1

Gyro PowerBoard A gyroscopic single wheeled transportation device.

Final Design Report EEL4924 – Electrical Engineering Design 2

April 19, 2014

Team Members: Sara Karimi, Jordan Williams

PROJECT ABSTRACT

For our project we built a single-wheel transportation device which combines the

portability of a skateboard with the functionality of a Segway. The single-drive wheel is

mounted directly in the center of the driver’s legs and the driver will ride facing laterally

with respect to the motion of our device, as they would on a skateboard. A

microprocessor is used to stabilize and facilitate automated motion, given gyroscopic

and acceleration information collected from on-board sensors. The rider will tilt the

board forward in order to increase his/her velocity, and tilt back to slow down, stop or

even reverse direction. The main microprocessor output is fed to a motor drive control

which contains a microcontroller used to generate the PWM signals for BLDC motor

operation.

2

TABLE OF CONTENTS

page

LIST OF TABLES ............................................................................................................ 2

LIST OF FIGURES .......................................................................................................... 2

INTRODUCTION ............................................................................................................. 4

Project Features ....................................................................................................... 4

Analysis of Competitive Products: ............................................................................ 5

TECHNOLOGY SELECTION .......................................................................................... 6

IMPLEMENTATION METHODOLOGY ........................................................................... 8

Project Architecture .................................................................................................. 8 Bill of Materials ....................................................................................................... 16 Implementation Timeframe ..................................................................................... 17

REFERENCES .............................................................................................................. 19

LIST OF TABLES

Table page Table 3-1: Bill of Materials ............................................................................................. 16

Table 3-2: Major Activity List with Anticipated Start Date and Task Duration ................ 17

LIST OF FIGURES

Figure page Figure 3-1: Project Block Diagram .................................................................................. 9

Figure 3-2: Stabilization Schematic Diagram ................................................................ 10

Figure 3-3: Voltage Supply Regulation Schematic Diagram .......................................... 11

Figure 3-4: Motor Controller (Processor) Schematic Diagram ....................................... 12

Figure 3-5: Motor Controller (Drive) Schematic Diagram .............................................. 13

3

Figure 3-6: Motor Controller Software Flowchart ........................................................... 14

Figure 3-7: Stabilization Software Flowchart ................................................................. 15

Figure 4-2: Gantt chart of Anticipated Project and Activity Duration .............................. 18

4

CHAPTER 1

INTRODUCTION

Our board is intended for riders of all abilities for both leisure and short-distance

commuting purposes. To keep even the most inexperienced rider balanced on the

board, our device relies on gyroscopic stabilization via PID control. This will allow the

user to balance on the wheel axis when stationary and to remain balanced while

controlling the motor speed with their physical orientation.

Most electrically powered transportation systems in the market today are large

and bulky; our device will be a lightweight, portable alternative to these products. Other

similar solutions are currently being developed, but we hope to differentiate our product

in the future by integrating solar charging of the device by placing solar cells on the

deck of the board. In the future we are also considering developing a wireless hand-

held speed control which will allow the rider to continually vary his/her maximum

possible speed and which provides the rider with pertinent information such as his/her

current speed, remaining battery life and GPS location of the board.

Project Features

Although the project could be expanded to include many advanced features for

monitoring and improving general usability we have decided to limit the feature set to

only those required for basic functionality. We have designed the board in such a way

that these additional features could be easily added without changing the existing

circuitry or structure of the board.

The functional features applicable to the project at hand are as follows:

A vehicle with one wheel that provides a self-balancing surface to carry

a payload (in this case a rider).

5

The vehicle’s velocity must be controllable only by moving the deck of

the board.

The vehicle must mechanically contain all electronics batteries and

additional operational parts in order to maintain a clean deck for the

rider to stand.

The vehicle must be capable of steering with forces on the deck

perpendicular to the direction of motion

The vehicle must have a speed and battery life that is acceptable for

both indoor and outdoor operation.

The vehicle must be of a reasonable size and weight such that

transportation by hand is possible if necessary.

