FOBOT

1. FOBOT The Hexapod Walking Robot • Authors: • Balázs András • Pécskai Balázs • Supola Balázs • Vámossy Zoltán • Molnár András Budapest Polytechnic, John von Neumann Faculty of Informatics, Hungary 23 March 2004

2. Contents • The main purposes of the robot • Similar development • Common features • Particular purposes • Construction of the system • Mechanical structure • Electric structure • Movement of the legs • Communication • PC side control • Planning of the walking strategies • Walking strategies • Global Positioning System • Global positioning • Eye-based navigation • Processing of the PAL-optic picture • Position determination step by step • Results I • Results II • Further information

3. The main purposes of the robot The robot is able to: • Move quickly (apart from the quality of the terrain) • Have duplex communication channel with the controlling PC • Have remote control option • Partially explore its environment • Avoid obstacles • Reach a designated target by self-navigation

4. Similar development • Autonomous hexapod robot • Only one actuator per leg • Speed: 2.25 m/s • 3700 m distance on one set of batteries • Swims, and climbs stairs • Onboard control of the robot and wireless access to the command interface is supported by RHexLib Rhex Source: www.rhex.net

5. Has got six legs Similar movement Structure Six legs can be controlled independently from each other Curved legs Common features

6. Particular purposes • Development of the construction (number of the legs) • Solution of the problem of the motor control: • Turn direction, speed, setting feet options • Programming of the central process unit: • Duplex communication between CPU and PC • The execution of the various walking strategies • Joining of the GPS module to CPU: • Data pre-testing and pass it on to PC • Developing the PC-side software: • User interface • Communication module and test environment alternatives • Map manager module • Virtual environment building module* • Avoiding obstacles, route-planning and navigation module* *optional modules

7. Construction of the system * * * * *optional modules

8. Mechanical structure Dimensions: • Length: 420 mm • Width: 265 mm • Height(standing): 175 mm • Leg height: 115 mm Aluminumskeleton Evolution of the legs: Early stage Curved spiral Plan-parallel Straight

9. Electrical structure Printed electric circuit: • Main parts: • 6 pcs. DC motor (12 Watt) • 6 pcs. PIC 16F873 microcontroller • 6 pcs. L6203 motor controlling IC • Interfaces on the robot: • 2 pcs. serial port socket (communication + GPS) • Programmer interface for PICs • Sockets for GPS and camera • Interfaces for optional sensor and structure

10. Movement of the legs • Leg movement: • Determination of velocity and direction (automatic and/or by PC) + setting to position • Speed: • PWM modulation is created by PIC • Regulation: • Speed of the obtaining of the desired position is in direct proportion to square of distance • Speed’s derivative is similar to the aforesaid • Advantage: regulation time is short, increased burden is easier solved

11. Communication • FOBOT communicates on the serial port(RS232) with own protocol. • All PICs have different address. • 1th. byte: address + instruction’s type • 2nd. byte: desired position or velocity • PICs send back two bytes: • Actual speed • Actual position • Advantage of serial communication: • Easy programmable • Single transmission • Wireless communication is realizable by two one-channel transceiver-receiver pairs

12. PC side control Control & test: The test of the communication and errata continuously Test of the leg-control: • Simple leg-control • Walking description Option of the succession control Simulation: Simulated motion of therobot and position-diagram of the legs

13. Planning of the walking strategies Position plotted against time Plan: Items of target points Speed Tripod walking:

14. Walkingstrategies • Turning: • the legs move just like at the tripod strategy, but the two sides move in different direction Tripod: Quattro: Worm:(the slowest)

15. Global Positioning System GPS signals: NMEA sentences (National Marina Electronics Association) - GPGGA, GPRMC, GPGSA, GPGSV Example: $GPGGA,123519,4807.038,N,01131.324,E,1,08,0.9,545.4,M,46.9,M,,*42 Degree of latitude Degree of longitude Height above sea-level. • Measuring controlled by the software: • Minimum number of the used satellites • Applied filters: average, median • Displaying the properties of the satellites

16. Global positioning • Planning route: • Placing sub-targets • Route following: • Filtering input signals • Actual position on the map • Calculating of the direction of the sub-targets • Properties of the satellites: • Positions • Range of the input signals

17. Eye-based navigation Step of the real-time image processing: • Digitalization (Video for Windows) • Modified input image by filters: • Dilatation • Erosion • Edge detection • SUSAN algorithm • Skeleton • Binarization • Position and orientation determination based on edge detection

18. Processing of the PAL-optic picture PAL = Panoramic Annular Lens (invented by Prof. Pal Greguss) Real-time mapping and effect of filters: Centric-minded imaging

19. Position determination step by step Add filters Selection of the followed points manually Layout of the PAL-image Edgedetection Schoolyard Here is FOBOT PAL-image Determination of the spatial vectors from the PAL-image Determination of the vertical position of the FOBOT 3D transformation, mapping the points

20. Results I. Movement: • Speed: 5,8 meters / min • Turning around: 36 sec • Simple walking development possibility • Several walking strategies are developed • In progress: • Eye-based navigation • Obstacles avoidance • Wireless communication and local power-supply

21. Results II. Tested GPS receiver: GNV12 (Lowrance), Summit (Garmin), PS1 (µblocks), Navistar (BAE Systems), Jupiter (Connexant) Test of the navigation on road and the court of the college (football pitch) Football pitch

22. Further information project homepage: fobot.bmfnik.org