Playing with Gears

Chapter 2 is basically about the relation betw een v elocity and torque by the means of gears.

Gears have two basic properties; they transfer motion from one axle to the other, and two axles turn in opposite directions. Torque is a new quite c omplicated(at least to me) concept that first appeared in this chapter. Torque is the product of force and distance, which can be increased by either increasing the applied force, or increasing the distance from the center of rotation.

Gears are originally used to make changes in velocity of rotations. For example, when two gears which are 8t and 24t are connected, the gear ratio i

s 3:1 and 8t spins three times than 24t. When two gears are meshing together, if the velocity increases while the torque is reduced, it is called "gearing up". On the other hand, it is called "gearing down" when the velocity is ruduced whereas the torque increases.

The geartrain is a way to convey energy with the same direction of rotation with changes in speed which can be modified easily. However, for more smooth running of the robot, less process is needed because of the friction caused between gears. There are many types of gears such as worm gears and bevel gears that change direction of transferred energy, clutch gears that limit the applied strength and knob wheels which are

actually not gears but have same roles as the bevel gears. Except gears, there are other efficient devices. Pulleys and Belts transfer energy to the romote place keeping the direction of energy.(clockwise or anticlockwise) Chains have same properties as the pulleys and belts but they don't have any likelihood of any slippage and accurate calculations are available. By using several types of gears in a complex form, another type, the differential gear is created.

Get in Gears investigation

Today, we've rebuilt the taskbot and put some changes in the gear ratio in order to experiment relations between their speeds and the numbers of their teeth or their sizes.

There are basically two gears: the driving gear and driven gear. The driving gear is a gear that is directly connected to the motor with a stick that goes though centers of both of them, and the driven gear is a gear that is attached to the wheel and connected to the driving gear.

Today, we put a 24t for the driving gear and a 8t for the driven gear, which resulted in the really high speed. Based on it, I could've reached a conclusion that as the size of the driving gear increases, the speed of the driven gear increases as well, whereas as the size of the driving gear decreases, the speed of the driven gear decreases.

Classic Projects

The chapter 14 is a kind of review chapter revealing connections of what we have learnt such as gears(which are going to be learnt soon), a differential drive, bumpers, ultrasonic sensor, light sensor and general assemblies of components for a best suitable form for each cases.

In this chapter, there are a few points that are needed to be reminded. When touch sensors are used, it is better to have a long stick attached to it so as to lengthen the range of the detection of the sensor. It makes sure that the robot is away from damages, detecting objects more precisely. However, there is a disadvantage of using it, which is a possibility for the robot to get stuck in the gap at a wrong place. As a possible solution, it can be replaced with the ultrasonic sensor. 

There can be changes in gear ratio for safety by slowing down and reducing the impact when colliding.

Ending of obstacle challenge 19/11

As what I've predicted, friction of the carpet has been the most borthersom obstacle. However, after dozens of experiments and modification of the robot, we managed to overcome the friction more often; it didn't have a certain pattern all the time, but it just changed time to time. 

When we began the challenge, for the stability of the robot, we tried to add one more wheel at the each side, which ended up with an unidentified problem; we took them out again. By adding some beams at the sides of the wheels, the robot could've had more stability. After it, other obstacles were smoothly done.

While finishing the obstacle challenge, I had a feeling of accomplishment as a result of such a hard mission. I'm delighted to have had the challenge as it is a great help for future projects and it gave me some lessons about how to build a robot and how to cooperate.

Beginning of obstacle challenge (13/11)

Today, we started working on programming, aiming accomplishing two challenges with the light sensor and touch sensor. Its overall result is considered to be good. However, another obstacle surfaced: the friction. Just 1cm of change in direction when starting made a great difference at the end. It is still not solved and remaining as a hardest challenge that we are going to spend most of the time on. So far, it is considered that if the friction problem is solved, others would be done without any problems.

Application of chapter 6

1. Connected parallel beams (page 117)
The most apparent use of them is the beams that connects the rear caster and the main part.

2. A modular assembly (page 119)
Frankly, I've done my job not knowing it so it is not used much but there IS mocular assemblies of main three parts, the NXT, where the motors are and where several sensors and a rear caster are.

3. Balanced the load on your robot (page 121)
Thanks to Loren, my partner who continuously reminded me the point, we've kept supporting beams, wheels and gear closest without disturbances in their own jobs.

