Quadcopter Challenge

Steps

I.  Assembling the Internals
II. Chassis Digital Design
III. Making Prototypes
IV. Testing and Iteration
V. The Quadcopter Challenge

I.  Assembling the Internals – 2 Hours

1. Teams begin the project by soldering their receiver and motor wires together, with educator permission and supervision.
   • Please note that younger students may be given pre-soldered receivers and motors.
2. Provide teams with soldering stations.
   • Review soldering safety tips.
   • It is beneficial to have students practice soldering on old and broken parts, when available. Allow students as much time as possible to get used to this skill. Another good source of soldering practice is broken Christmas lights or old LEDs, which may be soldered to a conductive surface and tested with a battery.
3. Review the following images of a finished receiver. Students can compare the images to the parts in front of them. Teams should pay close attention to how each soldering point on the receiver has a positive and negative terminal, and a specific color wire that solders to each. If wires happen to be soldered in reverse, the motor will spin the opposite direction, making the quadcopter incapable of Further, the orientation of the receiver in relation to the color of the wires is just as important. The blue/red motors spin clockwise and the black/white motors spin counterclockwise. If soldered correctly, the spin of the motors cancels each other out, resulting in zero net torque and the ability to hover.
   • A correctly soldered receiver board is shown below
   • Quadcopter fabricators must carefully study these images in order to solder positive wires (red/white) to positive terminals and negative wires (black/blue) to negative terminals:
4. Begin soldering, making use of the PowerPoint slides to keep students on task.
   • This image shows the easiest way to lay out hardware for soldering:
   • Note that in the next image, the receiver has been taped to This ensures it does not move during soldering. Cardboard, construction paper, or foam core all work well as disposable or recyclable workspaces.
     
   • Referring back to the slides when necessary, allow teams to solder their motor wires to the receiver board. Students should carefully consult the slides in order to make sure their work is correct. As mentioned, if motors are not soldered correctly, they will either fail to spin or spin in the wrong direction. Once complete, receivers should appear like the example in the following image:
     
   • When soldering is complete, stations should be cleaned, and students can move onto the next phase of the lesson.

II.   Chassis Digital Design – 2 Hours

1. Teams now move to the chassis digital design phase. Groups need a “skeleton” framework to hold their motors, receivers, and batteries in place. For the purpose of this lesson, teams will work with digital design software (CAD) and a CNC machine (preferably a laser cutter) to create their chassis. This lesson can be adapted for classrooms lacking such technologies by having students draw on source material and cutting it out manually. If adapted as such, please allot more time for this phase, as utilizing CAD software and CNC machining greatly expedites the iterative design process.(photo courtesy of Penn College)
2. Examine the science behind quadcopter
   • Watch “Quadcopters: An Inside Look” found at: https://youtube.com/watch?v=YmGUrjdpAv8
   • Watch “Quadcopters: An Inside Look” found at: https://youtube.com/watch?v=YmGUrjdpAv8
     1. Answer: Earth’s gravitational pull of 9.807 m/s2.
   • Question: Which force can counter Earth’s gravitational pull?
     1. Answer: Lift, created by spinning propellers. Lift is the upward force. It varies depending upon how fast the motors are Further, the amount of thrust provided varies with the throttle.
     2. An interesting point to present is the difference between an airplane and a quadcopter. On an airplane, lift is provided by wings, while thrust is created by some sort of separate motor, such as a jet engine. On a quadcopter and helicopter, the motor and wing are merged into a single unit. This allows the quadcopter to hover, whereas airplanes must be moving forward to create lift. Airplanes have an advantage of being able to fly faster and higher than quadcopters / helicopters.
   • Review the slides that cover what sort of major engineering characteristics need to be considered when designing a quadcopter.
     1. Students should be cognizant to not block too much airflow, thus restricting lift. If a majority of the airflow is blocked, the quadcopter will not lift off of the ground. Quadcopters are very sensitive to even small changes in design. Thus, if one particular design does not work, removing a small amount of material from beneath the propellers may result in the next iteration flying well.
     2. Students may, at some point, wish to block some airflow to make the quadcopter easier to fly. Teams should be reminded that quadcopters that fly fast and high can be difficult to control, and may work against winning the The most precision-controlled quadcopters will probably win. Designs can be a mix of maneuverability, speed, and ease of flying. Teams should choose the best mix of properties for their goals.
     3. Teams need to consider the span of the propellers. If they are placed too close together, the quadcopter blades will hit each other and break. The provided digital design template incorporates scale propellers, in order to allow virtual modeling of designs before fabrication.
     4. Designers need to consider the length of the motor wires. They can only be stretched so far. The digital design template incorporates scale motor wires, in order to allow virtual modeling of designs before assembly.
3. Use Inkscape (CAD) software to create multiple prototype chassis.
   • Work through the following steps to create, with teams, an example chassis. Depending on the skill level of designers, the amount of direct instruction can be shortened or lengthened. The following steps assume that students have had minimal-to-zero previous design experience. If students are experienced with such software, the facilitator may choose to simply let teams experiment with the template, or, perhaps, a blank document.
   • Before beginning, make sure to have students select their source materials: cardboard, foamcore, or any other material able to be used in the CNC machine of choice.
4. Load the “Quadcopter Challenge Chassis Design” template onto each design computer.
5. The shapes under the shape library are vector lines. They tell CNC machines where to remove material. Select and move one of the squares into the workspace. The workspace represents a 4.5” x 4.5” piece of source material, as viewed from above. Work contained within this space can be exported to a CAM program and a CNC machine. Any work outside of the workspace will not be exported.
   
