Stepping Motors 1

2 Please visit YouTube

3 YouTube video

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

Stepping Motors 7

8 Step 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.

9 Variable Reluctance Motors Unipolar Motors Bipolar Motors

10 The 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 Winding Winding Variable Reluctance Motors

11 Advantages 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

12 Types 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.

13 In 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 off a2 off on off off a3 off off on off a4 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 off b2 off on on off b3 off off on on b4 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 off b2 off on on off a3 off off on off b3 off off on on a4 off off off on b4 on off off on This gives twice as many stationary positions between steps Unipolar

14 The 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 Winding 1b Winding 2a Winding 2b time ---> Winding 1a Winding 1b Winding 2a Winding 2b time ---> Unipolar Motors How to generate sequence electronically ?

15 Winding 1a Winding 1b Winding 2a Winding 2b time ---> Winding 1a Winding 1b Winding 2a Winding 2b time ---> Unipolar Motors How to generate sequence? Digital sequential machine based on flip-flops,... Sequence to generate

16 These 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 diagram

17 The 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 Winding Winding Variable Reluctance Motors

18 12 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.

19 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.

20 12 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.

21 (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 degrees 3 steps = 1/4 turn: 12 steps = one full revolution of shaft Full step, one phase on

22 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 (a) (b) (c) (d) (a) (b) (c) Full step, one phase on

23 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. Full step, two phases on Step (a) (b) (c) (d) (a) (b) (c)

24 Half 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.

25 Half 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.

26 Microstep mode Finer 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.

MEMS Motors Linear 27

28 Previous slide extracted from “Principle of virtual work”

29 Previous slide extracted from “Principle of virtual work”

MEMS Motors Rotation 30

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Laser Driven Motors 34

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36 Cylinder orientation in focused laser beam

37 Torque versus orientation angle Cylinder in focused laser beam

38 Torque versus orientation angle Cylinder in focused laser beam

39 Step motor operation of cylinder in laser beams Equations of motion

40 Smooth Rotating motor operation of cylinder in laser beams.

MEMS Laser Driven Motors 41

42 Activation of micro-components using light for MEMS and MOEMS applications Robert C. Gauthier, R. Niall Tait, Mike Ubriaco Department 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.

43 X L W T Y Z Incident Laser Beam Gear Plane r WoWo   b b

44 Laser Objective Lens Substrate Gear on Post CCD Filter Light Source

45 X L W T Y Z Incident Laser Beam Gear Plane r WoWo  bb

46 Laser Objective Lens Substrate Gear on Post CCD Filter Light Source

47 Experimentally measured data points From the slope of the line, the damping factor is determined to be b = 3.14x Nms. From the X axis intercept the stiction torque is determined to be 200 pN  m.

48 Test chip layout

49 Other aspects of the micro-gear work Meshed gears Micro-pumps

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Selecting a Motors 51

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