Measure simulated forces of impact on a human head, and test if forces are reduced by wearing a protective headgear.

Transcription

1 PocketLab Science Fair Kit: Preventing Concussions and Head Injuries This STEM Science Fair Kit lets you be a scientist and simulate real world accidents and injuries with a crash test style dummy head. Includes an award winning PocketLab scientific sensor that measures high resolution acceleration data in all 3 axes. Be an inventor! Design and test your own creative protective headgear ideas. Learn about head injuries and safety: Simulate collisions, falling, sports injuries and more. Includes life size styrofoam head, PocketLab One sensor, getting started cards, and printed instructions including full procedure and data collection ideas. Contents: Styrofoam head PocketLab One Introduction cards: how do sensors work? Printed instructions Objective Measure simulated forces of impact on a human head, and test if forces are reduced by wearing a protective headgear. Abstract A person can experience impacts to the skull from falling, sports, vehicle accidents, and many other sources. These impacts can come from any direction, and can range from mild to catastrophic. Helmets and other protective headgear can be used to reduce these forces. In this project, you will use a PocketLab, with a highly sensitive 3 axis accelerometer, to measure force in g s on a test dummy (a styrofoam head), and you can simulate collisions, falling, blows to the head, and can try different headgear to reduce forces. You can even create your own experimental headgear and safety ideas and measure the effectiveness. Background Measuring Acceleration First thing is to learn how the PocketLab measures acceleration data. Your PocketLab has 5 sensors in it that can be used for many other projects in the future, but for now we will just use the accelerometer.

2 Your PocketLab comes with a printed Getting Started Guide that will help you get connected to the app on your smartphone or computer. Immediately after you connect, the PocketLab app defaults to the accelerometer, and you should start seeing data right away. If you shake the PocketLab, turn it in different directions, or just set it down, you will start to see how the accelerometer works and what the data means it is very intuitive. There is a printed Accelerometer card included in this kit that will explain the detail of the three different axes (x, y, and z), and how to observe the effect of gravity and different types of motion.

3 Also very important for this science fair activity, look closer at your Pocketlab and you ll see that it has a logo that actually shows the directions of the forces it measures. This is a handy thing to know and to refer to whenever you attach your PocketLab to anything. If you get stuck at this point, there are also getting started videos available on the PocketLab forums that show you how to connect to an app to receive data, and how all the sensors and the app functions work. Getting started video for ios (ipad, iphone) and Android: support video getting started pocketlabmobile app Getting started videos for Chromebooks: support video getting started pocketla b web app full video Materials So far you have been introduced to the PocketLab One in this kit. Don t forget that the PocketLab has many functions beyond just this one science fair activity you can attach it to carts, rockets, pendulums, and you can measure much more than acceleration, for example you can measure rotation, altitude, temperature, magnetic fields. PocketLab has almost unlimited uses, and there are hundreds of activities available on the PocketLab website. First Step: Think about the Goal This project will be much easier to finish in a reasonable amount of time and with meaningful results if you think about a clear goal first. An example of a clear could be, Compare the

4 amount of protection between bicycle helmet and a motorcycle helmet, or Does a helmet reduce the chances of concussions?, or How much force does a players head experience in a football tackle?, or Test out a new idea for preventing head injury during a fall. As you can see, each goal narrows down the possibilities quite a bit, and that will help focus your project. For our goal, we decided on this: how much does a bicycle helmet protect your head from impact. So to test this goal, we decided we would drop a weight onto the head from different heights, and then with and without a helmet. While thinking about the goal, try to think about what interests you (for example riding bicycles), what kind of equipment may be available (if you have different helmets at home or can borrow something like a football helmet from school), or maybe important news topics (sports teams concerned with players head injuries). That will make your project more fun and relevant. Attaching the PocketLab to the styrofoam head There is only one step to getting your crash test dummy head ready to measure data and have some fun testing things out, and that is to attach the PocketLab firmly to the head. The method we tested and would recommend is to cut a rectangular hole to fit the PocketLab into the top of the head lengthwise. To use this method of attaching the PocketLab, cut a rectangular cavity straight down in the top head. The styrofoam is soft and easy to cut, but still, please handle sharp instruments with care, and enlist the help of a teacher or parent. A a pocket knife, or a box cutter are fine for cutting the rectangular cavity. A thinner sharper knife will make the cleanest cut.

