UAV Performance Test: Battery Lifetime

Goal

Students will conduct a simple performance test of aUAV (Unmanned Aerial Vehicle or "drone"). They will determine how long the UAV can remain airborne before its battery runs out of power.

This activity can serve as the first scientific, quantitative analysis of UAV performance after students have learned to fly UAVs with basic proficiency. This activity provides additional opportunities for students to gain more experience and hone their skills flying a UAV. It can also serve as the precursor to other activities, including a UAV Performance Test:Carry a Payload activity that reduces flight duration due to the extra weight carried.

We recommend that students complete the Learn to Fly! UAV Flight School activity as prerequisites to this activity.

Activity Objectives

  • Students will conduct a series of tests to determine the amount of time a UAV can remain airborne on a single battery charge.
  • Students will record and analyze data.
  • Students will compare data from flights using different batteries.
  • Optionally, students will conduct tests with different UAVs to determine whether variations between UAVs as well as variations between batteries influence results.

Time

  • Preparation time: 30 minutes to practice flights, test the duration of UAV batteries, and to prep UAVs for student use (charging batteries, etc.).
  • Class time: at least 20 minutes - The amount of class time depends on how many students can do the activity at the same time, which depends on the number of students in your class, the number of UAV's available, the number of adults available to supervise student groups, and the amount of space available for flying. The amount of time needed also depends on how many students you want to have involved with flying UAVs during this activity, versus observing and recording results.

Materials

For each Student:

  • safety goggles

For each Group:

  • one or moreUAV ("drone") and the controller used to fly it
    • Note:we used the SYMA X5HW-I. Some of the instructions and images are specific to this particular model, but most aspects of this activity can be done equally well with other UAV models.
  • multiple batteries for the UAV
  • a stopwatch or other timer to measure battery lifetime

For the Class:

  • an open space in which to fly (We recommend flying indoors in a large open space like a gymnasium. An area at least 20x20 feet and a ceiling height of 15 feet or more should suffice.)

  • markers and/or tape to place unique identifying numbers on each battery

Preparation

  • Before working with students, conduct a few test flights to determine how long the UAV batteries last and how much variance there is between batteries.
  • Charge batteries for the UAV, including spares.
  • Mark each battery you intend to test with a unique identifying number. Use a marker or a piece of tape with a number on it.
  • If your UAV model includes a detachable camera, remove that from the UAV for this activity. Though not strictly essential, we recommend this to make the UAV lighter (which will make batteries last longer) and help students focus on the activity at hand (instead of taking photos or videos).

Directions

Assign Roles to Team Members

  1. Have students form groups of four. Explain that there are four student roles in this activity:UAV Pilot, Range Safety Officer(RSO),Timer, and Data Recorder. Describe these roles to students.
    1. The Pilot uses the hand-held controller to fly the UAV, power up the UAV's propellers in preparation for flight, and power down the propellers after the UAV lands.
    2. The Range Safety Officer has three responsibilities; explain these to the students:
      • Make sure all students involved with the flight wear safety goggles.
      • Verify that the launch area and airspace are clear before the flight and signal to the Pilot "all clear" when ready.
      • Alert the Pilot if any safety hazards arise during the flight.
      • If a safety issue occurs, the RSO should instruct the Pilot to land the UAV and stop the propellers by pulling down the left lever on the joystick and holding it down.
    3. The Timer starts the stopwatch at the beginning of each flight and stops it at the end of each flight.
    4. The Data Recorder writes down the times for each flight.

Prepare UAV for Flight

  1. Place battery inside the UAV, connect the UAV wire to the battery wire, and close the battery compartment.

Flights

  1. Discuss with the students the nature of their timed flight. Ask the students how they will make sure they are conducting a "fair test" with similar conditions on each flight.
    1. One simple option that provides students with practice flying the UAV and simulates aspects of a "real" flight or mission is to have the UAV fly laps forward and backward along a set distance.
    2. Another option is to simply have the UAV hover in place until the battery runs out. This might make the battery last as long as possible, and would be easy to replicate from one test to another. However, it is less like a "real" flight during which the UAV would move around.
    3. Students might wish to design a more complex series of maneuvers to more fully mimic the range of motions a UAV might fly during a "real" mission, such as moving up and down, left and right, and so on. If they choose such an approach, have them write down and/or explain to the teacher their "flight plan" before they fly the UAV. Designate a Pilot, Range Safety Officer, Timer and Data Recorder for this flight.
  2. Have the Data Recorder prepare a simple table (see sample below), in a lab notebook or on a piece of paper, to record battery lifetimes for each of the batteries students will test.
  3. Make sure the Timer is familiar with operation of the stopwatch.
  4. Place the UAV in the center of the space you have available for flying.
  5. Provide the Pilot with the UAV controller.
  6. When it is safe to fly, have theRange Safety Officer indicate to the Pilot that she can take off.
  7. The Pilot should control the UAV to take off. The Timer should begin timing the flight.
  8. The Pilot should control the UAV to fly laps over the set distance (or to conduct a previously agreed-upon series of maneuvers) until the battery runs out.
  9. The UAV model we used to develop these activities will begin flashing its lights when the battery's charge is low. You may find the UAV more difficult to control once the battery charge is low and the flashing lights come on. If that is the case, we recommend that you have the Pilot safely land the UAV and conclude the test once the lights start to flash. The teacher should test the behavior of the UAVs your class is using beforehand to see if your UAVs become difficult to control once the flashing lights indicate a low-battery condition.
    1. The UAV model we used will rapidly descend and automatically land when its battery's charge is used up. Again, the teacher should test the behavior of your UAVs before conducting this activity with students.
  10. When the UAV lands, the Timer should stop the clock and report the time to the Data Recorder. The Data Recorder should write down the duration of this flight.
  11. Repeat these procedures for however many batteries you have.
  12. This activity could become tedious if each group tests several batteries. To counteract this, you might:
    1. Make this a whole-class group project. Have one group test battery #1, a second group test battery #2, and so forth. If you use this approach, discuss with your students how having different UAVs and Pilots may impact the battery tests.
    2. Or, you can have students switch roles (Timer becomes Pilot, etc.) during each subsequent battery test. This can provide all students with more practice piloting the UAVs, especially if they fly laps or a more complex path while testing the batteries. If you use this approach, discuss with your students the possible impact on your tests of having different Pilots flying the UAV during different battery tests.
  13. After all test flights have been completed, discuss with students the range of values obtained for battery lifetime and how this duration might affect their ability to conduct various "missions" or "challenges" using UAVs, such as taking pictures or flying around an obstacle course.

