Some Initial Programming

A quick bit of programming to see if the buggy was working once constructed:

Sensor Input Program:

main:
READADC 0,B0
READADC 1,B1
READADC 2,B2

Debug

If b0>100 then b3=1


GOTO main:

Motor Test Program:

Main:

High 0 `Run Motor 1(?) Forwards(?)
Low 1
Pause 3000 `Pause for 3000
Low 0

High 2 `Run Motor 2(?) Forwards(?)
Low 3
Pause 3000 `Pause for 3000
Low 2

Goto Main:

Initial Buggy Program Idea:

Main:

Read 0,B0 `Left Sensor written to Bo
Read 1,B1 `Sensor 2 Written to B1
Read 2,B2 `Right. Sensor written to b2

Low 5 Low 4 Low 6 Low 7

Debug `To check working correctly

If B0=1 Then high 5 Low 4

Else If B2=1 Then high 6 low 7

Endif
Goto Main

Evolution Of Buggy

Group feedback and product development.

After the testing of the product resulted in it failing two tests, and only completing the main line following task with a little prod now and again, the group have decided that implementing the following steps would help produce a successful design:

1. Supply a greater voltage to the motors. This could be done by either using the 9V battery, the connection to the motor being controlled by a seperate motor board circuit, or running a further voltage source in parallel with the current supply; maintaining the voltage (4.5V) but increasing the current supply to the motors. This extra step would increase the torque of the motors.
2. Introduce a gearing system to the drive mechanisms. This would allow the buggy to travel at a slower speed, giving the LDR's plenty of time to sense changes in the road conditions and corrective conditions to be implemented appropriately.
3. Change the jockey wheel. The existing jockey wheel would often be mis-aligned when the buggy would try to change its direction of drive; the friction produced fighting against the motors. The installation of two jockey wheels, one in each rear corner, would elimainate this problem and allow the buggy to move more easily.

Fault Diagnosis

Upon finding the motor circuit was not operating correctly it was decided to trace the fault; so that appropriate action could be taken.
1. Using a continuity tester all the PCB was tested to ensure that no solder had 'tracked' across between lines. Only one case was found and quickly rectified but did not resolve the fault.
2. Using a voltmeter all voltages were inspected. Starting at the main battery pack and traced successfully to the motor circuit board. All voltages entering the motor circuit board were correct but the expected voltages that should have been seen on the motor terminals were not there. This suggests that there is a fault with the motor chip; which willneed replacing.

Final Design

The final and new buggy has been made as a team this weekend. Its chassis built from Durable modelling plastic ,and all the circuit boards soldered up nice and neatly. The jockey wheel has been far improved, and the whole buggy moves in a straight line and does not veer off to one side. The new Sensor array has been made with 4 White LEDS and 3 LDR's placed underneath the vehicle. With testing these appear to work really well giving constant values untill a black line is moved underneath them. However during Testing the motor circuit board has not been working this could either be a fault with the circuit or a blown motor chip.

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A second prototype has been constructed and a few changes have been made. The chassis design has been altered slightly. A plastic container has been used, which has had holes drilled to allow mounting points for both the motors at the front and the jockey wheel at the rear of the buggy. The buggy appears to be able to move straight, left and right, however it only appears to do this while the jockey wheel is mounted at the back of the vehicle, hence why they are that way round. The new motors are a definent improvement, now that they aren't buckled. Additional improvements that can be made are as follows:

- A more stable jockey wheel.
- A better chassis for the buggy to sit in.

After a lengthy group meeting today, we have decided on a few more changes for the buggy as a whole.

- The inner circuitry will be redone and neatened.
- The inner circuitry will be mounted on a semi-removable board for aesthetics and practicality.
- The jockey wheel is to be reconstructed.

Tracked Robot Research:

The idea of having a tracked line following robot has been floating around in our group for a bit now and so here is a bit of research in order for us to make a better decision for our final design.

Pros of having a tracked robot:

1. It will make our robot look really cool.

2. It will be fairly easy to implement.

3. Each track will be individually driven, allowing on the spot turning.

4. The tracks act as a break allowing greater accuracy of movement (turning).

Cons of having a tracked robot:

1. The robot will have to have special wheels in order for the tracks to stay on in motion especially when turning.

2. Could add cost to the project.

3. Might need a slightly greater power through the motors in order to achieve the same performance that a non-tracked robot might achieve.

All in all, I think giving our robot tracks will give it a slight edge over the other robots and I think it will be easy to do. Looking for ways of providing the tracks, Lego Technic looks the better bet over simpler ideas such as elastic bands due to the fact that it will address the 1st con. As for the other cons, 2, I think will be a pretty small cost and 3, I think we wont even notice a drop in performance at this level.

My final view would be to implement the track idea on the robot and if it goes horribly wrong, then change to the 3 wheeled option.

Here is a nice web page on how to construct a tracked robot:

http://roboticsforyou.blogspot.com/2007/01/tracked-robot-fabrication-techniques.html

Below are some images of track possibilities:

Chassis/Casing Design Ideas:

Looking on the internet at similar projects, I have seen that the chassis/casing is only dependent on a few things;

1. Size of the internal circuit.

2. Any Sensors that might interfere with the casing.

3. Method of propulsion.

Due to these factors being limited in number, you can make the chassis/case as simple or as complicated as you want it to be. Here are a few pictures of examples:

As you can see here a number of different method for constructing the Chassis, a few more ideas are listed below:

1. Lego.

2. Meccano.

3. Airfix.

Luke Hildred