power. Two-Coil Excitation Each successive pair of adjacent coils is energized in turn. Step Coil 4 Coil 3 Coil 2 Coil 1==== ====== ====== ====== ======b1 on on off offb2 off on on off b3 off off on onb4 on off off on This is not as smooth and uses more power but produces greater torque.Interleaving the two sequences will cause the motor to half-step Step Coil 4 Coil 3 Coil 2 Coil 1 ==== ====== ====== ====== a1 on off off off b1 on on off off a2 off on off offb2 off on on off a3 off off on offb3 off off on on a4 off off off onb4 on off off on This gives twice as many stationary positions between stepsUnipolar Stepping Motor14The idea is to produce a discrete quantum of angular rotation in response to an applied pulse. To produce quasi-continuous rotation, you need to apply a coded pulse train to the stator windings (using digital electronics) that will create an incrementally rotating TM pattern.

Winding 1a 1000100010001000100010001Winding 1b 0010001000100010001000100Winding 2a 0100010001000100010001000Winding 2b 0001000100010001000100010 time --->Winding 1a 1100110011001100110011001Winding 1b 0011001100110011001100110Winding 2a 0110011001100110011001100Winding 2b 1001100110011001100110011 time ---> Unipolar MotorsHow to generate sequence electronically ?Stepping Motor15

Winding 1a 1000100010001000100010001Winding 1b 0010001000100010001000100Winding 2a 0100010001000100010001000Winding 2b 0001000100010001000100010 time --->Winding 1a 1100110011001100110011001Winding 1b 0011001100110011001100110Winding 2a 0110011001100110011001100Winding 2b 1001100110011001100110011 time ---> Unipolar MotorsHow to generate sequence?

Digital sequential machinebased on flip-flops, ...Sequence to generateStepping Motor16These motors are wired exactly the same way as unipolar step motors, but the two windings are wired more simply, with no center tap. Thus the motor itself is simpler but the drive circuitry needed to reverse the polarity of each pair of motor poles is more complex. Bipolar Motors

Single phase wiring diagramStepping Motor17The idea is to produce a discrete quantum of angular rotation in response to an applied pulse. To produce quasi-continuous rotation, you need to apply a coded pulse train to the stator windings (using digital electronics) that will create an incrementally rotating TM pattern. Winding 1 1001001001001001001001001Winding 2 0100100100100100100100100Winding 3 0010010010010010010010010

Variable ReluctanceMotors

Stepping Motor1812 Step per revolution Hybrid Motor

Rotor: Is magnetized along its axis so that one end is north (N) and the other end is south (S). In this design each end of the rotor has three teeth for a total of 6. The N and S teeth are offset.Stator: Can be energized in various ways has 4 poles pieces, each extending the length of the motor. We will assume at the moment that coils 1A and 1B are connected in series, and that coils 2A and 2B are separately connected in series.

Stepping Motor19

12 Step per revolution Hybrid Motor

No current: There is a minimum reluctance condition when N and S poles of the rotor are aligned with the two stator poles. There is a small detent torque.You can feel the detent torque when you rotate the motor by hand.

Stepping Motor2012 Step per revolution Hybrid Motor

Current in 1A and 1B: N pole on top in stator, S pole at the bottom of stator. There are now three stable positions for the rotor with respect to the energized stator coil 1. The torque needed to move the rotor irrevocably away from a stable position is now much larger and is called the holding torque.When both halves of the coil are energized at the same time, this is called bipolar drive.Stepping Motor21

(a) Coil 1 --> N and S --> attract rotor teeth of opposite polarity.(b) Coil 2 --> N and S --> The stator field rotates through 90 degrees and attracts rotor teeth of opposite polarity and the rotor shaft rotates 30 degrees in one step.(c) Coil 1 --> S and N --> The stator field rotates through 90 degrees in the same direction as (b) and attracts rotor teeth of opposite polarity and the rotor shaft rotates 30 degrees in one step.(d) Coil 2 --> S and N --> The stator field rotates through 90 degrees in the same direction as (b)(c)and attracts rotor teeth of opposite polarity and the rotor shaft rotates 30 degrees in one step.Full step mode: The idea is to provide currents in coils 1 and 2 such that the rotor is induced to rotate, in steps, in one direction. (d) same as (a) except rotated by 90 degrees3 steps = 1/4 turn: 12 steps = one full revolution of shaftFull step, one phase onStepping Motor22

