motors & motor drivers
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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
Brushes
Stator (permanent magnets)
The most common. Toys, battery powered tools, electric machines.
6
Brush DC Motors
Identify:• Stator• Rotor• Brushes• Commentator
http://mot-sps.com/motor/tutorial/blac.html
7
Brush DC MotorHow does it work?
8
Pulse Width Modulation(PWM)
Centered PWM
9
Brushless DC Motor
http://mot-sps.com/motor/tutorial/blac.html
Identify:• Permanent Magnets• Rotor• Brushes• Commentator
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Brushless DC Motor
1. Housing
2. Laminated steel stack
3. Winding
4. Permanent magnet
5. Shaft
6. Ball bearing
1
2
3
4
5
6 6
Less common. Higher efficiency, less friction, less electrical noise. Requires electronic driver.
11
Brushless DC MotorHow does it work?
12
DC Servo Motor
http://www.societyofrobots.com/actuators_servos.shtml
A DC Servo Motor is a DC Motor withGears and Electronics with limited angular rotation (typically 90, 180 or 360º)
Why the addition of gears?• Nylon• Karbonite• Metal
Why electronics?• Digital• Analog
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DC Servo Motor
http://www.seattlerobotics.org/guide/servos.html
2.00 ms
1.50 ms
1.00 ms
0.50 ms
0.00 ms
0
1
2.00 ms
1.50 ms
1.00 ms
0.50 ms
0.00 ms
0
1
2.00 ms
1.50 ms
1.00 ms
0.50 ms
0.00 ms
0
1
1.50 ms: Neutral
1.00 ms: 0 degrees
2.00 ms: 180 degrees
Req
uir
es c
on
stan
t p
uls
ing
(
50
tim
es /
sec
on
d)
14
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
1
1
1
Full-Step Stepper Motor
1
16
Half-Step Stepper Motor
1
1
1
1
1
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Motor DriversSimple, 1- dc motor (brushes), on/off driver
D11N5817
(Schottky)M
M1DC Brush
+9 V
Q12222A(NPN) R1
1 k
On: to +9 VOff: to GND or
disconnected
B
E
C
18
Transistors
NPN Bipolar Transistor
PNP Bipolar TransistorC
B
E
C
B
E
http://www.kilowattclassroom.com/Archive/AN0007.pdf
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Motor DriversSimple, 1-motor, on/off driver
D11N5817
(Schottky)M
M1DC Brush
+9 V
Q22907A(PNP)
R21 k On: to GND or
disconnected Off: to +9 V
B
C
E
20
Motor DriversClassic Bipolar H-Bridge
D11N5817
(Schottky)
M
M1DC Brush
+9 V
Q22907A(PNP)
R21 k
B
C
E
R11 k
D21N5817
(Schottky)
Q12222A(NPN)
+9 V
Q42907A(PNP)
R41 k
B
C
E
R31 k
Q32222A(NPN)
D31N5817
(Schottky)
D41N5817
(Schottky)
On: to +9 VOff: to GND or
disconnected
On: to +9 VOff: to GND or
disconnected
On: to GND or disconnected
Off: to +9 V
On: to GND or disconnected
Off: to +9 V
B
E
C
B
E
C
Taken from Intermediate Robot Building by David Cook
21
Motor DriversClassic Bipolar H-Bridge
D11N5817
(Schottky)
M
M1DC Brush
Q22907A(PNP)
R21 k
B
C
E
R11 k
D21N5817
(Schottky)
Q12222A(NPN)
Q42907A(PNP)
R41 k
B
C
E
R31 k
Q32222A(NPN)
D31N5817
(Schottky)
D41N5817
(Schottky)
B
E
C
B
E
C
4427
1
2
3
4
8
7
6
5
NC
GND
IN A
IN B
NC
VDD
OUT A
OUT B
+9 V
from microcontroller
from microcontroller
GND
Taken from Intermediate Robot Building by David Cook
22
Motor DriversTypical H-Bridge Motor Driver
MM1
DC Brush
OUT B
+5 VDC
Disconnected or from microcontroller
From microcontroller
SN
754410
1
2
3
4
ENABLE A&B
OUTPUT A
INPUT A
GND
5
6
7
8
GND
INPUT B
OUTPUT B
VMOTOR
VLOGIC
OUTPUT C
INPUT C
GND
GND
INPUT D
OUTPUT D
ENABLE C&D
16
15
14
13
12
11
10
9
M
from microcontroller
M2DC Brush
Disconnected or from microcontroller
From microcontroller
From microcontroller
0.1 F220 F
+4.5 to +36 VDC
0.1 F220 F
Taken from Intermediate Robot Building by David Cook
23
H-Bridge LabComponents
1. Construct the H-Bridge as shown using components from your Robotics Kit.
2. Identify those configurations that short circuit the H-Bridge and on the enclosed table enter “Short Circuit” under the Results column
3. Show this table to either the Instructor or the TA before proceeding any further.
4. 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.)
5. 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.
24
Motor DriversClassic Bipolar H-Bridge
D11N5817
(Schottky)
M
M1DC Brush
+9 V
Q22907A(PNP)
R21 k
B
C
E
R11 k
D21N5817
(Schottky)
Q12222A(NPN)
+9 V
Q42907A(PNP)
R41 k
B
C
E
R31 k
Q32222A(NPN)
D31N5817
(Schottky)
D41N5817
(Schottky)
On: to +9 VOff: to GND or
disconnected
On: to +9 VOff: to GND or
disconnected
On: to GND or disconnected
Off: to +9 V
On: to GND or disconnected
Off: to +9 V
B
E
C
B
E
C
Taken from Intermediate Robot Building by David Cook
25
H-Bridge Test Results
# Q4 Q3 Q2 Q1 RESULT
1 Off Off Off Off
2 Off Off Off On
3 Off Off On Off
4 Off Off On On
5 Off On Off Off
6 Off On Off On
7 Off On On Off
8 Off On On On
9 On Off Off Off
10 On Off Off On
11 On Off On Off
12 On Off On On
13 On On Off Off
14 On On Off On
15 On On On Off
16 On On On On
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