6. Move the receiver and motor wire virtual model onto the workspace, within the square vector box. Explain to teams that this represents a true-to-life scale model of the receiver and motors in front of them. Therefore, if they design their chassis to fit within the parameters of the virtual model, their CNC machined chassis will be scaled correctly. The wires represent their longest reach. As long as the motor holes appear somewhere along the wire line, the chassis design should work. Slack in wires can be taped down. Finally, resize the square smaller.
   
7. Select, move, and resize another vector box from the shape library. Position it on one corner of the main chassis.
   
8. Rotate and resize the motor arm.
   
9. Copy and paste the remaining arms in place.
   
10. Rotate the arms. Use guide lines to make the design symmetrical. The arrow keys on the keyboard are useful for micro-movements.
    
11. Remove the virtual receiver and wires.
    
12. Click on view -> guides to hide the rulers. Select all of the pieces. Use the path -> union function to join them into a single unit, so that the CNC machine only traces the outside of the If the vector lines are not joined, the CNC machine will actually remove nine shapes from the source material.
    
13. Click on view -> guides to bring back the rulers. Copy and paste circles at the end of each arm. Align them with the guidelines. These will act as motor mounts.
14. Hide the guide lines. Select every object within the workspace. Use path -> union to remove superfluous internal vectors.
    
15. Bring back the guide lines. Move the motor holes into place, making sure to adjust the diameter depending on the source material. If working with material that has “give,” such as corrugated plastic or foamcore, the holes should be smaller than the .276” diameter of the motors. If time permits, students can measure the diameters of their motors. Generally, .27” works well for cardboard, .26” for foamcore. Motors should fit snugly into the holes. Have teams experiment with different sizes.
    
16. Utilize the virtual propellers, as well as the battery model, to see if the hardware will fit on the chassis. Teams should pay close attention to the propeller blades. By clicking on each blade then rotating them using the [ and ] keys, students can make sure the tips of the propellers do not touch.
    
17. Remove the virtual models (propellers, battery, and chip). The chassis is now ready to export to a CAM program and cut on a CNC machine. This is another good time to discuss that this chassis will act as a prototype. Teams can change the design as they see fit, after initial test flights. Depending on the material, the design can be cut twice and layered together, adding strength.
    
18. If time and designer skill level permits, students can experiment with changing their initial prototype to strengthen it, for example.
    
19. Move files via a cloud or USB drive to a CAM program and a CNC machine to cut prototypes.

III.    Making Prototypes – 2 Hours

1. Teams lay out their quadcopter hardware kits:
   • Radio receiver and motors
   • Battery
   • Propellers
   • One or more chassis
2. Groups share the following materials:
   • Groups share the following materials
   • Various styles of tape
   • Hot glue
3. Fabricators must differentiate between the top and the bottom of the radio  receiver.
   
