Quad Performances and Manoeuvrability of TWQH platform

Accurate dynamic modelling of the Tandem Wing Quadcopter Hybrid (TWQH) platform is becoming increasingly important, as strict requirements are progressively being imposed on the UAV (unmanned aerial vehicles) control system in the transition phase from vertical to level flight and vice versa. This work aims to present preliminary design performances in the steady and manoeuvring flight of the platform thrusted by only four rotors directed upward. The aerodynamic effects of tandem wings make a significant contribution to the evaluation of performance, controllability and manoeuvrability in hovering and low speed phase. More specifically, steady, level, symmetrical pull-up and coordinated turns approaches of the quad model are considered and the results obtained in the simulation study are presented and discussed

Automatic approach procedure of a flying vehicle on a mobile platform using backstepping controller

This paper presents the automatic approach procedure of a flying vehicle, attached to an ABB 7600 robot, and a mobile platform, attached to a Stewart platform. Due to a nonlinear dynamic behavior, it is necessary to implement complex control, stabilization and guidance schemes. The proposed solution for this system includes the development of an algorithm based on a backstepping control method, the controller design methodology being based on Lyapunov's stability theory. The proposed command law requires that the states are known, but it is also necessary to introduce a series of state estimators. Tracking a mobile platform is critical in surveillance, reconnaissance and tracking missions, with the control methodology defining a clear distinction between translational and rotational dynamics. The proposed algorithm is developed by separating two types of states involving an inverse kinematics, known as algebraic kinematics, in which the dynamic movements of the two pieces of equipment are used. The dynamics of the ABB 7600 robot involves a movement with seven degrees of freedom, while the Stewart platform can be used with a movement of six degrees of freedom. The proposed algorithm is implemented in both Matlab software and experimental testing. This paper provides results in terms of generating dynamics for both devices that can be used for simulating different scenarios of aerospace missions

Using PID Controller and SDRE methods for tracking control of Spacecrafts in Closed-Rendezvous Process

Rendezvous process of spacecrafts is one of major issues in study of aerospace engineering. Tracking control in Rendezvous process is very complex due to the need to fulfill the conditions and constraints to determine the control forces to bring Chaser toward Target. The paper will implement the control of the trajectory of the relative translation movement between Chaser and Target in the Closed-Rendezvous stage through two different approaches: the first using PID Controllers, and the second using the SDRE (State Dependent Riccati Equation) technique. Then based on obtained results, a comparison between two methods is carried out

Interpreting historical, botanical, and geological evidence to aid preparations for future floods

River flooding is among the most destructive of natural hazards globally, causing widespread loss of life, damage to infrastructure and economic deprivation. Societies are currently under increasing threat from such floods, predominantly from increasing exposure of people and assets in flood-prone areas, but also as a result of changes in flood magnitude, frequency, and timing. Accurate flood hazard and risk assessment are therefore crucial for the sustainable development of societies worldwide. With a paucity of hydrological measurements, evidence from the field offers the only insight into truly extreme events and their variability in space and time. Historical, botanical, and geological archives have increasingly been recognized as valuable sources of extreme flood event information. These different archives are here reviewed with a particular focus on the recording mechanisms of flood information, the historical development of the methodological approaches and the type of information that those archives can provide. These studies provide a wealthy dataset of hundreds of historical and palaeoflood series, whose analysis reveals a noticeable dominance of records in Europe. After describing the diversity of flood information provided by this dataset, we identify how these records have improved and could further improve flood hazard assessments and, thereby, flood management and mitigation plans

Trigger event – a key factor in adverse Aircraft/Rotorcraft Pilot Couplings

An important element that interacts unfavorably with pilot and aircraft is the triggering event. Without a trigger event (or a chain of triggering events) A/RPC does not appear. This study presents an overview of different classes of triggers that can initiate an A/RPC phenomenon. Based on extended analysis of triggering events a new definition is proposed

Attitude Dynamics and Tracking Control of Spacecraft in the Presence of Gravity Oblateness Perturbations

