Posbot

built by David Mitchell

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Target Environment Locomotion Method
Indoors 2 Wheels
Sensors / Input Devices Actuators / Output Devices
4 bump sensors Geared DC motors
LED bargraph
Control Method Power Source
Autonomous Battery
CPU Type Operating System
Intel 80x86 MS-DOS
Programming Lanuage Weight
C N/A
Time to build Cost to build
weekend N/A
URL for more information
N/A
Comments
Posbot was built over a weekend in 2000 and its construction illustrates the corner cutting to get the posbot finished in this time. It is a 486 mini tower case on wheels. The case is mounted on a one inch (25.4 mm) square extruded aluminium frame, with two casters (front and rear), differential drive wheels (Geared DC motors), 4 bump sensors (soft covered scotch-T hinges bent in a 'G' shape with push buttons). The bump sensors are read via the joystick port 'fire button' switches, the parallel port drivesa set of 4 relays and LED bargraph. The relays are SPDT type and switch the 12 Volts (or ground) to either pole of the motor so that the motor can run forward or backward or brake by dumping EMF. The wiring is a combination of soldering and using Alligator clip leads. The power is supplied by two Gell cells and regulators, the power for the motors comes from the same supply as the PC, so on rare occasions the system hangs, when I get back to the Posbot I will work on some suppression. The system OS is dos 5.0 (I think), the control program was written in a DOS version of C and performs several functions. The robot runs off the floppy (floppy system disk, no harddisk) and the Autoexec.bat runs the robo.exe file which uses the LED display to indicate status and uses the keboard to enter a which "function" mode. The first function is "kickme", which the robot remains at rest until you kick on of the bump sensors and moves in an arc in away from the quadrant it was kicked for about a second and stops again, with this mode you can manually move the bot around the room, like a soccer ball. The second function remembers the "kicks" and can be replayed back - But not with accuracy as there are no encoders for dead reckoning. The third function is a simple 'braitenberg' bumpbot. The fourth and final function is to run an include file which is non-functioning becon searcher - the RCA plug on the front panel is the input signal for this (38k IR receiver - one day).

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