1. Precision Sub-Fractional Motor Technologies:
How to Match the Best Technology for Your Application
Day 2: DC (Brush) PM & Piezo Motors, Advantages/Disadvantages, Examining Selected Precision Application Examples for Sub-Fractional Motors

2. Motor Technology in Precision Applications Using Small Motors
Day 1- Brushless PM
Day 2- Brush DC PM
Day 3- Stepper (focus on PM)
You are here

3. Brush DC PM Technology Review Outline
Introduction
History: Concept to Commercialization
Motor Technology Advantages
Motor Technology Disadvantages
Expected Enhancements, Changes, etc.
Suppliers of Note
Application List and/or Examples

4. History: Concept to Commercialization

5. The First DC Motor
Built by Thomas Davenport in his shop in Vermont in 1837.
He used magnetized railroad track spikes secured to a wooden drum for the rotor.
He purchased an electromagnet for the stator winding.
His wife sacrificed a silk dress for the wire insulation.
The electric source was a 3 cell Grove battery.
The invention was a technical success but a dismal commercial failure.

6. Brush DC motors have evolved into high-performance energy converters with the advent of permanent magnets.

7. Evolution of PM Brush DC Motors and Piezo Actuators
1950s – Alnico Torque Motor
Invention of the self-supporting motor coil, without need for an iron core (slotless) by Dr. Faulhaber
1960s – Ceramic Motor and Tachometer
1970s – Rare Earth Motor (SaCo)
1980s – Rare Earth Motor (NeoFe)
1990s – Bonded Rare Earth Motors in Higher Volume Applications
2000s- First piezo actuator developed by PiezoMotor AB, supported by Faulhaber and later in the decade introduced to MICROMO customers

8. Brush DC PM Basics: Advantages and Disadvantages

9. Brush DC PM Advantages

10. Brush DC PM Advantages
Getting a motor moving requires the proper timing of current in the motor windings. This function is called “motor commutation.”
The simplest commutation system is a mechanical one in the form of a metal ring electrically divided in segments, where each segment is connected to part of the motor windings.
As the commutator ring and windings rotate together, the timing of the current in the windings depends on which “commutator” segments are in contact with the metal brushes.

11. Brush DC PM Commutation: Simple, Inexpensive
DC Volts
to winding
current
to winding
Commutator
and Windings
Rotate Together
Brush Is
stationary
DC Volts

12. Brush DC PM Advantages
Simple linear relationship between voltage and speed. Easy to control.
Low cost approach to variable speed drives and positioning.
Well down the manufacturing cost curve.

13. Brush Motor Cross-section
Drive, Control
Circuitry
Rotating
Windings
Stationary
Magnets

14. Next two slides show relative simplicity of Brush control compared to Brushless DC motor control <Toggle back and forth to illustrate>

15. Brushless DC PM Motor, Drive, Feedback Connections
Rotating
Magnets
Sponsored by:

16. Brush DC PM Motor, Drive, Feedback Connections
Rotating
Windings
Drive
Circuitry

17. Brush DC PM Motor Exploded View
DC Voltage
Applied to
Brushes
‘Armature’
coils on iron core
rotates
Brushes ride
on ‘commutator,’
a segmented copper
ring rotating with armature
Brushes provide
current to rotating
windings through
the ‘commutator’

18. Dewalt Drill brush DC PM Motor Exploded View
Sponsored by:

19. Faulhaber Coreless DC Motor
Rotating coils (armature)
special winding (‘floating,’ no core)
Very low inductance
Very high speed
Challenge to wind stator coils

20. Faulhaber Flat Coreless DC Motor
Stator, Flat
No Iron Core
Commutation
Board - Brushes
Rotor
Magnets
Planetary
Gears
MICROMO 1512-SR Motor
Sponsored by:

21. Faulhaber Coreless DC Motor
Stator Windings
Basket Style, No Slots
or Stator Iron
Graphite Brushes and Holders
Rotor
Core
MICROMO 3890 BDC PM
High Power
Rotor
Magnets
High strength
Neo
Sponsored by:

22. Linear Device: Easier To Control, More Predictable
The linear nature of the operating curve compared
with AC induction
Technology makes it easier to control
Speed
Increases
Linearly
with
Voltage
Sponsored by:

23. Linear Device: Easier To Control, More Predictable
Stall
Current
Torque
Increases
Linearly with
Current
Sponsored by:

24. Trade-offs Are Inevitable
Note that max power and max efficiency and operating point rarely coincide
Sponsored by:

25. Brush PM Motor Torque/Speed Curve
No Load
Speed
CONTINUOUS
TORQUE ZONE
Intermittent Torque Zone
Peak
Torque

26. Brush DC PM Disadvantages

27. Negative Impact on Environment
Brush DC PM Disadvantages
Negative Impact on Environment
Brush-to-commutator (metal-on-metal) sparking presents potential hazard.
Brush-to-commutator (metal-on-metal) also creates excessive EMI/RFI electrical noise/interference.
Brush wear creates particle contamination.
Limited speed range due to mechanical brush-commutator resistance as brushes ‘ride’ on the metal commutator.