The orbital docking represents a problem of great importance in aerospace engineering. The paper aims to perform an analysis of docking maneuvers between a chaser vehicle and a target vehicle in permanent LEO (low earth orbit). The work begins with a study of the attitude dynamics modeling intended to define the strategy that facilitates the chaser movement toward a docking part of the target. An LQR (linear quadratic regulator) approach presents an optimal control design that provides linearized closed-loop error dynamics for tracking a desired quaternion. The control law formulation is combined with the control architecture based on SDRE (State Dependent Riccati equation) technique for rotational maneuvers, including the Earth oblateness perturbation. The chaser body-fixed frame must coincide with the target body-fixed frame at the docking moment. Then the implementation of the control architecture based on LQR technique using the computational tool MATLAB is carried out. In simulation of the docking strategy V-R bar operations are analyzed and the minimum accelerations needs the control of chaser vehicle. The simulation analysis of those maneuvers considered for a chaser vehicle and a target vehicle in LEO orbit is validated in a case study

Prediction of the handling qualities and pilot-induced oscillation rating levels

The basis for the aviation development is the ambition of increasing the efficiency and safety of flight. Improvements include flight performance and extended flight envelope, new flight regimes and tasks. However, all of these factors lead to the increase of pilot workload which can reduce the accuracy and safety of flight. Fixed and rotary wing pilots are being confronted with potential instabilities or with annoying limit cycle oscillations, known as Aircraft/Rotorcraft Pilot Couplings (A/RPC) that arise from the effort of controlling the vehicle with high response actuators. This paper deals with the unified theory of predicting handling qualities level (HQSF) and pilot-induced oscillation rating levels (PIOR) based on the structural model of human operator, developed by Hess. HQSF and PIOR are capable of capturing the prominent features of human pilot dynamics characteristics for a large class of aerial vehicles and tasks. The key element in this method is to unify the topics of vehicle handling qualities and RPC/PIO, applied to the analysis of a medium weight helicopter model

Oscillation Susceptibility Analysis of the ADMIRE Aircraft along the Path of Longitudinal Flight Equilibriums in Two Different Mathematical Models

The oscillation susceptibility of the ADMIRE aircraft along the path of longitudinal flight equilibriums is analyzed numerically in the general and in a simplified flight model. More precisely, the longitudinal flight equilibriums, the stability of these equilibriums, and the existence of bifurcations along the path of these equilibriums are researched in both models. Maneuvers and appropriate piloting tasks for the touch-down moment are simulated in both models. The computed results obtained in the models are compared in order to see if the movement concerning the landing phase computed in the simplified model is similar to that computed in the general model. The similarity we find is not a proof of the structural stability of the simplified system, what as far we know never been made, but can increase the confidence that the simplified system correctly describes the real phenomenon

Practices to identify and preclude adverse Aircraft-and-Rotorcraft-Pilot Couplings - A design perspective

Understanding, predicting and supressing the inadvertent aircraft oscillations caused by Aircraft/Rotorcraft Pilot Couplings (A/RPC) is a challenging problem for designers. These are potential instabilities that arise from the effort of controlling aircraft with high response actuation systems. The present paper reviews, updates and discusses desirable practices to be used during the design process for unmasking A/RPC phenomena. These practices are stemming from the European Commission project ARISTOTEL Aircraft and Rotorcraft Pilot Couplings - Tools and Techniques for Alleviation and Detection (2010-2013) and are mainly related to aerodynamic and structural modelling of the aircraft/rotorcraft, pilot modelling and A/RPC prediction criteria. The paper proposes new methodologies for precluding adverse A/RPCs events taking into account the aeroelasticity of the structure and pilot biodynamic interaction. It is demonstrated that high-frequency accelerations due to structural elasticity cause negative effects on pilot control, since they lead to involuntary body and limb-manipulator system displacements and interfere with pilot's deliberate control activity (biodynamic interaction) and, finally, worsen handling quality ratings