5 You can use a sharpie pen to draw an outline to guide your cut. Place some tape around the outline to prevent the edges of the styrofoam to break off and crumble.

6 Cut the hole so that the PocketLab fits in lengthwise. It works best if the PocketLab fits firmly inside the hole. If you accidentally cut the whole too large, some extra tape could be used to make sure it is a firm fit. If the PocketLab is loose in the hole, it will add errors to the data as the PocketLab shakes. The head and the PocketLab should move as one unit.

7 The orientation of the data is going to be very important. If you haven t yet, read the Accelerometer card that came with your PocketLab. You will see that it measures in three directions, x, y, and z. In the picture below, are are inserting the PocketLab so that y faces forward (towards the nose), x faces up and down through the top of the head, and z is facing left and right, through the ears. This will be very important to remember when you collect data to see that it is making sense. You can insert the PocketLab in any direction of course, but this is the direction we chose.

8 In this picture below, the data axes are noted of our PocketLab. If you decide to attach your PocketLab in a different way, draw your data axes so that you remember them for the experiment. You should include this diagram in your science fair presentation. (here is a blank picture if you want to draw your own:). Test it Out! Once the PocketLab is attached firmly to the styrofoam head, you can have a lot of fun testing it out! Now is a good time to connect your PocketLab to your device (iphone, ipad, Chromebook,

9 whatever you are using), and experiment with how the head reacts to moving, turning, hitting, dropping, etc. Right away you will see the accelerometer data and what kinds of impacts make interesting data. See if you can figure out the axes on your diagram and what happens if the head is struck from different directions does the graph make sense? This is a good time to do some prototype testing and data collection. For example, if you plan to use a football helmet, then put the head in the helmet and see what happens either dropping it or striking different objects. Create a Control run, and Collect Control Data Trials After playing around with collecting some data for fun, it is time to put together your control. A control is necessary to test your measurement strategy is working and to provide control data to compare test run scenarios. The control will be the foundation for how you collect data, and you should try to set up the control so it is easy to replicate and collect data. Even if the project takes several days to test different protective headgear ideas, you can always go back to the control set up and verify everything is working correctly and the data collection makes sense. You need to decide how you will collect data throughout the experiment. You have several options that you can explore. For example, you can simply drop the head onto the floor at various heights and measure the impact to simulate falling. Or you can drop a weight onto the head from different heights. Or you can make a pendulum and weight would swing and hit the head. In a real world experiment, you would try to pick the method of impacting the head that matches your goals the closest. As mentioned earlier, for our goal we wanted to drop weights on to the head with and without a helmet, and then from different heights. Someone in our office had a 4 pound padded exercise ball, so we used that to drop onto the head from various heights and with no protective headgear vs various helmets. Try to be creative and use things you may have available and are easy to use. Maybe you have sports equipment at home or at school, different helmets, or maybe some spare old pillows you could take the foam from. Many great science projects have been done by being creative with what you have available.

10 Maybe you can use your creativity to come up with an interesting test method? For example, crash test dummies in cars are run into barriers on a sled. Maybe this can be done with rubber bands like a water balloon launcher?

11 A crash test dummy in action at the Allianz Center for Technology. Eventually you have to make a final decision on designing your control and test cases. When you have done this, then you can set it up the control and get ready to measure control data. Determine your Independent Variables The two main variables in an experiment are the independent and dependent variable. An independent variable is the variable that is changed or controlled in a scientific experiment to test the effects on the dependent variable. A dependent variable is the variable being tested and measured in a scientific experiment. The dependent variable is 'dependent' on the independent variable. As you change the independent variable, the effect on the dependent variable is observed and recorded. For this project, you need to decide on your independent variables, and they will relate to your goal and to the control. For example, if you are going to test the impact by dropping a weight onto the head, then you would pick the height that you drop from as an independent variable. If you are using a pendulum and a weight, you can use the size of the weight, and how far you draw back the weight as two independent variables. You can also consider changing the position the head before it falls or as it is struck to measure the impact from different directions.

12 A possible matrix of test run conditions could look like this: Test run: Drop Height 12 Drop Height 24 Top of head Front (directly toward face) Left or Right (directly toward left or right ear) (You should come up with your own table of measurement conditions) Multiple trials per test run The purpose for multiple trials is to improve the quality of data. For each test condition (for example, drop height 24, facing up) you would repeat the trial at least 3 times, and the report the average of the three trials.