   • If the top of the receiver is not oriented correctly relative to the tops of the motors, where the propellers attach to the spindles, the quadcopter will not fly or, at best, fly erratically.
   • Discuss with students why this is the case: quadcopters can fly in the positive and negative x, y, and z dimensions.
   • Discuss with students why this is the case: quadcopters can fly in the positive and negative x, y, and z dimensions.
     1. Modern smartphones are also equipped with similar sensors, allowing them to know where they are located in space.
     2. Higher tech and more expensive quadcopters also feature magnetometers, which measure Earth’s magnetic field; pressure sensors, to measure air pressure and provide altitude readings; and even GPS sensors, to triangulate location based on information received from geosynchronous satellites.
     3. Quadcopters can even be equipped with cameras, mass spectrometers, and other useful tools.
   • The receiver has software embedded in its onboard memory to read and interpret input from these sensors.
   • When the sensors are correctly positioned and calibrated, the receiver’s software will automatically make tiny adjustments to the amount of electrical current flowing to each motor, stabilizing the quadcopter’s flight. Imagine if a pilot had to make such adjustments, hundreds or thousands of times per second, to four or more motors! Luckily, the receiver’s programming makes this impossible feat possible.
4. Secure the receiver to the center of the chassis using scotch tape. During later iterations, students may wish to apply hot glue the receiver in place.
5. Insert the motors so the receiver and motors are both face up. The motors will have to be gently forced through the material, since the motor holes should have been cut to be slightly smaller than the motors. While inserting the motors, use caution with the wires, which are thin and easily damaged. Any slack in the wires should be taped down, so that they do not catch on anything during flight and cause damage to the quadcopter.
6. Add propellers to the quadcopter motor spindles. Since two of the motors spin clockwise and two spin counterclockwise, teams must carefully note propeller placement, as two of the blades will be for clockwise motion, two for counterclockwise. Each propeller is labeled with a small raised letter, “A” or “B.” Propellers labelled, “A” go on the red and blue wired motors. “B” propellers mount on the black and white wired motors. Different colored propellers can be positioned so that there is a clear differentiation between the front and rear of the quadcopter.
7. Gently squeeze the center of the propeller and align it with the spindle. Support the bottom of the motor while pushing down on the center of the propeller.
   • There should be a tiny gap between the top of the motor and the bottom of the center of the propeller. If students make a mistake in placing propellers, make sure they use a U-wrench to remove them, not their fingers.
8. Attach the battery to the chassis with scotch tape. Line up its cord with the receiver’s power cord. The battery’s location on the chassis will depend on where the receiver is placed. If the receiver is on the bottom of the chassis, tape the battery to the top. If the receiver is on the top of the chassis, tape the battery to the bottom. Regardless of the location of the receiver and battery, they should roughly align with the middle of the chassis, maintaining a balanced center of gravity. If the battery or receiver is placed too close to the edge of the chassis, flight characteristics will be negatively affected.Multiple charged batteries can be kept on hand, since they only provide three to five minutes of flying time and take more than thirty minutes to charge. Using scotch tape allows the batteries to be quickly swapped. If students are unfamiliar with electronics and circuits, the battery would be an excellent example to use in communicating how they work. It uses Lithium ions to pass electrons through a polymer. The electrons can move both from positive to negative ends (charging) and from negative to positive ends (discharging).Lithium-Polymer batteries are favored for quadcopters because they do not have a rigid metal shell, thus making them lighter.

IV.     Testing and Iteration – 3+ Hours

1. Quadcopters are now ready for test flights.
2. Review safety tips with teams:
   • When flying a quadcopter, always wear safety goggles.
   • Never turn on the throttle while a quadcopter is in someone’s hands. The blades can cut or scrape skin.
   • Only turn on the quadcopter when it is on the ground, in a large, open room.
   • In the event of a crash, watch out for errant propellers. They may dislodge from the spindle during harder collisions. They have lots of momentum and can spin off in unpredictable directions and speeds, potentially damaging uncovered eyes.
   • Make sure the flying area is clear, especially of other quadcopters.
   • Be ready to shut off the throttle at any time.
   • Be aware of surroundings.
3. Connect the receiver and battery.
4. The blue LEDs on the receiver will flash alternately.
5. Turn on the controller. Its power indicator light will shift from red to green.
   • Note: If more than one quadcopter will be flying at the same time, make sure that receivers and controllers are powered on one at a time. Controllers can sync to any powered receiver. This can cause confusion if more than one receiver and controller is powered on at the same moment.
6. After a few seconds, the LEDs on the receiver will flash at the same time. If the lights stop flashing and shine solidly, the quadcopter is ready to fly. Be aware that when multiple quadcopters and controllers are turned on at the same time, they may connect to each other. Use caution when turning on the throttle for the first time.
7. Before attempting flight, the quadcopter should be calibrated, in order to allow the receiver’s sensors to orient themselves in space. To calibrate the sensors, lay the quadcopter on a flat surface, move the throttle to the bottom right corner, then quickly move the right stick from left to right, until the receiver’s LEDs flash.
8. Basic controls –
   • Left stick:
     1. – Pushing the left stick forward or back controls the throttle, or the amount of battery power flowing to the motors. This should be first attempted in small increments. Try to hover the quadcopter a few inches off the ground. If students push the throttle all the way on, the quadcopter will uncontrollably fly away, more than likely damaging it.
     2. – Nudging this stick left or right will cause the quadcopter to rotate laterally.
   • Right stick:
     1. – Pushing the right stick forward or backward causes the craft to tilt that direction, resulting in forward or rearward movement.
     2. – Moving the stick left to right causes tilting in those directions, creating sideways movement.
9. In the event of a crash, make sure the throttle is all the way off. Put the controller down. Pick up the quadcopter and inspect it for damage, making sure all of the motors and propellers are in place. Once the vehicle is operable, give it another try.
10. Becoming a skilled quadcopter pilot will take students many hours of practice, many iterations, and many accidents. Encourage them to keep at it!
11. Remember: when switching between chassis, use the U-wrenches to remove propellers. This will limit accidental damage during removal.
12. After a few test flights, return teams to the design process, encouraging them to make changes to their designs to better help quadcopters fly.
13. Students should be encouraged to evaluate their different quadcopter models.
    • Students should be encouraged to evaluate their different quadcopter models
    • Encourage them to take notes on the performance of different prototypes and note how they did according to the criteria that the groups create.
    • Be sure to make the connection with the students that evaluating designs like this is exactly what engineers do.
14. Be sure to make the connection with the students that evaluating designs like this is exactly what engineers do.
15. Allow teams to practice flying, in preparation for the upcoming competition.

