Vertical Takeoff Landing Research Articles

Efficient conversion of Euler angles to quaternion for practical aerospace applications

Abstract Current methods for converting Euler angles to a rotation quaternion are computationally intensive and have limited practical applications in aerospace. This study introduces an efficient approach that directly converts Euler angles in any desired sequence to a rotation quaternion, eliminating the need for intermediate Euler angle transformation matrices, which leads to a significant improvement in computational efficiency. Moreover, it is general because it works with all 12 possible sequences of rotations. A case study is presented, demonstrating the application of the algorithm in converting between the launch frame and the missile frame of a vertical takeoff vertical landing (VTVL) rocket. The results show more than a ninefold improvement in computational efficiency compared to the classical Euler angle method while maintaining consistency of results.

High-fidelity aero-acoustic evaluations of a heavy-lift eVTOL in hover

Electric Vertical Take-off Landing (eVTOL) vehicles can transform aviation, but the unconventional aircraft development currently requires an extensive knowledge base. This paper presents a high-fidelity aerodynamic and acoustic evaluation of a heavy-lift multi-rotor eVTOL design in hover. The design, known as Skybus, has an MTOW of 14,000 kg, and six tiltable rotors attached at the tip of three sets of tandem wings with flaps. High-fidelity scale-adaptive CFD simulations of the full-scale Skybus vehicle in hover, with three design variations, were conducted using the HMB3 framework. The aerodynamic performance and interactions were analysed in detail. The baseline airframe caused a blockage force of about 13% of the MTOW, and the compact hovering rotors induced a sinusoidal single-blade loading variation, blended with small local interactions. The near-field acoustics were then directly extracted from the high-fidelity CFD results, and far-field acoustic propagation was computed using the acoustic analogy, following reference acoustic measurements for eVTOLs proposed by EASA. Different aerodynamic interactions and propeller acoustic characteristics showed strong impacts on the vehicle acoustics. The EPNL metric was also computed and analysed assuming various hover duration, and restrictions on maximum EPNL and hover duration are recommended for future rotorcraft hover noise certification. These novel results provide valuable guidance for eVTOL acoustic design, infrastructure planning, and policy-making.

PID Control Tuning Based on Wind Speed Sensor in Flying Robot

The problem that is often faced by flying robots when carrying out the Vertical Take Off Landing (VTOL) process is the lack of stability of the vehicle due to differences in wind speed at any time. This is because the PID that has been pre-tuned is the PID at a certain wind speed and it is possible that during the race the wind speed suddenly changes, causing the vehicle to be less stable in carrying out the mission. Therefore, this study proposes a PID Control Tuning Control system based on the Wind Speed Sensor. In experiments that have been carried out with anemometer readings of 1-5 m/s, the ideal tuning results are obtained with each parameter P_roll = 0.1453, I_roll = 0.0892, D_roll = 0.004, P_pitch = 0.144, I_pitch = 0.09, D_pitch = 0.004, P_yaw = 0.184, I_yaw = 0.0184, D_yaw = 0.00309. In experiments with anemometer readings of 6-10 m/s, the ideal tuning results were obtained with each parameter P_roll = 0.148, I_roll = 0.0905, D_roll = 0.004, P_pitch = 0.1444, I_pitch = 0.09, D_pitch = 0.004, P_yaw = 0.1867, I_yaw = 0.0181, D_yaw = 0.0037. In an experiment with an anemometer reading of 11-15 m/s, the ideal tuning results were obtained with each parameter P_roll = 0.1494, I_roll = 0.09, D_roll = 0.004, P_pitch = 0.1457, I_pitch = 0.0902, D_pitch = 0.004, P_yaw = 0.1894, I_yaw = 0.018, D_yaw = 0.0037. PID adjustment based on this anemometer sensor utilizes the latest real-time wind speed data to support the robot in order to overcome instability in certain wind conditions by tuning PID so that the vehicle can maintain stability when carrying out certain missions.

