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Optimized Modular Design and Development of a Tilt-Rotor Bicopter Drone
Saideep Verma, Nimisha Tatapudi, Akshay Arjun, Danwada Sharanya Sukka, Abhishek Sarkar, Joyjit Mukherjee
TL;DR
Tilt-rotor bicopters must combine VTOL and fixed-wing capabilities while maintaining static and dynamic stability. This paper develops a modular design through structural, aerodynamic, thrust, and power analyses, then validates it with a hardware prototype and flight experiments. The experiments report stable attitude behavior and measured power consumption across hover and pitching conditions, alongside simulated endurance estimates.
Problem
Tilt-rotor bicopters require optimized designs that combine VTOL capability with static and dynamic stability, structural integrity, and adequate endurance.
Method
The paper develops a modular bicopter and evaluates its structure, propulsion, flight-time characteristics, and prototype performance through simulations and hardware experiments.
Results
65 W at approximately 11% throttle during hover and 88 W at approximately 14% throttle during pitching were measured experimentally.
Takeaways & Limitations
The analyzed and prototyped design supports short- to mid-duration missions, with estimated flight times of 7 minutes at 100% throttle, 11 minutes under mixed use, and 14.5 minutes in stable hover.
Abstract
from arXiv · showhide
Hybrid systems like tilt-rotor bicopter drones combine the beneficial characteristics of both fixed-wing and rotary-wing technology, enabling long endurance and VTOL capability. However, such drones also require an optimum design to ensure both static and dynamic stability. The modular design of a traditional bicopter is developed in this paper based on extensive analysis and in-depth structural and aerodynamic simulations. The structural analysis has been performed to ensure that the aircraft's structure withstands the stresses encountered during different flight modes. Controlling the relative positions of the Center of Gravity (CG) and Neutral Point (NP) is an essential aspect of the design, ensuring stability during hover and positive stability during forward flight. The thrust and power analyses have been conducted to assess the flight performance and endurance. After analysis, the drone has been developed, and flight tests with a basic flight controller were conducted to validate the performance metrics obtained in the simulation.
I. INTRODUCTION
Hybrid aircraft combine rotorcraft and fixed-wing advantages to provide VTOL capability, maneuverability, and aerodynamic efficiency. This paper develops an optimized tilt-rotor bicopter design targeting stability, structural performance, power capability, and experimental validation.
- Hybrid aircraft combine traditional rotorcraft and fixed-wing advantages, motivating designs that provide VTOL capability alongside improved maneuverability and aerodynamic efficiency.
- Winged bicopters are designed to improve stability, payload capacity, and flight duration relative to conventional multirotors.
- The paper develops an optimized tilt-rotor bicopter methodology addressing static and dynamic stability, structural stresses, thrust, power, flight time, and air speed.
- The design process includes static analysis, dynamic flight simulations, prototype development, and experimental validation using throttle commands in an open-loop configuration.
II. BICOPTER DESIGN AND STATIC ANALYSIS
The bicopter uses a modular, compact frame whose layout supports accessible components and a low center of mass. Structural analysis evaluates motor-arm integrity under thrust loading and identifies stress and material adequacy.
- A. Design Overview: The modular frame uses a compact fuselage with accessible battery, flight controller, ESC, and servo compartments, while replaceable arms balance torque and airflow.
- A. Design Overview: The design has a total mass of 1 Kg, fuselage dimensions of 14.43 × 12.98 × 6.98 cm, arm length of 15.4 cm, and COM-to-thrust-center distance of 3.8 cm.
- B. Stress Analysis: Structural analysis evaluates Von Mises stress, total displacement, and safety factor for the motor and arm assembly under thrust loading.
- B. Stress Analysis: 14.98MPa peak Von Mises stress occurs near the motor-arm junction under a 100 N downforce test, while PLA Aero has approximately 24 MPa yield strength.
C. Safety Factor
The safety-factor analysis evaluates structural margin in the motor-mount region and relates the result to potential reinforcement of critical stress zones.
- 1.38 is the minimum safety factor, occurring at the motor mount region.
- The result suggests the design is suitable for development and safe for flight under the analyzed load conditions.
- Additional reinforcement or material additions may enhance safety in critical stress zones.
D. Displacement
The displacement analysis evaluates deformation under loading and relates it to motor alignment and flight stability. Dynamic motor characteristics further assess efficiency, thrust consistency, waste power, and thermal behavior.
- Displacement: 2.537 mm maximum displacement occurs at the motor housing and decreases gradually along the arm.The deformation is reported as acceptable and not expected to greatly affect flight stability or propeller alignment.
- Displacement: The displacement results are reported in Table II, while the broader analysis results are summarized in Table III.The supplied material identifies these tables but does not provide their internal row or column values.
- Dynamic Performance Insights: Peak motor efficiency occurs around 12A, while the RPM curve remains relatively flat beyond 8A.These characteristics indicate consistent thrust across throttle ranges and an identified efficiency optimum.
