Handling Qualities Research Articles

Variable Stability In-Flight Simulation System Based on Existing Autopilot Hardware

A variable stability in-flight simulator has the capabilities to change the response of an aircraft in-flight, often without changing the physical properties of the aircraft. The ability to adjust the aircraft response characteristics and handling qualities has various purposes, such as pilot training, control system development, and handling quality research. A variable stability control system is designed for a medium-range business jet using incremental nonlinear dynamic inversion. The performance of the in-flight simulator is verified by two experiments, one conducted in a fixed-base flight simulator and one in a Cessna Citation II laboratory aircraft. The fly-by-wire actuation system in the Cessna Citation II is based on its existing autopilot, inheriting the limited performance and safety protections. The simulator experiment shows differences between the experienced handling qualities for a reference model and the designed controller combined with aircraft dynamics. These differences mainly arise due to actuator saturation for specific handling quality settings. The in-flight experiment supports the simulator findings but also reveals how the available control authority around the initial condition is limited due to constraints of the fly-by-wire system.

Robust Helicopter Sliding Mode Control for Enhanced Handling and Trajectory Following

Helicopters in tactical missions require superior handling and stability in turbulence. This paper proposes a sliding mode control (SMC)-based helicopter trajectory controller for enhanced handling qualities (HQs) with robustness to endogenous (modeling) and exogenous (turbulence) uncertainties. The flight control problem is posed as one of attitude, angular rate, and translational rate command tracking with closed-loop axial responses conforming to predicted level 1 HQs. The required closed-loop behavior is then enforced by a two-loop output-tracking SMC treating interaxis coupling and turbulence as matched, bounded uncertainties. To mitigate the chattering effect of SMC, a continuous control approximation using the boundary-layer concept is applied. The stability and tracking performance of the two-loop controller are analyzed. Furthermore, actuator saturations encountered during aggressive maneuvers are mitigated by reference command adaptation based on pseudo-control hedging. The proposed controller is evaluated against selected HQ temporal response criteria, two mission task elements requiring moderate to aggressive agility, and a shipboard approach in high-intensity turbulence. Simulation results highlight the controller’s trajectory tracking accuracy, adequate axial decoupling, and insensitivity to disturbances.

Evaluation of an advanced slung load control system for piloted cargo operations

Helicopter operations with externally slung loads are highly demanding for the flight crew. As the pilot does not have a direct view of the load, assistance is required from an additional crew member to achieve operational requirements (e.g., for load handling to achieve precise load positioning). An automatic load stabilization and positioning system for cargo operations has been designed with the aim to reduce pilot workload, damp load pendulum motion and to improve the load positioning performance. This system uses the concept of load-motion feedback to the rotor control. To avoid degradation of Handling Qualities (HQs), as found in previous investigations, a function has been developed that monitors pilot control inputs. Dependent on the amplitude and duration of pilot control stick deflection, the feedback signal for slung load damping is blended between two different gain sets. One set provides improved HQs during piloted control and one set provides good load damping when the pilot is passive. A further novel aspect is the evaluation of an automatic load control system using a Translational Rate Command as a method of helicopter control. A piloted simulation study has been conducted using this advanced load control system with automatic load stabilization and positioning. Three test pilots evaluated the system in different control law configurations using a Mission Task Element simulating an external load cargo operation. HQs and pilot workload were evaluated using the Cooper-Harper Rating Scale and NASA Task Load Index, respectively. The results of the study show that improved HQs and reduced pilot workload in combination with improved task performance can be achieved with the advanced slung load control system.

Piloted Simulation Evaluation of Tracking Mission Task Elements for the Assessment of High-Speed Handling Qualities

Updates to the military rotorcraft handling qualities specification are currently being considered that address the high-speed flight regime envisioned for the Future Vertical Lift platform of the U. S. Army. A team that features industry and academia has developed and evaluated a set of mission task elements (MTEs) that are defined to address vertical takeoff and landing (VTOL) high-speed handling qualities. Following the mission-oriented approach upon which ADS-33E-PRF is based, the MTEs were designed to meet different levels of precision and aggressiveness. Tracking MTEs based on a sum-of-sines (SOS) command signal were defined for precision, aggressive, and precision, nonaggressive applications. The command signals were derived from fixed-wing analogs that have long been used to evaluate aircraft handling qualities. While the precision, aggressive SOS tracking tasks, the primary subject of this paper, are surrogates for air-to-air tracking and nap-of-the-earth tracking, the known forcing function allows for complete open- and closed-loop pilot—vehicle system identification. The MTE objectives, descriptions, and performance criteria were assessed and refined via several checkout piloted simulation sessions. Formal evaluations were then conducted by Army test pilots at four simulator facilities, each featuring a unique high-speed platform including a generic winged-compound helicopter, two tiltrotor configurations, and a compound helicopter with coaxial rotors. To aid in the MTE evaluation process, baseline VTOL configurations were varied to achieve different handling qualities levels. Quantitative measures based on task performance and qualitative measures based on pilot ratings, comments, and debrief questionnaires were used to assess MTE effectiveness. The piloted simulation results demonstrated that the SOS tracking MTEs provided an effective means to discern precision, aggressive handling qualities in high-speed flight.

