Chapter 2 - Gears

Chapter 2 was mainly about gears, what they are used for, and how they work. The main reason for using gears, is to apply a torque to velocity ratio. This allows an engine or rotating axle produce either more pushinf power or a higher rate of speed. In a race car for example, where the vehicle is light, the large gear is the driving gear, and the small gear is the driven gear. This would mean that the driven gear would turn a lot more times for each rotation of the big gear. In a bulldozer, a device which requires lots of pushing power, the small gear is the driving gear,the driven gear is the large gear. This would mean that the driven gear would only turn once for more than one turn of the driving gear, increasing overall torque, but reducing speed.

Getting in Gear Investigation : Torque vs Speed

Today, we explored the wonder of gears. Every day, in millions of cars worldwide, gears turn, and change to serve different purposes. We explored this phenomenon today in class, using our NXT taskbot. The first thing we did, was to put the largest gear we had on the driving gear, this gear had 24 teeth. We then put the smallest, 8 tooth, on the driven axle, and watched our robot go at amazing speeds! Just a few minor modifications to the steering mechanism, and ramping the speed up to 100, and we were really flying. This is beacause the driving gear was 3 times as big as the driven gear, meaning that there was a 3:1 gear ratio, in turn meaning that the driven gear turned 3 times for every time that the driving gear turned. Afterwards, we traded spaces, and put the small gear into the driving spot and vice versa. This created mountain-moving torque capabilites, and gave our bot amazing pushing power.

Questions and Answers - Chapter 6

Kenny sent me these questions to answer using the book. The first one was,
Black and blue pegs provide much more friction than the other pegs. The gray and tan pegs have no friction, because they are meant for moving parts. The next question was about parallel linkage. Parallel linkage is when you link two parallel beams with one beam perpendicular, or multiple perpendicular beams at intervals. Tension and compression are both forces. Tension attempts to stretch or lengthen an object, and compression will attempt to shorten or compact an object. Inhertia is the tendency that object have to resist changes when in a state of motion or rest. The added beam on fig 6.10 on page 123 reduces gear slip, and allows the gear to stay on steadily.

Introductions..

Hey guys, today I would like to introduce a new friend of mine. His name is The Beast.

Today, Kenny and I finally tested our self constructed robot! After writing a quick program, we set it to the test, and it performed beautifully. With nervous gazes our robot approached the final stretch, with only cans in it's way, and to raging applause, it fired its cannon into the obstacles, and rode to victory! (it forgot to stop though) After a few tests, we managed to tune some of the turns and various parts of the program in order to complete the course successfully. The only thing that we still have to do by wednesday, is finish the extreme fine tuning, and perhaps find a better steering mechanism, since our robot veers off course quite disruptively at some points.

Building Strategies -

We have many different ideas to increase the versatility and strength of our robot, but one that I am currently focusing on is the truss. A triangular shape provides extraordinary strenght, because of its remarkable capability to divide weight evenly on all sides, and maintain a sturdy structure and shape. They are used in a variety of constructions, from bridges, to roofs, because they are so incredibly stable. We are striving for ultimate strength, while maintaining the maximum amount of versatility possible, and in order to do so, our robot must be compact, yet be very structurally stable. more to come..

Obstace Course Challenge!

We have been faced with a difficult task. We are to build a robot, to maneuvre an obstacle course, consisting of 6 sections.

1. Clap, to activate your robot. Our plan is just to add a simple sound sensor, and add programming to activate the overall program when a clap is heard.

2. Stop in the marked square. We have decided to add a light sensor on the back of the robot, so that it stops after it enters the square. Since it is at the back, the robot should already be in the square when it stops.

3. Hit the wall, and turn right. We plant to build some sort of bumper onto the front of the bot, and then have it back up and turn to head to the next obstacle.

4. Sense the wall, and then before hitting it, turn right. We plan to use an ultrasonic sensor and set it to a 15cm threshold in order to detect the wall, then turn right when it detects an object within 15cm.

5. Sense or Hit the cans, then move around. This is where it gets interesting. We have already designed an intricate firing mechanism, utilizing the 3rd motor. When the ultrasonic sensor detects the cans, it will fire the cannon, obliterating all in our path.

6. Stop after the line. Same deal as step 2, only now it is a line instead of a box.

And there is a short outline of our plan.

Niclas recently sent me some questions to answer, and here they are.

The first question was : 
1. Tom made a chassis in his robotics class and he has to re-create one side at home but he can only remember that the size of the vertical and the diagonal Lego bits. The diagonal beam was five units and the vertical was three units. How long was the Horizontal beam? I realized that the pythagorean theorem could be (should be) used in this question, as it is a right triangle. So, 3squared + x squared = 5 squared. This is a commonly known "special triangle, 3,4,5. 9 + 16 = 25 Then, we move onto the next question, when was lego technic introduced? Well it was first introduced in 1977 as the expert builder series, then in 1984 it was renamed to the now famous Lego technic. Lego bricks are measured in units called FLUs or Fundamental Lego Units, but can also be measure in the metric system as seen above. 

You can visit our ISKL robotics blog here.

Bart's Field of View Experiment (with Niclas, Navid and Kenny)

Today, we did a new experiment to test the range and visual (ultrasonic) limitations of our NXT's ultrasonic sensor.

First, I would like to introduce our trusty NXT

Other materials -

- Hard surface

- Meterstick(s)

- Tape

- Something to record data with.

In order to complete the experiment, we used the suggested set up, placing the NXT on one side of the board, and a long stretch of tape across. Then we were able to examine whether the NXT was able, or unable to detect a coke can. We started off by placing the can at the limit of the NXT's range, to determine the furthest it could see in a straight line. Then, the closest. From here on, we moved forward at intervals and found out how wide the field of view was for the NXT, by moving the can all the way to the maximum horizontal range of the ultrasonic sensor.

When we had finished, the board looked like this. Concluding that the field of view is somewhat parabolic, yet it has a maximum point, which is somewhere along the center which is when the field is at it's widest.

Recap:

1. Place NXT on one side of board, place straight stretch of tape approx 1 meter long leading away from robot.

2. Using can technique, measure furthest distance robot can detect, then nearest.

3. Measure in between furthest and nearest point at equal intervals.

4. Using a ruler/meterstick, measure actual distances in cm/in.

5. Record data in either a data table or on a graph.

-Bart