Analysis of Competitive Products:

Investigation of competitive products leads us to two major competitors. First and

in existence for the longest time is the Segway. It is a two wheeled balancing vehicle

where the rider faces parallel to the direction of motion. This product is heavy and is not

as portable as the Gyro PowerBoard. Until recently the only other products with a single

wheel like the Gyro PowerBoard were built by students and engineers and there were

only a handful in existence. The oldest one we could find was built in 2008.

Coincidently, during the course of construction of our product a company unveiled a

prototype and raised over $600,000 to begin construction of a commercial version of the

board. There advertised price was approximately $1700 per unit. The best advantage

of their product was its weight but there was a significant trade off with respect to

battery life.

6

CHAPTER 2 TECHNOLOGY SELECTION

Our design was able to respond quickly to changes in stability and provide

enough torque for the motor to compensate. It included the following major

technologies.

Main microprocessor must have a fast enough clock speed to make

adjustments to changes in sensor readings to keep the board stable. For

this processor we decided to use a TI MSP430F5152. It was capable of

operating at speeds of up to 25MHz and had plenty of communication

interfaces to interface with the other processor and with our digital IMU

sensor.

The digital IMU was chosen because it provided both accelerometer and

gyroscope readings in a small and convenient package. A single package

eliminated the need to align multiple sensors as well as saved on board

space.

The motor controller is based on all N type MOSFETS which are driven by

high side low side drivers attached to a TI MSP430F5340. This processor

was chosen to because of its 25MHz clock speed and special PWM port

as well as its ability to interface with the main balancing microprocessor.

We chose to use all N type MOSFETS because they are well known to

provide the best power transmission in applications such as this

7

An aluminum frame was designed to provide a safe area to house all of

the electronics as well as a sufficient base to mount the mechanical

system while still remaining light enough to consider portable.

Energy storage is provided by 16 LiFePO4 battery cells, each with a

nominal voltage of 3.2V and capacity of 10Ah. The battery should provide

enough power for continued operation up to 40 minutes, although exact

capacities have yet to be determined. Low-voltage shut-off and over-

current protection circuitry should was added to ensure safe management

of the battery.

The motor selected was a 700 watt BLDC motor. It was designed for

automation applications but we felt it would work well for our application.

8

CHAPTER 3 IMPLEMENTATION METHODOLOGY

Project Architecture

The project was designed to have all of the electronics on 4 separate boards.

These electronics were intended to work together to facilitate the successful operation

of the vehicle. In addition to the electronics there are a few other systems in play which

allow the board to function.

The main controller board includes the digital IMU and the controller

microprocessor. The IMU takes gyro and accelerometer readings which are read by the

control microprocessor via SPI. With these readings the control microprocessor decides

on the appropriate torque and direction and sends them to the other side of the vehicle

where the motor control is listening via UART.

The motor controller board consists of high side low side drivers as well as 6 N

channel MOSFETS, a control processor and associated current sense circuitry. This

board is responsible for taking torque and direction commands from the controller and

commutating the motor accordingly. This processor also initiates electronic braking if it

is required to expeditiously change direction.

Both processors require 3.3V, the drivers 12V, the motor’s hall sensors require

5V and the actual drive voltage required on the motor is 48V. In order to make our

vehicle as stream lined as possible we created an independent power supply board to

be housed near the batteries. It is the responsibility of the circuitry on this board to step

down the battery voltage from 48V to the necessary levels which are then distributed

around the vehicle. The exception is the 48V power for the motor is delivered directly

from the BMS to the motor controller.

9

The fourth and final electronic system involved in the functionality of the Gyro

PowerBorad is the battery management system of BMS. This circuit monitors each cell

individually as well as the temperature of the pack and the charge and discharge

current. It waits for any irregularities and takes the batteries offline before something is

damaged.

Mechanically the motor uses a belt with a 4:1 reduction ratio to turn the wheel.

This gives us the appropriate mechanical advantage for a vehicle of this size. The wheel

is mounted on an axle in the center of the frame. A 12x7” pneumatic tire was chosen to

ensure the appropriate stability to turn ability ratio while still providing a smooth ride.

