Motors

1
Motors Motor Drivers

• ECE 450

2
AC or DC Motors

• AC
• Few robots use AC except in factories
• Most of those that use AC first convert to DC
• DC
• Dominates in robotics
• Must be bidirectional

3
DC Motor Types

• Continuous-duty (run continuously when power
  supplied)
• Brushed
• Brushless
• Servo
• Intermittent-duty(power must be pulsed to run
  continuously)
• Stepper Motors

4
Motor Specifications

• Operating voltage
• Current draw
• Speed
• Torque
• Stalling or Running Torque

5
DC Motor Brush Motors
The most common. Toys, battery powered tools,
electric machines.
Stator (permanent magnets)
Brushes
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Brush DC Motors

• Identify
• Stator
• Rotor
• Brushes
• Commentator
• Permanent Magnets
• Armature
• Field

Electrical Engineering Terms Armature The
power-producing component of an alternator,
generator, dynamo or motor. The armature can be
on either the rotor or the stator. Field The
magnetic field component of an alternator,
generator, dynamo or motor. The field can be on
either the rotor or the stator and can be either
an electromagnet or a permanent magnet.
http//mot-sps.com/motor/tutorial/blac.html
7
Brush DC MotorHow does it work?
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Pulse Width Modulation (PWM)
Centered PWM
9
Brushless DC Motor

• Identify
• Permanent Magnets
• Rotor
• Brushes
• Commentator
• Armature
• Field

http//mot-sps.com/motor/tutorial/blac.html
10
Brushless DC Motor

• Laminated steel stack
• Winding
• Shaft
• Permanent Magnets

Less common. Higher efficiency, less friction,
less electrical noise. Requires electronic
driver.
11
Brushless DC MotorHow does it work?
12
DC Servo Motor
A DC Servo Motor is a DC Motor with Gears and
Electronics with limited angular rotation
(typically 90, 180 or 360º)

• Why the addition of gears?
• Nylon
• Karbonite
• Metal

• Why electronics?
• Digital
• Analog

http//www.societyofrobots.com/actuators_servos.sh
tml
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DC Servo Motor
Requires constant pulsing (? 50 times / second)
http//www.seattlerobotics.org/guide/servos.html
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Stepper Motor
Very common. Required driver. Very strong, when
not rotating. Easy to control rotor position.
Full Step
Half Step
http//mot-sps.com/motor/tutorial/blac.html
15
Full-Step Stepper Motor
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Half-Step Stepper Motor
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Using an Atmel Tiny2313 and SN754410 H-Bridge
http//www.instructables.com/id/Drive-a-Stepper-Mo
tor-with-an-AVR-Microprocessor/
18
Motor DriversSimple, 1- dc motor (brushes),
on/off driver
9 V
M1 DC Brush
D1 1N5817 (Schottky)
M
C
Q1 2222A (NPN)
B
On to 9 V Off to GND or disconnected
R1 1 k?
E
19
Transistors
PNP Bipolar Transistor
NPN Bipolar Transistor
http//www.kilowattclassroom.com/Archive/AN0007.pd
f
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Motor DriversSimple, 1-motor, on/off driver
9 V
R2 1 k?
E
On to GND or disconnected Off to 9 V
Q2 2907A (PNP)
B
C
M1 DC Brush
D1 1N5817 (Schottky)
M
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Motor DriversClassic Bipolar H-Bridge
On to GND or disconnected Off to 9 V
On to GND or disconnected Off to 9 V
Terminal 2
Terminal 4
Terminal 1
Terminal 3
On to 9 V Off to GND or disconnected
On to 9 V Off to GND or disconnected
Taken from Intermediate Robot Building by David
Cook
22
Motor DriversClassic Bipolar H-Bridge
9 V
R2 1 k?
R4 1 k?
E
E
D2 1N5817 (Schottky)
D4 1N5817 (Schottky)
B
B
C
Q4 2907A (PNP)
C
Q2 2907A (PNP)
from microcontroller
M
GND
Q3 2222A (NPN)
Q1 2222A (NPN)
from microcontroller
M1 DC Brush
R1 1 k?
R3 1 k?
C
C
D1 1N5817 (Schottky)
D3 1N5817 (Schottky)
B
B
E
E
Taken from Intermediate Robot Building by David
Cook
23
Motor DriversTypical H-Bridge Motor Driver
Taken from Intermediate Robot Building by David
Cook
24
H-Bridge LabComponents

• Construct the H-Bridge as shown using components
  from your Robotics Kit.
• Identify those configurations that short circuit
  the H-Bridge and on the enclosed table enter
  Short Circuit under the Results column
• Show this table to either the Instructor or the
  TA before proceeding any further.
• Using your H-Bridge, determine how the motor
  performs under each of the 16 different
  combinations of the four transistors
• DO NOT verify the short circuit combinations
  identified earlier!
• Pay attention to the transistor numbering in the
  table compared to the schematic.
• Be sure to identify whether or not the motor
  turns clockwise or counterclockwise
• For any breaking actions, identify which
  direction the motor is turning when breaking
  occurs. (In some configurations, breaking only
  occurs when the motor is turning in one direction
  but not the other.)
• Lab Report
• To drive larger motors, an H-Bridge with higher
  capacity currents would be required. Using the
  components in this lab, determine the
  component(s) that limit the current for driving a
  dc motor. Describe your analysis and results in
  your lab report.
• Include the table showing your results for the 16
  different combinations for powering the H-Bridge.

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Motor DriversClassic Bipolar H-Bridge
Taken from Intermediate Robot Building by David
Cook
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H-Bridge Test Results