Rear Rotor Research Articles

High-Fidelity Simulations of Rotors in a Compact Configuration

High-fidelity computational fluid dynamics (CFD) simulations of seven rotors in compact configuration at three different flight scenarios are performed. The cases are hover as well as 50 and 100 km/h forward flights. For comparison, each rotor is simulated as an isolated rotor with the same RPM and pitch angle as in the configuration. Additionally, a bigger isolated rotor with the same diameter as the complete configuration is simulated. For the configuration as well as the bigger rotor a flight mechanics trim is performed using the flight mechanics tool VFAST. The CFD simulations are performed with FLOWer. In hover, only the center rotor showed a significant figure of meritdrop of 16% compared to the isolated rotor. The thrust of the outer rotors is increased at the tip areas facing outwards, while the tip areas towards the center and the tip areas of the center rotor showed reduced thrust compared to the isolated rotor. The wake contraction at the outer rotors is increased compared to the bigger rotor. For the 50 km/h forward flight, the efficiency of the front rotors is increased (10???17%) and the rear ones decreased (11???16%). In this case, the wake is directly convected from the front rotors into the rear rotor planes and strong vortex interactions occur. For the 100 km/h case, the efficiency of the front rotors increases by 3???11%, while it decreases by 5???9% for the rear rotors. Due to the higher pitch, the wake of the rotors flows away from the rotor plane and the rotor???rotor interactions are reduced.

CFD simulation of the aerodynamic performance of co-axial multi-rotor wind turbines using the actuator line method

Multi-rotor wind turbines (MRWTs) have attracted widespread attention due to their high efficiency and large generating capacity, and they have become a potential solution for offshore wind turbines. A co-axial MRWT has the advantages of high power density and a small footprint. The actuator line method-large eddy simulation (ALM-LES) is applied to investigate the aerodynamics and near-wake characteristics of unidirectional and counter-rotating co-axial MRWTs. The influence of the blade tip vortices on rotor-to-rotor interactions, wake mixing, and recovery are analyzed. The results show that the unidirectional co-axial twin-rotor wind turbine has a good aerodynamic performance. The torque of the two rotors fluctuates significantly and periodically when the twin rotors rotate in reverse. A distance of 0.3 R between the rotors causes the front rotors to impact the aerodynamic performance of the rear rotors, whereas exceeding 0.5 R minimizes the influence of the rear rotor on the front rotor. And an appropriate azimuth angle should be selected to avoid adverse effects on aerodynamic performance.

Effects of rotor–rotor interaction for a small tandem rotor operating in a crosswind

This study investigates the effects of rotor–rotor interaction on the wake and thrust characteristics of a small tandem rotor operating in a crosswind. Flow velocity and force measurements were conducted in a wind tunnel with two rotors arranged parallel to a crosswind. The results show that the rotor–rotor interaction significantly influences the wake characteristics and thrust generations of the tandem rotor and its effects vary depending on the crosswind speed and distance between rotor tips. In the tandem rotor configuration, the front rotor wake prevents the crosswind flow from reaching the rear rotor wake, thereby reducing the crosswind influence on it. However, under the strong rotor–rotor interaction, such as that caused by high crosswind speeds and short distances between rotor tips, the wakes of both rotors collide with each other and rapidly break down as they proceed downward. Tip-vortex characteristics are also affected by rotor–rotor interaction, which is investigated in terms of variations in the time-averaged tip-vortex trajectory and dissipation ratio with the strength of rotor–rotor interaction. These wake variations by rotor–rotor interaction lead to a decrease in thrust coefficients of the front and rear rotors, with a more significant reduction observed for the rear rotor. The thrust of the rear rotor is more significantly reduced as the crosswind speed increases and the distance between rotor tips narrows. This is mainly attributed to the increased axially induced velocity near the leading tips on the advancing side, retreating side, and centerline.

Investigation of the performance of a horizontal-axis dual rotor wind turbine

Recent years have seen a rise in interest in wind energy as a useful alternative to harmful energies like fossil fuels. The dual rotor wind turbine (DRWT) offers more rapid rates of wind energy extraction. The current study intends to compare the performance of the turbine with and without the addition of a second rotor. Additionally, it examines how tip speed ratio and phase shift angle will affect DRWT performance. Realizable k-shear stress transport turbulence models are used to solve the three-dimensional, turbulent, stable, and incompressible flow equations for the performance of dual-rotor wind turbines. Domain-independence tests and an impartial mesh test are run to assess the results and ensure their accuracy. The researcher relies on previous studies while constructing the single rotor wind turbine model. This model uses an S826 airfoil. The front and rear rotors are given streamlined representations using ANSYS, according to the researcher. The independent mesh test indicates that the mesh density has 11.5 million elements. The experiment's results show that the DRWT has a significant effect on the efficiency of wind energy.

