The novel type of multi-rotor design is to enhance payload and endurance in performance over traditional electric multi-rotor. The bottleneck of battery defeats the multi-rotor endurance. A new idea to introduce internal combustion (IC) engine together with electric brushless DC (BLDC) motor to endurance multi-rotor system performance is proposed. Taking the advantage of energy density of gasoline being more than 40 times to Lithium Polymer (Li-Po) batteries, significant improvement over endurance and payload can be expected. The proposed multi-rotor designs an IC engine drive quad-rotor to provide main lift and work with a conventional LDC motor quad-rotor for attitude controls. Conceptually, it is a Quad-rotor-in-Quad-rotor (QiQ) Dual Powered multi-rotor system for improving endurance performance. The force moment dynamics of two quad-rotors is formulated to present main lift and control stability. Equal engine speed control strategy is implemented to stabilize high thrust control with an incremental PID controller. Noise reduction and vibration suppression are designed and fabricated into system integration. The flight control system including state estimation, sensor and actuator network and suitable controller is designed to realize the flight stabilization of the proposed QiQ design. System verification and flight demonstration show great improvement in system performance and flight stabilization. The QiQ multi-rotor concept is proven to be a solution from experiments to multi-rotor endurance and performance improvement.

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