28. Brush DC PM Disadvantages
Electrical Wear of Brushes and Commutator Ring Is Not Predictable
Wear characteristics non-linear and depend on current, motor inductance, temperature, and other environmental conditions.
Wear varies from 2nd power to 4th power.

29. Brush DC PM Disadvantages
Mechanical Wear Is Not Easily Predicted
Brush DC motors have been used for over 120 years, and we still do not know how to predict brush wear with any mathematical certainty.
It is operating life uncertainty that has plagued the brush DC motor.
Stiction creates initial resistance to motion.

30. Enhancements, Improvements, etc., to Brush DC PM Technology

31. Brush DC PM
Better Brushes
Better Materials
Motor Consistent Manufacturing Processes

32. Brush DC PM
Material improvements in magnets (stronger, more rugged), iron (better steels), and insulation (magnet wire, potting, slot liners, separators) will continue to evolve, raising motor performance characteristics.
Application of new, higher performing plastics and other materials to replace aluminum and metal parts will help lower manufacturing costs.

33. Brush DC PM Suppliers of Note

34. Major Supplier Brush DC Motors
Brush Motor Supplier
Affiliate Company or HQ Country
Alcatel
Germany
Allied Motion
USA
Astromec
Baldor Electric
ABB
Barber-Colman
Baumueller
Bison Gear
Bodine Electric
Bosch
Buehler Motors
Canon
Japan CE
India
China Dragon
China
Chongsha
Copal Electric
Crouzet
France
DCM
Dumore
ElectroCraft
EAD
Sponsored by:

35. Major Supplier Brush DC Motors
Brush Motor Supplier
Affiliate Company or HQ Country
Foster
Danaher
Fufa Motor
China
General Industrial
USA
Globe Motors
Groschopp
Germany
GSK
Harowe Servo
Heidenhein
Hitachi
Japan
IMC Hansen
Emerson
Johnson Electric
King Clean
Leeson Electric
Regal Beloit
Lexel
Mabuchi
Mabuchi Motors
Mamco
Maxon Motors
Switzerland
MICROMO (FAULHABER Group)
USA, Germany
Moog Motion Components Group
Motor Products
Sponsored by:

36. Major Supplier Brush DC Motors
Brush Motor Supplier
Affiliate Company or HQ Country
MTI
SLI
Muirhead Vactric UK
Pan Air
Taiwan
Panasonic
Japan
Parvex
France
Pittman Motors
Ametek
PMI
Danaher/Kollmorgen
Portescap
Danaher
RAE
USA
Saggu
India
Sanyo Denki
Sawamura Denki
SEM
Shaanxi Beyond
China
Siemens Energy & Automation
Germany
Tamagawa Seiki
Telco
Tiebaq
Torque Systems
ITT
Toshiba
Tyoki
Sponsored by:

37. Applications for Brush DC PM Motors

38. Application Characteristics Favorable to Brush DC Motors
Speed control with low cost.
Speeds under 2000 rpm for larger motors but capable of 20,000 rpm in micro motor sizes.
Lower duty cycle applications.
Fractional horsepower needs.
Power Source: Battery powered.

39. The Universe of Application Segments
Brush DC PM technology is broadly used in many major application segments:
Transportation
Personal Vehicles
Commercial Vehicles
Off-Road Vehicles

40. motors in a car are Brush DC PM
About 80% of electric
motors in a car are Brush DC PM

41. Sample of Automotive Applications
Door Locks Window Lifts
Seat
Adjust
Engine
Fan
Climate Control
Fuel and Exhaust

42. The Universe of Application Segments
Brush DC PM technology is broadly used in many major application segments:
Factory Automation
Conveyor Systems
General Industrial Equipment
Material Handling
Packaging
Semiconductor Processing Equipment
Special Industrial Equipment

