Chapter 14: Classic Projects

This chapter deals with several projects can be the inspiration of several others of your own creation. The first project is exploring your room.

In this project, the aim of the robot is to move around the room, detecting objects and change it route accordingly. For simplicity of design, and for the robot to turn in place, it is suggested to make the robot from differential drive architecture. If you coose a gear ratio that makes the robot rather sow: 1:9, obtained fro two 1:3 stages. This ensures th at if you make some error in the code and the except everything to go well on the first try but it won't.

The second project is detecting edges. If you're room has a flight of stairs going down, simply equipping the robot with an ultrasonic sensor facing the floor to sense the edge can avoid a bad fall. You could also use a touch sensor instead, connecting the touch to a feeler flush with the ground. When the feeler in front of the robot drops, you have detected an edge.

The third project is following a line. You must follow the edge the tape and te floor, reading an average value between dark and bright so that when you read dark or too bright you know which direction to turn to fnd the route back. You must remove the bumpers and mount a light sensor facing down.

Chapter 2 Gears

This chapter discusses about the different types of gears that we can use in a robot. A single gear wheelis not very useful- it isn't useful at all. We need atleast two gears. The most imprtant property of a gear is its teeth. Gears are classified by the number of teeth they have. An example is that a gear with 24 teeth wll become a 24t gear or a gear with 8 teeth will become an 8t gear. The fundamental property of a gear is that they transfer motion from one axle to another. Another important thing you should notice is thaat you are not required to apply much strangth to make them turn. Their teeth match well and there is only a small amount of friction. A fourth, and subtler, property you should have picked up is that the two axles revolve at different speeds. To get an increase in speed, you have to sacrifice a decrease in torque. Torque is a measure of the tendancyof a force to rotate an object.

The largest gear is the geartrain. It has 40 teeth (40t). Geartrains give you incredible power because you can trade as much velocity as you want with the same amount of torque.

Idler gears usually help you connect distant axles. An advantage is that they change the direction of the output.

Backlash is the amount of oscilation a gear can endure withou affecting its meshing gear. Backlash is amplified when gearing up, and reduced when gearing down. It generally has a bad effect on a system, reducing the amount of precision with which you cannot control the output axle, and for this reason, ti should be kept to a minimum.

Pulleys are like wheels with a groove (calleda race) along their diameter. Photo of a pulley below.

A worm gear is a strange gear that resembles a sort of cylinder with a spiral wound around it. A photo of a worm gear below.

A crown gear is a secia gear with front teeth that can be used like an ordinary 24t, but can also combinewith another straight gear to transformotion in an orthogonal direction, possibly achieving at same time a ratio different from 1:1.

Get in gear investigation

If the driving gear was bigger than the driven gear, then the robot would travel faster because the rotation of the robot would once cause the driven gear to rotate multiple times for each .
If the driven gear was bigger than your driving gear, then the robot would be stronger causing the wheels to be slower. The robot would become slower and the distance travelled would be shorter if you were using a rotation sensor.

Today we basically finished making the taskbot and by next class we will be finished with the get in gear activity. Avery and Clare made the robot while I made the program.

The Obstacle Course overview

History was created today when R.O.B. V2.0® became the first robot in the history of ISKL to be given an A+ in the obstacle course challenge set by the robotics teacher Mr Inskeep. R.O.B V2.0® was the first and only robot to finish the course in one go. Other robots like the big Goliath which was constructed magnificently by Bart and Kenny failed to perform when it mattered despite doing really well in its trial runs. Well, they always say that David always triumphs over Goliath. R.O.B V2.0® beat all the other robots which were still doing their trial practices, to finish the obstacle course in its first try. There will be other robots to complete their obstacle course challenge by next class but this day truly belonged to R.O.B V2.0®.

Some things were learned today. One thing was that the balance of the robot plays a big role in how your robot will perform. The robot which we had created first, was very imbalanced and would always hop like a frog while R.O.B V2.0® is probably the one of the most stable robots in the class due to the usage of treads. This challenge was not an easy one but, with the work divided, it becomes simpler and easier to do.

The next topic we will be doing will be Gears. We will be looking forward to that topic.