V.    The Quadcopter Challenge – 2+ Hours

1. After teams have had an opportunity to practice flying their quadcopter, they should select the best pilot to enter into the competition.
   • Remind students that, during a collaborative effort, each team member brings a valuable and variable skillset to the others. Some will excel at design, others hands-on building, others at flying, and so on. This models careers in most any science, technology, engineering, and mathematical field.
2. The competition is the most adaptable portion of the lesson, and can easily be tailored to skill and age level, as well as curriculum goals.
3. After the final slide in the included PowerPoint presentation, create a slide that details the rules of the competition. Review these rules with teams.
4. An example competition:
   • Select an indoor, large, open area, free of Gyms, community rooms, and multipurpose rooms work well. Outdoor competitions are possible, but wind and weather make for uncontrollable variables.
   • Set up an obstacle course.
   • In order to challenge pilots, create a course that requires multiple skills to complete. Cones can create a pathway that students must follow, or weave between. Hula-hoops make great gates, if set up vertically, as well as landing sites, if placed horizontally. The course, therefore, will be a mixture of in flight maneuvering, landing, taking off, and avoiding obstacles.
   • Before each pilot begins the course, model the flight path.
   • The beginning and end of the course should be the same spot, allowing for continuous laps.
   • Since batteries provide around five minutes of flying time, pilots should be given three minutes to navigate the course. They must complete each section before moving on to the next.
   • If a pilot completes the course in under three minutes, allow that pilot to continue on to the next lap. Students receive credit for partial laps. For example, one pilot may complete two and quarter laps, the next pilot three and a half, the final pilot four and a third, and so on.
   • The team that completes the most laps wins.
5. No matter what style of obstacle course is utilized, difficulty level can be increased by not allowing students to see the course before the competition begins. The difficulty level can be lowered by permitting students to practice on the course in the time leading up to the competition.
6. If a pilot crashes and breaks the quadcopter during the competition, they may be permitted to fix the drone and attempt the course again at a later time. Alternatively, the pilot may be given a finite amount of time with a “pit crew” to fix their drone.
7. After the competition, bring students back together and recap the lesson’s vocabulary, new skills learned, discoveries made, and so on. Students also like to watch video and pictures taken of the project by both staff and students.

Differentiated Instruction (Extension Activities)

3D printing can be added to make several of the component on the quadcopter if the tools and time allow. Design software could be either Tinkercad, Fusion 360, Solidworks or any other package with similar capabilities. These parts include:

1. Example 3D printed chassis for the Hubsan H107 receiver and motors can be found at:
   • http://www.thingiverse.com/thing:636591
   • http://www.thingiverse.com/thing:435484
   • http://www.thingiverse.com/thing:532432
   • http://www.thingiverse.com/thing:532432
2. Battery holder. Once students are further along in the design process, they may wish to utilize 3D CAD software to design and 3D print a battery holder. This will be much more efficient than using tape every time a battery must be switched.
3. Propeller guards. These will help save propellers from damage during hard landings and crashes