Handling-Qualities Perspective on Rotorcraft Load Alleviation Control

The objective of this research effort is to assess the impact of load alleviation control on the quantitative handling-qualities specifications (also known as predicted handling qualities) of both conventional helicopters and compound rotorcraft in forward flight. First, an overview on how the harmonic decomposition methodology is used toward load alleviation control is presented. Next, flight control laws are developed based on an explicit model-following architecture. Parametric studies are performed to provide insights on how both the feedforward and feedback paths of the model-following control laws can be used to alleviate the rotor loads. The impact of load alleviation on predicted handling qualities is studied. It is shown that, for the standard helicopter configuration considered, load alleviation comes at the cost of a degradation in handling qualities. However, for the compound rotorcraft considered, allocation of the control signal to the redundant control surfaces provides load alleviation without degradation in predicted handling qualities. The flight control laws are subsequently optimized using the Control Designer’s Unified Interface to meet a comprehensive set of stability, handling-qualities, and performance specifications for specific mission task elements while minimizing the unsteady rotor loads.

Operator Perception of a Single-Use Flexible Bronchoscope: Comparison With Current Standard Bronchoscopes.

Single-use flexible bronchoscopes have gained popularity in recent years for various advantages over the traditional reusable bronchoscope. There are several commercially available disposable bronchoscopes; however, all have limitations compared to reusable bronchoscopes. The Vathin H-SteriScope is a single-use flexible bronchoscope that may have overcome some of these limitations. We designed a survey to evaluate the performance of this new single-use bronchoscope on a bronchoscopy model with operators who are familiar with current single-use and reusable bronchoscopes. The operators were asked to rank overall assessment, scope quality, handling, maneuverability, tool interaction, and image quality of the H-SteriScope on a scale of 0-100. These operators were then asked to rank their current single-use and reusable bronchoscopes with the same scale. The results were evaluated to determine the operator perception of the H-SteriScope. The H-SteriScope and current reusable bronchoscopes were perceived to have significant differences compared with currently available single-use bronchoscopes in overall assessment of the scope, scope quality, handling, maneuverability, tool interaction, and image quality (P < .001). The H-SteriScope was perceived to have similar maneuverability as the reusable bronchoscope (P = .86). There were no differences among the H-SteriScope (P = .88), the current single-use bronchoscope (P = .84), and the current reusable bronchoscope (P = .89) between the training and nontraining interventional pulmonology subgroups. In terms of operator perception, the H-SteriScope appears to have similar maneuverability as the reusable bronchoscope. Both the H-SteriScope and the reusable bronchoscopes performed better in all measured sectors than the current single-use bronchoscope. Additional studies are required to evaluate the practicality, safety, and cost efficiency of the H-SteriScope in clinical practice.

Design optimization of multi-objective proportional–integral–derivative controllers for enhanced handling quality of a twin-engine, propeller-driven airplane

Herein, the design optimization of multi-objective controllers for the lateral–directional motion using proportional–integral–derivative controllers for a twin-engine, propeller-driven airplane is presented. The design optimization has been accomplished using the genetic algorithm and the main goal was to enhance the handling quality of the aircraft. The proportional–integral–derivative controllers have been designed such that not only the stability of the lateral–directional motion was satisfied but also the optimum result in longitudinal trim condition was achieved through genetic algorithm. Using genetic algorithm optimization, the handling quality was improved and placed in level 1 from level 2 for the proposed aircraft. A comprehensive sensitivity analysis to different velocities, altitudes and centre of mass positions is presented. Also, the performance of the genetic algorithm has been compared to the case where the particle swarm optimization tool is implemented. In this work, the aerodynamic coefficients as well as the stability and control derivatives were predicted using analytical and semi-empirical methods validated for this type of aircraft.

