Drone Boat Sails Seattle

March 11, 2021 by Lewin Day 11 Comments

Thanks to the availability of cheap, powerful autopilot modules, building small autonomous vehicles is now well within the reach of the average maker. [rctestflight] has long been an enthusiast working in this space, and has been attempting long range autonomous missions on the lakes of Washington for some time now. His latest attempt proved to be a great success. (Video, embedded below.)

The build follows on from earlier attempts to do a 13 km mission with an airboat, itself chosen to avoid problems in early testing with seaweed becoming wrapped around propellers. For this attempt, [Daniel] chose to build a custom boat hull out of fiberglass, and combine both underwater propellers and a fan as well. The aim was to provide plenty of thrust, while also aiming for redundancy. As a bonus, the fan swivels with the boat’s rudder, helping provide greater turn authority.

After much tuning of the ArduPilot control system, the aptly-named SS Banana Slug was ready for its long range mission. Despite some early concerns about low battery voltages due to the cold, the boat completed its long 13 km haul across the lake for a total mission length of over three hours. Later efficiency calculations suggests that the boat’s onboard batteries could potentially handle missions over 100 km before running out.

It goes to show that, even with an off-the-shelf autopilot and mapping solution, there’s still a huge amount of engineering that goes into any successful long-range mission, whether land, sea or air.

Continue reading “Drone Boat Sails Seattle” →

Lost A Lightweight Quadcopter? Here Are The Best Ways To Find It

March 6, 2021 by Donald Papp 24 Comments

Lost aircraft are harder to find when they are physically small to begin with. Not only are they harder to see, but the smaller units lack features like GPS tracking; it’s not normally possible to add it to a tiny aircraft that can’t handle much more than its own weight in the first place. As a result, little lost quads tend to be trickier to recover in general.

Fluorescent tape adds negligible weight, and will glow brightly at night under a UV light.

The good news is that [Eric Brasseur] has shared some concise tips on how to more easily locate and recover lost aircraft, especially lightweight ones. Recovering aircraft is something every aircraft hobbyist has had to deal with in one way or another, but [Eric] really has gathered an impressive list of tricks and techniques, and some of them go into some really useful additional detail. It occurs to us that a lot of these tips could apply equally well to outdoor robots, or rovers.

Even simple techniques can be refined. For example, using bright colors on an aircraft is an obvious way to increase visibility, but some colors are better choices than others. Bright orange, white, and red are good choices because they are easily detected by the human eye while still being uncommon in nature. Violet, blue, and even cyan on the other hand may seem to be good choices when viewed indoors on a workbench, but if the quad is stuck in dark bushes, those colors will no longer stand out. Another good tip is to consider also adding a few patches of fluorescent tape to the aircraft. If all else fails, return at night with a UV lamp; those patches will glow brightly, and be easily seen from tens of meters.

Some of the tips are used while the device still has power, while others don’t depend on batteries holding out. [Eric] does a great job of summing up those and many more, so take a look. They might come in handy when test flying quadcopters that are little more than an 18650 cell, motors, and a 3D-printable frame.

Attack Of The Flying 18650s

March 3, 2021 by Tom Nardi 31 Comments

When somebody builds a quadcopter with the express purpose of flying it as fast and aggressively as possible, it’s not exactly a surprise when they eventually run it into an immovable object hard enough to break something. In fact, it’s more like a rite of passage. Which is why many serious fliers will have a 3D printer at home to rapidly run off replacement parts.

Avid first person view (FPV) flier [David Cledon] has taken this concept to its ultimate extreme by designing a 3D printable quadcopter that’s little more than an 18650 cell with some motors attached. Since the two-piece frame can be produced on a standard desktop 3D printer in a little over two hours with less than $1 USD of filament, crashes promise to be far less stressful. Spend a few hours during the week printing out frames, and you’ll have plenty to destroy for the weekend.

