Subsystem Build & Test

Team Vision for Subsystem Level Build & Test Phase

Design Updates

Sensor Subsystem

Motors and Servos

Power Distribution & Signal Interconnects

Schematic

The above schematic describes almost all the electrical connects that need to be made.

• 12 V Power from the LiPo will directly go to the ESCs.
• The servos will draw 5V from the output of the ESC.
• The rangefinders will not be connected directly to the PCB. The rangefinders will connect to the PCB via cable. 
• The IMU will be centralized on the PCB.

PCB Layout

Please note that not all components of the system will be on the PCB. The rangefinders for example will be connected to the PCB via cables. Same goes for motors.

Option 1:

• Power components, uControllers, Telemetry grouped together.
• Advantage: It keeps high power and low power components separate
• Disadvantage: Microcontrollers in the middle of board, might cause accessibility issues, longer traces required between sensors and K64.

Option 2:

• The K64 and the raspberry pi are separated since they perform different task without much interdependency.
• Advantage: Better accessibility, shorter traces due to arrangement of boards.
  
• Disadvantage: The power components are in the middle and the uControllers are seperated.

Mechanical Design and Assembly

Parachute Canister

All parts of the parachute canister were printed successfully, Above you see the parachute canister, the battery holder fitting a 9V battery as designed and then the final picture shows the spring cap and the top of the canister. The spring cap is what we will push down with the parachute and it will aid in deploying the parachute as well. We have found a pin that will allow the top to be connected to the canister but other options are still being researched.

Fuselage

As stated above due to the electronics holder being scrapped as an idea and the EE and CE team creating a custom PCB the fuselage had to be updated accordingly. Also changes to the conceptual wing sparked changes as well.

The conceptual wing was changed to add more spars in order to add more stability to the overall system. So the first change came from removing the rear spar and changing it to two smaller sized spars in the rear.

As mentioned above the EE and CE team are working to creating their very own PCB replacing the old electronics holder idea. This is a conceptual design that they provided as to how they want to adapt the PCB to the fuselage. Basically they wanted a way to slide the PCB in and out for easy installation and maintenance however, in order to complete this the rear of the fuselage must have an access port.

This slot in the back will allow for the PCB to be put inside and removed whenever we please. 

Other ideas came to move the parachute canister, which was planned to be attached on the outside of the fuselage, inside the fuselage We also wanted to maintain the tail of the UAV as well.

Additionally, since we are going to have an FPV camera for flying a set up was created to allow us to insert the FPV camera and mount it securely and run the wires with the rest of the electronics (see final picture). Pictured you see one of our motor mounts but that is just a placeholder for an idea to create a camera mount to securely attach the camera and add stability to the images captured. The slot in the back can allow wires to run through

Since the PCB design is not finalized/at the manufacturing stage yet the top or cover of the fuselage has not been desinged as the height constraints of the PCB are unknown. But the idea is a very simple design as seen below.

This will be held on with Safety Strap locks. They are strong flexible and relatively cheap we can put them all around the top which allows the user easy access to taking the top off as they see fit.

Motor Mounts

Motor mounts were successfully printed and are much smaller then the previous mount that was attached to the versa wing. They are just big enough to hold the motors which is exactly what we intended with the design. We did run into a small issue which is that the current configuration of the mounts are too long and lead to propeller interference (see pictures below).

The props barely hit the mounts so these will be reprinted with the length slightly decreased to remove this issue. Once reprinted we are ready to finally attach these to the versa wing and hopefully get it up in the air with all the other modifications.

Conceptual Wing

The suggestion was made to increase the number of spars in the wing and have them run the full length of the wing, to improve stability. The rear wing spar, which until recently was a 4mm x 15mm carbon fiber spar (identical to the fore wing spar, was replaced by two 2mm x 10mm carbon fiber spars. These spars are situated at right angles to each other to resist bending in both the vertical and horizontal plane. The two spars run the length of the entinre wing, as opposed to the original rear spar, which only extended five or six ribs from the fuselage.

At this point, we began preparing the ribs for laser cutting.

Originally, the plane was to produce them from balsa wood (know for its low density and high strength-to-weight ratio). This would allow us to have relatively wide ribs to support more of the wing skin.

Alas, balsa wood is hard to come by and very expensive. We finally managed to find Baltic birch in large enough sheets. The Baltic birch has about three times the density of the balsa, but is also three times thinner than planned for, so we anticipate the trade-off will be negligible. As of time of writing, we are still troubleshooting the file conversion of the individual rib files into one PDF that retains scale.

Due to the changes made to the struts, the motor nacelle would also have to be changed, as it was originally designed to accommodate both struts. The nacelle was redesigned in SolidWorks for the new strut configuration, and it was also lengthened to allow the motor clearance away from the wing's leading edge once it is mounted on.

As of time of writing, it has been submitted to the Construct to be 3D printed, and is printing.

The elevon brackets were originally intended to be machined out of aluminum for airworthy-grade durability. It was decided that this would make the brackets heavy, and the decision was made to 3D print them instead. this will reduce the weight of the part, and since we are working on such a small scale, we don't anticipate an issue of durability. The issue we have identified is friction between the bracket and the axle. Our immediate solution was to expand the holes that will accommodate the axle. As of time of writing, the bracket has been submitted to the Construct to be 3D printed, and is printing. Once we have a prototype, we will test the amount of friction empirically and go from there.

Finally, the decision was made during the last phase to change elevon actuation method. The original method involved the elevon actuated axially via a servo mounted in the fuselage. This was done to save weight in the wings and improve aerodynamics. We have since decided that aerodynamics aren't going to be a huge issue at the speeds we intend to fly, and that the fuselage-mounted servo will take up space and draw lots of power. We pivoted to a servo mounted in-wing that will operate the elevons via a lever (as is common on many RC planes and even industry-grade fixed-wing drones). This new servo will pull less power and be lighter.

(courtesy of Servo City; https://www.servocity.com/hs-53-servo/)

Of course it needs to be mounted. A mounting bracket for the servo was designed.

This simple mount will fit around the rear two spars. As of time of writing it has been submitted to the Construct to be 3D printed, and is printing.

Versa Wing

The landing legs for the Versa Wing test bed were printed successfully. Upon initial fitting we found that, while they do they job admirably, they are awful heavy. such weight would cause the drone to be rear-heavy and require constant trimming just to fly level. This would not only hamper maneuverability, but would also burn out the elevon servos pretty quickly. This is not to mention the extra required thrust and the compromised payload.

The decision was made to laser cut the legs out of Baltic birch, along with the ribs for the conceptual wing. This will happen next phase. We are in the process of troubleshooting appropriate file conversion.

Test Results Summary

Summarize Requirements and Testing.xlsx and assess effectiveness of test plans to unambiguously demonstrate satisfaction of the engineering requirements

Instructions

1. Quantitatively summarize the capabilities, performance, throughput, and robustness of your subsystems as demonstrated by execution of the text plan. Document your testing with photos or videos in addition to test data.
2. Evaluate how well the test plan was able to confirm satisfaction of subsystem requirements
3. Include snapshot of testing completed to date, and include link to live Requirements and Testing.xlsx

Inputs & Source

1. Test Plan
2. Subsystem fabrication

Outputs & Destination

1. Test Results
2. System integration

Risk and Problem Tracking

• Update your Risk Management template.xlsx
• Update your Problem Tracking Template.xlsx

Functional Demo Materials

Include links to:

• Pre-read
• Presentation and/or handouts
• Notes from review
• Action Items

Plans for next phase