Transcript RC Car - UCF EECS

Project Overview
 Autonomous valet parking vehicle with search,
park, and return functionality
 Provides a low cost solution to automatic valet
parking with potential use in real world
vehicles
 Cars with this functionality would have their
own designated row of spaces
Requirements
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Front-end parking
Cardboard surface with no incline
Avoid objects in path
Park in space without colliding with neighboring
cars
All parking spaces uniform and designated
Return to drop-off position
Low cost to implement
Simulate potential real world environment
Battery powered
Specifications
 Minimum RC car dimensions: 15”L x 13”W
 Max Speed: 6 mph
 Max search and park time: 5 minutes
 Max pull out and return time: 5 minutes
 Parked front end clearance: 3 in
 Safe distance from obstacle during park
search mode: 3 in (formerly 10 in)
 Max cost: $400.00
Components Overview
 RC car platform
 DC motor for forward and reverse propulsion
 Motor speed and motor direction control
 Steering servo for left and right maneuvers
 LCD Display
 Power Supplies
 Transmitter/Receiver pair
 Obstacle avoidance sensors
 Microcontroller
RC Car
 Requirements:
 Needed an electronic speed control module (ESC)
w/attached motor to control the motor speed and
direction .
 ESC needed to be easy to interface with an Arduino
microcontroller.
 Needed 3-wire steering servo motor for easy interfacing
with an Arduino microcontroller. (some, believe it or
not, came with 5-6 wires)
 Needed to have a large enough chassis to support
multiple battery packs, obstacle avoidance sensors, and
PCB. (minimum: 15” L x 10” W)
RC Car Comparison
 Option 1: Ready-to-run (RTR)
car
 Left/Right /Center steering (not
proportional)
 Large and fit budget, but did not
have desired ESC for controlling
motor speed and direction
 Option 2: Hobby grade RTR car
 Fully proportional steering
 ESC for motor control
 Large enough to fit all essential
components on chassis, full
function, fit budget
 Purchased: Duratrax Evader
EXT
• Dimensions:
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Length: 16.1”
Width: 12.9”
Height: 6.6”
Motor
 Utilize existing motor in
R/C car
 Model: Duratrax Photon
Speed 20
 Operating voltage: 7.2 v –
8.4v
 Max speed: Up to 30 mph
Motor Control
 Requirements:
 Needed to control the motor’s forward and reverse
direction
 Needed to control the motor’s forward and reverse
speed
 Speed to be kept under 3 mph for accurate movement
 Needed to support current draw of motor
 Motor start-up could potentially meet or exceed 20 A.
Motor Control Options
 Option 1: Implement H-bridge IC
 Easy interfacing with Arduino microcontroller.
 H-bridge IC’s that supported up to 20 A per channel cost up
to $50
 Option 2: Use existing ESC on RC car
 Model: Duratrax Sprint ESC with reverse
 Maximum constant current for forward 128 A & for reverse 64
A
 Easy interfacing with Arduino microcontroller.
 Chose to utilize existing ESC
Dynamite Tazer 15T
 Specifications:
 Operating Voltage: 4.8–
8.4 V
 Controls forward and
reverse movement
 Peak current 700 A
 Continuous current 110 A
 Designed for 20 – 27 turns
motors
 Dimensions:
• Length: 1.7”
• Width: 1.5”
• Height: 1.1”
Steering Servo
 Use RC car’s existing servo
 Operating Voltage: 6V
 3-wire servo motor
 Speed 0.20 sec/60 degrees
 128 oz-in torque
LCD Display
 Requirement:
 Display currently running function for viewing
 Description:
 Character Display
 White text on blue background
 Backlight
 Standard Hitachi HD44780 controller
 16 characters wide x 2 columns
 Utilize six data lines (D4 – D7 )
Transmitter & Receiver
 Motivation:
 Basic functionality
 Send signal to begin parking spot search
 Send signal to pull out of parking spot and
return to point of origin
 Allows for expansion if different wireless
features want to be added
Transmitter & Receiver
Methods Considered
 Bluetooth
 Too expensive to implement
 Infrared
 Poor range, line of sight
 Wi-Fi
 Components needed to implement system are too large
 Chose: RF
 Good range
 Easy to implement on microcontroller chosen
 Inexpensive
RF Transmitter
 MO-SAWR-A
 Transmits at a frequency
of 315Mhz
 Range up to 500 ft.