While [David] says the overall performance of this diminutive quadcopter isn’t exactly stellar, we think the 10 minutes of flight time he’s reporting on a single 18650 battery is more than respectable. While there’s still considerable expense in the radio and video gear, this design looks like it could be an exceptionally affordable way to get into FPV flying.

Of course, the argument could be made that such a wispy quadcopter is more likely to be obliterated on impact than something larger and commercially produced. There’s also a decent amount of close-quarters soldering involved given the cramped nature of the frame. So while the total cost of building one of these birds might be appealing to the newbie, it’s probably a project best left to those who’ve clocked a few hours in on the sticks.

We’ve seen quite a few 3D printed quadcopter frames over the years, but certainly none as elegant as what [David] has created here. It’s an experiment in minimalism that really embraces the possibilities afforded by low-cost desktop 3D printing, and we wouldn’t be surprised to see it become the standard by which future designs are measured.

Demonstrating The Mars Rover Pendulum Problem With A Drone On Earth

February 25, 2021 by Danie Conradie 39 Comments

The sky crane system used on the Perseverance and Curiosity Mars rovers is a challenging control system problem that piqued [Nicholas Rehm]’s curiosity. Constrained to Earth, he decided to investigate the problem using a drone and a rock.

The setup and the tests are simple, but clearly illustrate the problem faced by NASA engineers. [Nicholas] attached a winch mechanism to the bottom of a racing-type quadcopter, and tied a mass to the end of the winch line. At first, he built a foam model of the rover, but it proved to be unstable in the wake of the quadcopter’s propellers, so he used a rock instead. The tests start with the quadcopter taking off with the rock completely retracted, which is then slowly lowered in flight until it reaches the end of the line and drops free. As soon as the rock was lowered, it started swinging like a pendulum, which only got worse as the line got longer. [Nicholas] attempted to reduce the oscillations with manual control inputs, but this only made it worse. The quadcopter is also running [Nicholas]’s own dRehmFlight flight controller that handles stabilization, but it does not account for the swinging mass.

[Nicholas] goes into detail on the dynamics of this system, which is basically a two-body pendulum. The challenges of accurately controlling a two-body pendulum are one of the main reasons the sky crane concept was shelved when first proposed in 1999. Any horizontal movement of either the drone or the rock exerts a force on the other body and will cause a pendulum motion to start, which the control system will not be able to recover from if it does not account for it. The real sky crane probably has some sort of angle sensing on the tether which can be used to compensate for any motion of the suspended rover. Continue reading “Demonstrating The Mars Rover Pendulum Problem With A Drone On Earth” →

Manned Electric Helicopter With 7 Tail Rotors

February 16, 2021 by Danie Conradie 56 Comments

One of the best things to come from the growing drone industry is the development of compact and powerful brushless motors. We’ve seen several multi-rotors capable of carrying a human, but electric helicopters are rare. [OskarRDA] decided to experiment with this, converting his single-seat ultralight helicopter to electric power and giving it seven tail rotors in the process. Flight footage after the break.

The helicopter in question started life as a Mosquito Air, a bare-bones kit helicopter originally powered by a two-stroke engine. The engine and gearbox were replaced with an EMRAX 228 109 kW brushless motor. Initially, he used the conventional drive-shaft powered tail rotor but wanted to experiment with multiple smaller rotors powered by separate motors, which has several advantages. He only really needed four of the 5008 or 5010 size motors with 18″ props to get comparable thrust, but he added more for redundancy. The new setup was also lighter, even with its independent batteries, at 7.5 kg compared to the 8.1 kg of the old tail rotor assembly.

One of the major advantages of a conventional helicopter over a multirotor is the ability to autorotate safely to the ground if the engine fails. A coupled tail rotor bleeds some energy from the main rotor while autorotating, but since the tail rotor has independent power in this case, it allows all the energy to be used by the main rotor, theoretically decreasing decent speed by 120 feet per second. [OskarRDA] did some engine failure and autorotation test flights, and the results were positive. He likes his new tail rotors enough that he doesn’t plan on going back to a single large rotor.

