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Project Collisions

Posted by on January 25, 2019

Blog Post:

In Project Collisions, I am creating a system to deliver mice, computer cases, earbuds, and portable chargers by drones. The drone will release the package from a height up to 10 meters and my job as an engineer is to develop a solution so that the package is protected in its fall. For Drop 0, a package with the dimensions of 36cm by 26cm was dropped from a height of 5 meters. Below is a photograph of the package:

The package will hold a portable charger for computers. Inside, items are organized like this:

 

The purpose of Drop 0 is to get baseline data about our package. Our group developed a testing procedure so that we can be consistent on how data is collected throughout the design cycle.

  1. Plug the force plate wire into the laptop  
  2. Carry bag to recognized drop area  
  3. Use ruler to make sure distance package away from area is correct (40)
  4. Hold the package so that it’s directly above the force plate
  5. Start to record in slow-Mo and regular speed, push play button
  6. Drop package at 5 meters
  7. Record drop data in the data table
  8. Measure distance object bounced from force plate    
  9. Repeat steps 2 to 7 two times through

During the drops, I noticed that the package hits the force plate very hard and then bounces a little. I am a little concerned about the overall well being of the package. This will be fixed as we move through the project. I also wondered if a parachute would help slow down the fall of the package. The following data was collected during the drop:

Drop 0 Data Table:

Mass of Box (g) Force Accuracy Velocity Time (sec)
Drop 0 A 51.6 132.9 On the force plate 12.6 0.3
Drop 0 B 51.6 126.4 On the force plate 10.4 0.3
Drop 0 C 51.6 669.9 On the force plate 10.7 0.3

The average time it took for our package to fall the 5 meters was 0.3 seconds. Not even a full second or half of one!  Then, using LoggerPro, we plotted out the fall of the package.

   

Drop 0 A

Drop 0 B

Drop 0 C                                         

The package fell along the line we plotted, so we were happy, we hope to keep on predicting the fall of the package correctly every time.

A force plate at the bottom of the drop was used to collect data on the impact force of the package. Our group was very succesful at hitting the force plate. Here is a picture below to show:

As a project metric for accuracy, we want our project to keep landing spot on the force plate. If not, only a few centimeters away from it.

The average force on impact was 844.9. As a project metric, our group has decided to ____________________<do what? What is it that the team wants to set as a target for your design. For example, if your  measured force during Drop 0 was 243 N (Newtons) and you want a “soft landing,” what will you have as your initial design target: a 25% reduction? 50%?>.

Summary: Project Metrics

Our team has decided that the three most important criteria to design towards are accuracy, force, and time. Below, each metric is described and the goals were determined by data from Drop 0.

  •   Metric 1: Force– the force of drop A and B is around 130 grams, however the force of drop C is around 660 grams. That is a very big difference. So, that makes the average of the three drops 482.6. That s a lot of force. To decrease that big number, our group’s goal for Drop 1 is to reduce 25% of the force.
  •   Metric 2: Time- it took the package 0.3 seconds to fall the last 2 meters all of the three times we dropped it. It is the only constant found in the data table. Anyway, my group and I hope during that Drop 1, it will take the package at least 0.5 seconds to drop the last 2 meters.
  •   Metric 3: Accuracy-  the package fell exactly on the force plate all 3 times. Our group hopes the package will continue hitting the force plate when we do Drop 1. If the package keeps on hitting the force plat as we continue doing drops, it will be one less thing to worry about fixing in the future.

Our group is now building the first prototype. I hope that we find a way to slow the package and keep on hitting the force plate. We also will add some more padding to the package for design one to make sure it is safe during the fall/drops.

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