 No line of sight needed for
transmission
 Common in car alarm
remotes, beepers, and
many similar devices
 Operating voltage: 2 to 12v
RF Receiver
 MO-RX3400-A
 Receives signal at 315Mhz from
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RF transmitter
Range of up to 500 ft.
Common in car alarm remotes,
beepers, and many similar
devices
Operating voltage: 5V
Current draw: 2.3 to 3 mA
Digital signal to
to microcontroller for easy
data processing
Sensors Considered
 Infrared Sensors
 Sharp IR GP2D12 Sensor
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450 –750 nanometer range of visible light
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Covers a range of 10 to 80cm with a optimized distance of 24cm
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Operating Voltage: 0.3 to 7 volts
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Max current draw: 10mA
 Imaging Sensors
 TSL 1401 Linescan Imaging Sensor Daughterboard
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128-pixel sensor chip
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7.9mm focal length imaging lens
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Operating voltage: 3.3 to 5 volts.
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Max current draw: 5mA
Sensors Considered cont’d
 Ultrasonic Sensors
 Chose: Ping Ultrasonic Range Finder
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Emit a short 40 kHz signal
Range 0.8 in to 118.8 in (3.3 yd)
Operating Voltage: 5 volts
Max current draw: 35mA
Sensors
Advantages and Disadvantages
 Ultrasonic sensor
 Fastest response time at 115 us up to 18.5 ms
 Smallest at 0.84 in W x 1.8 in L
 Best range at 0.8 in to 118.8 in
 Infrared sensor
 Poor range
 Imaging sensor
 Poor range
 Slow response time
 Expensive
Ultrasonic Sensor
Considerations
 The sensor must be
mounted perpendicular to
the floor for accurate
performance
 Echo-free environment for
the most accurate readings
 The object that the sensor
will detect has to be large
enough for the ultrasonic
waves to deflect off of it
Ultrasonic Sensor Mounting
 The small size of the sensors
make it easy for mounting onto
the frame of the car
 There will be three sensors
mounted on ParkBot one in
the front and one on each side
of the car
 These sensors will be
connected in series to keep the
current draw low
 Sensors will be mounted at
different heights to determine
optimal height
Power Supply
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Decided to divide the power system of ParkBot into
two separate power supplies:
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One will power the drive motor and servo.
The other will power the remaining components.
Transmitter has its own power supply.
Voltage (V)
Current
(mA)
Power
(mW)
Sensors (x3)
5
105
525
MCU
5
40
200
Receiver
5
3
15
LCD
5
4
20
Voltage (V)
Current
(mA)
Power
(mW)
Motor
7.2
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Servo
6
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-
Voltage
(V)
Current
(mA)
Power
(mW)
Transmi
tter
5
20
525
MCU
5
40
200
Voltage Regulation
 Voltage regulation to 5VDC required
for the following components
 Microcontroller
 Ultrasonic sensors (x3)
 RF receiver unit
 Rf transmitter unit
 Decided to use a simple linear
regulator for the power supply in
order to power the components
listed above. A LM7805 5VDC
voltage regulator will be used.
 Voltage Regulation to 6VDC
required for the:
 Servo system drive
Main Power Supply
 Chose: Duratrax 7.2V Ni-MH 4200mAh
rechargeable battery pack.
 Will be directly connected to ESC module
(no voltage regulation needed).
 Will be connected to a LM7806 6VDC
fixed voltage regulator to power the
steering servo motor.
 Was chosen based on the amp/hours and
voltage needed to properly operate the
other components for the minimum time
specification.
7.2v Ni-MH
Electronic
Speed
Controller
LM7806
Voltage
Regulator
Steering
Servo
Motor
Secondary Power Supply
 Chose: Chose: Digital Energy 9.6V Ni-MH 1600mAh rechargeable
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battery pack.
Will be connected to a LM7805 5VDC fixed voltage regulator to power
Ultrasonic Sensors (x3), RF Receiver unit, and microcontroller unit.
Was chosen based on the amp/hours and voltage needed to properly
operate the steering servo and rear motor for the minimum time
specification.
