Author: lchilamk

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.

This week I spent time working on the pretests and the design document. For the design document, according to feedback I adjusted the block diagram, because I forgot the motor controllers in the presentation. We did a drop test and a test of propeller thrust to conclude our pretest phase.

The drop test gave us an idea of the amount of time available for onboard computations and movement. The propeller test would verify the 1kg thrust metric from the product listing. We put together the parachute and the weight and headed to the Pausch Bridge, where I released the items from the top, while Vikram waited below to retrieve and ensure no passers by. Daniel filmed from the street exit on the fifth floor of the Gates Center. 

The propeller test was somewhat successful, though we had some problems with the PWM generator while getting started. All in all, we completed the tasks on our schedule that require our combined attention. My individual task during this week and going into next week involves digital filtering of the RSSI data we collected last week.

This week I helped with the slides for next week’s presentation and the pretests we conducted over the weekend. I created a block diagram using a third-party software and redid our Ghant chart in response to the feedback we received during proposals. I set out to be as specific as possible at this stage of the project, given that we have developed our device design more according to the specs of some of our parts. Over the weekend we integrated the directional antenna with the ESP32 board. We then took several measurements in the grassy area outside Hamerschlag Hall, to check the RSSI measurements.

We were unsatisfied with the direction finding algorithm we proposed earlier. The previous idea was to move in the direction of greatest RSSI by maximum value. After I researched the RSSI quantity further it is actually feasible to get the exact angle of the direction then vectorize that quantity among the three propellers we will have. This will add more precision to the programming portion of this project, with very little added computational complexity. These and other more descriptive tasks were determined this week, like the need for a digital filter. We plan to do more pretests in the coming week when our parachutes arrive.

This past week, our proposal presentation occurred on Wednesday, so I spent the first half of the week practicing. Mainly I familiarized myself with the slides and focused on explaining our visuals and calculations in an organized manner. Our group received feedback regarding the slides yesterday via Slack. Overall, some helpful questions were brought up both in the comments and in the Q/A portion of the presentation. For example, whether we were considering other steering systems and the tradeoffs associated with them. In turn, I am researching other methods of steering like compressed air, and how they would affect the device’s weight and robustness (against weather and other confounding variables).

After the proposal presentation we ordered some parts to try out. Namely, we ordered one directional antenna and a chip to control the signal reception on the antenna. We expect to be able to compute RSSI and find out the range of our directional antenna. Hopefully, these items will meet the needs of our perception task.

This week we have been preparing the proposal presentation for the upcoming week. In order to quantify the requirements of our project,  we have been researching current technology related to our topic and modelling the kinematics of our device in action. Personally, I have been editing the proposal slides and typing up the equations we used in LaTeX for readability. I also looked around for potential drop sites around campus in person and on Google Maps.