In this lab session we will try to make a robot racer that races to the top of a mountain as defined in Lesson7 - Also called the Alishan Train Track.
Duration of activity: 7 hours
Group members participating: Ole Rasmussen, Kasper Sørensen
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| Figure 1: The Alishan Train Track |
Goal
To build the fastest robot to complete the Alishan Train Track.
Plan
We will execute the following in sequence:
- Create a super fast robot using gearing
Constructing and experimenting with a self-built NXT robot which maximizes speed. - Make a control program for the robot
Here we will create the control program for the robot created in the previous step.
1. Create a super fast robot using gearing
In this step we will construct a fast robot. In a later step, we will make this robot complete the Alishan Train Track.
We decided to develop two distinct robots in paralleled.
We decided to develop two distinct robots in paralleled.
- One which uses two motors and gearing on these to achieve speed. Lets call it Speedy.
- A second robot, which uses three motors for each wheel with gearing for maximum speed. Lets call it The Rock.
1.1 Speedy
Our speedy robot can be seen on Figure 2. It has a large gearing but only two motors, one for each wheel.
It can drive at very high speeds. The gearing can be seen in Figure 3. Our idea is to make this robot "fly" up the Alishan Train Track and win the competition. As you will see, we did not manage this.
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| Figure 2 - The Speedy Robot. It would drive in the opposite direction. |
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| Figure 3 - The Speedy gearing |
1.2 The Rock
The Rock robot is an experiment where we wanted to use three motors to drive one wheel, which should be massively geared for an even higher speed. It can be seen on Figure 4.
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| Figure 4 - The Rock. As can be seen, it is massive and consists of two NXT's. The gearing can be seen in the lower left corner. |
We did not manage to actually make The Rock drive, thereby the name. The power from the motors were too much for the gearing, which always gave in and needed to be repaired. Also, at one point, we erroneously uploaded a program for the Speedy robot to The Rock, which made a pair of the motors turn opposite of each other This skewed both of the "sticks" which were inserted in the motors. See Figure 5.
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| Figure 5 - Skewed "stick" - destroyed by the force of The Rock. |
2. Make a control program for the robot
Since we only made Speedy actually move, this is the only robot we have tried to implement a controller program.
Our idea was to create a sequential program which did not have any sensors. We only had to get to the top and back once, and have that on video, if we tried this enough times, one of the times should be good enough. This was at least the intuition behind our program.
We measured the distance from the bottom of the track up to the first corner, in the number of tacho counts needed. Our program would then move forward for that amount of tacho counts, make a turn, and then forward for the same amount of tacho counts.
We inserted sleeps between each action (forward, turn, ...) to see how it behaved. This is one of the test runs:
As can be seen, we did not do very well. This is not the best run we have had. We had a run which got to the second turn and fell off the track when going to the top. However, we did not get that taped.
Our robot is very susceptible to changes of the track, the battery level, inconsistencies of motor power and both wheels must drive straight.
We were not able to get it to the top. If we had more time, our next attempt would be to add a light sensor in the front to detect on which side of the line we were, and correct a little bit to stay on track.
