Author: vgbhat

This week, I first worked on preparing for our final presentation. I practiced for the first few days of the week memorizing and rehearsing the slide deck and what I would say to make sure that the presentation went smoothly.

We also worked further on assembling our new housing out of 3D printed arms and acrylic body panels. We also installed a hinge for the top for easier access to the inside. We glued the bottom inside the hexagon and fixed the side panels with custom 120 degree brackets to form an even hexagon. The arms are bolted on, and the walls are tacked together with glue at the top. I also made the wiring adapters that go from the 2mm bullet connectors from the motors to the 3.5mm connectors for the ESCs.

Lastly, we performed about 7 drops with our system to characterize performance. While doing this, we noticed an issue with the ability to SSH into the raspberry pi above the drop zone because of wifi, so we amended our script to wait until it receives signal over UART from the Arduino to start the detection script. This way we run the python script while indoors and then when we hit the button to start the Arduino, it triggers the python script to start without needing to SSH in and run it directly. This helps our efficiency with performing drops. Additionally, we tested in a few different lighting conditions, ranging from bright sunny to very dark and with tuning our threshold, we were able to detect the target circle in both scenarios. A future possibility is to have a dynamic tuner that changes threshold based on amount of light or another metric. After some more testing, we will be looking to create our video and write up our testing data in the report.

This week I worked on the CAD models for the updated housing. We also did tests with the camera at the bridge to the performance of different cameras.

The new CAD model has the frame of the device being made out of laser cut 1/8 inch acrylic, and the arms made out of 3d printed material. We were able to cut 5 of the 6 new walls and bottom plate. Access to 3D printers has been difficult, so the new arms have not been printed yet.  The updated housing will use brackets internally to keep rigidity, as well as a hinge on the top for ease of opening/closing.

For the camera tests,  we found that the fisheye lens just wasn’t conducive to detection because it shrunk everything close to the center, making even large circle detection markers impossible to make out over video. We have switched to a larger target, and a webcam which has much better performance at distance. In addition to a straight up vertical test, we also tested the performance/detection range of the webcam horizontally, testing 3 different lateral distances from the marker, as well as 3 different resolutions.

Next, I would like to measure the latency of our system to see responsiveness to different commands. This will help us gather more data, in addition to the drops we conducted (and will conduct).
The trade studies for the camera are ongoing and for the propulsion system we hope to characterize different proportional thrust values, as well as just using constant thrust vectors.

This week, after we demo’d I went to work on improvements to our physical drop system. First, I wanted to explore whether we were getting peak thrust from our motors by using a higher-gauge wire from the controllers to the motors. This change yielded a gain of 70g of thrust per motor, which was not insignificant. We will be moving all of our connectors to this 16AWG wire. Additionally we ordered 7 inch propellers that fit our shaft diameter, which are a 1 inch step up from our current props. I also measured our battery voltage and realized that it needed to be charged because on some of our pre-drop tests, the motors were struggling to keep thrust. I hope with topped off batteries, larger propellers, and thicker wires we will be able to push the most thrust possible out of our motors.
We also did a drop with the added weight to try and reduce swinging. This succeeded, but the added mass was a bit much, and we didn’t swing but we also didn’t move very much laterally. I think that using a solution in-between, where we decrease the added weight slightly, and use the aforementioned thrust changes will help balance the variables so that purposeful movement is possible.

Additionally, we went to the bridge again to test our perception system, where we found that the camera lens was working against us, and the fisheye made it hard to see the circle at the bottom with our processing added on. Using a standard camera or different lens should help to alleviate this, especially because the ultra wide fisheye is overkill when dropping from such height.

This week, I worked mostly on the hardware platform for the device, and the Arduino software. We are using an Arduino for now communicating with the Pi over UART in order to control the motors. This is in the interim, and we may remove this in the long term using threads or something similar to allow for continuous control of the motors during flight. The new code took PWM values from the raspberry pi python vectorization code and runs the motors accordingly, and handles I/O and start/stopping. I also worked on a new custom soldered perfboard that integrates all the I/O and PWM cables to make the inside of the system less cleaner, and have it mount to the Arduino so there isn’t risk of disconnecting a cable during flight. I added another power splitter to the power distribution board I made as well, in order to drive 3 ESCs/motors concurrently for the demo.  In addition, I helped during the drop tests this week where we diagnosed some issues with motors causing spin and swing, and are working to address those issues. We believe that adding some weight to the system can help reduce this issue as well. I also helped develop the interim demo test apparatus we want to use to demonstrate our project working in a smaller scenario. We are currently working to calibrate our mounted camera such that the target detection will reflect in motor driving correctly. We are mostly on schedule currently, with basic integration essentially complete for the demo. The final housing got pushed because the interim one is functioning. In the coming weeks, I hope to continue flushing out bugs in the integrated system, as well as verifying that our thrust tests were accurate and that we can reduce the swaying by adding a little more mass to the system.

This week we attempted multiple powered and unpowered drop tests. In addition, I noticed in one of the videos that our two parachute configuration was creating a axis upon which our device would sway back and forth. To try and mitigate this, we attempted to add and drop with an additional parachute. While this seemed to remove some of the swaying, the third parachute did not fully deploy, so we weren’t able to reap all of it’s benefits.