Design and Aerodynamic Analysis of Fixed-Wing Vertical Take-Off Landing (FW-VTOL) UAV

This study aims to produce a Fixed Wing-Vertical Takeoff Landing (FW-VTOL) design that has good aerodynamic characteristics on its wing and fuselage. The design process begins with determining the Design Requirement and Objective (DRO). According to DRO, the aircraft is designed to be able to operate at speeds of 14 m/s and an altitude of 120 m (cruise phase) above ground level. The Maximum Takeoff Weight (MTOW) of the planned is estimated using previous research data. Based on calculations, for it to have a flight time of 30 minutes, the MTOW of the FW-VTOL is 5.2 kg. The fuselage and wing of the FW-VTOL design were carried out by referring to the MTOW of 5.2 kg. Three candidate airfoils were proposed, and their aerodynamic characteristics were determined using XFLR5 software. The aerodynamic characteristics of the three proposed fuselage candidates are also calculated. At an angle of attack of 30, the Eppler 66 airfoil produces the most lift coefficient and the lift-to-drag ratio of 0.8775 and 94.152, respectively. While the NACA 4412 and S9000 airfoils create lift coefficients of 0.7963 and 0.7963, respectively. From the calculation of aerodynamic characteristics, the first, second, and third fuselage candidates produce drag coefficient values of 0.1397, 0.1576, and 0.1368, respectively. The aerodynamic characteristics of the airfoil and fuselage are then input into the decision matrix table. As a result, the selected airfoil candidate is Eppler 66, while we choose the fuselage design is the third fuselage candidate.

Integrating drones into NHS patient diagnostic logistics systems: Flight or fantasy?

Healthcare accounts for approximately 5% of emissions in developed nations, and the public healthcare provider in the United Kingdom (UK), the National Health Service (NHS), has set a target to reach net-zero emissions by 2040 without detriment to its quality of patient care. With Uncrewed Aerial Vehicles (UAVs; a.k.a. drones, UAS, or RPAS) starting to be used in healthcare systems outside the UK, there is interest in how they could be integrated into NHS operations to transport diagnostic specimens. Reflecting on a business-as-usual analysis of current NHS diagnostic specimen logistics across the Solent region (southern UK), this paper critically evaluates the practical reality of integrating UAV deliveries of this commodity, identifying the benefits and challenges that must be addressed to realise commercial services, including dangerous goods legislation, cargo stability, routing, and weather. In the analysis, 14 out of 79 surgeries could be realistically served by a 5m wingspan vertical take-off/landing (VTOL) UAV: seven directly, and seven via ground-based transfers. The results suggested that an average of 1,628 samples could be served by UAV each week, resulting in 42 flights/week with 10 taxi services to cover periods where weather limited flying. This equated to an approximate total service cost of £2,964/week if regulations develop to relax UAV personnel constraints. The introduction of UAVs reduced the marginal external costs (greenhouse gas emissions, congestion, and air pollution) by £196 per week and cut travel times to UAV served sites by 72% (weather permitting). Tailpipe emissions (excl. taxis), vehicle-kilometres travelled, and van costs were reduced by 20%, 20%, and 23% (respectively), but the overall system cost increased by 56%. Whilst this increase is likely to make the introduction of UAV services financially challenging, the benefits in terms of emissions and journey time savings may offset some of the additional cost and warrant further investigation.

Numerical study of drag force on the UAV tilt and fixed wing model during vertical take off landing

A hybrid vertical take-off landing (VTOL) UAV combines the concepts of fixed-wing and rotary-wing UAV aircraft in one platform while performing in both conventional and vertical take-off landings. This aircraft has a drawback of significant drag force generated due to fixed-wing. Therefore, a Tilt-Wing often utilized to overcome this obstacle whereby it could be adjusted to the vertical and horizontal directions. To enhance the understanding of generated drag force on both wing model, this study was performed by examine the drag characteristic of the VTOL UAV. The simulations were carried out in the wind speed range by 1.4 m/s, 4.17 m/s, and 6.94 m/s. Simulation results showed that the drag of the UAV Hybrid Tilt-Wing and Fixed-Wing increased at the speed of 1.4 m/s to 6.94 m/s while the highest drag value was 177.51 N on a Fixed-Wing UAV aircraft and 1.97 N on a Tilt-Wing UAV aircraft. The result concluded that Tilt-Wing UAV has less drag which was more efficient than fixed-wing.

