Aasimon.org Wiki

Date: October 7th 2008
Duration of activity: 8-13
Participants: Kasper, Bent and Johnny

The purpose of this exercise is to make a line following robot to compete in the robot race.

We decided to continue from the basis program from Lab5. To improve the car's turning ability we now decrease the motor power when turning. We found that the turning ability was highly affected when we changed from small diameter tires to large diameter tires. Of course the top speed was improved, but it seemed that the steering suffered from the high speed. In order to improve this we need to reduce the motor power while turning. After some trials we found that 90% power while turning improved the car's ability to stay on track. We now await what happens when the battery power is reduced.

Here another attempt is made to find the optimal lengt of the sensor arm as it seems that the sharpness of the turns and the following oscillations between left and right could be reduced by reducing the lenght of the sensor arm. Some tests seemed to make oscillations even worth and the ability to track sharp corners on the track was reduced. This led us to reconsider the software once again to implement a memory of the last sensor inputs in order to use this memory to turn with different angles. This idea was proposed in Lab5, but was not implemented

We have implemented a counter, which is incremented each time the program decides to make a turn in a similar direction. This allows us to increase the turning angle as the counter is incremented by adding more power to the turning wheel. The tests have shown better performance, but it is difficult to find the right numerical values of the parameters. The main problem is still oscillations between right and left as they make the car run slowly or in worse case - it gets lost. At least now we have a more adaptive approach to the turning problem that increase the turning angle proportional to the sharpness of the turns.

In relation to this test we have adjusted on the motor power in forward mode. If this power is too big e.g. the car is coming out of a right turn and into a left turn, the car will spin off the track since the sensors will detect a forward mode between the turns

In this test we have changed the tires and made further mechanical improvements to stiffen the coachwork of the car. Thereafter we needed to change the numerical values of the light sensor variables in the program, because the distance from the sensors to the lane had been changed. The first tests showed some problems, but we adjusted the readings to the following

White: RCX=32, NXT=55
Black: RCX=26, NXT=37
Blue: RCX=26, NXT=39

After implementing the new values the car ran proporly again, but the battery was now too low to measure any improvements regarding time trials. We also implemented a read out of the time from start to end by using the function currentTimeMillis(). The elapsed time is shown in the display after each testdrive.

The fastest time we ended up with was 28.7 seconds according to the readout fra Marvin.