About 1600mAh/152mA = 11 hours and 31 minutes
Good amount of battery life for testing and running
LCD
7.2v Ni-MH
LM7805
5VDC
Microcontroller
Ultrasonic Sensors (x3)
RF Receiver unit
MCU Requirements
 I/O pins needed:
 4 digital (for obstacle avoidance sensors and RF receiver)
 3 digital PWM (for DC motor control and servo control)
 Open source
 Well documented with online examples
 Uses a familiar programming language
 Sufficient memory and processing power
 Operating voltage of 5V
 Chose: Atmel ATMega328
MCU Specifications
 Atmel ATMega328
 With Arduino
Bootloader for use with
the Arduino language
 Arduino language based
on C/C++
 Max frequency: 20MHz
 32KB of program space
 23 I/O Pins
 Operating Voltage: 5V
Pin Configuration Overview
Overall MCU Diagram
Steering servo
digital PWM
output
PING))) Ultrasonic
Sensor (x3)
digital
input
Atmel
ATMega328
digital PWM
output
LCD
Display
ESC
digital
input
MO-RX3400-A
RF Receiver
Programming the MCU
 Use a SFE FTDI USB to
Serial Basic Breakout
Board that interfaces with
the MCU
 Optimized to work with 5V
Arduino boards and cloned
5V Arduino boards
 Easy loading of code onto
MCU through USB port on
PC
 Cheaper than buying USB
to serial converter cable
($33 vs. $14)
PCB
 We decided to purchase a
punchboard and utilize the
Aruduino layout for the
Atmega328
microcontroller.
 We soldered the PCB after
successful testing of the
implemented parts on the
board
 Optimized Arduino
configuration will be used
for maximum performance
for our system
 Size: 4.5" x 3.3
Testing Area Specifications
 Our RC car is 1:10 Scale (scaled down to 1/10th the size of real world car)
 Real World Measurements
 Typical parking space
 240 in L x 120 in W
 Dimensions of average mid-sized car
 185 in L x 70 in W
 (120 – 70) / 2 = 25 inches in between parked car and left and right ends of
parking spot. Multiply this number by 2 to get 50 inches in between the
parked car and each of the neighboring parked cars.
 Also there is an approximately 60 inch rear clearance assuming the car parks
5 inches away from the front barrier.
 Scaled Down Testing Area Measurements
 Dimensions of our RC car
 16.1 in L x 12.9 in W
 In order to achieve 5 inch (50 / 10) clearance in between parked cars and a 6
inch rear clearance (60 / 10), parking spaces in the testing area will have the
following dimensions (left and right ends of the parking spot will denote the
side of the neighboring parked car, not the ends of the actual parking space):
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22 in L x 22.9 in W
Software Class Diagram
ParkBot
- int occupiedSpotCount
- int openSpotLocation
- Servo steerServo
- Servo esc
+ void moveForward(int milliseconds, int dir,
int multiplier)
+ void moveForward(int milliseconds, int dir,
int multiplier)
+ void straightenWheels()
+ void turnLeft()
+ void turnRight()
+ double timeToDistance(long sensorReading)
+ double getDistance(int sensorPin)
+ void searchForSpot(boolean search)
+ void park(int whichSide)
+ void pullOutOfSpot(int whichSide)
 int occupiedSpotCount
 Keeps track of the number of
occupied left and right spots.
Increments after each occupied
pair of spots is detected
 int openSpotLocation
 Set to 1 if a left spot is available,
2 if right spot is available, and 0
if spot is detected as occupied
 Servo steerServo
 Servo object that will represent
the steering servo
 Servo esc
 Servo object that will represent
the electronic speed controller
Collision Avoidance Algorithm
Decision
YES
Front collision
avoidance algorithm
Front
obstacle distance
< 3 in.?
YES
NO
Check front sensor
at 2 Hz
Return to
algorithm
execution
Front
obstacle distance
< 3 in.?
NO
Parking Spot Search Algorithm
Wait for signal
to begin execution
Check parking
spot to the
left
Go to front
collision avoidance
algorithm
ParkBot moves
forward 2 inches
NO
Process
Check parking
spot to the
right
Open?
NO
YES
Open?
YES
Begin parking
algorithm
Parking Algorithm
Back up
until front
wheels are
lined up with
front of spot
Left or
right spot
open?
