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Vikram’s Status Report for 10/30/2021

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.

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Lahari’s Status Report for 10/30/21

This week we had several tests to carry out. The first was a drop test, which we did again at the Pausch Bridge. This test would tell us whether we had eliminated spin by adjusting the parachutes, and the amount of thrust in our propellers. Last week, I made a few design changes to avoid the spinning that was happening during the drop. I shortened the straps of the parachute and attached them to the body with carabiners. In testing this proved successful by eliminating spin during the fall.  A picture of the parachute attachment now:

Initially, I tested the circle detection CV using a small image of a circle. Adjusting the parameters of the script, I found a range and line thickness of a circle that would make it visible. I scaled this up linearly to estimate we need a target diameter of at least 1 meter with 10cm thickness. I then printed the 1 meter circle piecewise on several letter size papers and stuck them to a board (pictured in team status report). We tested the large circle and found it was detected at a range fit to our use case, i.e. it was detectable close up and from 43 feet away (the height of the Pausch Bridge).

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Team Status Report for 10/30/21

This week we improved on the drop test from last week, the problem was that the device spun during most of the descent and the parachute ropes twisted together. To fix this, we shortened the ropes and mounted them on opposite sides of the top. This solution would ensure that the parachutes were separated during the whole drop. Spinning would otherwise interfere with our perception method, which ultimately determines the relative angular position between the device and the target. When we tested this version on Monday there was no noticeable spinning. 

We then shifted our focus on movement from our propulsion system. We wanted to see how far the propeller at full thrust would move the device. Wednesday was more appropriate for the lateral distance test, because it was not windy. By this time, another set of parachutes had arrived, so we added a third parachute to the body, so the drop time would be longer. The test showed an additional parachute did not achieve this. We would like to test this a few more times before we reject this option, especially because there is more weight that needs to be added, including the payload and extra propulsion. 

At full thrust, the device could not move three meters laterally, a key technical requirement of our project. We decided that each arm of our device should have two propellers instead  of one. We already had an extra motor, ESC, and propellers, so we put double propellers on one of the arms. We plan to test the new thrust capability on Monday, and decide whether to order more parts.

Meanwhile, we conducted a few tests on the circle detection code. We found the 1m diameter circle (pictured below) was detected between 48 feet and 10 feet of distance. It is approximately the same indoors and outdoors. We plan to find the angular range of detection at a few fixed distances next week.

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Daniel’s Status Report for 10/30/2021

This week, I mainly helped the team complete more tests to understand how our device behaves under its proposed use case. We noticed during our last tests that a lot of spin was induced from the unsynchronized dropping of two people letting go of the device. As a result, we decided one person should drop it. During each test, I held up the parachutes from their center, held the device over the edge of the Pausche bridge and waited for Lahari to initiate the system using the buttons we installed. Once she pressed it, I waited for the motor to spin up, and let go of the parachutes once it was on full thrust. The spin issue was solved, yet we found that there was insufficient thrust.

To fix this, we are going to add an additional motor to each side. After Vikram cut out a new piece of wood that has enough space for two motors, we worked together to measure various distances to ensure the motors were equidistant from the middle mounting point, as well as to drill the necessary holes for mounting. I then drilled the holes and attached the motors. To test both motors working at the same time, I suggested we use the lab clip wires with banana plug ends to quickly prototype a splitter without needing to solder anything just yet. Then, we worked together to hook up the system. Finally, as Vikram held the splitter, I held the motors and Lahari held the wires in place, I turned on the servo tested and we found that the two motors worked together. As for my vectorization algorithm in regards to this change, I will simply feed in same PWM duty cycle to both motors on any given side since they are both pointing in the same general direction, so the output should still remain as 3 PWM duty cycle values.

Additionally, I also helped the team draw a circle to test the circle detection algorithm at a larger scale. We tied a string to a sharpie, and while Vikram and Lahari held the string in place, I drew on the foam-core, creating a circle as the string acted as the radius (of 0.5 m based on previous calculations described in the past based on scaling up the detection of a 5 cm radius circle from 1 meter away). Due to the uneven nature of this process, our circle was not perfect, and the resulting edge was too thin (even after we filled it in). To solve this, Lahari then printed a perfect circle with a much thicker edge, and glued it to the foam-core. I then ran the python detection script on my laptop, holding up the camera as Vikram moved the circle further and further away. At first, we noticed the range was no where near our required 40 feet range. I noticed the camera quality was set to 640×480, so I proposed that we change it to 720p (1280×720). We tested this both indoors and outdoors, and found a maximum detection range of around 50 feet, which fits our use case.

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Vikrams Status Report for 10/23/2021

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.

 

 

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Lahari’s Status Report for 10/23/21

During the week of Oct 10-16 we set about creating the MVP for our project, while working on the design report. This version of the device was made of Foam core, because the material is lightweight and easy to modify. I helped fabricate the housing by tracing, cutting and gluing various pieces. We decided early on that three propellers was the minimum necessary to achieve omnidirectional movement, so we chose a hexagonal shape for the body. This would achieve less air resistance and a symmetrical design. The design had three arms to extend the propellers outwards, so that airflow would not be obstructed by hitting the sides of the housing. The goal was to see how far our propulsion system could move the object during a drop test. The week culminated in another drop test which was unsuccessful, because the device spun during most of the fall. 