- Dynamic Performance Insights: Waste power and thermal rise increase gradually but remain well below critical thresholds.The selected motor and propeller specification is therefore safely loadable up to 15A of continuous current.
B. Thermal Efficiency Insights
The paper evaluates motor thermal behavior and efficiency to assess sustained operation. Simulated temperatures and efficiency values indicate operation within the motor’s effective range.
- Thermal Efficiency Insights: The maximum motor temperature is 400C, while the estimated hover temperature is 330C.The paper attributes efficient cooling to passive airflow and proper load distribution.
- Thermal Efficiency Insights: Motor efficiency is approximately 78% at hover and reaches 80% at the 12A optimum operating point.The motor is reported to operate within its optimal RPM and torque range.
- Thermal Efficiency Insights: The hover power-to-weight ratio is about 145.7W/kg, balancing agility and energy use.The paper reports no overheating or efficiency drop under varied flight conditions.
C. Hover and Power Metrics
Hover and power analysis sizes the propulsion system for stable lift while checking operating power against the battery and ESC capabilities.
- Hover and Power Metrics: 850 grams total model weight requires each motor to produce at least 640 grams of thrust for stable hover.The selected EMAX 1700 KV BLDC motors and 10” × 4.7” propellers meet this requirement.
- Hover and Power Metrics: Approximately 2:1 thrust-to-weight ratio provides lift and maneuverability with control margin for differential thrust and tilt-servo stabilization.The analysis also calculates a maximum thrust of 31.18N(3.17kg) per motor, while using 2:1 as the operational baseline.
- Hover and Power Metrics: Hover draws around 6A per motor and requires nearly 125 watts total.At maximum throttle, the system draws about 25A and consumes 260.5W, within the stated 3S LiPo battery and 30A ESC capabilities.
- Hover and Power Metrics: A center of mass 35mm above the ground and three contact points provide static stability during takeoff.The support area combines the fuselage base and rotor-motor bases.
D. Flight Time Estimates
The flight-time analysis estimates endurance across maximum-throttle, mixed-use, and stable-hover conditions. The results support short- to mid-duration missions and include range estimates at specified air speeds.
- Flight Time Estimates: 7 minutes is the estimated minimum flight time at 100% throttle.This is one of three endurance cases evaluated using a 2200mAh 3S LiPo battery.
- Flight Time Estimates: 11 minutes is the estimated mixed-use flight time under a moderate throttle cycle.The estimate is based on the same 2200mAh 3S LiPo battery with 1980mAh of usable capacity.
- Flight Time Estimates: 14.5 minutes is the estimated stable-hover flight time.The battery discharge is reported as nearly fully utilized without exceeding safe discharge limits.
- Flight Time Estimates: The simulation indicates outstanding hovering stability, efficient motor loading, sufficient thrust, extended hover times, and safe thermal performance.A hardware prototype and experimental setup were developed for flight testing.
IV. PROTOTYPING AND EXPERIMENTAL RESULTS
The proposed bicopter was prototyped and experimentally evaluated on a gyroscopic testing stand under hover and pitch-forward conditions. Measurements addressed attitude stability, throttle, voltage, and current.
- The hardware prototype was experimentally verified for power, attitude, and actuation metrics.The experiments used a gyroscopic Drone Testing Stand.
- Hover and pitch-forward attitudes were tested with the bicopter on a gyroscopic Drone Testing Stand.
- Fig. 8 reports hovering throttle, while Figs. 9 and 10 report corresponding attitude and voltage-current measurements.
A. Prototyping Overview
The prototype uses a modular, 3D-printed bicopter structure with integrated electronics and passive cooling, then evaluates stability and power consumption during hover and pitch-forward operation.
- A. Prototyping Overview: The prototype was developed from a hardware design whose components and specifications are listed in Table IV.
- A. Prototyping Overview: The fuselage and arms were 3D printed in PLA Aero using FDM to produce lightweight parts with stiffness and layer bonding.
- A. Prototyping Overview: Passive cooling vents in the fuselage dissipate heat from ESCs and other electronics during extended flight times.
- A. Prototyping Overview: The experiments assess attitude stability and power consumption against throttle in hover and pitch-forward conditions.
- A. Prototyping Overview: 65 W at approximately 11% throttle was measured during hover, compared with 88 W at approximately 14% throttle during pitching.
V. CONCLUSION
The paper presents a modular hybrid tilt-rotor bicopter designed through structural and aerodynamic analysis, followed by prototype experiments validating basic attitude stability and power consumption.
- The design combines modularity with in-depth stress, structural, aerodynamic, thrust, and power analyses across flight modes.
- Prototype experiments verified basic attitude stability and power consumption after the analytical design process.
- Future work will develop path-planning and control algorithms for trajectory tracking during flight tests.