43. The Universe of Application Segments
Brush DM PM technology…more application segments with broad penetration:
Medical Equipment
Air moving (Sleep Apnea, Ventilators, Respirators, etc.)
Diagnostic Equipment (Centrifuges, Scanning Machines, etc.)
Tools, Hand Helds, Surgery and Dental
Mobility Equipment
Medical:
Pump and
Ventilator
Motors
Sponsored by:

44. The Universe of Application Segments
Brush DC PM technology application segments with moderate penetration:
Aerospace
Commercial Aviation
Military Aviation
Missiles/Drones/UAVs
Military/Defense
Vehicles
UAVs and UGVs
Autonomous Vehicles in Commercial, Security, Farming Applications

45. The Universe of Application Segments
Brush DC PM technology application segments in home and commercial uses:
Home Appliances
Hand Tools
Commercial and Industrial HVAC
Sponsored by:

46. Precision Applications Using Small Motors

47. Remote Presence Robot Challenge?
Need expertise located remotely with a patient in immediate need? Need remote control to move about, see, hear, and be seen and be heard? Need to be able to operate on batteries; quiet; reliable?
Motor Need?
Highly reliable, efficient, lighter weight, small, higher power per volume.
Motion Solution?
Coreless brush motor, geared
(planetary, low backlash, precise)
to translate higher speed to higher
torque. Electronics for precision camera positioning; mitigation of EMI/RFI emissions. Innovative feedback combining potentiometers and magnetic encoders to achieve absolute and relative positioning inexpensively.

48. Autonomous All Terrain Vehicle
Challenge?
How do you go where it may be unsafe or difficult for humans to assess a problem; rescue miners or earthquake victims; inspect or analyze farm land; inspect nuclear plants; inspect construction in progress or hazardous industrial areas? All in extremely varied and at times difficult terrain?
Motor Need?
Operate at very low voltages (battery, solar powered); high torque per weight; easy to
control.
Motion Solution?
Coreless brush motor, geared (planetary, low backlash, precise) with precious metal commutator for minimum size and ability to operate at lower voltages. Small and light weight are also important in mobile applications.

49. Rosetta Comet Exploring Space Probe
Challenge?
Ever land on a comet orbiting the Sun for exploration? No one has! So…you need to be ready for almost any situation with motorized sub-systems for controlled landing, anchoring, orienting the landing probe.
Landing Probe
Motor Need?
Reliability of the highest order; simple controls; space ready. Small, lightweight. High torque per volume.
Motion Solution?
14 brush DC motors and controls, geared
(planetary, low backlash, precise)
to translate higher speed to higher
torque. Motor functions include: precision camera positioning to search for good landing site; act as motors and generators to capture precious power from kinetic motion; draw anchor lines taught; actuating analytical instruments.
Anchoring
Actuator

50. Piezo Actuators Overview
Piezo technology, while not electromagnetic in nature, is an interesting and alternative approach to actuation where physical contact (like brushes in a DC PM motor) help convey the energy needed for motion.
Like a DC motor, piezo technology is energized by applying a voltage to the mechanism and that electrical energy is converted to mechanical energy in the form of vibrations.
By controlling the application of the energy and the structure of the stationary and moving elements, linear or rotary motion is initiated. Many camera auto-focuses use piezo rotating motors. Metrology applications (small movements) are also an important area of use.

51. Piezo Advantages/Disadvantages
Capable of very small moves (nano motion).
Very high holding torque with almost no power consumed.
Fast response (micro-seconds) compared to electromagnetic devices (high milli-seconds).
Operate in harsh environments such as vacuums, extreme cold, high magnetic fields, high energy radiation where typical electro-magnetic and PM actuators require special designs or materials.
Disadvantages (compared to electromagnetic devices)
Operate primarily at very slow speeds.
Travel is limited.
Limited at high temperature levels (200 deg C).
Made of brittle material.
High hysteresis (does not return to original position) and creep, but both controllable.

52. Surgical Robot Inside An MRI
Challenge?
If you can position a surgical probe remotely, while you view an active MRI image you can increase the accuracy of the surgical procedure and reduce surgery time. But the extremely strong magnetic field of the MRI
creates significant challenges for standard
electric motor-driven robots. Screws, gears,
motors become hazards within the MRI unit.
Motor Need?
Unaffected by the strong magnetic field of the MRI machine. Accurate, micro positioning. Audibly and electrically quiet.
Motion Solution?
Piezo-electric ceramic actuator. Creates motion
when a voltage is applied. No magnetic/metal parts.
Special design to increase speed. Inherently safe as loss of power brings
the motion to a stop.