LEFT
RIGHT
Turn wheels to
the left
Turn wheels to
the right
Go to front collision
avoidance algorithm
above
Move forward
until 90 degree
turn is completed
Turn wheels
straight and
move forward
Has <
3 inch front
clearance
NO
Pull Out and Return Algorithm
Decision
Wait for
signal to
pull out
NO
Signal to
pull out
received?
YES
Turn wheels in
opposite direction
as pulling into
spot
Move backwards
until ParkBot
completes a 90
degree turn
Go to front
collision avoidance
algorithm
Move forward
until point of
origin is reached
Motor and Steering Servo
Functions
 void moveForward(int milliseconds, int dir, int multiplier)
 Moves ParkBot forward for a designated amount of time and
in the given direction (0 = forward, 1=left, 2=right)
 void moveBackward(int milliseconds, int dir, int multiplier)
 Moves ParkBot forward for a designated amount of time and
in the given direction (0 = forward, 1=left, 2=right)
 void straightenWheels(), void turnLeft(), void turnRight()
 These functions straighten out the wheels of ParkBot, turn
the wheels of ParkBot to the left, and turn the wheels of
ParkBot to the right, respectively
Obstacle Sensor Functions
 double getFrontDistance(int whichSensor)
 This function will return the distance value read from
whichever sensor is passed in the parameters. The parameter
is the pin that the sensor is connected to on the Arduino
 long timeToDistance(long sensorReading)
 Sensor-read helper function. Takes in a time in
microseconds (i.e. reading from an Ultrasonic sensor) and
converts the time into a distance in inches (i.e. distance from
nearest object to sensor).
 According to Parallax's datasheet for the PING))) Ultrasonic
sensor, there are 73.746 microseconds per inch. Also the
sensor reading in microseconds is the total time, outbound
and return, so we must divide by 2 to get the distance to the
obstacle. This gives us the following conversion:
distanceInInches = sensorReading / 73.746 / 2
Algorithm Functions
 void park(int whichSide)
 Does the process of pulling ParkBot into a parking spot. If the
whichSide parameter is 1, ParkBot will pull into the parking spot on
the left side. If the whichSide parameter is 2, ParkBot will pull into
the parking spot on the right side
 void searchForSpot(boolean search)
 Does the process of searching for an open parking spot if the search
parameter is true. If the search parameter is false, this functions is
used to return to the point of origin
 void pullOutOfSpot(int whichSide)
 Does the process of pulling ParkBot out of a parking spot. If the
whichSide parameter is 1, ParkBot will pull out of a parking spot
that it pulled into on the left side. If the whichSide parameter is 2,
ParkBot will pull out of aparking spot that it pulled into on the right
side
Testing Scenarios
 The following scenarios were mastered:
 Spot available on left
 Spot available on right
 Future endeavors:
 No spots available
 Spot too small on the left
 Spot too small on the right
 Detect traffic when pulling out of spot
Future Design Improvements
Wait for signal
to begin execution
Go to front
collision avoidance
algorithm with
front distance
< size of lot
ParkBot moves
forward until
spot is detected
(sensor checked
every 1ms)
Process
ParkBot moves
backwards until
beginning of open
spot is reached
(sensor check
every 1ms)
Begin parking
algorithm
Budget
Parts
Quantity
Price
Total Price
(Incl tax &
shipping)
RC Car
1
$ 68.00
$ 81.51
Ultrasonic Sensors
3
$ 26.95
$ 80.85
MCU
1
$ 5.50
$ 9.91
RF Transmitter
1
$ 3.50
$ 5.72
RF Receiver
1
$ 4.81
$ 6.93
Voltage Regulator
2
$ 3.00
$ 5.95
Battery
1
$ 26.99
$ 28.76
H-Bridge Chip
1
$ 2.53
$ 4.15
PCB
1
$ 25.00
$ 25.00
USB to Serial Board
1
$ 13.95
$ 18.95
LCD Display
1
$ 12.00
$18.75
$100.00
$100.00
Miscellaneous
Total Budget =
$ 416.48
Timeline
All parts
ordered
Software
completed
Initial component
testing completed
Feb. 25
Feb. 10
All parts
received
Feb. 20
Final testing
completed
Apr. 1
Mar. 10
Hardware
circuitry
completed
Initial Complete
System Testing
completed
Mar. 1
Mar. 25
Questions???