Blimp-o-matic - a Lighter-Than-Air UAV Platform

Hey there, DIY drone enthusiasts and fellow aerial adventurers! Welcome to our Instructable for building your very own Autonomous Lighter Than Air UAV! Have you ever dreamt of building a blimp-like drone that can navigate indoor spaces, carry payloads, and capture aerial footage? In this project, we explore the fascinating world of buoyant aircraft, where we the buoyancy and propulsion to create a lighter-than-air UAV.

Background

So why build a blimp, anyway? Blimps and hot-air balloons have a unique ability to achieve superior payload efficiency, extended range, reduced vibrations, and impressive endurance compared to traditional aircraft. By delving into the world of lighter-than-air UAVs, we want to explore the full potential of buoyant flight and leverage it for various applications.

The versatility of an autonomous blimp UAV opens up a world of possibilities. From assisting in indoor monitoring and signage to serving as a platform for low-power sensing and AI at the edge, this project offers an exciting opportunity to delve into unique missions and use cases. Whether it's finding a coworker in a large office or conducting cutting-edge research, the potential applications of this platform are limited only by your imagination.

Overview

The Manual will include the following

• How to build the product
• Products identification Information
• What tools need to be used
• Parts needed
• Products specifications
• Hardware
• Software
• Operate 
• Troubleshooting
• Safety precautions
• Drive with designs and supplemental information

Project Team

This project is the result of a Portland State University (PSU) Electrical and Computer Engineering (ECE) Senior Capstone Project for 2023 sponsored by Galois, Inc.

Meet the awesome minds behind this project:

• Ibrahim Zreik
• Jose Juarez
• Constantine Hatzidakis
• Mustafa Alazzawi

Tools

The Tools and Software used for this project:

• Laptop or Computer
• Betaflight configurator 
• 3D printer 
• Soldering kit
• Hot glue gun
• Eye protection

Parts

All the parts used in this project:

• Brushless F4 flight controller(BetaFPV) 
• 4 brushless motors(BetaFPV)
• Blimp shaped envelope 
• Velcro
• Hot glue
• 3D filament 
• Remote controller(BetaFPV)

1. Start by ordering the brushless F4 flight controller and the 4 brushless motors from Beta Flight 
2. Assemble the flight controllers if not already assembled, soldering may be required.
3. If an adequate envelope can not be found, it may have to be manufactured. (A suggestion was to use mylar blankets to create a mylar balloon)

After ordering the flight systems you can start by 3D printing. There are two parts that are going to be printed. The first one is the one that is going to have all the motors attached to it and the other is the one that is going to be attached to the envelope. 

1. The motors are mounted on the 3D-printed component. In our design, there are four spots: one for each motor, two in the center, and one on each of the two edges. It is built with a large circle in the center and three smaller ones surrounding it for the screws. 
2. The 2 holes in the middle is there so we can screw the F4 controller on it and it will be safe and not move around 
3. As for the batteries you can place 2 velcro dots on them and 2 on the 3D design and you can secure it that way. 

Party balloon helium will be placed inside the envelope. Many stores carry party balloons with helium, which we purchased from Target. We specifically received "12" Jumbo Helium Balloon Tank Kit Red."

1. Velcro dots were used to affix the drone from Figure 4 to the envelope. We placed the velcro dots at the bottom of the second 3D printed component and in the middle of the envelope. Fishing line can be used to further secure it and make sure it won't fly when not in use. 
2. The next step in assembling the hardware is to adjust the weight until the envelope is leveled. Since the drone and both 3D Parts are around 45 grams, the envelope must weigh roughly 165 grams to maintain balance and prevent flying away. So that it can remain balanced, we added 120 grams to it and distributed them properly around the envelope. 

1. Install Betaflight configurator software on a computer. https://github.com/betaflight/betaflight-configurator/releases
2. Using the USB-C cables included with the flight controller(FC) connect it to a computer.
3. Start the betaflight software and ensure the FC is communicating with the software properly
4. Under no circumstances should you use the reset settings option. This will completely reset the FC and will remove any firmware installed on the FC.
5. Check the configuration tab and ensure AIRMODE is turned off.
6. Ensure Maximum ARM angle is set to 180 degrees.
7. All other settings may be adjusted as needed.
8. Ensure the ‘Save and Reboot’ button is pressed before switching to any other tab. This is done for any settings update on each tab.
9. Use the motor tab to enable MOTOR_STOP and set motor idle to a reasonable percentage.
10. Use the command line interface (CLI) to set a custom motor mix based on the motor mounting positions and motor numbering. Use the motor tab to reorder the motors as necessary.The motor mix can be adjusted as necessary to determine the most intuitive control for the operator.
11. Set the mixer in the motor tab to custom.
12. Any motor testing can be accomplished in the motor tab. A battery must be connected for any motor power.
13. Motors can be reversed for the parts mentioned in this manual. This is helpful when trying to achieve best thrust.
14. Receiver testing can be done in the Receiver tab. Any receiver inputs will be mirrored on this tab.
15. With the controller and motors mounted onto the envelope, click ‘Calibrate Accelerometer’ in the Setup tab.Regardless of physical orientation of the FC on the blimp mounting, the tab should show a 0 deg roll and pitch. This will ensure the FC does not auto compensate when arming and will ARM correctly.
16. FC is set up to propel the blimp at this point!

Table 1: Motor mix settings code (May need adjustment depending on motor mounting locations).

#mmix [Motor index] [throttle] [roll] [pitch] [yaw]
mixer custom
mmix reset
mmix 0 1, 0, 1.0, 0.0
mmix 1 1, 1, 0.0, 0.0
mmix 2 1, 0, -1.0, 0.0
mmix 3 1, -1, 0.0, 0.0
save

1. On the receiver, all inputs should be set to neutral with throttle off. The AUX 2 switch should be set to the top setting, preventing ANGLE and HORIZON hold modes. The AUX 1 switch should be set down to have the ARM flag off.
2. Connect a battery to the FC if not already connected.
3. Wait for the FC to show a solid green light.
4. Set the AUX 1 switch to up to ARM the FC.
5. Two solid green lights will illuminate if FC is armed.
6. With the MOTOR_STOP enabled, all inputs can be used as a short burst.
7. Use the controller and set the stick to the desired input, based on the motor mix. In the case for the above mix, pitch up is designed to send the blimp forward. 
8. With the stick held to the desired input, quickly increase and decrease the throttle, sending the command as a short burst.
9. Longer bursts can be used as necessary, short bursts will conserve battery life. 
10. Setting throttle to zero must be done after each burst in order to prevent FC from attempting to compensate for uneven throttle inputs
11. You are now flying a blimp drone!