This Clever Helicopter Achieves Stable Flight Using a Pair of Rotors in Tandem

What is a bicopter?

Helicopters, with their large central rotating set of blades at the top and stabilizing rotor at their rear, are quite commonplace nowadays, as they are used for purposes such as surveillance, transportation, and even recreation. However, this design is not the only one around, as the bicopter can also achieve stable flight using a pair of similarly sized rotors that are offset from each other. Some famous bicopters include the V-22 Osprey and Boeing CH-47 Chinook, and Redditor CCCanyon (Chia-Chi Chang) wanted to create his own variant weighing less than 250 grams.

Designing the frame

CCCanyon's design was largely inspired by Boeing's Chinook helicopter and its unique look of two rotors where the back one is elevated slightly. The front of the frame features landing skids to make returning to the ground a bit safer, and the angular design assists in making a better aerodynamic profile. Best of all, the entire thing was constructed from 3D printing, thus achieving a very light weight.

Control circuitry

Helicopters are far more difficult to pilot than airplanes, owing to their method for moving across the horizontal plane by tipping to one side, which means CCCanyon's project needed a very good flight control system. The one he came up with is based around an Arduino Nano 33 IoT due to its fairly fast processor and integrated sensors. In order to determine the orientation of the bicopter, the Nano 33 IoT uses its built-in LSM6DS3 6-axis inertial measurement unit along with some trigonometry. In order to perform a course adjustment, both rotors were placed upon Emax's ES09MD servo motors that are able to swing left and right to provide tilt.

Power is provided to the unit by a set of 2S Li-ion battery packs that are able to provide the brushless DC motors with up to 20A of current and have a capacity of 2500mAh. Finally, the DIY transmitter features a single stick and is capable of tuning PID parameters and calibrating the IMU while in use. It contains a LoRa SX1276 wireless transceiver module that sends data to the corresponding one on the bicopter.

Some specialized programming

Perhaps the most difficult part of the project was the software for the flight controller, as it had to not only respond to inputs made by the user, but also maintain a stable position/orientation. To accomplish this, the Arduino Nano 33 IoT continually runs altitude and heading reference system algorithms, which CCCanyon impressively coded from the ground up. Although there was originally an issue with the PID controller, he was eventually able to correct it and maintain proper flight orientation.

Taking flight

This project is nothing short of impressive, and as can be seen in this demonstration video, the bicopter smoothly glides through the air without a hint of wobble. CCCanyon is also working on a second, improved version of his design.