Oil Facilities Surveillance Using an Autonomous Quadrotor

This work addresses using the autonomous quadrotor or unmanned aerial vehicle (UAV) for surveillance of oil fields, Facilities and pipelines since that can be very costly and dangerous specially in dangerous zones. This topic is very important because of the money consuming to repair and protect these oil facilities. Quadrotors are very small Vertical take-off landing (VTOL) helicopter, cheap, easy to use and has many other fields of applications. Quadrotor’s dynamic model involves nonlinearity, uncertainties, and coupling which makes the Quadrotor has a very complex system. PID controllers are proposed for controlling the quadrotor altitude through different environments during different missions. To drive the quadrotor to follow the desired trajectory pure pursuit algorithm (PPA) will be use. The simulation results will be pretested using the visual simulator named Gazebo with the aid of ROS to connected with the MATLAB to show the movement of the quadrotor insides different environments.

Fractional-order sliding mode control with a predefined-time observer for VTVL reusable launch vehicles under actuator faults and saturation constraints

For vertical takeoff vertical landing (VTVL) reusable launch vehicle (RLV) with actuator faults and saturation constraints, this paper presents a composite control system including a high-order predefined-time extended state observer (HO-PTESO), a predefined-time anti-saturation compensator (PTASC), and a fractional-order practical predefined-time sliding mode control law (FO-PPTSMC). The HO-PTESO accomplishes the precise estimation of disturbance in a time interval predefined by only one design parameter, resulting in a simple and weakly conservative parameter tuning process for temporal demands. Moreover, the peaking value problem is well addressed. The PTASC serves to ensure the stability of the saturated system. Auxiliary variables of the PTASC remain bounded during the saturation process and vanish within the predefined time interval after the saturation process ends, avoiding long-term impacts on the attitude tracking that are common concerns for existing ASCs. Using the estimated disturbance, the FO-PPTSMC enforces unsaturated system states to a predefined residual set of the origin in a chattering-alleviated manner within the predefined time interval. Two parameters respectively predefine the convergence range and time, resulting in a considerably simplified synthesis procedure. Ultimately, numerical simulations on the double integrator system and VTVL RLV model validate the efficiency of the proposed control system.

Fin actuation, thrust vector control and landing leg mechanisms design for the RETALT VTVL launcher

To foster the competitiveness of the European industry in the global launcher market, the need arose to build up the necessary know-how on state-of-the-art vertical take-off vertical landing (VTVL) concepts and corresponding technologies. In the EU Horizon 2020 project RETALT (RETro propulsion Assisted Landing Technologies), the VTVL approach applying retro propulsion is investigated for two-stage-to-orbit (TSTO) and single-stage-to-orbit (SSTO) reusable launch vehicles, these configurations are named RETALT1 and RETALT2. In the project framework investigation of both reference configurations is performed in several areas: aerodynamics, aerothermodynamics, flight dynamics and guidance, navigation, and control (GNC), as well as thermal protection and structures and mechanisms. Focusing on solutions for the RETALT 1 launch vehicle, Almatech contributes with the design of mechanisms to actuate the aerodynamic controls surfaces, retain and deploy the landing legs and provide means to dissipate energy during touch-down. Demonstrators of these mechanism are also built during the project. In addition to the above activities, Almatech proposes thrust vectoring solutions. This paper presents an overview of these activities and results obtained so far.