13 Keep in mind, PocketLab will allow you to measure 3 data points for each trial (x, y, and z), so this is a lot of data! It is important to be organized and document everything carefully so that you can keep the data straight. Many hours of confusion often arises from a simple data collection error. Design your test run cases Once you have your control, and the independent variables, you can think about your test cases. For example if your goal is to determine if a bicycle helmet provides as much protection as a motorcycle helmet, it would be simple enough to drop a weight onto the unprotected head (control), and then the bicycle and motorcycle helmets, and compare the results. You can drop the weight from different heights to simulate small are large impacts and see if the size of the impact makes a difference. Collecting Data

14 If you have two drop heights, impacting top, front, left/right of the head, and then with a helmet and without a helmet, and three trials of each condition, you would have a table like the one below. If you wanted to try two different helmets, you would add 3 more rows for the second helmet. No Helmet Drop Height 12 Drop Height 24 Top of head Front (directly toward face) Left or Right (directly toward left or right ear) Bicycle Helmet Drop Height 12 Drop Height 24 Top of head Front (directly toward face) Left or Right (directly toward left or right ear) As you can see this is a lot of data. But collecting data can be very easy if you approach it in a very organized fashion, and get everything set up and tested before you start, and especially think about how you are going to collect the data. For example, you can have a partner help you write down the data in a notebook, or you can type it into a table in a computer as you collect. And with PocketLab, you can also save the data and take snapshots of the graphs which is very helpful (refer to the PocketLab getting started guide and instruction manual for all the ways you can collect and store data). The main thing to remember is that if you are very organized up front, this is a much faster and easier task than it seems. You want to start from the beginning, have everything ready to go, and collect the data in one session, writing it down or storing it electronically. Then wait untile the end to look through the data and do more analysis.

15 Interpreting Accelerometer Data We ran this experiment ourselves, and here is an example of one test run. We made three trials of dropping the weight onto the head with a bicycle helmet. If you look at the diagram of the x, y, and z direction of the sensor from our drawing, the x axis is the axis facing straight up and down through the head. Here is the ball dropping again, with the helmet in place: Here is the same diagram from before of x, y, and z (notice x is the direction the ball is dropping):

16 And here is some data. This data was created by selecting the accelerometer, setting the frequency to maximum, pressing the record button, then dropping the ball 3 times, and pressing stop. The graph picture was made below by a screenshot of the ipad screen (hold the power button and press the home button). On the PocketLab App graph, you can pinch and zoom the data to examine the points and graph closer as needed. As expected, most of the force is in the x direction. Notice the x data is the red graph line. There is also some force of acceleration in the y direction (front and back), and less yet again in z (left to right). It is important to observe the graph and the ball in the test run. In our case, there are two peaks for each trial on the x graph. Why is that? The ball hit the helmet (the first peak), and then rolled off the back of the helmet, and landed on the table (the second peak). We learned this by observing, and then we took the data from the first peak for each of the three trials and averaged that data.

17 To average the data, you can pinch and zoom and touch the peaks and get the value. Write down the 3 values and take the average. It only took a few seconds to collect this graph, so as you can see, if you are organized, the data collection can be done quickly. We were able to fill out the first 3 rows of the table in about 5 minutes. So even if it looks like a lot of work, if you are organized and have everything ready, it will go much faster than you think. Analyze the results and draw conclusions After filling out all the rows in the table, you can start to analyze the results and try to answer your initial question. For our experiment, we were curious whether the force of impact was reduced by wearing a typical bicycle helmet. In our case we measured the heavy exercise ball dropped from two different heights, and on to the top, front, and side of the head. Then with and without the helmet. For each specific test run, we took 3 trials and averaged the data. We were able to see differences with and without the helmet, and from the different directions and heights. When we researched other studies on line about head injuries, we learned a lot of interesting information about how helmets are designed to work. Do they actually prevent concussions? Or are they designed to prevent trauma (cuts and bruises)? Do they work in all situations, or are they better in some than others? You should be able to compare your data to real on line head injury studies and learn how protective headgear is designed to work. You can also learn enough to design your own protective system that can have a specific goal, or work for a specific sport. For more information on line, visit or contact us at contact@thepocketlab.com