Sample Data Table

The simple data table (with sample data) the students should generate might look something like this:

Battery Number Flight Time
1 7m 42s
2 8m 3s
3 7m 31s

The data table could also include the number of laps flown and the name of the Pilot for each flight.

Teaching Tips

Safety

  • Avoid wind (we recommend flying in a large indoor open space such as a school cafeteria or gymnasium).
  • Before flying indoors, check the space you plan to use for safety. Are there any light fixtures, A/V equipment, or other sensitive objects suspended from the ceiling that could be damaged if the UAV collided with them? Are there any fire sprinkler heads that might be set off if disturbed by the UAV, flooding the room? Carefully inspect the space for hazards and fragile objects that could be damaged by the UAV. A gymnasium can be a good choice for indoor flying since the fixtures in a gym are generally designed to withstand being hit by objects heavier than a small UAV, such as basketballs.
  • Before each flight, check to make sure the student Pilot knows how to quickly land the UAV and how to quickly stop the UAV's propellers. In the event of a crash, sometimes the propellers will continue to spin (if the UAV is leaning against a wall or is upside down) until the Pilot turns off the propellers. In the case of the SYMA UAV model we used while developing this activity, the Pilot must pull the left joystick towards herself and hold it for a couple of seconds until the UAV propellers stop. Check the instructions for your UAV to make sure you know your model works. Students can become a bit flustered when a UAV crashes, so it is a good idea to review this "emergency" shut down procedure immediately before each flight.
  • Whenever a student who is inexperienced at Piloting is controlling the UAV, it is important for the teacher to be near the Pilot and offer assistance as necessary during the flight. In the event of an unsafe situation, help the student in need or take control from the Pilot to ensure that everyone is safe.
  • Practice at low altitudes.
  • Set and observe flights in safe places with boundaries clear of hazards.
  • Be alert. Don't let enthusiasm overcome common sense.
  • If there is a potential danger, stop and change the situation.

Extensions and Variations

Depending on how much time you'd like to devote to this activity and how much depth you'd like to go into regarding the statistics of multiple trial or variance of multiple factors in an experiment, you can optionally extend this activity in a couple of ways.

Multiple Trials

Performance of a particular battery will change from one flight to another. The battery might be more fully charged one time compared to the next. The flight pattern, even when students attempt to perfectly replicate the same pattern each time, will vary slightly, draining the battery more or less quickly.

Test each battery more than once. This could involve different groups of students testing each battery. Discuss with your students the range of outcomes. What was the average flight time across all batteries? For a particular battery? How much variation was there between batteries? How much variation was there from flight to flight with each battery? Were some batteries more variable than others?

Different UAVs

Discuss with your students the ways that one UAV might vary from another. Might the motors be better in one than in another? Might one UAV have better propellers than the next? Help them realize that the performance of a particular battery in one UAV might be different than in a different (though supposedly identical) UAV of the same model.

Test batteries in different UAVs. Try battery #1 in UAV #1, then in UAV #2. Then try battery #2 in each UAV. Compare the results. What matters most, which battery is being used or which UAV it is flying in? What is the range of variation: a little or a lot?

Discuss with students the factors they should keep in mind to conduct "fair tests" as they move forward with their UAV flights.

Different Batteries

You could buy batteries from different companies and see if there is any systematic variation between brands.

Some UAV models may support use with batteries of different capacities. For example, the SYMA model we used in our tests shipped with a battery rated at a capacity of 500 mAh (milliampere-hours). Higher-capacity 1200 mAh replacement batteries are also available via online shopping sites. Do the higher-capacity batteries last more than twice as long as the lower-capacity models, as one might assume based on their respective ratings? This would make a good comparison for students to explore.

UAV Performance Test: Carry a Payload activity

Credits

The initial concept for this activity was developed by members of the Earth Science Information Partners (ESIP) Education Committee, which focused their 2016 educational efforts on the use of UAVs in education.

Further development of this activity was conducted by Randy Russell and John Risvey as part of their work at the UCAR Center for Science Education as part of Engineering Experiences, a National Science Foundation-funded ITEST project (Award #1513102) with the Division of Research on Learning in Formal and Informal Settings (DRL). Engineering Experiences is designed to introduce and engage middle-school students to engineering during out-of-school time, and foster long-term interest and pathways into the field. Any opinions, findings, and conclusions or recommendations expressed in this activity are those of the author and do not necessarily reflect the views of the National Science Foundation.