High Level Design

            The inspiration for the robot and its functionality, as mentioned briefly in the summary, came from our second-last project in ECE 314. We had to design a mechanism using the philosophy of state machines to make a robot move from its home to a target to steal a flag and then come back, all the while avoiding collision with tricky obstacles and also simultaneously avoiding and beating the competitor’s robot which was trying to do the same.

    Obstacle avoidance seemed fairly straight forward and there were a number of sensors on the market that would do the job. We chose the Sharp IR Distance ranging sensor due to its low cost. Accuracy in distance was not an issue for us since we just needed to know if or not there was an obstacle in our way. We thus decided against using the Devantech sensor which was fairly expensive and would eat into our budget completely.

    Target finding was a more difficult thing to implement from both the hardware and software perspective. We experimented with various IR led transmitters and photo     transistors but were unable to acquire any decent signal beyond 2 feet. We also experimented with the idea of using dead reckoning.

    Given that we were using stepper motors for movement, it was theoretically possible to measure the distance moved by each wheel. Also knowing that our bot turned in the same place we could track the angle that the bot rotated by and use that for any subsequent distance measurements with respect to our target location. This however failed since the stepper motors skipped a considerable amount as they were not powerful enough to deliver a steady torque to the wheels.

 Two weeks into the project we stumbled across the idea of using a standard TV remote control for target finding. From experience we knew that the IR remote control had a fairly good range of about 10 feet or so. What we needed were some sensors that could pick up this signal. We were able to sample 4 IR 38 Khz Vishay sensors from Newark One Electronics. The combination of the IR remote and sensor helped us address the problem of target finding.

    The bot body was constructed out of a simple cardboard box. Minute maid caps were used as rear wheels and a ping pong ball was used as a third supporting wheel.