1. Collaborative mobile robots Rory McGrath 05000874 Progress Report

2. Index Indroduction Technology Background System Design And Operation Progress To Date/Remaining Work

3. Introduction

4. Overview Build a small swarm of robots Control a robot over a wireless PC based GUI Addition of collision detection Porting of a control application to a mobile handset Develop software to illustrate collaborative tasks.

5. Milestones (1) ‏ Construction of an operational robot. Movement is to be controlled over a wireless interface from a PC based application Addition of collision detection sensor on the robot. Porting of control application to a mobile handset

6. Milestones (2) ‏ Construction of multiple robots and integration of functionality to support a “locating” capability in the swarm. Demonstration of collaborative movement of the robot swarm. Development of an application to illustrate the practical use of a collaborative robot swarm

7. Technology Background Duty Cycle Pulse-Width Modulation (PWM) ‏ Opto-isolators Gumstix

8. Duty Cycle The term “Duty Cycle” is used to describe the time that a system is in its “active” state. The proportion of time during which a system is operated is defined as its “Duty Cycle”.

9. Pulse-Width Modulation (PWM) ‏ The pulse width modulation (PWM) of a signal involves the modulation of its duty cycle. A square wave is used. The pulse width of the square wave is modulated resulting in the variation of the average of the waveform.

10. Opto-isolators Opto-isolators are made up of a light emitting device and a light sensitive device. The two devices are not connected by any wire or electrical means. The only connection is a beam of light

11. Gumstix The micro-processor being used Speed of 400MHz - (Intel Xscale PXA255)‏ 16MB flash memory Bluetooth wireless connectivity 64MB of RAM

12. System Design & Operation

13. Hardware Motors Gumstix

14. Motors Each robot has two motors. Two 5 volts motors are used. 5 volts are placed on the motors red wire with 0 volts on the black wire and a 3-5 volt pulse on the white wire with a width of 0.75 to 2.25ms and a period of 18ms.

15. Gumstix The Gumstix generates the PWM signal used to power the motors. The outputs for the PWM of the Gumstix are the General Purpose Input Output (GPIO) pins 16 and 17. These are set to output the PWM signal rather than operate as GPIO.

16. Gumstix It was found that the Gumstix outputs a PWM signal of a maximum 3V. More than 3 volts is required for the 4N25 chip in the opto-Isolator circuit to activate. To compensate for this an extra power supply (5V), a 2N3904 transistor and a 100kOhm resistor are needed to successfully power the motors.

17. Python PWM Initialization The 2 GPIO pins required for PWM are initialized for PWM output through a python script. The PWM functions are controlled by 3 registers. The 3 registers are PWM_CTRL, PWM_DUTY and PWM_PERVAL.

18. Python Bluetooth Bluetooth is the inter-robot communications medium. It will allow the lead robot (server) to communicate with the other robots (clients).

19. Python Server import bluetooth server_sock=bluetooth.BluetoothSocket( bluetooth.RFCOMM )‏ port = 1 server_sock.bind(("",port))‏ server_sock.listen(1)‏ client_sock,address = server_sock.accept()‏ print "Accepted connection from ",address data = client_sock.recv(1024)‏ print("Data Recieved... %s"%data)‏ client_sock.close()‏ server_sock.close()‏

20. Python Client import bluetooth bd_addr = "00:80:37:2E:46:37" port = 2 sock=bluetooth.BluetoothSocket( bluetooth.RFCOMM )‏ sock.connect((bd_addr, port))‏ sock.send("Hello World")‏ sock.close()‏

21. J2ME

22. Work done (1) ‏ An Opto-isolator circuit has been successfully built and tested using the Signal Generator. The PWM pins have been successfully initialized via a python script. Values where hardcoded to the PWM pins and successfully outputted to the oscilloscope. A python script was written which successfully outputted “forward” motion PWM signals to the oscilloscope. The Gumstix was connected to the motor via the Opto- isolator and it was found that an extra voltage was needed to activate the 4N25 chip

23. Work Done (2) ‏ Changes were made to the Opto-isolator to allow for the Gumstix to successfully run the motors. A J2ME client was created for a mobile phone. A J2ME GUI was created for the client. Changes were made to Gumstix folders to allow for a successful Bluetooth connection with a laptop. A Gumstix Server was written and the Client for a PC and mobile phone were successfully tested.

24. Remaining Work The construction of multiple robots has still to be carried out The locating capability of individual robots in swarm is required. The swarm must demonstration collaborative movement. (movement in formation & Orderly dispersion)‏ Illustration of the use of collaborative movement has yet to be shown.

25. Summery

26. Questions?