Programming for the Obstacle Course

Today, basically we just used the class time to work on our robot. Avery and I worled on the robot while Clare worked on the program for the robot. We tried numerous things with the robot. We had setbacks such as not being able to use the scythe for hitting down the cans. Our robot is still under modification. We have finished a little more than half of the modification. We just need to add the cannon which we will use for destroying the cans. and the NXT which will be added when all the modification is done.
The other part of the team which was Clare, worked on the program using a spare robot. She has finished programming the robot until it hits the wall using the touch sensor. We will then be trying to work out the problem on the robot turning when it hits the wall. If all goes well (and I'm sure it will) we will be ready to complete the challenge by Monday.

Building Strategies for the Challenge-Bot

The key points to remember from chapter 6 when you are building are, modularity, balance stability, proper structual suppport and making it lightweight and as strong as possible.

The new Obstacle course

The obstacle course which we will do next week will not be easy. We have to guide the robot through a course filled with obstacles. This will be hard because we have to use all four of the NXT's sensors in this course. The sensors are the touch sensor, the light sensor, the sound sensor and the ultrasonic sensor.
THe course starts of with a clap. We will have to gather our threshold value for the sound sensor. the robot will then move. The hard part is when we have to make it stop in the box. we might have to put the light sensor in the back of the robot. To make it wait therefor 5 seconds, i will put a wait for block. Then the robot will turn and there will another obstacle(a table). We will have to turn the robot before it hits the table. The ultrasonic sensor will cometo place here. Then there will be the final obstacle which will be to destroy 2 cans. I think that we will have to have a sort of mini toy gun to shoot them away.

Chapter 1: Understanding LEGO Geometry

Chapter 1 in the LEGO MINDSTORMS deals with the basic building material we use to build our robots with. LEGO bricks are usually represented in three numbers, representing Length, widt and height. The standard way to use LEGO bricks is "studs up". The width and lenght are expressed in terms of studs, also called LEGO units.
The LEGO system includes a class of components whose height is one-third of a brick. The most important element of this class is the plate. If you stack three plates, you get the height of a standard brick. It takes 9plates to make 3 bricks.
In 1977, LEGO decided to introduce a new line of products which targetted older audiences. It was called LEGO TECHNIC. It turned the 1xN brick holes into what we call a TECHNIC brick or beam. THese holes allow axels to pass through them, and permit the beams to be connected to each other via pegs.
If you want to construct a robot that needs to be strong but light, you would have to use a number of beams, plates, and pins to create the frame, and potentially you would need to cross-brace it. You should create a strong chassis. Building a strong and light chassis is pretty straightforward.
We shold not have everything in right angles because of the advent of studless parts, diagonal connections are mainstream now, makinf our world a bit more varied abd interesting and giving usanother tool for problem solving.
There is a question some people will ask. How would you bace a stack of beams with a diagonal beam?
First you must look at the diagonal bea as though it were te hypotenuse of a right-angled triangle. Then proceed to measure its sides, remembering not to count the first holes, because we measure lengths in terms of distances from them. The base of the triangle is 8 holes. Its height is six holes . Remember that in a standardized grid, every horizontal beam is at a distance of two holes from those immediately below and above it. It counts 10 holes in lenght. For people who have never been introducedto Pythagoras theorem, it is this.
Pythagoras Theorem is a theorem which is used in right angled triangles. The sides of the right angled triangle are called opposite, hypotenuse and adjacent. Lets call opposite and adjacent A and B and lets call the hypotenuse C. The equation is this:
(AxA)+(BxB)=(CxC)
(8x8)+(6x6)=(10x10)
64+36=100
100=100.

Aarshin's Field of View Experiment

On Monday, th 3rd of November, we did an experiment which was called "Field of View". The aim of this experiment was to see how far the NXT 's ultrasonic sensor could "see" an object. I had Michael Cummings, Drew Luthy and Avery Kennedy. We first used a ruler to measure 110 cm from the where we had statoned the NXT. We would then put tape on that line. We would then put our object (a 100 Plus can) anywhere between there. If the robot could "see" the object, we would place a pece of tape there. One thing we found out was that the robot cannot see objects that aren't straight in its path. The ultrasonic sensor couldn't detect any object that was towards the side. Our robot detected the object almost wherever we had put it (except if it was in the side). All of us put equal effort into this experiment.