Numerical Analysis of Unsteady Phenomena in a Contra-Rotating Stage Based on the Reduction of Local Entropy Production

Abstract The primary purpose of this study is the reduction of local entropy production in a contra-rotating stage. As such, the unsteady flow phenomena and the impact of radial load distribution on these phenomena and local entropy production need to be clarified. In this study, the stress-blended eddy simulation (SBES) turbulence model is utilized to capture the vortices in the flow separation zone, and the γ-Reθ transition model is employed to predict the transition phenomenon within the boundary layer. Entropy production rate models suitable for different turbulence models are constructed separately to calculate local entropy production. Vortex visualization is achieved according to the λci criterion, and the relative vorticity change rate is used to analyze the components of the tip clearance vortices. The transition phenomenon is analyzed from the perspectives of both the Euler and the Lagrange descriptions. The primary findings can be summarized as follows: the transition begins earlier and progresses more rapidly in the rear rotor. Wake propagation, occurring at double the frequency, entropy production rate within the boundary layer changes in synchrony with the wall shear stress at the same frequency. Additionally, an investigation of the tip clearance vortices concludes that the main structure of the tip clearance vortices coincides with the flow pattern of the high entropy production rate region, and the flow structure related to the high divergence area is essential for considering subsequent optimization with the aim of reducing the entropy production rate.

Research on the influence of initial parameters of water droplets on the performance of counter-rotating axial-flow compressor

This paper employs a numerical simulation method to investigate the wet compression working characteristics of a counter-rotating axial-flow compressor (CRAC) in an air-inlet, water-containing environment under different water droplet parameters at a designed rotational speed. The influence of initial water droplet parameters on the overall performance of the CRAC and the variations in the flow field characteristics under different wet compression conditions was investigated. The initial diameter of water droplets exhibited the most significant impact on the wet compression effect. Under an appropriate inlet water content, water droplets with smaller diameters effectively reduced the temperature of the CRAC’s internal flow field, increasing the air density. Consequently, the axial velocity decreased, altering the velocity triangle and increasing the rotor working capacity, which enhanced the performance of the CRAC. Additionally, wet compression influenced the flow field of the rear rotor stronger than that of the front rotor. When the initial diameter of water droplets is too large, the evaporative cooling effect cannot be fully exploited so wet compression only slightly improved the compressor performance. These findings may help understand the working characteristics of the CRAC in water-containing environments better, offering guidance for CRAC design using wet compression technology.

Acoustic mechanisms and tonal noise control of contra-rotating ducted fan by rotating speed regulation

The contra-rotating ducted fan (CRDF) involves more tonal noise modes compared with rotor/stator and single-rotor ducted fans. According to the present experiment on small-scale CRDF the dominant tone is concentrated at the harmonics of blade passing frequencies of front-rotor and rear-rotor as the modes of (m,0) and (0,n), as well as the modes (m,m) respectively. To investigate the flow mechanisms and sound propagation characteristics of these three types of tonal noise, unsteady three-dimensional numerical simulation was implemented under different rotational speed matching for CRDF and isolated rotor. Steady load and thickness noise were systematically analyzed using Hanson model. And the generation mechanisms of wake interaction noise and their contribution ratios were analyzed utilizing the duct sound model.It was indicated that tonal noise at the mode of (m,0) (0,n) of CRDF is primarily determined by the blade thickness and steady load. Compared with the single-rotor, the contra-rotating rotors could improve the load allocation between the front and rear rotor, resulting in the forward noise reduction with the constant thrust. Increasing the rear rotor speed enhances the contribution of potential flow interaction noise from the front rotor. Subsequently the front rotor load and wake interference are weakened, leading to noise reduction of approximately 0.3 dB for the rear rotor. However, the potential flow disturbance is intensified which causes noise increase by approximately 3.5 dB on the front rotor. But, increasing the front rotor speed will strengthen both the potential flow interference intensity on the pressure surface of the front rotor blade and the wake disturbance intensity on the leading edge of the rear rotor blade. This generates approximately 3 dB and 3.5 dB noise level increases for the front and rear rotors, respectively. As a result, appropriately raising the rear rotor speed can achieve a reasonable load allocation, and balance the potential flow interaction and wake interaction to realize the whole noise reduction without thrust loss.

