1. ELEC 3105 Basic EM and Power Engineering
Stepping
Motors

2. Context: Lorentz Force
Please visit YouTube

3. Context: DC Motors
YouTube video

4. Context: Motor and Generator
Link here

5. Context: Electromagnetic Wave
Link here

6. Context: Brushless Motors
Here is another link to the brushless motor.
Gives more detail on motor concept and design.
Link here

7. ELEC 3105 Basic EM and Power Engineering
Stepping Motors

8. Stepping Motor
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. Stepping Motor Unipolar Motors Variable Reluctance Motors
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.
Unipolar Motors
Variable Reluctance
Motors
Bipolar Motors

10. Stepping Motor
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.
Variable Reluctance
Motors
Winding
Winding
Winding

11. Stepping Motor Disadvantages Resonance effects and long settling times
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. Stepping Motor 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. Stepping Motor Unipolar
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.
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
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.

14. Stepping Motor How to generate sequence electronically ?
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
Unipolar Motors
How to generate sequence electronically ?

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

16. Stepping Motor Bipolar Motors Single phase wiring diagram
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. Stepping Motor Variable Reluctance Motors
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.
Variable Reluctance
Motors
Winding
Winding
Winding

18. Stepping Motor
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.
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.
12 Step per revolution Hybrid Motor

19. You can feel the detent torque when you rotate the motor by hand.
Stepping 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.
12 Step per revolution Hybrid Motor

20. Stepping 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.
12 Step per revolution Hybrid Motor

21. Stepping Motor Full step, one phase on
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.
(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.
(d) same as (a) except rotated by 90 degrees
3 steps = 1/4 turn: 12 steps = one full revolution of shaft

22. Stepping Motor Full step, one phase on Step 1 2 3 4 5 6 7
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.
Step
(a) (b) (c) (d) (a) (b) (c)
3 steps = 1/4 turn: 12 steps = one full revolution of shaft

23. Stepping Motor Full step, two phases on Step 1 2 3 4 5 6 7
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.
Step
(a) (b) (c) (d) (a) (b) (c)

24. Stepping Motor Half step mode
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.
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.

25. Stepping Motor Half step profiled mode
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.
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.

26. Stepping Motor 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.

27. ELEC 3105 Basic EM and Power Engineering
MEMS Motors Linear

28. Previous slide extracted from “Principle of virtual work”

29. Previous slide extracted from “Principle of virtual work”

30. ELEC 3105 Basic EM and Power Engineering
MEMS Motors Rotation

34. ELEC 3105 Basic EM and Power Engineering
Laser Driven Motors

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.

41. ELEC 3105 Basic EM and Power Engineering
MEMS Laser Driven Motors

42. Robert C. Gauthier, R. Niall Tait, Mike Ubriaco
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. Micro-motor design Z Y T L W Incident Laser Beam  b Gear Plane r Wo X
 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 Wo 
 b

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

47. Experimentally measured data points
From the X axis intercept the stiction torque is determined to be 200 pNm.
From the slope of the line, the damping factor is determined to be b = 3.14x10-14 Nms.

48. Test chip
layout

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

50. Slides not used in lecture

51. ELEC 3105 Basic EM and Power Engineering
Selecting a Motors

52. MOTOR SELECTION CHART