Hello UAV enthusiasts and experts,

I am currently working on a quadcopter drone project where we are exploring a unique motor configuration. Specifically, we are considering a hybrid setup where the front two motors are inverted (facing the ground), while the rear motors are in the standard upward-facing position. Due to inversion, front propellers are closer to ground as compared to rear propellers.

I understand this is less common and also poses challenges in terms of flight dynamics and control algorithms, but this is a required structure for our project. Our major emphasis is on the control portion of the quadcopter. We are building the control algorithm ourselves for a better understanding. The control algorithm currently built consists of PID loops similar to PixHawk, and works fine on the standard quadcopter config (all 4 motors upwards).

The frame size has wheelbase of around 600mm (Diagonal motor-to-motor length) and is symmetric X shaped, Tri-propellers are 10 inch in diameter. And the quad weighs about 3 Kgs due to additional equipment required for the project. And we have kept into consideration the motors rotating directions for this specific config.

Some issues that I can think of is:

  • Unequal thrust being generated by pusher & puller props.
  • Front propellers being closer to ground experience greater ground effect when taking-off.

Let me know if these would effect the dynamics or can be ignored. And here are my main questions:

Feasibility: Has anyone experimented with this motor configuration in their projects? What are the primary technical challenges associated with this setup?

Control Algorithms: How should the flight control algorithms be adjusted to accommodate the mixed orientation of the motors? Are there specific considerations for PID tuning or stability control?

Aerodynamic Effects: How does the inversion of the front motors impact the aerodynamics of the drone? What can be done to mitigate any negative effects?

Practical Insights: If you have implemented a similar setup, could you share insights on the performance changes compared to a traditional configuration? Any data or case studies would be highly helpful.

Resources: Are there any studies, papers, or resources that discuss such configurations? I am looking to deepen my understanding and potentially connect with experts in this area.

Any advice, experiences, or resources you could share would be greatly appreciated. Thank you for helping me navigate this complex topic!

  • $\begingroup$ With a decent tune, heck even a bad one, this motor configuration should not cause any unexpexted or negative downsides beside needing landing gear so that the front props don't hit the ground when landing. $\endgroup$
    – Jacob B
    Commented May 11 at 15:41


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