My Evaluation

Testing the buggy

last lecture we tested the buggy's line following capabilities around a simple track and while doing this we encountered two big problems. The first of which was calibration. We found that initially the buggy would turn the corners only about 60% of the time, this was because it was taking the LDR's too long to read and react to the change in light as it passed over the black line. So to get around this problem we had to change the case values so that they were exactly on the threshold of when the LDR's began to detect less light, this lessened the time it took the LDR'S to react and the buggy began to turn the first couple of corners. However there was a disadvantage to this heightened sensitivity, we noticed that the track was darker toward the end, although it was a slight variation in light intensity it was enough to make our LDR's read 'dark' and cause the motors to turn seemingly 'on their own'.

The second problem was that the front wheel was having difficulty turning due to the fact that the black line was slightly raised and the wheel kept getting wedged between it. we did try to adjust the wheel by making it slightly higher however this had little affect and we had to resort to manually twisting the wheel when it got stuck.

Comparison of our buggy to other groups

• Building quality- there was a wide variety of materials used by the other groups to build their chassis, some used acrylic others used reinforced cardboard. However it was apparent that those who built the chassis using mecano, as we did, had a much stronger and stable frame, therefore although our wires were slightly messy I feel our buggy was well built.
• line following ability - many groups couldn't get their buggy to read the line at al,l and those that did didn't do any better than we did so i feel our buggy was fairly on par.
• symbol reading - unfortunately we didn't have time to implement a switch therefore we, like many groups failed miserably on this test, however the buggy did manage to reverse.
• Number of LDR'S- some groups managed to used 3 LDR's (group B) which made their buggy alot more accurate when turning and correcting itself. our buggy had only 2 LDR's and as a consequence of that turning was difficult as the buggy would over turn.

What I would do differently

1. Firstly we spent the majority of our time trying to create a decent front wheel, this task could have been made much easier had we used a caster wheel instaed of trying to construct one from mecano.
2. Had we used a caster wheel we would of had enough time to implement a switch and write a second programme containing interrupts in the correct places so that the buggy could of read the symbols.
3. we had constant problems with our LED's as they kept short circuiting due to the metal mecano struts, this made calibration difficult as their light intensity would change. To get around this problem we would completely insulates the LED's properly before connecting them to the chassis.
4. We would try to use 3 LDR's, one in the centre and two one the sides, this way the buggy wont over turn as the middle sensor would detect the black line and cause the buggy to travel forward.
5. finally and most importantly, we would create a better guard for the LDR'S and LED'S ideally using a dense material such as plastic, this would create a constant environment for the LDR'S and would make calibration a lot more efficient and effective.