To build the great fixed-wing mapper with long flight times, higher quality camera, simple to launch/land and secure during the flight a seemingly simple set of requests. Well, not exactly.
Going from minimal knowledge of drones to constructing a fixed-wing mapper has a seriously steep learning curve. The learning curve would have pushed the patience of even the most enlightened Yogi. Here you’ll find a breakdown of the time it will take to build a mapping drone.
The Wish List
The desired duties that this drone should be able to perform.
- Capture photos remotely
- Hand launched
- Minimum 30 minute flight period
- Automatically fly preset flight paths and also a return to home function.
- Desirable but not essential.
- About a 60-minute flight period
- Internal distance to allow for a parachute landing update
- High-performance battery, engine & servos for acrobatics, if you get bored and fancy a loop or two.
1. Shoot Photos Remotely
The essential part of the drone, especially any mapping drone, was the camera. Each mapping drone is, at its core, simply a camera. Some drones like the Wingcopter 178 can double up for both mapping and delivery. However, this a rarity as opposed to a rule.
After taking off a drone into the air, you can’t precisely press the camera to capture images precisely once you want. There must be a method to capture pictures in flight automatically.
Sticking to the small budget, an inexpensive solution was found in a Cannon handheld digital camera. This camera was chosen because it was cheap and because it was compatible with the Cannon Hacking Development Kit’ (CHDK). CHDK provides certain Cannon cameras to be hacked, providing the user more functionality than canon’s inventory performance.
With this loaded onto the S.D. card at the camera, settings such as shutter speed and ISO could be altered with greater simplicity and flexibility. Having control over important camera settings is perfect when trying to conduct a drone survey. Particular configurations can compensate for weather and flight speeds, allowing picture quality to be preserved.
CHDK is what made remote image capture possible. A simple period script, publicly available on the internet, enabled the camera to capture images in a set period constantly. This is somewhat primitive in that pictures are being recorded from take-off until landing instead of only during the actual mission. This is the nature of a budget construct and figuring it out as you go. It did the job well.
2. Launch By Hand
Unpack, switch on and toss with gusto. Hand launching provides simplicity.
The ability to hand launch a drone eliminates the requirement to set up a spring-loaded railroad system upon which the drone will be launching, military-esk. Hardly any survey drones use this technique of take-off, and with hand launch down as a requirement, this restricted two chief elements of the drone—the airframe and weight. The airframe couldn’t be too large, and the weight couldn’t be too much! If either weren’t respected, hand launch could be impossible or very likely cause an immediate crash.
Placing weight aside for the moment, the airframe was the first important holistic thought’. In other words, the ideal solution for a single portion of the drone might not have been the ideal solution for any other region of the drone. The juggling act started.
How will the camera fit? Where will the battery go? How can it fly? How can it land? Will the stall speed be too large? Will the flight control and electronics fit, if so, where? The list goes on!
Not only this but every one of these questions had to be answered under the umbrella of efficacy. How will flight time be maximized? Can the camera and battery be easily accessed? Will future fixes be on par with heart operation or completed with only a couple of tweaks?
Such concerns led to hours of internet meandering through pages and pages of drone hobby stores.
The four benefits of the airframe were its huge internal space, flight efficiency, stability, and hand launching capability. Each of these alone was very important. Nevertheless, the most important aspect for me was that the large internal space. Being able to experiment with an assortment of configurations and updates was a significant selling point.
Two downsides to this airframe are its high landing rate and tendency to tip stall launch. A suggestion stall happens when there is insufficient lift over one of the wings. At low speed, for example, immediately after launching, this is asking for a crash.
High landing speeds raise the size of the needed landing area and limit landings to mostly smooth areas. But with an eye on parachute landings, you can place this disadvantage down the list of importance.
Another small drawback was that the layout of the nose. After some consideration, it became apparent that the nose could very likely dig in the ground upon landing. A solution was observed by 3D printing a custom-fitted bumper sourced online.
3. Flight Time – Minimum Of 30 Minutes
Why goal 30 minutes?
The two advantages all mended wings should have over multirotor drones are battery life and the capacity to cover larger areas or distances in one flight. The latter is more or less a guarantee; though, the former, longer battery life, isn’t.
Mainstream multirotor drones like those marketed by DJI and Parrot have a battery life of approximately 20-30 minutes. Keeping this in mind, payloads being equal, all mended wings need to fly for at least the maximum flight time of those multi-rotors. That’s because traditional wings create lift themselves instead of relying entirely on always rotating propellers. Therefore, a lot of the load can be carried by the wings, conserving battery life.