 

Another issue we found was that the power of our system didn’t seem enough to move the drop unit a meaningful amount. We are working to fix this by attempting to add an additional motor to each side, to double the thrust. Hopefully this will address this problem, but may add more complexity as we need to double the amount of motors and controllers, so weight may increase considerably. This is what I will continue to focus on this week. If this works however, we are on schedule. The other concern I had is that with a proper housing made out of a robust material, our total weight will be significantly higher, perhaps putting a restriction on the payload weight we can withstand during a drop.

Last week we focused on making an MVP housing out of foam core and populating it with a few components needed to do thrust testing during a drop. We had our first test with it last week, which failed due to spinning, and hope test again next week. We also performed tests that showed that our directional antennas were not a viable perception method because of their lack or resolution and inability to tell direction with enough accuracy. This involved around in a fixed radii and seeing if the antenna could discern if the beacon was in the “center” of it’s beam path.

This week, I focused on improving the state of.our MVP, with new code for our Arduino test platform, an ultrasound sensor to detect when to stop when our device is above the ground, and a new protoboard where many of our connections were soldered in order to make sure everything is secure now in the event of flipping or spinning. This new board houses I/O in the form of buttons to start and reset the motor spinning up process, in addition to the ultrasonic sensor. Additionally, I’m starting to model our new design for the housing that is based on the hexagonal shape that we prototyped out of foam core. This will hopefully be lighter than our original 3d printed design, and easier to manufacture (time-wise) as well. Some key issues we found with our original design was the print time and the estimated weight in PLA plastic that it would take on. The next steps are to use this updated test platform for another powered drop test, and hopefully for a perception test with our new camera system soon. This camera system will detect a black and white marker placed on the ground and use that to do it’s direction-finding. This way the control method doesn’t have to change much, just the perception method turning an image into a direction to travel in instead of an antenna array. This will hopefully allow us to do more fine-grained control as well, should we need it. Currently, we are on schedule and the new and updated housing will be continued over the next week in order to have our final build housed in a weather-proof container. The indicator LEDs and I/O buttons should also make setting up/ using our system significantly easier.

 

 

I continued to work on the CAD modeling this week for the housing, as well as getting the motor and controller test working. From our test, the results have shown some improvements that need to be made to the design, where our motors are mounted. In order to make enough thrust to move, there needs to be a significant amount of space between our motors and the housing. Also our motor controller needed to be factory reset and have the throttle range calibrated in order to work correctly. I did some research into alternative methods of perception, in the event that our antennas do not work as intended. So far, thermal cameras seem like a potentially promising idea, as they have low resolution for low processing time, and do not require infrastructure or daylight to work, because of the heat of a body or fire/flare. So, I did some research looking into them and specifically the FLIR Lepton camera that could potentially work with a big/hot enough source like an open fire (or for testing a heat gun/heating pad) . So far we are right about on schedule, but the CAD design is not finalized yet because of our recent findings on motor thrust. By next week I would like a relatively finalized CAD design ready and hopefully have it printable/ready to be 3D printed.

This week, I worked on the design of certain aspects of our project. Specifically I focused on the new CAD model of our device, using some of the specific components that we ordered like motors, propellers, controllers, and raspberry pi zero. I also added some of the housing design elements we proposed, like a domed bottom for aerodyamics and fins to help stop spinning.  This CAD model will help us get a better idea of how everything will fit together, and the physical design that will be 3D printed. In addition, I helped edit the design presentation, and added in figures and drawings that are useful to help illustrate and exaggerate points to the viewers. We also developed a test fixture together and ran some pre-tests to see if the directional antenna is a viable option for direction finding. Our initial results are promising, but further testing is required in order to truly determine how reliable direction sensing with the antennas will be. This progress is in-line with our schedule, and as long as the antennas remain viable this will put us in the correct position for next week, as long as the parachutes and other items arrive on time. In the next week, I hope to have a drop time test completed, as well as more antenna testing and if possible (will happen last or the following week probably) at least 1 motor drive test, in order to measure approximate thrust.

This week, after the proposal presentation I focused on two major fronts; starting the design phase of our project and reviewing and coming up with answers to feedback we got from the presentation. On the design front, I helped the team find options for off-the-shelf components for our antennae perception system, as well as motors for propulsion. These motors ranged from brushed DC motors without speed control to brushless DC motors that need designated speed controllers, like those used on drones. Picking the right propulsion will depend on thrust values, weight, and power draw. Correctly spec’ing the motors will be very important for ensuring our ability to maneuver during “flight”. This involves putting together spreadsheets with those requirements spelt out, especially with regards to weight, as that impacts our drop time. Thrust will be hard to measure as well, without being able to empirically determine how much is needed. Right now I am on schedule, hoping to start pre-tests with antennae and perhaps motors in the coming week. Hopefully be the end of next week we will have preliminary results on the ALFA directional antennae we ordered, and if they will work for our direction-finding system.

This week, I worked on the proposal presentation with my team. I focused on some of the numerical aspects of calculating our requirements, as well as some of the updated drawings for the proposal. The calculations are important because they have to support our quantitative requirements, and the drawings because they can convey a lot more information about the physical footprint of our project than a description.
So far, I think we are on schedule. The next phase, design, will be important for us, especially for testing some subsystems so we know that they are viable avenues for implementing on our system.
In the next week, I hope to have a more clear idea on the individual parts we are looking for, in order to get a close estimate for the weight and function of our device.