В презентации описан опыт создания робота с нуля на базе Raspberry Pi и недорогих актуаторов и сенсоров. Представлены примеры двух разработанных поколений роботов, детально описана одна из последних версий, собранная на базе деталей конструктора Trik. Описанная модель имеет дифференциальное управление (используются два мотора с энкодерами), ультразвуковой сенсор, камеру. Питание организовано от 11.1V батареи через UBEC. Прошивка робота реализована на базе ROS и состоит из нескольких модулей.

1. Design of mobile robot on Raspberry Pi
Arthur Huletski, Dmitriy Kartashov
The Academic University, Saint-Petersburg
2015
Artur Huletski, Dmitriy Kartashov (APTU) 2015 1 / 9

2. Motivation
Why do we need physical robot for research related to robotics?
Drawbacks of software simulators
don’t provide precise sensor model
don’t simulate unwitting environment changes
aren’t such fun as physical robot
Robot requirements
framework should be firm enough to carry sensors
robot should be extendable with sensors and circuits
robot should be assembled from affordable parts
Artur Huletski, Dmitriy Kartashov (APTU) 2015 2 / 9

3. The first prototype
Parts
Lego Technic
SG90 (steering)
HCRS-04 (sonar)
28BYJ-48 (s. rotation)
noname DC (movement)
Drawbacks
Ackerman steering
fragile
Artur Huletski, Dmitriy Kartashov (APTU) 2015 3 / 9

4. The second attempt: Steel Lemon (SL)
Artur Huletski, Dmitriy Kartashov (APTU) 2015 4 / 9

5. Hardware scheme
Raspberry Pi B
Arduino Uno
L298-based PCB
JGA25-375
JGA25-375
HCSR-04 Camera
UBEC
3:2 Voltage Divider
3:2 Voltage Divider
11.1V battery
11.1V
5V
5V
5V
Motors On/Off
11.1V
11.1V
Encoder Data
Trig request
5V response
3V response
5V
5V
5V
USB
5V ping
3V ping
[I2C]
Movement
request
Artur Huletski, Dmitriy Kartashov (APTU) 2015 5 / 9

6. SL description: Hardware
Used parts
Bones: Trik parts (Meccano-like clone)
Brain: Raspberry Pi B (RPi)
Spinal Cord: Arduino Uno (ArdU)
Legs: 2 x JGA25-375 (DC motors with encoders)
Eyes: HCSR-04 (sonar) + usb camera
Details
UBEC is used to convert battery voltage to 5V
L298 PCB is used to control direction of motors rotation
ArdU is used to control movement distance
RPi and Arduino communicate via I2C
voltage divider is used to connect HCSR-04 to RPi
Artur Huletski, Dmitriy Kartashov (APTU) 2015 6 / 9

7. SL description: Software
ROS framework is used as base.
Implemented modules
HCSR-04 driver. Idea: measure duration of high signal on Echo port
Motor driver
RPi part converts distance and angle to encoder ticks
ArdU part counts encoder ticks, controls motors rotation
Artificial landmark detector
Main controller that provides command line robot interface
Detector
Main
controller
Camera Sensor Motors
Artur Huletski, Dmitriy Kartashov (APTU) 2015 7 / 9

8. Consclusion
Designed robot meets initial requirements and has already been used for
development artificial landmark detector.
Future
merge ArdU and L298 PCB into single circuit to save space
add support of arc trajectory movement to motor driver
add sonar-motor direct communication
Artur Huletski, Dmitriy Kartashov (APTU) 2015 8 / 9

9. SL: Current version
New parts
Sharp GP2Y0A021YK
(IR range finder)
28BYJ-48 (rotation)
I2C voltage level
regulator
Issue
BCM2835 hardware bug
related to I2C clock
stretching
“WA”
Slow down I2C baud rate
Artur Huletski, Dmitriy Kartashov (APTU) 2015 9 / 9