Semi-globally smooth control for VTVL reusable launch vehicle under actuator faults and attitude constraints

The present paper deals with the control problem of vertical takeoff vertical landing (VTVL) reusable launch vehicle (RLV) under actuator faults and multi-type attitude constraints (unilateral constraints, symmetric/asymmetric bilateral constraints, or without constraints). A semi-globally smooth control system is proposed based on a novel barrier function (BF) to realize the finite-time convergence of attitude tracking errors into a small neighborhood of the origin. Moreover, the attitude constraints unviolated under multiple disturbances are guaranteed. To further enhance the disturbance rejection ability, a BF-based adaptive disturbance observer (DO) is derived and incorporated into the control system, which is responsible for reconstructing the disturbance in finite time. The proposed control systems are characterized by the following four points. One is to ensure the finite-time convergence of attitude tracking errors and guarantee the non-violation of constraints without requiring any prior information regarding the Lipschitz constant and upper bound of the disturbance. The second is to provide a unified instrument for control problems with the aforementioned multi-type state constraints. The third is the smoothness property contributing to the chattering-free convergence of attitude tracking errors. The high performance and robustness concerning non-Lipschitz disturbance (such as the sudden actuator faults) are the fourth. Ultimately, the effectiveness of the proposed control systems was demonstrated by the numerical simulation results.

URBAN COMMUTERS’ EXPECTATION LEVELS ON THE e-VTOL VERTICAL AIRPORT DESIGN IN KUALA LUMPUR, MALAYSIA

The world’s urban dwellers are rapidly growing by 60.3% over six decades (1960-2019) (The World Bank Group, 2020), and two third of the world’s population is projected to reside in the urban setting by 2050. The same issue occurred in Malaysia, where the shifting from 73% rural to 73% urban population is real (Mohd Hussain, N. H.; Byrd, H.; & Ahmad, N. A., 2017), and this phenomena contributed to the increasing number of population in big cities such as Kuala Lumpur. Therefore, it is expected that the existing challenging traffic congestion will worsen if a better traffic dissemination planning strategy is not developed. Hence, the development of an e-VTOL (electrical vertical take-off landing) vehicle is a possible strategy to ease the urban traffic congestion problem. Serious collaboration among the departments such as planning, engineering, architecture, aviation developers, policy makers, and the sponsors, is important to establish sustainable future urban mobility and connectivity. This study aims to obtain information on the needs and expectations of urban commuters on the development of a vertiport in the city of Kuala Lumpur. A series of surveys involving 157 commuters using public transportation within the city centre, and a case study analysis, were conducted to gain an understanding of the viability of building a vertiport in Kuala Lumpur. Initially, findings show that nearly 50% of the respondents totally agree with the proposed development idea, while approximately 13% are really against this future urban air mobility strategy.

Design and Implementation of Morphed Multi-Rotor Vehicles with Real-Time Obstacle Detection and Sensing System.

Multirotor unmanned aerial vehicles (MUAVs) are becoming more prominent for diverse real-world applications due to their inherent hovering ability, swift manoeuvring and vertical take-off landing capabilities. Nonetheless, to be entirely applicable for various obstacle prone environments, the conventional MUAVs may not be able to change their configuration depending on the available space and perform designated missions. It necessitates the morphing phenomenon of MUAVS, wherein it can alter their geometric structure autonomously. This article presents the development of a morphed MUAV based on a simple rotary actuation mechanism capable of driving each arm’s smoothly and satisfying the necessary reduction in workspace volume to navigate in the obstacle prone regions. The mathematical modelling for the folding mechanism was formulated, and corresponding kinematic analysis was performed to understand the synchronous motion characteristics of the arms during the folding of arms. Experiments were conducted by precisely actuating the servo motors based on the proximity ultrasonic sensor data to avoid the obstacle for achieving effective morphing of MUAV. The flight tests were conducted to estimate the endurance and attain a change in morphology of MUAV from “X-Configuration” to “H-Configuration” with the four arms actuated synchronously without time delay.

