Blog Post #7: Making a Punching Bag

Up until now, all I had been doing to test the effectiveness of my robots was to put a copy of the plastic robot's chassis into the test box, maybe prop it up on something, and see what my robots do to it. With all of this project time on my hands, I decided to create a more advanced punching bag that I could use to do experiments and collect quantitative data. 

In order to add data collection to this robot, I decided to place an Arduino inside the chassis of my punching bag. I have used Arduinos in the past for data logging for some class projects and during my short stint in the rocketry club. The sensor that I am using is a BNO085 Inertial Measurement Unit (IMU) which allows me to measure the acceleration and position of the punching bag which allows me to calculate the force applied by the robots. The Arduino will be mounted in the middle of the punching bag with zip ties to make it easy to add and remove.

The Arduino setup

I had some trouble when originally trying to figure out parts of the code. While I could read the sensor outputs with no problem, I ran into some problems while trying to log the values. I had to change the boot file to allow the Arduino to write to files but accidentally made it so that I couldn't modify the code. I was eventually able to fix the code and successfully log some data. While I don't have time now, I do want to design a way to better visualize the outputs into more understandable formats.

Log output

I decided to add a couple of interesting things to the design of my punching bag instead of making it just a simple box. The first thing that I did was add fake wheels to the back in order to raise the chassis up a bit and make it a more realistic experience. These wheels are separate parts in order to make printing easier. When printing them I decided to use the fuzzy skin setting out of curiosity which makes the outer wall layer a bit random to add texture and hide the layer lines. I also added forks on the front of this chassis similar to my first plastic robot. This was to stretch out the length of the chassis a bit more and elevate the parts that will actually be hit to create a more realistic experience. 

In order to not reprint this punching bag every time I wanted to test something, I needed to print this as durable as I could. I printed all of the parts with a lot more wall layers and infill than I had previously as I was not worried about weight. In order to avoid direct damage to the main chassis, I added a place to mount armor plates to the front of the chassis. This would allow me to test the robots on easily replaceable components. This would also allow me to test other materials and settings easily without wasting time printing out whole chasses.

Final punching bag