Машина для вычесывания сорняков: эффективность обработки посевов бахчевых

The cultivation of melons and gourds is a rather laborious process and the main costs fall on the treatment of crops from weeds and harvesting. Before the weed damage threshold is reached, three or four row spacing treatments with cultivators are required, which ensures soil compaction. The number of treatments can be reduced by loosening the row spacing 0.1 to 0.12 m with a device capable of affecting the root system of weeds. It is established that weeding out is affected by the gear ratio between the weed extractor rotors. In order to determine the optimal value of the gear ratio on the technological process, the author conducted laboratory and field studies. The distance, on which the root diggers interact with the soil, was determined in the soil channel when varying the gear ratio from 1.0 to 4.0 and the depth of cultivation of 0.05 and 0.1 m. In field conditions, the author measured the length of weed roots removed from the soil at a working depth of 0.05 and 0.1 m, at the gear ratio of 1.0 to 4.5, and with a pitch of 0.5. As a result of research, the author observed the optimum length of traces of the front sections of the digger equaling 0.35 m and that of rear ones equaling 0.08 m at a gear ratio of 4.0. The greatest length of weed roots extracted to the surface with the digger blade of 0.26 to 0.32 m was observed at a gear ratio of 4.0 and a depth of 0.1 m. It is concluded that the efficiency of tillage depends on the gear ratio between front and rear rotors and the depth of tillage. The highest weeding-out efficiency was observed at a gear ratio between the weed extractor rotors of 4.0.

Investigation on the Airworthiness of a Novel Tri-Rotor Configuration for a Fixed Wing VTOL Aircraft

In this paper, a novel tri-rotor configuration is proposed with the goal of granting vertical take-off and landing capabilities to a future concept of tiltrotor, fixed-wing, aircraft while minimizing the overall mass of the propulsive system and the amount of aerodynamic drag developed during horizontal flight. The novelty of the presented configuration is related not only to the thrust vectoring capabilities of all three rotors but also to the constraints surrounding the action of the rear rotor, which will be required to provide thrust during both vertical and horizontal flight stages while drawing power from an internal combustion engine fixed inside the aircraft's fuselage. Another distinctive feature of the proposed configuration is related to the 20/80 thrust distribution which exists between the front and rear rotors respectively in vertical flight, unlike the more conventional approach of having all three rotors evenly loaded. The proposed rotorcraft configuration was then translated into a test vehicle which was subjected to several stages of ground and flight testing, with the ultimate goal of evaluating the airworthiness of this multi-rotor configuration as a concept. This process also encompasses the development of a custom flight control firmware in PX4, required to operate not only this vehicle but also any other multi-rotor or Vertical Take-Off and Landing system with such configuration. Finally, a frequency-response based system identification technique is applied to the collected flight data as to obtain a suitable flight dynamics model for future autopilot tuning.

Impact of solidity and speed ratio on the performance of a contra-rotating fan

In this study, the effects of solidity and rotor speed ratio on the performance of a contra-rotating fan are investigated numerically. Simulation results have been validated by experimental tests. The test stand construction and the measurements have been performed according to ISO-5801 standard. In order to investigate the effect of blade solidity, simulations have been conducted with constant blade count of the front rotor and four configurations of the rear rotor (having 6, 8, 12 and 16 blades), and also constant blade count of the rear rotor and three configurations of the front rotor (having 8, 12, and 16 blades). Results suggest that there is an optimum solidity for the rear rotor, which gives maximum pressure rise and efficiency. Furthermore, the effects of the rotor speed ratios have been investigated in this study. It is shown that the speed of the front rotor is more effective on the fan performance, as compared to the rear rotor. Results reveal that the performance drop caused by a 25% reduction in the rear rotor blade count, can be compensated by 5% increase of the front rotor rotational speed. Therefore, a suitable choice of the speed ratio can result in light-weight and high-performance contra-rotating stages.

