motors & motor drivers

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


Identify:• Permanent Magnets• Rotor• Brushes• Commentator

10

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

13

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


15

1

1

1

Full-Step Stepper Motor

1

16

Half-Step Stepper Motor

1

1

1

1

1

17

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

19

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)


disconnected


disconnected

On: to GND or disconnected

Off: to +9 V


Off: to +9 V

B

E

C

B

E

C

Taken from Intermediate Robot Building by David Cook

21


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


GND


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


M2DC Brush

Disconnected or from microcontroller



0.1 F220 F

+4.5 to +36 VDC

0.1 F220 F


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


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)


disconnected


disconnected


Off: to +9 V


Off: to +9 V

B

E

C

B

E

C


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

motors & motor drivers

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