 

Meanwhile, we performed final tests which helped us rule out directional antennas as our perception method. The new WiFi board had arrived, so we tested it out with the directional antenna. Daniel and I went out to the grassy area outside Hamerschlag to find at what distances and angles a phone hotspot would produce higher RSSI. The signal was stronger in a usable horizontal angle of about 30 degrees, but only within 20 feet. The range of the vertical angle where the phone could be detected was very narrow. Lastly, the back of the antenna also had some range where the signal was as strong as in the front. This meant the antennas were not practical for perception for much of our use case, it would not be possible to detect relative direction based on these antenna data. At the end of the week we decided to switch to computer vision instead of antennas for perception. 

 

During the week of Oct 17-23 we continued working on our device. I am now in charge of computer vision instead of signal processing because we have switched to cameras. We decided to use circle detection, so that the use case would remain simple. The user would only have to place a circle marker on the ground. I implemented a circle detection script in Python with OpenCV. The script converts the frame from a camera feed to black and white, applies median blur, then HoughCircles (from cv2 library). The result was the coordinates and radii of the circles in the image. Daniel and I integrated this code with the Raspberry Pi camera, and found that the detection was robust. What remains to be done is to find out the latency associated with the code, we may consider using C++ to remove some of it. We also want to go outside and see whether it works at a distance of about 40 feet and with different lighting conditions. I may have to adjust the parameters, such as circle radius and blur kernel, based on these tests.

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Team Status Report for 10/23/21

Oct 10-16:

This week, we worked on creating out first prototype as a way to test our propulsion, then our perception after we determine our propulsion works. We chose foam-core as our material so we could rapidly prototype for cheap. Below is the completed housing with the motors attached:

We then needed to run the motors. At first, we tried a Raspberry Pi to generate the necessary PWM signal; however, we found that the Raspberry Pi only has 3.3V logic, whereas the ESC required 5V. We moved to an Arduino Uno for the meantime as it has 5V logic, but are planning to use logic-level converters to step up to 5V. We also decided that for testing purposes, we should have a start and stop mechanism. For starting, we used a single button that once pressed, started the device after 30 seconds. For stopping, Vikram suggested 3 buttons on the bottom of the device that stop the device once pressed under its own weight. The device looked like this:

After this was done, we put all the electronics inside and were ready to test the motors. Since it was raining, we had to test the thrust indoors first, so we tied string to the device as one of us stood on a ladder. We found that the motor at 100% had  power to move the device (total weight 1.4 pounds. without payload). Here is the link to the video: Motor Test

At this stage, we also received a new ESP32 Board that we could directly connect an external Antenna to without any soldering. This way, we could actually test the performance of the directional antenna and decide if it is usable. We found multiple issues with the antenna approach:

  1. The antenna had two discernable peaks at the edges of the 30 degree beam width, such that you could not discern from the RSSI if you were to the left or right of the antenna (RSSIs were equal at these two points).
  2. The middle of the beam width had a trough in RSSI, such that the RSSI read right in front of the antenna, was the same as the RSSI read outside the 30 degree beam width.
  3. The back of the Antenna resulted in a peak in RSSI similar to being in front of it.
  4. The Antenna was only able to get reception up to a range of 20 feet. Our drop height is in the range of 30-40 feet, meaning that for the first half of the drop, the perception system would not perceive much.
  5. The vertical sensitivity of the antenna was very low, meaning  as the signal source moves with respect to its vertical position, RSSI changes only towards the very middle of the sweep. This is crucial as the device will be falling downwards.

To mitigate this, we have decided to move forward with a CV based approach using a camera, and a circular visual market.

Oct 17-23:

This week, we dropped our device with motors for the first time to test the propulsion. Here is the video: Drop Test.

We found that A. the unsynchronized drop caused a spin in the device and B. the parachute set up created even more spin. Due to how the motors are set up, any small amounts of spin will cause the device to continually spin as the motor fires. To mitigate this risk, we have shortened the parachute slack, and attached the parachutes properly using carabiners with holes in the housing (instead of tape). We must now drop it again to see if this fixes the spin issue. If this does not, we plan to design an arm system that will place the parachutes further from one another in a square formation, with the addition of two more parachutes (which we have ordered)

 

Lastly, as we moved to a CV based approach, we ran the Hough circle detection algorithm on the Pi and found that it is successfully able to detect circles (5 cm radius from a 1 meter height). We plan to print a 0.5 m radius circle and test the detection from the Pausch bridge next (0.5 m radius found from scaling up the 5 cm example to the height of the bridge). According to how well this works, we may need to use a larger circle, or tweak the algorithm by changing some sensitivity parameters.