Coal handling quality from pits to stockpiles to market specifications

In the coal trade, coal quality becomes the main thing that must be consider. The quality of coal that is not following the specifications desired by consumers causes coal prices below. Parameters of coal quality consist of calorific value, water content, an ash content of flying substances, and sulfur content. The quality of this coal will always recheck with every change of place. Before coal is sold, it is better to monitor the quality of the coal starting from the pit. At the coal quality monitoring location, there are four seams, including seam A1, seam A2, seam B and seam C. Monitoring of coal quality is carried out at seam C to be mined. Monitoring of coal quality from the pit to the stockpile is done by taking representative samples from drilling, mining, and stockpile activities. Then the samples were analysed by proximate analysis. Drilling samples was taken by coring sampling from eight drill points. Sample from the pit are taken by channel sampling method, in the mining pit sample are divided into three parts, namely the upper part (coal with 10 cm thick clay insert, called layer 1), the second middle part (coal with 20 cm thick clay insert, called layer 2 ) and the bottom three (coal without clay insertion, called layer 3). The purpose of the division is carried out as a handling coal from being mixed into three parts. Samples from the stockpiles are taken by grab sampling method from three stockpiles originating from layer one, layer two, and layer three. For layer one coal, the difference in ash content in pits and stockpiles is 1.6%, the difference in total sulfur content in pits and stockpiles is 0.7%. For layer two coal, the difference in ash content in pits and stockpiles is 1.5%; the difference in total sulfur content in pits and stockpiles is 0.7%. In layer three. The difference in ash content in pits and stockpiles is 1.5%, the difference in total sulfur content in pits and stockpiles is 0.7%.

SIMULATED PILOT-IN-THE-LOOP TESTING OF HANDLING QUALITIES OF THE FLEXIBLE WING AIRCRAFT

This article aims to indicate the differences between rigid and flexible wing aircraft flying (FQ) and handling (HQ) qualities. The Simulation Framework for Flexible Aircraft was used to provide a generic cockpit environment and a piloted mathematical model of a bare airframe generic high aspect ratio wing aircraft (GA) model. Three highly qualified test pilots participated in the piloted simulation trials campaign and flew the GA model with both rigid and flexible wing configurations. The results showed a negligible difference for the longitudinal HQs between rigid and flexible wing aircraft. However, significant changes were indicated for the lateral/directional HQs of the flexible wing aircraft. A wing ratcheting phenomenon manifested itself during the roll mode tests, the spiral mode exhibited neutral stability and the Dutch roll mode shape changed from a horizontal to a vertical ellipse. The slalom task flight tests, performed to assess the FQs of the aircraft, revealed the degradation of both the longitudinal and lateral/directional FQs.

Automation for Safety and Precision in Flight Testing

Abstract. The first flight of any new aircraft remains a potentially dangerous event. Test pilots face many unknowns when a prototype leaves the ground for the first time. In a time when remotely piloted and autonomous aircraft fly every day, the question about using their technologies to avoid losing a test pilot arises. This study investigates the advantages of using a machine to test another machine. It also discusses the disadvantages of relying on airborne sensors instead of using the test pilot’s cognitive capabilities and judgment. The analysis of collected flight testing data suggests that aircraft handling qualities may be more precisely tested adding specific automation. However, remote control and autonomous flight testing bring new safety constraints that cannot be ignored.

Study on the Handling Qualities Enhancement of Fixed-wing Aircraft Using Adaptive Neural Network

This paper intends to propose the integrated design framework of a model-following controller (MFC) combined with both an adaptive neural network (ANN) and a linear observer to enhance the handling qualities (HQ) of a fixed-wing aircraft. To achieve this objective, the HQ requirements (HQRs) applicable to a light sports aircraft and the controller structure have been defined. And, the controller design parameters are optimized to meet HQRs using the CONDUIT®. Thereby, the integrated design environment can determine the control gains and ANN’s tuning parameters in an optimum manner and the level of HQ achievable with the designed parameters can be automatically evaluated. The paper tries to clarify the effect of the ANN with the linear observer on the HQ enhancement. To achieve this, the control laws in the attitude command response types have been designed and their tracking performances are investigated with and without ANN elements to identify the improved HQ with the ANN. In addition, a series of comparative simulation studies on the effects of external disturbances on the attitude tracking performance are carried out to show the enhanced robustness with the proposed controller structure. The results show that the ANN control can dramatically improve the level of HQ and provide the favorable robustness to external disturbances. Therefore, the results of the present study can provide the efficient ways of the HQ enhancement by adopting the ANN in the conventional MFC structure and by designing the controller parameters with the integrated design processes of CONDUIT®.

