Debriefing

Performance

Overall, RoboPele performed well in that it could adapt to a wide range of input speeds without much difficulty. RoboPele's cart could hit any ball coming off the ramp; from the slowest and lowest angled ramp to the fastest and highest angled ramp. It was disapointing that the second sensor, even after the switch to a light sensor, would fail at high speed. But that was only at the fastest speeds and was approaching the maxiumum velocity that the cart could go. The two greatest contributing factors to this was the removal of the RCX from the cart as well as the feedback mechanism for catching slow balls after a fast start.

Robustness

The physical robustness of RoboPele was quite admirable. Due to initial design failures where the torque produced by two motors would rip the cart apart after a couple level zero to level eight power changes, subsequent designs could take survive in well in an adverse environment. A few accidental, and later not so accidental, thigh height drops demonstrated this execllent behaviour. The team is quite proud of RoboPele's surviability.

Limitations

The most disappointing element of RoboPele is the temporal sensitivity of the input sensor. Neither the light nor the touch sensors trigger if they are not in the triggering state long enough. This of course limited the sensitivity of the ball speed input. Additionally, there were a limited number of sensors which could be connected with the RCX unit. Had more of these been available as well as a greater temporal accuracy the original design of measuring the amount of time spent under a light sensor could have been possible. In fact with suffienct light sensors an array of light sensors could be setup such that RoboPele could respond to any ball coming at in angle and any velocity.

Due to the limitations of the Lego Mindstorms programming language there was one feedback loop the team wanted to build, but could not. The feedback loop we wanted to build was one that would take inputs on the sensors after a trial in such a way as to inform RoboPele if the delay and/or colision speed of the previous trial's ball speed was to short, too long or just right. In order to implimt this learning feedback, RoboPele would have required variables more advanced that Mindstorms's counter unit. Had this been available then it would have made the process of training internal to RoboPele and a self contained closed loop control.

 

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