Cross-coupling control design of a flexible dual rotor wind turbine with enhanced wind energy capture capacity

In order to improve the reliability of wind turbine grid connection and reduce the cost of wind power generation, this paper studies a counter-rotating dual rotor wind turbine (DRWT) which consists of decoupled driven-train subsystems, a triple-terminal converter and a dual rotor generator. For this new-type wind energy conversion system, its modeling and control strategy need to be studied. Firstly, mechanism model of the DRWT with a new structure is constructed. By investigating the effects of pitch angles and rotor speeds on output power, respectively, the maximum power output condition of the DRWT is obtained. Considering the overall energy conversion efficiency and mechanical load constraints, the optimal regime of the DRWT is established. Based on the optimal torque algorithm and cross-coupling control strategy, this paper presents a novel cross-coupling control strategy for the DRWT to track maximum power. The proposed strategy can regulate the rotor speed of the front and rear rotors, enabling DRWT to operate on the optimal speed combination curve. Finally, the hardware-in-the-loop experiment is built to test the performance of the proposed strategy under various wind conditions. The simulation results verify that the proposed strategy can improve power generation, and analysis shows that the proposed strategy fundamentally alters the energy capture ratio between the front and rear wind turbines to optimize total output power.

Dynamic mode decomposition for the tip unsteady flow analysis in a counter-rotating axial compressor

Counter-rotating axial compressor (CRAC) is a promising potential technology to improve the thrust-to-weight ratio of aero-engines, but its special aerodynamic layout usually causes more pronounced flow unsteadiness. Understanding the unsteady flow features and mechanism in the CRAC contributes to the aerodynamic optimization design and flow control strategy organization. A data-driven dynamic mode decomposition method is introduced to investigate the tip flow unsteadiness in a CRAC, and the unsteady features of the tip flow at the design point (DP) and near-stall point (NSP) conditions are revealed. The results show that the 1.0 times blade passage frequency (BPF) and its multi-order harmonic frequency are the dominant frequencies for both rotors at the DP condition. At the NSP condition, the 1.0 BPF is no longer the dominant frequency causing the tip flow unsteadiness, and the low frequency fluctuation of the tip leakage flow becomes the dominant frequency to induce the flow unsteadiness. In the front rotor R1, the unsteady dominant frequency is 1.0 BPF, whereas in the rear rotor R2, the frequency (0.801 BPF and 0.803 BPF) of the tip leakage flow is the dominant frequency. By reconstructing the flow field under the NSP condition, the spatiotemporal evolution of the tip flow during the unsteady stable manifests that the interference effect between the rotors is an important source of the tip flow unsteadiness. The increase in flow unsteadiness leads to an increase in the reconstruction error, indicating that more modes are required to obtain a more accurate reconstruction flow field.

Influence of the number of front and rear rotor blades on the hydrodynamic performance of counter-rotating horizontal-axis tidal turbines

The coaxial rotor structure presents significant potential for the development of tidal turbines. In order to study the effect of the number of front and rear rotor blades on the hydrodynamic performance of counter-rotating horizontal-axis tidal turbines (CRHATTs), three models (CRHATT 3-2, CRHATT 3-3 and CRHATT 3–4) are established at the same tip speed ratio (TSR), and the accuracy of the numerical method is verified by experiments. The effect of blade number on the performance coefficients, velocity and pressure pulsations and vortex structure of CRHATTs are calculated based on CFD method and spectral analysis. The results show that the relationship of the power coefficient for the three models is: CRHATT 3–4 > CRHATT 3-3 > CRHATT 3-2. The turbulent kinetic energy in the flow field can be transferred more quickly from the large-scale vortex structure to the small-scale as the number of rear rotor blades increases. By weighing aspects such as load fluctuation and power coefficient, the CRHATT 3–4 can produce the largest power coefficients, the best stability during operation and the least vibration on the blades among the three models. This paper provides significant guidance for the engineering design and optimization research of CRHATTs.