Power for the main motor is provided by a 7.8 kWh, 40 kg LiPo battery pack mounted beneath the seat. Theoretically, this would allow flight times of up to 27 minutes, but [OskarRDA] has kept most of his flights to 10 minutes or less. He didn’t add any electronic gyro for stabilization, but he did add some electronic coupling between the main motor and tail motors, to reduce the torque correction required by the pilot. Even so, it is clear from the flight footage that [OskarRDA] is a skilled helicopter pilot. Continue reading “Manned Electric Helicopter With 7 Tail Rotors” →

DRehmFlight: Customizable Flight Stabilisation For Your Weird Flying Contraptions

February 15, 2021 by Danie Conradie 10 Comments

The availability of cheap and powerful RC motors and electronics has made it possible for almost anyone to build an RC flying machine. Software is usually the bigger challenge, which has led to the development of open-source packages like BetaFlight and Ardupilot. These packages are very powerful, but not easy to modify if you have unconventional requirements. [Nicholas Rehm] faced this challenge while doing his master’s degree, so he created dRehmFlight, a customizable flight controller for VTOL aircraft. Overview video after the break.

dRehmFlight runs on Teensy 4.0 with a MPU6050 or MPU9250 IMU

[Nicholas] has been building unique VTOL aircraft for close to a decade, and he specifically wanted flight stabilization software that is easy to modify and experiment with. Looking at the dRehmFlight code, we think he was successful. The main flight controller package is a single file of fewer than 1600 lines. It’s well commented and easy to figure out, even for an inexperienced programmer. A detailed PDF manual is also available, with full descriptions for all the functions and important variables, and a couple of tutorials to get you started. Libraries for interfacing with accelerometers and RC gear is also included. It runs on a 600 Mhz Teensy 4.0, and all the programming can be done from the Arduino IDE.

[Nicholas] has repeatedly demonstrated the capabilities of dRehmFlight with several unique aircraft, like the belly flopping RC Starship we covered a while ago, a VTOL quad rotor biplane, VTOL F35, and the cyclocopter seen in the header image. dRehmFlight might not have the racing drone performance of BetaFlight, or advanced autopilot features of Ardupilot, but it’s perfect for getting unconventional aircraft off the ground. Continue reading “DRehmFlight: Customizable Flight Stabilisation For Your Weird Flying Contraptions” →

Orphaned Gimbal Gets Second Chance To Fly

February 3, 2021 by Tom Nardi 1 Comment

A reality of flying RC aircraft is that at some point, one of your birds is going to fall in the line of duty. It could get lost in the clouds never to be seen again, or perhaps it will become suddenly reacquainted with terra firma. Whatever the reason, your overall enjoyment of the hobby depends greatly on how well you can adapt to the occasional loss.

Based on what we’ve seen so far, we’d say [Rural Flyer] has the right temperament for the job. After losing one of his quadcopters in an unfortunate FPV incident, he decided to repurpose the proprietary gimbal it left behind. If he still had the drone he could have slipped a logic analyzer in between its connection with the motorized camera to sniff out the communication protocol, but since that was no longer an option, he had to get a little creative.

Figuring out the power side of things was easy enough thanks to the silkscreen on the camera’s board, and a common 5 V battery eliminator circuit (BEC) connected to the drone’s 7.4 V battery pack got it online. A cobbled together adapter allowed him to mount it to one of his other quads, but unfortunately the angle wasn’t quite right.

[Rural Flyer] wanted the camera tilted down about 15 degrees, but since he didn’t know how to talk to it, he employed a clever brute force solution. After identifying the accelerometer board responsible for determining the camera’s position, he use a glob of hot glue to push the sensor off of the horizontal. Providing this physical offset to the sensor data caused the camera to automatically move itself to exactly where he wanted it.

Continue reading “Orphaned Gimbal Gets Second Chance To Fly” →