Figure 3-1: Project Block Diagram

As shown above in figure 4-1, the project consists of two main components—the

stabilization control and motor control. Communication between the two modules takes

10

place via UART. Schematic layouts of each component, in addition to the voltage

regulation system, are shown below.

Figure 3-2: Stabilization Schematic Diagram

NC1

NC2

NC3

NC4

NC5

NC6

AUX_CL7

VDDIO8

SDO/AD09

REGOUT10

FSYNC11

INT12

VDD

13NC

14NC

15NC

16NC

17GN

D18

RESV19

RESV20

AUX_DA21

nCS22

SCL/SCLK23

SDA/SDI24

IMU1

IMU

P1.0

/PM

_UCA

0CLK

/PM

_UCB

0STE

/A0*

/CB0

1P1

.1/P

M_U

CA0T

XD/P

M_U

CA0S

IMO/

A1*/

CB2

P1.2

/PM

_UCA

0RXD

/PM

_UCA

0SOM

I/A2*

/CB2

3P1

.3/P

M_U

CB0C

LK/P

M_U

CA0S

TE/A

3*/C

B34

P1.4

/PM

_UCB

0SIM

O/PM

_UCB

0SDA

/A4*

/CB4

5P1

.5/P

M_U

CB0S

OMI/P

M_U

CB0S

CL/A

5*/C

B56

PJ.0

/SM

CLK/

TDO/

CB6

7PJ

.1/M

CLK/

TDI/T

CLK/

CB7

8PJ

.2/A

DC10

CLK/

TMS/

CB8

9PJ

.3/A

CLK/

TCK/

CB9

10P1

.6/P

M_T

D0.0

11P1

.7/P

M_T

D0.1

12P2

.0/P

M_T

D0.2

13P2

.1/P

M_T

D1.0

14P2

.2/P

M_T

D1.1

15P2

.3/P

M_T

D1.2

16DV

IO17

DVSS

18P2

.4/P

M_T

EC0C

LR/P

M_T

EC0F

LT2/

PM_T

D0.0

19P2

.5/P

M_T

EC0F

LT0/

PM_T

D0.1

20P2

.6/P

M_T

EC0F

LT1/

PM_T

D0.2

21

P2.7

/PM

_TEC

1CLR

/PM

_TEC

1FLT

1/PM

_TD1

.022

P3.0

/PM

_TEC

1FLT

2/PM

_TD1

.123

P3.1

/PM

_TEC

1FLT

0/PM

_TD1

.224

VCOR

E25

DVSS

26

DVCC

27

PJ.6

/TD1

CLK/

TD0.

