Blog 8 - March Updates!

03/26/2022

Video Transmitter Test

A test was done on the video transmitter (VTX), to understand the limitations that a drone would have operated indoors, when receiving a signal. These limitations include the range and operability of the VTX. This test was conducted using a camera, video transmitter, battery, and an antenna that matched with the UAV design. An antenna receiver was also an addition that was attached a cell phone to output the video on a screen. The mockup was tested around 2 buildings, Engineering Building 1 and the Architecture building, to test the range of the transmitter. Different ranges of power were used for video transmitter, which unfortunately did not change the results for overall video signal.

Figure 1: Video Transmitter Setup (excluding the transmitting and receiving antenna, phone and the battery)

Testing involved two group members that communicated about the video transmitter signal via phone. There were four stages to the video quality from best to worst: colored, black and white, jittered, and completely out of signal. Worst case when determining that the signal was not safe for the drone was determined to be when the signal jittered.

The results were that the range of the vehicle is significantly lower than anticipated in the Engineering Building 1 with an estimated 131ft radius before disconnecting. After talking to Robert Dial, the reason for this was because the Engineering Building was designed to be shielded from electromagnetic radiation. To prove this, the test was moved to the Architecture building with the same setup and found a 185ft radius. The overall results is shown in this table.

Table 1: Range Calculations for the VTX

Table 1 is available upon request.

Printing and Manufacturing

The ECE and MECE team had planned over the spring break to manufacture the drone parts. The drone consists of the frame and the electronics box. Some parts are being 3D Printed using PLA to verify accurate CAD design that might need to be changed, and others were CNC'd by a machinist. Currently, Modifications to the bumpers has been made and reprinting is required. The electrical box is also going through a design change and is planned to in production this upcoming week. The ECE and MECE team are going to assemble the entire drone next week to check that the electrical components fit in pairs of 2(1 ECE and 1 MECE). Afterwards, the PLA parts will be replaced by CNCing the same parts (because PLA has a low melting point and only used for design purposes as it is not ideal to use for a drone). Below is a table of parts we need to build.

Figure 2: Manufacturing Parts to CAD or CNC

Below is the final product of our current drone build. Parts need to be readjusted and added as mentioned prior.

Figure 3: Incomplete Drone Build with PLA Parts

Onboard Computer & Camera

Due to time constraints, the software task is now shifted from image processing to simply prioritizing the camera feed display, especially on bootup without manual input. This decision has been made to allow a prototype of the drone to run within the scheduled demonstration. Once feedback is received and the demonstration is completed, further work will continue into image process.

In terms of bootup, .bashrc and init.d are candidates for potential solutions to running the camera. However, the selected method has not been made yet due to ongoing testing with the current method used to display visuals (rapivid). Additional time has been spent to test the camera under low light conditions. Current issues are arising as the camera interface does not automatically control its output in dark settings as currently expected, which leads to the camera only functioning during the day currently. Further testing will be performed next week.

In terms of outlook, the hardware setup is finalized. Once the camera is able to display its video output through the HDMI interface and automatically adjust its visuals, the data will be fed to the transmitter for broadcast.

Motor Setup

Since the previous update, the motor testing rig has made more progress. An additional 20-30 thrust tests were performed. The results are highlighted below.

Table 2: Gathered Motor Data

Table 2 is available upon request only

In terms of efficiency, it was found to be less than advertised. But unfortunately, this may be a side effect of the high frequency of the motor controller vs. the relatively low sampling rate of the current sensor, so our data is not entirely reliable. Our data suggested a range of 2.5-4 g thrust per Watt of battery power, while the advertised efficiency is 4.5-9 g thrust per Watt of battery power.

Despite the possibly unreliable power data, the thrust is enough to fly the drone, and efficiency is still relatively high compared to other motor/propeller combinations even if our data was correct. This means we should expect at least 10 minutes of flight time, and possibly 20 if the efficiency is close to the advertised rates.

With the data gathered, the thrust testing rig is now disassembled and returned, with next plans being to assemble the motors onto the drone along with the battery. 

Figure 4: Last documented photo of the testing rig. Farewell!

Designing the Electronic Housing

The electronics box reaches its second iteration as of last week. As planned, all the electronics, including the flight controller, motor controller, video transmitter, onboard computer, and camera(s), will be stored within. Access ports will be available for the motors and any other needed connectors, such as the battery, which will not be stored in the electronics box due to its size.

Figure 5: Most recent iteration of the electronics box.

We hope to conduct our first test in April 8th, in Engineering Building 1 Pit, with regular PLA parts (Not CFRP) just to check the frame and electronics. At this point, we believe that's achieveable.

Limited Technologies, Inc. 
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