Effect of axial slot casing treatment on the flow instability for different speed ratios in a counter-rotating axial flow compressor

This paper numerically investigates the effectiveness of axial slot casing treatment (ASCT) at different speed ratios and its flow control mechanism in a counter-rotating axial flow compressor (CRAC). The effect law of ASCT on the stall margin with speed ratio is revealed. Furthermore, the impact of ASCT on the first stall stage of CRAC is explored. The results show that the compressor stall margin at different speed ratios is improved by the ASCT. The combined effect of suction and injection of the ASCT suppresses the spillage at the blade leading edge in the rear rotor (R2) and delays the occurrence of stall inception. Quantitative analysis shows that the ASCT reduces the reverse axial momentum and deflection angle of the tip leakage flow (TLF), which contributes to improving the flow stability. Moreover, the blockage at the rotor tip with the ASCT is reduced, which improves the tip flow field of the R2. Although the stall inception of spike-type keeps unchanged with the ASCT, the first stall stage of the CRAC under the ASCT is switched from the R2 to the front rotor when the speed ratio is not greater than 1.0. When the ASCT is employed on the R2, the significant stall margin improvement can only be obtained if the R2 is still the first stall stage under the ASCT.

Effect of yaw on aerodynamic performance of co-planar multi-rotor wind turbines

The multi-rotors wind turbine (MRWT) is a promising alternative to the large-scale single-rotor wind turbine for reductions of cost. Noteworthy, yawing in MRWT is a key engineering issue for its significant effect on the output power and structural aerodynamics. In this study, the aerodynamics and near wake dynamics of a co-planar multi-rotor wind turbine with different yaw modes (self-yaw and whole yaw) are investigated through the ALM-LES method. Comparatively, the effects of the blade tip vortex interactions between adjacent rotors on both the torque and thrust of the rotor and the mixing and recovery of the wake are taken into account as well. The numerical results show that the wake vortices of the two rotors attract and approach each other under self-yaw conditions. In the whole yaw conditions, the blade tip vortex in the region between rotors appears to neutralize each other due to the opposite direction of self-rotation of the wake vortex. Moreover, the wake enhancement effect increases the inlet velocity on the blades and has almost no effect on the lift-to-drag ratio. Nevertheless, the direct influence of the blade tip vortex increases the lift-to-drag ratio and decreases the inlet velocity at the location of 0.8∼1R on the front rotor blades in the self-yaw condition; it also decreases both the lift-to-drag ratio and the inlet velocity on the rear rotor blades. Furthermore, under the whole yaw condition, such a direct influence decreases the lift-to-drag ratio on the blades of the two rotors at the location of 0.8∼1R, and increases the average inlet velocity. Conclusively, among the investigated two yaw conditions, a 15°yaw angle shows a more considerable effect on the aerodynamics MRWT than the interaction of blade tip vortex.

Simulation of Rotor-Rotor Interaction and Noise of an Axial Counter-Rotating Fan

The Counter-Rotating Fan (CRF) offers higher aerodynamic performance, in terms of pressure head and aerodynamic efficiency, compared to the single rotor fan, thus making it an attractive solution for equipment cooling and ventilation of mines and tunnels. Nevertheless, further investigations are required to understand the flow interactions between the front rotor (FR) and the rear rotor (RR), as these interactions are sources of noise emission. This numerical study used the Unsteady Reynolds Average Navier-Stokes (URANS) flow simulations and the Fast Fourier transformation (FFT) to analyse the rotor-rotor interactions and consequences on the aero-acoustic performance. The static pressure fluctuations were recorded at several locations and analysed by FFT to reveal the mechanisms of flow interactions and the effects of axial inter-distance between the two rotors. The inter-distance seems to influence the aerodynamic loading of RR more than that of FR and the total-to-static isentropic efficiency tends to drop. Over one chord distance, the noise level decreases but at the expense of isentropic efficiency. The balanced performance does not seem to improve for an inter-distance greater than 1.5 chords, considered the optimum distance in this study. Finally, a graphical correlation which can be used to estimate the Sound Pressure Level (SPL) is developed for this category of CRF.

Flight Performance with Respect to Rotor Rotation Directions of Multirotor Aircraft

A multirotor electric vertical takeoff and landing (EVTOL) aircraft is specialized for intracity point-to-point urban air mobility services due to its advantages of efficient hover performance, high gust resistance, and relatively low noise. Because of its multiple rotors, rotor–rotor interference inevitably affects flight performance, mainly depending on inter-rotor distance and rotor rotation directions. It is assumed that there exists an optimal rotation direction for a given lot of multiple rotors. In this study, the aim is to investigate rotor–rotor interference for various rotation directions and the resulting flight performance. We propose a concept of rotor rotation direction that achieves the desirable flight performance in forward flight. The concept is called front-retreating/rear-advancing (FRRA), in which the retreating side of the front rotor and the advancing side of the rear rotor are aligned in a straight line. To this end, a multidisciplinary flight simulation framework was developed to predict the flight performance of a general multirotor EVTOL aircraft. It was found that the FRRA concept minimizes thrust loss due to rotor–rotor interference in high-speed forward flight. For a generic mission profile, the rotation direction set by the FRRA concept reduces the battery energy consumption by 7% in comparison to the rotation direction of unfavorable rotor–rotor interference in operation.

