Gears and Gyro Sensor

Unit II Robotics

ObjectivesBenchmark # 03.03Benchmark Text: Describe the types of sensors and ways in which they can be categorized.Learning Goal: The student will be able to describe the types of sensors and ways in which they can

be categorized.

Benchmark # 06.01Benchmark Text: Describe the steps involved in the engineering design process and the activities

performed in each step.Learning Goal: The student will be able to describe the steps involved in the engineering design

process and the activities performed in each step.

Benchmark # 06.04Benchmark Text: Explain and demonstrate how gear ratios are used for increasing or decreasing power

or speed.Learning Goal: The student will be able to explain and demonstrate how gear ratios are used for

increasing power or speed.

Engineering Project 1• Student will be able to build a toothpick and popsicle

stick device that with the drop of a marble will accurately propel a ping pong ball to a half ceiling tile square on the ceiling.

• Student will create a marble dropping device that reliably aims the marble at the correct location of their device AND releases the marble at a height capable of providing enough kinetic energy to their ping pong ball.

Engineering Project 1 Scoring• 10 pts each for detailed plan sheet for their device and their

marble drop device.• 20 pts for the data sheet and modify sheet created with the

facts of how their tests performed prior to demonstration day• 20 pts for a marble drop device that is dependable and

available on test and modify day• 10 pts for a complete project that is ready for test and

modify day• 10 pts for a device that has a 90% or better performance• 5 pts extra for a device that can work from the floor• 5 pts extra for a device that is prepared early• 70 pt Total

Gears• Part of a simple machine – gear and axle – that can

change the direction of motion, change the speed of the output and/or change the input force

• A gear will have some number of teeth• Gears that work together will have teeth that are

similar if not the same size

Gear Vocabulary• Spur gear – gear with teeth• Bevel gear – gear that has

curved teeth so that 90° angles can be created

• Worm gear – looks like a screw and can cause the axle to move out and back like a piston

• Idler gears – gears placed between the input and output gear; often serve to change output direction

Gear ratios• A gear ratio is a value calculated from a set of gears

interlinking and it indicates the change in speed• The first gear is the input gear (or driver gear) and its

speed is only dependent upon the motor it is attached to• The output gear (or driven gear) will move based on the

speed of the first gear and the gear ratio established. The last gear is the output gear.

• Gear ratio = • Gear ratio = = 2.8 2.8 : 1• The input gear has to turn 2.8 times for the output gear to turn onceHow is the speed affected?

Video Helps• How gears work• https://www.youtube.com/watch?v=vxehMTBQI6Y• Gears and Wheels Part 1• https://

www.youtube.com/watch?v=D_i3PJIYtuY#t=250• Simple LEGO Gear Train• https://www.youtube.com/watch?v=jrYROS8tipI• How to make a 4 speed LEGO gear box• https://www.youtube.com/watch?v=r05_Cq1XH8E

Gear Ratio – Show Me

30 ptsUsing the SAE kits you will prepare three setups with the kit and calculate the gear ratio

according to the following directions.

Set up 1• Choose any two gears that are different in size. Place them

in a line on the frame so that the gears interact. The gear on the left will be your input gear and the one on the right will be the output gear.

• Calculate the gear ratio. Gear ratio = . . . Write out the calculation before showing the answer.

• Position the gears so that the lines touch each other. Turn the input gear as many times as is necessary to see the output turn once. Write a sentence describing what you saw.

• What direction is the rotation of the output gear compared to the input gear rotation?

Set up 2• Choose any four gears that are different in size. Place them in a

line on the frame so that the gears interact. The gear on the left will be your input gear and the one on the right will be the output gear.

• For this one multiple each ratio between the pairs of gears. Then calculate the gear ratio of only the input gear and output gear. Gear ratio = . . . Write out the calculation before showing the answer. This part will have TWO calculations.

• Position the gears so that the lines touch each other. Turn the input gear as many times as is necessary to see the output turn once. Write a sentence describing what you saw.

• What direction is the rotation of the output gear compared to the input gear rotation?

Set up 3• Choose any three gears that are different in size. Place them in a

line on the frame so that the gears interact. The gear on the left will be your input gear and the one on the right will be the output gear.

• For this one multiple each ratio between the pairs of gears. Then calculate the gear ratio of only the input gear and output gear. Gear ratio = . . . Write out the calculation before showing the answer. This part will have TWO calculations.

• Position the gears so that the lines touch each other. Turn the input gear as many times as is necessary to see the output turn once. Write a sentence describing what you saw.

• What direction is the rotation of the output gear compared to the input gear rotation?

“How Fast?” Lab 30 pts.• Supplies: EV3 robot, Mindstorms Program (move steer

block), starting line, meter stick and timer.• Create data chart in Interactive Notebook:

Power Level Trial 1 Time Trial 2 Time Average

10

20

30

40

50

60

70

80

90

100

How?• For your designated test area there will need to be a tape

line for the start mark.• Be sure that at least 65 cms are in front of the line.• Program a move steer block program. Start with the power

at 10 and the rotations set to 5.• Set the robot on the test site with the tires lined up on the

back edge of the line. Run the program.• Time from the start to the stop. On this first run, also

measure and record the distance.• Repeat this test.• Repeat the above test with the next power level.• Repeat above until the chart is completed.• All data must be collected today with this robot.

AnalysisCalculate the averages for each power.Graph the Time taken average (y) vs. the Power level (x)Beside each average now calculate the speed. Distance /TimeGraph the speed in cm/sec(y) vs. Power level (x)Determine if there is or is not a relationship within each graph and if so, what is the relationship. Explain.

Follow the Line Expansion

Follow the Line Expansion Program

• Individual program 20 pts.• You will be assigned a mat that has three colors of

tape. Your robot needs to be able to go from one end of the mat to the other end of the mat following the line.

• 5 pt bonus if you make the robot walk the line smoothly!

• One possible way to do this • https://www.youtube.com/watch?v=ODAGVeeDagk

Gyro Sensor

• Gyro sensor – detects rotational motion. If you rotate the Gyro Sensor in the direction of the arrows on the case of the sensor, the sensor can detect the rate of rotation in degrees per second. You can use the rotation rate to detect, for example, when a part of your robot is turning, or when your robot is falling over.

EXAMPLE 1: TURN BY A SPECIFIED ANGLE

                                                                            

This program makes a robot turn 90 degrees to the left. It uses the Wait block with the Gyro Sensor - Change – Angle mode to wait for the rotation angle to change by 90 degrees.

Gyro Sensor Assignment – 30 pts.

• This is a pair assignment using the current maps. You will program your robot to follow the inked line to one obstacle using the gyro sensor to make the needed turns. Then you will do follow the line to return to the stop box. Note: there are two colors of tape to follow and black tape in the end box. These will need to be used as well.