 

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Daniel’s Status Report for 10/23/2021

Oct 10-16: 

During this week , I mainly assisted the team in constructing our first prototype. We chose to build it from foam-core, so I cut out some of the shapes needed to build the different parts of the device (such as the arms and sides). After constructing the basic skeleton, I wrote an Arduino program to control the device for preliminary tests. This involved  connecting some buttons to the Arduino on a breadboard, and writing code to generate the necessary PWM signal to run the brushless motor. We had two sets of buttons. One button was used to start the motor, and three buttons on the bottom of the device were used to stop the device when it hit the ground. After I tested this worked on a breadboard,  I then soldered wires to the buttons and with the help of the team, attached these and the remaining electronics onto the housing. We then ran some tests as a team indoors (as it was raining) to see if the motor was able to move the device, and it was (explained in the team status reports with videos). I also began thinking of how to create the vectorization algorithm for the control system, and with the help of Lahari and Vikram in the realm of matrices, we landed on an approach that I can begin to implement, keeping me on track,

 

Oct 17-23:

This week was mainly focused on testing the propulsion of the device outdoors, and seeing what modifications we needed to make. We worked as a team to figure out how to mount the parachutes to the device, and went out the Pausch bridge to drop it. Lahari and I dropped the device from the bridge, while Vikram was at the bottom in order to catch it. The results and consequences of our findings will be discussed in the team status report. Due to the rain, it was difficult for us to do more testing outdoors. At this point, we also found that the buttons placed on the bottom of the device to stop it were not ideal as they could sometimes not be pressed (if the device fell on its side, or on grass), so we decided to move to an ultrasonic sensor that would stop once the device was close enough to the ground. We have also moved to a camera approach for our perception (discussed in group status report), so I helped attach the ultrasonic sensor and camera to the bottom of the device, and cut a slit to allow the wires through. Lastly, as we needed to test the camera on our Raspberry Pi, we used an OpenCV example script to run the Pi Camera, and I helped integrate Lahari’s circle detection algorithm (which we will use to find our target) onto to the existing python script. We found that the script runs fairly well, but more testing needs to be done to determine the true latency of the script. The results from this script will be fed into the vectorization algorithm that I’m working on.

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Daniel’s Status Report for 10/9/2021

This week, I helped the team create a test setup for the motor to measure the thrust. We initially had the motor set up on a flat piece of wood with legs, standing on a scale so we could measure thrust; however, the lack of space under the motor did not allow the propellers to move enough air, and no thrust was generated. I suggested that we should attach the motor to an arm extending over the test setup such that the motor had clearance. When we did this, we were able to actually measure the thrust of the motor. In preparation for this, I soldered wires for the motor controller, and helped put the overall construction (drilling, screwing, gluing).

I also did research regarding potential boards to connect our antennas to, to be able to measure RSSI. We had trouble with our ESP32 board when connecting an external antenna to it; we had to move an SMD resistor to change the antenna from onboard to external, which proved difficult and resulted in a solution that could effect our antenna reading (excess wire, solder). So, I found a board that required no DIY work (SparkFun Thing Plus). Once we get the board, I will be able to run more Antenna tests to gauge the antenna sensitivity more accurately; Specifically, I will need to test multiple antennas to see the difference in RSSI observed from different directions (before we get multiple Antennas, I plan to use a single spinning one to replicate multiple ones). In the meantime, I will begin working on the design for the vectorization algorithm which takes in RSSI and outputs PWM duty cycles for each of the motors, so I continue to be on track for my tasks.

Lastly, in considering other perception methods (if the Antennas do not work sufficiently well), I brought an 8×8 Thermal Camera I had lying around for an Arduino to test if it is a feasible method. I soldered and wired it up to test it. However, the low resolution mixed with potential damage to the camera meant the data was not too useful. Additionally, the small sensor size meant that the range was highly limited. If we wanted to test this perception method again, we would need to acquire a higher resolution thermal camera.

 

 

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Team Status Report for 10/9/21

This week the items that we ordered last week arrived. This allowed us to do more pretests, namely the thrust of our propellers and the drop speed of a weight with a parachute. On Thursday we prepared these tests at the lab. First, we filled a tupperware container with water to weigh about 1kg, since this is the expected upper bound for our device weight. We then attached the two 54-inch parachutes to the container and secured it with the duct tape. 

We walked these items over the Pausch Bridge, and tossed them off, while one of us recorded a video of the drop from a distance. The video indicates a time from release to landing of about 3.8 seconds. This is approximately the amount of time during which the device can operate, and it is very close to the amount of time we anticipated. Video. 

Meanwhile, we also began creating an apparatus to measure the thrust of the motors and propellers. The apparatus consists mainly of a motor and propeller mounted to some wood, placed on a scale, with a battery and PWM generator. An image of the full setup is attached below. With the propeller at full speed, the change in weight indicated by the scale provided us with a verifiable measurement of the thrust: 400g. Our test was not ideal, and it appears that some of the thrust was exerted onto the scale, because the arm may have acted as a moment arm. To remain on schedule we are accepting these results and moving on. As a form of early risk mitigation, we are researching thermal cameras as an alternative to antennas.