Coaxial Forward Propulsion for Multi-Rotor Failure Attitude Control
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Solution Overview
Problem
Multi-rotor aircrafts face uncontrollability and high power demands due to the loss of a lifting rotor, leading to unbalanced moments and torque imbalances, especially in conditions like wind, turbulence, or forward flight, which necessitate heavy-duty motor designs and increased power consumption.
Innovation Solution
Incorporating two forward propulsion devices with coaxially arranged rotors that can independently control aircraft moments about the roll and yaw axes, allowing for balanced thrust and torque without unwanted aircraft motion, even in failure scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the aircraft uses conventional lifting rotors for vertical flight, then it can achieve hover and low-speed flight, but it becomes uncontrollable and experiences high power demands when one effector fails
Solution Approach 1:
The aircraft separates vertical lifting function (performed by lifting rotors) from forward propulsion function (performed by pushing units with coaxial rotors). This segmentation allows the pushing units to independently manage yaw and roll moments without requiring the lifting rotors to operate at excessive power levels during failure conditions.
Solution Approach 2:
The pushing units can independently vary the rotational speed of their coaxial rotors to generate differential thrust and torque. By changing the rotational parameters of the pushing units, the system can compensate for the loss of a lifting rotor and maintain controllability without overloading the remaining lifting rotors.
2Force
If the aircraft uses six lifting rotors, then it can provide sufficient lift, but the loss of one rotor creates unbalanced moments requiring heavy duty effector design
Solution Approach 1:
The aircraft divides the propulsion system into lifting rotors dedicated to vertical flight and pushing units with coaxial rotors dedicated to forward propulsion and moment control. This segmentation allows each subsystem to be optimized for its specific function, reducing the weight of individual motors while maintaining overall system capability.
Solution Approach 2:
The pushing units add a new dimension of control by providing independent forward propulsion capability with coaxial rotors that can generate differential thrust. This additional degree of freedom allows the system to control yaw and roll moments without requiring the lifting rotors to be oversized for failure compensation.
3Ease of operation
If the aircraft uses conventional single-rotor pushing units, then it can achieve forward propulsion, but it cannot independently control yaw and roll moments
Solution Approach 1:
The pushing units merge forward propulsion function with yaw and roll moment control by incorporating coaxial rotors that can operate differentially. This combination allows a single pushing unit to perform multiple functions: generate forward thrust while simultaneously controlling yaw and roll moments, reducing the need for additional separate control mechanisms.
Solution Approach 2:
The coaxial rotors on each pushing unit are designed to be multi-functional: they can rotate together to generate forward thrust, or rotate differentially to generate yaw and roll moments. This universality allows the same hardware to perform multiple control functions, simplifying the overall system architecture while enhancing attitude control capability.
Data Source
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AI summary
We propose a method of controlling a multi-rotor aircraft (1), said aircraft (1) comprising at least four lifting rotors (2; R1-R6), each having a first rotation axis which is essentially parallel to a yaw axis (z) of the aircraft (1), and at least one forward propulsion device (3), the at least one forward propulsion device or each of said forward propulsion devices having at least two rotors (P1_R1, P1_R2, P2_R1, P2_R2) that are arranged coaxially with a second rotation axis which is essentially parallel to a roll axis (x) of the aircraft, the at least one forward propulsion device or each of said forward propulsion devices (3, P1, P2) being arranged at a respective distance (+y, -y) from said roll axis (x), the method further comprising: using at least one of the rotors (P1_R1, P1_R2, P2_R1, P2_R2) of the at least one forward propulsion device (3, P1, P2) to control the aircraft's moment about the yaw axis (z) and/or the roll axis (x) independently from each other.