Flow effects of microperforated-panel casing treatments in a contra-rotating fan

The flow effects of microperforated-panel (MPP) casing treatments installed over the front rotor of a small contra-rotating (CR) fan are numerically studied, with emphasis put on the reshaped front-rotor tip leakage flow, the blade response to rotor-rotor interaction, and the unsteadiness of static pressure on blade surfaces. It is found that the secondary flow through the sub-millimeter holes of the MPP hinders the formation of the front-rotor tip leakage flow and reduces its circumferential stretching, resulting in an improved inflow to the rear rotor. Consequently, the unsteady characteristics of static pressure and lift force on the rear rotor are generally attenuated. An enlarged back cavity can enhance such attenuation, in which case a 14.5% decrease in pressure unsteadiness is observed. The first, second, and third harmonics of the unsteady lift force experience reductions of 15.6%, 37.4%, and 60.9%, respectively. However, the unsteady characteristics on the front rotor dominated by potential interaction are not significantly influenced by the MPP. Furthermore, analysis of blade-to-blade phase differences shows that, whether the CR fan is treated with the MPP or not, the phase differences are not precisely repeated but vary randomly and that the higher the order of the force harmonic, the more likely the phase relationship is disturbed by the treatments. The varying nature of the phase relationship would render the acoustic energy of an induced interaction tone leaked into shaft tones and broadband noise. Radiation efficiency analysis of force harmonics demonstrates that the front rotor is not an efficient contributor to interaction noise compared with the rear rotor, which radiates more interaction tones with much higher efficiency. The current work is expected to be useful not only for devising effective MPP casing treatments to control small CR fan noise but also for understanding their underlying flow effects on rotor-rotor interaction.

Effects of rotor-airframe interaction on the aeromechanics and wake of a quadcopter in forward flight

From small drones to large Urban Air Mobility vehicles, the market of vertical take-off and landing (VTOL) aircraft is currently booming. Modern VTOL designs feature a variety of configurations involving rotors, lifting surfaces and bluff bodies. The resulting aerodynamics are highly impacted by the interactions between those components and their wakes. This has consequences on the aircraft performance and on the downstream wake. Studying the effects of those interactions through CFD can inform the development of cheaper numerical models. In this work, we focus on the interaction between rotors and bluff bodies based on the example of a generic quadcopter in forward flight. Using the Vortex Particle–Mesh method, a CFD method well-suited for wake studies, we analyze the influence of the rotor-airframe interaction on the loads and on the development of the aircraft near wake. Our results show that the presence of the airframe induces a change in average thrust of maximum 2.4% on the rear rotors. Correspondingly, the contribution of the rotors to the overall aircraft lift and drag changes by less than 2%, suggesting that the airframe can be ignored if one seeks a simple model of the rotor forces. On the other hand, the airframe experiences peak loads due to its proximity with the blades. Thus, the rotor-airframe interaction must be accounted for in the prediction of airframe loads. Finally, comparing simulations with and without the airframe, we find that the trailing wake vortices converge to circulations less than 0.2% different. However, the vortex spacing decreases when the airframe is accounted for.

Adaptive Attitude Control for a Coaxial Tilt-Rotor UAV via Immersion and Invariance Methodology

Dear Editor, This letter is concerned with the attitude control for a novel tilt-rotor unmanned aerial vehicle with two pairs of tiltable coaxial rotors and one rear rotor. An immersion and invariance-based adaptive attitude controller for the tilt-rotor unmanned aerial vehicle is proposed. In the proposed control strategy, an adaptive update law is specially designed to compensate for the uncertainties of damping coefficients. The stability of the resulting closed-loop coaxial tilt-rotor unmanned aerial vehicle (CTRUAV) system is proved by the Lyapunov methodology and LaSalle's invariance theory. Finally, to validate the effectiveness of the designed control strategy, simulations and experiments are performed.