As hobbyists, we (@walter and me) are not yet sure if we will build a three-engine Transwing VTOL. Therefore we first made a “proof of concept” model and want to introduce our considerations:
From our point of view, the main advantage of Pterodynamics Transwing VTOL is when hovering against the wind, the wing surfaces do not generate downforce but even lift! This is a unique feature, because all VTOL types with transition-stable fuselage generate considerable downforce when hovering against wind. But there is no light without shadow: A single pivot joint must hold the wing in place.
Since four motors are luxury for the forward propulsion anyway and to reduce the forces on the wing, we planned only 2 motors (one motor per wing). A third motor is therefore required at the rear, like a tricopter. The model is used to quickly change the linkage geometry and to test the control electronics.
The linear actuator is controlled by Arduplane using an ESC32. From Arduplane’s point of view the linear actuator behaves like a normal tilt servo. The ESC32 runs an Arduino Sketch, which is connected via Mavlink. The position of this “virtual” tilt servo is communicated to the ESC32 via Mavlink. The ESC32 now controls a real servo output on the Pixhawk via Mavlink, which control the brushless motor in both directions via DSHOT - BLHELI_32. Telemetry outputs RPM and current. The stop switching at the ends of the linear drive is done by 2 Hall sensors.
Even if we are not sure yet if we will realize a Tri-Mot-Transwing, we wanted to present the idea of a “TMT”. Maybe someone has already finished it or it inspires someone to build it.