1/CB

1528

P3.2

/PM

_TD0

.0/P

M_S

MCL

K/CB

1429

P3.3

/PM

_TA0

CLK/

PM_C

BOUT

/CB1

330

P3.4

/PM

_TD0

CLK/

PM_M

CLK

31

TEST

/SBW

TCK

32

*RST

/NM

I/SBW

TDIO

33

P3.5

/PM

_TA0

.2/A

8*/V

REF+

*/CB

1234

P3.6

/PM

_TA0

.1/A

7*/V

REF-

*/CB

1135

P3.7

/PM

_TA0

.0/A

6*/C

B10

36

AVCC

37

PJ.4

/XOU

T38

PJ.5

/XIN

39

AVSS

40

EPAD

41

uP MSP

430F

5152

_RSB

_

.1u

C_IM

U_Vd

dCa

p2

3.3V

GND

GND

.1u

C_IM

U_re

gCa

p2

10n

C_IM

U_Vd

dio

Cap2

GND

GND

3.3V

GND

GND

GND

GND

3.3V

3.3V

3.3V 1

2

P_UA

RT_M

CHe

ader

2H

12

34

56

78

910

1112

1314

JTAG

_pro

g

Head

er 7

X2

GND

3.3V

10u

C2_J

TAG

Cap2

.1u

C3_J

TAG

Cap2

2.2n

C1_J

TAG

Cap2

47k

R1_J

TAG

Res1

GND

GND

GND

GND

3.3V

GND

11

22

powe

r

2pin

_con

necto

r

10u

C1_3

.3V

Cap2

.1u

C2_3

.3V

Cap2

GND

GND

11

Figure 3-3: Voltage Supply Regulation Schematic Diagram

10uF

Cin

_2

22uF

Cout_

2

620pF

Css

_2

L2

Rfb

1_2

Rfb

2_1

Rpg_2

EN

13

SS

/TR

9

GN

D15

FB5

DE

F8

FS

W7

SW1

VIN

11

VO

S14

PG

4

U2

27nF

Cboot_

1

1.8

nF

Cco

mp_1

22pF

Chf_

1

1uF

Cin

_1

22uF

Cout_

1

2.2

uF

Cout1

470pF

Cra

mp_1

2.2

uF

Crs

t_1

10nF

Css

_1

470nF

Cvcc

_1

790m

V

D1

27uH

L1

100V

M1

36.5

k

Rco

mp_1

1.9

1k

Rfb

b_1

16.9

k

Rfb

t_1

200k

Rra

mp_1

30m

Rsn

s_1

10.7

k

Rt_

1

2.6

1k

Ruv1

49.9

k

Ruv2

VIN1

EN

2

SS

3

RA

MP

4

RT

/SY

NC

5

GND6

COMP7

FB

8

OU

T9

RE

S/D

ITH

10

CS

G11

CS

12

SW

13

HG

14

BO

OT

15

VC

C16

LM

50

88

MH

X-1

/NO

PB

U1

Cin

_3

Cout_

3

Css

_3

L3

Rfb

1_3

Rfb

2_3

Rpg_3

EN

13

SS

/TR

9

GN

D15

FB5

DE

F8

FS

W7

SW1

VIN

11

VO

S14

PG

4

U3

11

22

33

44

mco

ntr

ol_

connec

t4pin

_co

nnec

tor

12V

5V

3.3

V

12V

5V

3.3

VG

ND

11

22

input_

connec

t2pin

_co

nnec

tor

11

22

stab

iliz

atio

n_co

nnec

t2pin

_co

nnec

tor

3.3

VG

ND

12

Figure 3-4: Motor Controller (Processor) Schematic Diagram

P6.3

/CB

3/A

31

P6.4

/CB

4/A

42

P6.5

/CB

5/A

53

P5.0

/VR

EF

+/V

eRE

F+

/A8

4

P5.1

/VR

EF

-/V

eRE

F-/

A9

5

AV

CC

16

P5.4

/XIN

7

P5.5

/XO

UT

8

AV

SS

19

DV

CC

110

DV

SS

111

VC

OR

E12

P1.0

/TA

0C

LK

/AC

LK

13

P1.1

/TA

0.0

14

P1.2

/TA

0.1

15

P1.3

/TA

0.2

16

P1.4

/TA

0.3

17

P1.5

/TA

0.4

18

P1.6

/TA

1C

LK

/CB

OU

T19

P1.7

/TA

1.0

20

P2.7

/UC

B0S

TE

/UC

A0C

LK

21

P3.0

/UC

B0S

IMO

/UC

B0S

DA

22

P3.1

/UC

B0S

OM

I/U

CB

0S

CL

23

P3.2

/UC

B0C

LK

/UC

A0S

TE

24

P3.3

/UC

A0T

XD

/UC

A0S

IMO

25

P3.4

/UC

A0R

XD

/UC

A0S

OM

I26

P4.0

/PM

_U

CB

1S

TE

/PM

_U

CA

1C

LK

27

P4.1

/PM

_U

CB

1S

IMO

/PM

_U

CB

1S

DA

28

P4.2

/PM

_U

CB

1S

OM

I/P

M_U

CB

1S

CL

29

P4.3

/PM

_U

CB

1C

LK

/PM

_U

CA

1S

TE

30

DV

SS

231

DV

CC

232

P4.4

/PM

_U

CA

1T

XD

/PM

_U

CA

1S

IMO

33

P4.5

/PM

_U

CA

1R

XD

/PM

_U

CA

1S

OM

I34

P4.6

/PM

_N

ON

E35

P4.7

/PM

_N

ON

E36

P5.7

/TB

0.1

37

DV

SS

338

P5.2

/XT

2IN

39

P5.3

/XT

2O

UT

40

TE

ST

/SB

WT

CK

41

PJ.