POSITION CONTROL OF VTOL SYSTEM USING ANFIS VIA HARDWARE IN THE LOOP

Electric motors have been widely applied in various equipment. One application is found in Unmanned Aerial Vehicles (UAVs). An electric motor speed control system that can balance the aircraft's position is one of the mandatory features that must be owned by the aircraft. The position balancer control also supports the Vertical Take-Off Landing (VTOL) system. This study's VTOL position control system uses Hardware-in-the-loop (HIL) method with MATLAB Simulink and Arduino. ANFIS (Adaptive Neuro-Fuzzy Inferences System) is used as a position control algorithm. The controller performance is compared with conventional PID and FLC (Fuzzy Logic Controller). The system is tested as an initial position variation and loading test. The experiment shows that HIL can help fast prototyping by faster changes in the controller algorithms and is easy to program. The result is varied in each experiment. In the ISE (Integral Square of Error) point of view, ANFIS is better than PID by 100 % and has a very small difference from FLC in the initial position test. ANFIS is better by 95.44% and 4.56% compared with PID and FLC in the loading test, respectively.

Phase-Shifted TAB Converter System for Electric VTOL Aircraft

This paper investigates a triple-active-bridge converter for an all-electric VTOL(Vertical Take Off&Landing) aircraft, based on the Dual-active-bridge converter, presenting four working scenarios which matching the operating of e-VTOL. The converter adopts a phase-shifting control strategy and decouples the control network. Different targeted settings of the converter system are made for the various operating states of the e-VTOL, and the operating states of the TAB converter in different modes are simulated in MATLAB. The experimental results show that the TAB converter has more diverse operating modes, which can match future e-VTOL use in urban applications.

Aerodynamic Analysis of Hybrid Drone

Drones are Unmanned Aerial Vehicles (UAV’s) or Remotely Piloted Vehicles (RPV’s) whose application ranges from photography to defence. There are two major classifications of drone, one, a fixed wing; and another, a quadcopter. A hybrid drone is a kind of drone which has a mix of features of the two kinds of drone. It has quad-rotors for Vertical Take-Off Landing (VTOL), and a fixed wing for cruise. Aerodynamic analysis for a hybrid drone is done using Computational Fluid Dynamics (CFD) as a tool. A virtual wind tunnel test is done by means of this analysis. It is done in order to examine the various technical edges of the hybrid drone over the rest of the types. Firstly, the main entity of the drone, the wing, of 3 different profiles(aero-foils), is analysed for better lift coefficient as it is the major contributor for the thrust during cruise (for 0 deg angle of attack). The velocity contours are viewed to interpret the aerodynamic advantage of each wing. Then the whole vehicle is analysed after inculcating the wing. The various aerodynamic parameters such as the lift force, lift coefficient, drag force and drag coefficient of the hybrid drone are determined from the analysis. A hybrid drone with optimum lift has been designed from the inference.

Surveillance FPV Drone with Obstacle Avoidance System

The unmanned air vehicle (UAV) is mostly used in inspection and surveillance operations recent. The UAV is also termed as vertical take-off landing (VTOL), since it is capable of vertical take-off and landing without need of a runway. The big tunnels, infrastructure and large bridges are inserted using UAV by photographic inspection. UAVs are also used for surveillance purposes by the military and by the security guards. Since this is a new technology of the last decade, deep research has to be done. UAVS have the cross structure arrangement to which the rotor blades are attached at the end points of cross beams. These rotors are driven by the DC brush motors and motors are powered by the lithium ion rechargeable battery. The working principle of quad- rotors is the same as the chopper by controlling the rpm of each rotor blade, due to which the gyroscopic torque will act and the vehicle will move in the desired direction. To hold the quad- rotor at a stationary position at some height constant rpm of all rotors has to be maintained. This signal is given by the controller from some distance, which is received by the, and then it processes the signal and drives the motor via the flight controller and drives the rotors. A quad- rotor is equipped with a high quality camera for photography and video shooting during surveillance. Since a quad rotor is manoeuvring in air, the wind may exert a drag force and take it along with it and the quad rotor may hit any obstacle or inspection objects. To avoid this, it is equipped with the ultrasonic sensors which is capable of sensing the obstacle and realize collision avoidance between wall or any object.