Full step mode: The idea is to provide currents in coils 1 and 2 such that the rotor is induced to rotate, in steps, in one direction. 3 steps = 1/4 turn: 12 steps = one full revolution of shaft

Step 1 2 3 4 5 6 7(a) (b) (c) (d) (a) (b) (c)Full step, one phase onStepping Motor23Full step mode: The idea is to provide currents in coils 1 and 2 such that the rotor is induced to rotate, in steps, in one direction. Full step, two phases on

Step 1 2 3 4 5 6 7(a) (b) (c) (d) (a) (b) (c)Stepping Motor24Half step mode

Finer angular resolution in shaft angular position is possible using the half step mode. Provides uneven torque due to (1 coil-2 coil) energizing sequence.Full step mode: The idea is to provide currents in coils 1 and 2 such that the rotor is induced to rotate, in steps, in one direction. Stepping Motor25Half step profiled mode

Finer angular resolution in shaft angular position is possible using the half step mode. Provides even torque due to double current when only one coil is energized.Full step mode: The idea is to provide currents in coils 1 and 2 such that the rotor is induced to rotate, in steps, in one direction. Stepping Motor26Microstep modeFiner angular resolution in shaft angular position is possible using the microstep mode. Two 90 degree out of phase sine waves can perform the same microstep fine control of the rotor position.

ELEC 3105 Basic EM and Power EngineeringMEMS Motors Linear27

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Previous slide extracted from Principle of virtual work29

Previous slide extracted from Principle of virtual workELEC 3105 Basic EM and Power EngineeringMEMS Motors Rotation30

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ELEC 3105 Basic EM and Power EngineeringLaser Driven Motors34

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Cylinder orientation in focused laser beam37

Torque versus orientation angle

Cylinder in focused laser beam38

Torque versus orientation angle

Cylinder in focused laser beam

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Step motor operationof cylinder in laserbeamsEquations of motion

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Smooth Rotating motor operationof cylinder in laser beams.

ELEC 3105 Basic EM and Power EngineeringMEMS Laser Driven Motors41

42Activation of micro-components using light for MEMS and MOEMS applicationsRobert C. Gauthier, R. Niall Tait, Mike UbriacoDepartment of Electronics, Carleton University, Ottawa, Ontario Canada K1S 5B6 Department of Physics and Astronomy, Laurentian University, Sudbury, Ontario, Canada, P3E 2C6 We examine the light activation properties of micron sized gear structures fabricated using polysilicon surface micromachining techniques. The gears are held in place on a substrate through a capped anchor post and are free to rotate about the post. The light activation technique is modeled based on photon radiation pressure and the equation of motion of the gear is solved for this activation technique. Experimental measurements of torque and damping are found to be consistent with expected results for micrometer scale devices. Design optimization for optically actuated microstructures is discussed. Micro-motor design43X

LWTYZIncident Laser BeamGear PlanerWo b

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LaserObjectiveLensSubstrateGear on PostCCDFilterLight Source

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LWTYZIncident Laser BeamGear PlanerWo b46

LaserObjectiveLensSubstrateGear on PostCCDFilterLight Source47

Experimentally measured data points

From the slope of the line, the damping factor is determined to be b = 3.14x10-14 Nms. From the X axis intercept the stiction torque is determined to be 200 pNm. 48

Test chiplayout49

Other aspects of the micro-gear workMeshed gearsMicro-pumpsSlides not used in lecture 50ELEC 3105 Basic EM and Power EngineeringSelecting a Motors51

MOTOR SELECTION CHART52

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