0/T

DO

42

PJ.

1/T

DI/

TC

LK

43

PJ.

2/T

MS

44

PJ.

3/T

CK

45

*R

ST

/NM

I/S

BW

TD

IO46

P6.1

/CB

1/A

147

P6.2

/CB

2/A

248

EP

AD

49

uP

MS

P430F

5340_R

GZ

12

34

56

78

910

11

12

13

14

JTA

G

Hea

der

7X

2

47k

RJT

Res

1.1

u

CJT

3C

ap2

10u

CJT

2C

ap2

2.2

n

CJT

1C

ap2GN

D

GN

D

GN

DG

ND

3.3

V

3.3

V

GN

D

GN

D

3.3

VGN

DG

ND

3.3

V

3.3

V

11

22

33

44

55

Hal

l_co

nn

ect

5pin

_co

nnec

tor

5V

GN

D

12

UA

RT

Hea

der

2H

20K

Rhal

U2

Res

1

20K

Rhal

V2

Res

1

20K

Rhal

W2

Res

1

10K

Rhal

U1

Res

1

10K

Rhal

V1

Res

1

10K

Rhal

W1

Res

1

GN

D

GN

D

GN

D

GN

D

10u

C1_5V

Cap

21u

C2_5V

Cap

2

5V

GN

DG

ND

11

22

33

pow

er3/5

V

3pin

_co

nnec

tor

OU

T1

GN

D2

V+

3V

IN+

4V

IN-

5

isen

se1

INA

19

8_

DB

V_

5

3.3

V

GN

D

OU

T1

GN

D2

V+

3V

IN+

4V

IN-

5

isen

se2

INA

19

8_

DB

V_

5

OU

T1

GN

D2

V+

3V

IN+

4V

IN-

5

isen

se3

INA

19

8_

DB

V_

5

3.3

V

3.3

V

GN

D

GN

D

12

34

56

78

910

11

12

13

14

15

16

17

18

19

20

PW

Mport

Hea

der

10X

2

12

34

56

78

910

11

12

13

14

15

16

17

18

19

20

isen

se_port

Hea

der

10X

2

5V

3.3

VG

ND

10u

C1_3V

Cap

21u

C2_3V

Cap

2

3.3

V

GN

DG

ND

pw

mU

H

pw

mU

Hpw

mV

Hpw

mW

Hpw

mU

L

pw

mW

Lpw

mV

L

pw

mV

H

pw

mW

H

pw

mU

L

pw

mW

L

pw

mV

L

sense1

sense2

sense3

sense

1

sense

2

sense

3

GN

D

13

Figure 3-5: Motor Controller (Drive) Schematic Diagram

VDD1

HB2

HO3

HS4

HI5

LI6

VSS7

LO8

EPADEPAD

Drv_U

UCC27210_DDA_8

VDD1

HB2

HO3

HS4

HI5

LI6

VSS7

LO8

EPADEPAD

Drv_V

UCC27210_DDA_8

VDD1

HB2

HO3

HS4

HI5

LI6

VSS7

LO8

EPADEPAD

Drv_W

UCC27210_DDA_8

100

Rg_ULs

Res1

1K

Rg_ULpRes1

100

RgVLs

Res1

1K

RgVLpRes1

1K

RgWLs

Res1

1K

RgWLpRes1

1K

RgUHs

Res1

1K

RgUHpRes1

100

RgVHs

Res1

1K

RgVHpRes1

1K

RgWHs

Res1

1K

RgWHpRes1

GND

48V

48V

48V

12V

12V

12V

.1u

CU1Cap2

10u

CU2Cap2

GND GND

.1u

CV1Cap2

10u

CV2Cap2

.1u

CW1Cap2

10u

CW2Cap2

GND

GND

GND

GND

GND

11

22

11

22

shunt1shunt_resistor

GND_48V

po

wer

po

wer

gn

dg

nd

48Vpower

2pin_molex_50A_sch48V

GND_48V

WW

VV

UU

motor

3pin_molex_50A_sch

11

22

33

44

55

6677

88

di_VW

TI_PDIP8_diode

11

22

33

44

55

6677

88

di_UV

TI_PDIP8_diode

10u

CbsUCap2

10u

CbsWCap2

10u

CbsVCap2

220u

C1_48VCap

220u

C2_48VCap

GND_48V

11

22

11

22

shunt2shunt_resistor

11

22

11

22

shunt3shunt_resistor

GND_48V

GND_48V

1 23 45 67 89 1011 1213 1415 1617 1819 20

isense_port

Header 10X2

1 23 45 67 89 1011 1213 1415 1617 1819 20

PWMport

Header 10X2

11

22

power12V

2pin_connector

GND12V

sense1sense2sense3

sense1

sense2

sense3

D

G

S

fetUHE3_heatsink

D

G

S

fetULE3_heatsink

D

G

S

fetVHE3_heatsink

D

G

S