Vertical Take Off Landing (VTOL) Untuk Drop Kits Pada Quadcopter

A structure due to natural disasters often occurs in Indonesia, and this is caused by the location of Indonesia in the path of earthquakes and volcanoes. Logistics delivery in the form of medicines and food has been hampered, and this is acknowledged by the Indonesian government, which experienced many obstacles when it had to reach an isolated location due to land transportation lines being cut off. So it was designed an Unmanned Aerial Vehicle (UAV) or drone that can deliver survival kits to some places that are isolated due to natural disasters autonomously. Flight orders will be made through the Mission Planner software, which is then sent to the drone using 433 MHz telemetries. Survival kits carried by drones will be dropped using a servo to a predetermined location. The work of Vertical Take-Off Landing (VTOL) for Drop Kits has successfully carried out a mission to deliver survival kits to 4 different locations in one flight. By using the 433 MHz Telemetry, the drone can travel a maximum distance of 120 meters in 5 minutes 10 seconds with a 9 Ah battery capacity.

Trajectory optimization for lunar rover performing vertical takeoff vertical landing maneuvers in the presence of terrain

This study presents a trajectory optimization framework for lunar rover performing vertical takeoff vertical landing (VTVL) maneuvers in the presence of terrain using variable-thrust propulsion. First, a VTVL trajectory optimization problem with three-dimensional kinematics and dynamics model, boundary conditions, and path constraints is formulated. Then, a finite-element approach transcribes the formulated trajectory optimization problem into a nonlinear programming (NLP) problem solved by a highly efficient NLP solver. A homotopy-based backtracking strategy is applied to enhance the convergence in solving the formulated VTVL trajectory optimization problem. The optimal thrust solution typically has a “bang-bang” profile considering that bounds are imposed on the magnitude of engine thrust. An adaptive mesh refinement strategy based on a constant Hamiltonian profile is designed to address the difficulty in locating the breakpoints in the thrust profile. Four scenarios are simulated. Simulation results indicate that the proposed trajectory optimization framework has sufficient adaptability to handle VTVL missions efficiently.

Trajectory optimization for lunar soft landing with complex constraints

A unified trajectory optimization framework with initialization strategies is proposed in this paper for lunar soft landing for various missions with specific requirements. Two main missions of interest are Apollo-like Landing from low lunar orbit and Vertical Takeoff Vertical Landing (a promising mobility method) on the lunar surface. The trajectory optimization is characterized by difficulties arising from discontinuous thrust, multi-phase connections, jump of attitude angle, and obstacles avoidance. Here R-function is applied to deal with the discontinuities of thrust, checkpoint constraints are introduced to connect multiple landing phases, attitude angular rate is designed to get rid of radical changes, and safeguards are imposed to avoid collision with obstacles. The resulting dynamic problems are generally with complex constraints. The unified framework based on Gauss Pseudospectral Method (GPM) and Nonlinear Programming (NLP) solver are designed to solve the problems efficiently. Advanced initialization strategies are developed to enhance both the convergence and computation efficiency. Numerical results demonstrate the adaptability of the framework for various landing missions, and the performance of successful solution of difficult dynamic problems.

Discrete-time static H∞ loop shaping control via LMIs

A new synthesis procedure is introduced for static H∞ loop shaping problem in discrete-time case. LMI conditions are derived to obtain a static output feedback controller that ensures the robust stability and performance of the closed-loop system. A numerical example illustrates the use of the proposed control method with application to a VTOL (“vertical take-off landing”) aircraft model.