Three of the most important factors discovering flight times are battery dimensions, weight, and weather. With the weather around the gods, under my hands were the battery size and total weight.
After more comprehensive research, we found that a 5000 mAh 4S battery would guarantee at least 30-minute flight times and supply sufficient electricity for the strange acrobatic maneuver. The smarter idea would have been to find a 3S instead of the 4S (S speaking to the number of battery cells) as the weight of the battery could be somewhat less. However, more cells provide more functionality allowing for steep climbs and rapid turns.
Desire longer flight times? Just throw a larger battery in! Once more, not exactly.
The connection between flight time and battery size is somewhat like rockets. And yes, we are now drawing similarities between this job and rocket science. Having a rocket, to go faster/higher/longer, you can add gas. But more fuels mean more weight, so you have to carry more fuel to maintain the functionality, which means more weight, which means more fuel than getting the idea.
The larger the battery, the more the flight, but just to the point where the system becomes inefficient and the benefit of a bigger battery is overshadowed by the sheer weight of the battery. And, of course, the battery has to be small enough to fit in the airframe!
4. Automobile Return To Home Function & Pre-Set Flight Paths
The ability to automatically fly preset flight paths is vital for any surveying drone of any type. It empowers the pilot/surveyor to pick the region in question on a phone, tablet, or laptop and create a perfect path into the drone that should follow for the best photogrammetric results. Key factors for great results overlap and coverage, both of which may be ensured with the software on the ground before flight.
Having a return to home function is by no means important in the objective sense of carrying out a flight; however, subjectively! With this function on the board means that, in the not so unlikely event that signal is lost together with the drone, the brain or flight control recognizes this and quite quickly sets a path for your home position. When the drone comes nearer to the pilot’s position, the signal is obtained, and manual control can be obtained.
So how is all this done? The flight controller.
Not unlike a full-size jet, the flight controller lets you engage autopilot. Once engaged, it uses telemetry from onboard GPS to fly according to preset parameters such as certain speeds, altitudes, and paths.
The flight control used for this drone is called ‘Pixhawk,’ with its own operation and programmable functions obtained through a software called mission planner.’
Building The Drone
With most of the required parts sourced and the plan marginally organized, the installation of this system can be started. The drone is composed of two major components, the airframe and electronics. The challenge at this point was how to match the network of wiring from the image below into the airframe.
As you may imagine, it is not simply a case of pile everything in, and it is going to be fine. Nearly every part needed to be in a particular location to carry out its purpose best or to have the ability to perform its function in any respect.
- Flight controller & battery placed at the center of gravity (center of the drone)
- GPS > Positioned externally for a sign, Orientated upwards and forward
- ESC (Electronic Speed Controller) > Located outside as it can find a little hot!
- Motor > Placed at the back (the airframe being in a ‘pusher’ configuration)
- Servos > One to the left-wing, one to the perfect wing, you to the left-back, and one to the right-back
- R.C. Receiver > Anywhere available and not covered up as to block signals
- System arming > Anywhere readily accessible externally
- This measure quickly resembled the back Of a T.V. set or a bird’s nest.
After lots of untangling and placement, A wholesome dose of paste was applied where required and that we had something that looked like it might fly!
In case you were thinking, the black tape on the wings wasn’t just for aesthetic design. During the first couple of flights, it was hard to tell which way the drone has been orientated. With two high-contrast stripes on the left and one on the right, let me know instantly which way the drone has been flying. As you can imagine, this was quite useful!
The final measure is to connect the drone to the notebook using the tiny USB antenna found in the picture above with everything in place. This turns the laptop into the ground station where flight plans can be uploaded, and live telemetry could be looked at.
New Appreciation For Drones And The Building Process
However, this project may seem complex, and it’s simple compared to the level of capacity offered by many survey drones on the market. One big takeaway from this project has been acquiring a newfound appreciation for drone producers and the level of R&D and trial and error that has to go into producing a workable system.
Probably the biggest learning outcome was the above juggling act’ otherwise known as systems engineering.’ With idealistic aims from the get-go, we believed that attaining these is a somewhat straightforward procedure. It wasn’t.
Attempting to perfect every aspect of the fixed-wing mapper drone instantly led to particular features butting heads where one or the other had to back down, such as needing a very long battery life but battery dimensions resulted in increased weight, reduced flight time maximization, and hand launch difficulty.
There are countless examples of this trade-off between one attribute over the other. This is a fixture inside all engineering jobs where the machine is the sum of its parts working together and collecting individual pieces.