Chapter 6 Summary

The Chapter 6 "Building Starategies" is generally about how to build robots effectively with subchapters divided into five: studless building tech, modularity, loading structure, assembly and hybrid robots. In the summary, it says things that are written are only suggestions but let's have a look at it and see how it can help us.

When several beams are connected, the mostly-used and helpful method is "parallel linkage" which is a method to connect beams in a parallel position. However, as the robot is being built, it is discovered that compression and tension by weight of a robot cause for the robot to be apart. To counter this, not only one support is used for each of them but two supports at both sides of each of them are used. The key point is that though more components are added to make the robot more rigid and strong, it should remain light to have less effects by inertia from weight of the robot, which disturbs immediate changes in motion.

Maximizing modularity is strongly recommended in this chapter for two main reasons; it is easier to attach additional components without affecting whole structure and mobility is improved since it can be taken apart and reassebled wherever I want. It can be done by building subassemblies.

Where should a supporting beam be to support an axle of a wheel? Can it be far from the wheel or can it be just close to a gear? All of the previous suggestions can happen but in a way of efficiency, the supporting bean has to be nearest to the wheel without disturbance. Plus, if it is a case that more than two gears are connected, then it is better for a supporting beam to connect them in a same direction as theirs. By the way, in a way of balance, the main part and the heaviest part, NXT, is better to face upward and to be near the two main wheels.

At the ending of this chapter, it suggests a way to reuse studded LEGO pieces from the previous version, which is called "Hybrid Robots" The term is used when both studless and studded pieces are used and generally it happens to be more flexible, more rigid and better looking.

Obstacle Course Challenge

Your team will need to design and build a robot that uses all 4 sensors. You will then need to program your robot to maneuver through the obstacle course in the quickest time.-Mr. Inskeep

The challenge is basically about whether all the functions that we've learnt can be applied. The steps of the challenge are following :

1. begin with reaction to a clap

2. stay in the bow for 5sec

3. run into the marked box on the wall in front and turn right using a touch sensor

4. turn right with an ultrasonic sensor

5. avoid a stack of cans and halt after the final line

I've not thought about it deeply but the first, third and forth steps are considered to be easy to be done. The second step can be done with a light sensor attached at the back of a robot so that when the light sensor reads the white line it stops in the box.

However, it is difficult to plan how to get to the final line without bumping into the cans since they will be placed randomly. If they are stable enough to endure the impact of a robot running into them, the touch sensor might be able to be used but the thing is they are not. Therefore, the ultrasonic sensor or projectiles are only ways in my thought. My solution for that is to detect the objects with an ultrasonic sensor right in front of them and to go around them. The direction has to be changed according to the position of the cans in each cases because if they are at the right side of the track and it is programmed to go around it in the right side, there's a possibility for the robot to move out of the track.

Something that is considered to affect the difficulty of the challenge most is to make the robot run properly regardless of the effects of friction of the carpet.

Chapter 1 Summary

This chapter is mostly about how to use components from bricks to TECHNIC liftarms, properly without confuse. It is essential to know basic concepts of the mathematical relations of those components for complex designs and applications. The LEGO system is based on the metric system and each of the components has its certain ratio of length and height. The most important and basic concept is that the proportion of height and length of the LEGO brick is the ratio 6:5 . In addition, the height of the brick is same as the height of the stack of three plates.
As further experiments go on, sometimes it is needed to build up frames and what makes them more stable is diagonal bracing. To measure the diagonal length to be able to fit in precisely, the Pythagorean theorm is used, which is basically a formula about the relations of the sides in a right-angled triangle. a^2+b^2=c^3(c is hypotenuse) It useful examples are 3:4:5, 15:8:17, 5:12:13 and so on.
Lastly, liftarm bracing with TECHNIC liftarms is illustrated explaining the advantages of using the TECHNIC liftarms, which were newly introduced to complement scant diversity of applications in the past.

Field of View

Purpose

- to be able to find the area where an ultrasonic sensor can detect objects.

Materials

- 1m ruler

- tape

- a maker pen

- a can

- a robot with an ultrasonic sensor

Procedure

1. attach 1m of tape along the line the robot is going to face.

2. mark every 10cms of the tape (unnecessary but convenient when measuring distances)

3. place the robot at the end of the line facing the other end

4. run the program of detection of an ultrasonic sensor in the "View"

5. place the can everywhere in front of the robot and test whether it detects

6. while moving the can further away from the robot along the line, examine how far the sensor can detect side to side.

7. mark where the sensor could detect with tape

8. label positions of the tapes like coordinates

9. record the positions in paper just in case.