fetVLE3_heatsink

D

G

S

fetWHE3_heatsink

D

G

S

fetWLE3_heatsink

14

Necessary programming for the motor control circuit involved the code written to

switch the PWM outputs to commutate the motor, as well as to receive values from the

stabilization system to set the motor torque. A flowchart of the implemented software

for this system is shown below.

Figure 3-6: Motor Controller Software Flowchart

15

For the stabilization system, readings from the IMU had to be taken periodically

and PID control implemented in order to determine the proper torque for the motor. A

flowchart of this software is shown below.

Figure 3-7: Stabilization Software Flowchart

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Bill of Materials

Table 3-1: Bill of Materials

Item Price

MSP430F5152 (uP) $3.00

MSP430F5340 (uP) $4.00

MPU-6500 (IMU) $12.00

LM5088 (Buck Converter) $4.00

TPS62140RGTR (Buck

Converter)

(2)$3.00

Miscellaneous passive

electronic components

$150.00

PCB Manufacturing $200.00

Aluminum Frame $250.00

Wheel and tire $70.00

BLDC 700 watt Motor $120.00

Drive components $150.00

Batteries $400.00

Battery Charger $70.00

Miscellaneous hardware $60.00

INA98 (Current Shunt Monitor) (3) $2.00

UCC27211 (Driver) (3) $2.00

CSD19531KCS(MOSFET) (6) $5.00

Total (EST) $1,541.00

17

Implementation Timeframe

The allotted time to complete the project is approximately three months. In order

to ensure successful completion of the project as desired it is important to create a

detailed schedule and attempt to adhere to it as much as possible. The most important

reason to schedule the project fully ahead of time is to minimize lag time waiting for

things out of our control such as supply lead time and third party manufacturing. In table

4-2 we have provided a preliminary activity list with start dates and durations. These

values have been portray in a Gantt chart in Figure 4-2.

Table 3-2: Major Activity List with Anticipated Start Date and Task Duration

Start Date Subtask 1 Subtask 2

Project Selection S&J 16-Jan-14 2 3

Feasibility and Preliminary Research S&J 22-Jan-14 3 6

Theoretical Design and Major Component Selection S&J 28-Jan-14 5 12

Motor Control Prototyping S 4-Feb-14 12 3

Frame and Drive Design J 4-Feb-14 10 5

Fabricate Frame and Drive Components J 10-Feb-14 21 7

Preliminary Frame and Drive Assembly J 1-Mar-14 10 2

Prototype Main Control System S&J 16-Feb-14 5 2

Write Control Softwares S&J 1-Mar-14 14 21

Test/Debug Software/Hardware Prototypes S&J 9-Mar-14 5 5

Finalize Design and Commision Manufacture of PCBs S 24-Mar-14 4 14

Assemble J 4-Apr-14 10 2

Test, Refine and Tune S&J 8-Apr-14 14 0

Presentation S&J 20-Apr-14 4 1

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Figure 4-2: Gantt chart of Anticipated Project and Activity Duration

19

CHAPTER 4 REFERENCES

http://sites.google.com/site/gyropowerboard