Scrap was a 6 wheeled 208 pound robotic entrant into the TLC's Robotica Competition. It was built using scrap materials found in my lab. The controller was based upon 2 PIC 16F84 controllers; one PIC for each motor side. Each PIC was programed to accept a custom data packet and execute a closed loop PD controller with velocity and position inputs. This allowed the robot to steer in precisely controlled pathways and execute preprogrammed movements (peroet to the left/right, turn 90/180 degrees, etc) There is also a slashing/lift fork on the front with a lifting capacity of 200 pounds and a swinging battle hammer (18 pounds) on the rear that is activated by centrifical forces during a spin move. The radio link was based upon Abacom Technologies RTF3-433 miniature FM TX/RX data modules (range 500 ft line of sight). The joystick was a gutted "Cyborg 3000 3DOF" joystick with another PIC 16F84 controller set to scan all inputs and relay the data packet to the radio module. The drive system was based upon two Ivacare electric wheelchair motors chain linked to 3 wheels per side. The middle wheels were lowered 1/5 inch from the outside wheels in order to reduce drag during "skid steering". This worked out quite well as we could "spin" the robot upto 45 RPM. The frame was made from 3 inch angle iron 1/4 inch thick welded into a "U" frame where the wheel stem and motors were bolted to. The lifting forks were made from 1.5 inch angle iron with a 500 pound capacity linear actuator. The slashing forks are made of hardened steel plate ground to a knife edge. Design time 3 weeks, construction time 8 weeks (including time for electronics), total cost $500 Canadian (not bad). The biggest problem with this system proved to be with the off-the-shelf components. The joystick grew sloppy with use and I am planning on replacing it with a custom mechanical joystick interface. The radio data links are too low powered and are easily swamped by EMI. I will also replace the control electronics with a higher level PIC and utilize thier associated hardware based PWM outputs. A second generation robot is also being designed and the autocad drawings should be ready by December. Email: dostrom@ryerson.ca