Technical Measures Perspectives in Selection of Handling Qualities Criteria for Flight Control Design

AbstractThe requirements of satisfactory pilot‐vehicle interaction in high workload precision flying tasks plays a very important and dominant role in the design of flight control systems. Based on the extensive flight test experience, quantitative handling qualities specifications to aid control law design have been derived and documented in relevant MIL Standards. In this paper an attempt is made to demonstrate methodology used for validation of Handling Qualities (HQ) requirements for a HighPerformance fighter Aircraft (HPA) using technical measurements in systems engineering i.e. Measure of effectiveness (MOE), Measure of performance (MOP) and Technical performance measure (TPM) as defined by INCOSE.A mission requirement such as Air to Air Refueling (AAR) is considered as a user need in qualitative form and is mapped to MOE as an indicator of achieving the operational objective. The MOPs are arrived from the handling quality specifications from MIL standards for the flight control design. TPMs enable an assessment of the system design by estimating the values of key performance parameters of the design through engineering analyses and tests.A piloted evaluation is performed for the given mission requirement. The flight data together with pilot comments on aircraft handling qualities are assessed to identify any mismatch between predicted HQ versus piloted evaluation which leads to iteration of flight control laws. Thereby, the use of technical measures keeps track of requirements to be met while maintain desired system performance as well anticipate any risk and mitigate the same during early stage of design cycle.

Defining Pilot Gain

A common topic of discussion among members of the flight-test community is pilot gain. Every seasoned flight-test professional is capable of identifying test pilots that are considered to be either high-gain or low-gain pilots. It is considered a given in the testing world that high-gain pilots are better at exposing shortcomings in aircraft handling qualities, including the potential for explosive pilot-induced oscillation. By inference, low-gain pilots are often judged to be just the opposite. Despite this interpretation, the concept of pilot gain is itself not well understood. How do we define, quantify, and (perhaps most importantly) modify pilot gain? Using recent research data, pilot gain can be identified as an element in the pilot–vehicle closed-loop system. It is demonstrated that pilot gain, in closed-loop control, is a misnomer and that more proper terms might be pilot–vehicle bandwidth or crossover frequency.

Implementation of tactical maneuvers with maneuver libraries

This study creates and combines the general maneuver libraries for fixed-wing aircraft to implement tactical maneuvers. First, the generalized maneuver libraries are established by analyzing the characteristics of tactical maneuvers required in battlefields. The 7th order polynomial is applied to both the creation of the maneuver libraries and the generation of the trajectories or flight paths for modal inputs. To track the desired trajectory, we design the Attitude Command Attitude Hold (ACAH) system and the Rate Command Rate Hold (RCRH) system using Model Following Controller (MFC). Moreover, the Line-of-Sight (LOS) guidance law is designed. In particular, the CONDUIT® is employed to optimize the gains so that the control systems meet the aircraft Handling Qualities (HQ) criteria. Finally, flight simulations are performed for the longitudinal loop, immelmann-turn, and climb-slalom-descent maneuvers to verify that tactical aggressive maneuvers are realizable via the combination of maneuver libraries. This study can contribute to the development of flight techniques for aircraft tactical maneuvers and to the revision of air force operational manuals.

Single-cell RNA Sequencing and Analysis of Human Pancreatic Islets.

Pancreatic islets comprise of endocrine cells with distinctive hormone expression patterns. The endocrine cells show functional differences in response to normal and pathological conditions. The goal of this protocol is to generate high-quality, large-scale transcriptome data of each endocrine cell type with the use of a droplet-based microfluidic single-cell RNA sequencing technology. Such data can be utilized to build the gene expression profile of each endocrine cell type in normal or specific conditions. The process requires careful handling, accurate measurement, and rigorous quality control. In this protocol, we describe detailed steps for human pancreatic islets dissociation, sequencing, and data analysis. The representative results of about 20,000 human single islet cells demonstrate the successful application of the protocol.

Development of a Multi-Directional Manoeuvre for Unified Handling Qualities Investigation

A slalom and alignment tracking manoeuvre was developed for multi-directional handling qualities analysis of large transport aircraft in simulation environments. The manoeuvre is defined and scaled as a function of aircraft characteristics, flight conditions using a simple set of mathematical models. Throughout the manoeuvre, the trajectory and overall performances are monitored at a set of gross position and alignment control checkpoints methodically distributed and sized to buoy the task and allow handling qualities analysis based on Cooper Harper Ratings and quantitative data analysis. Initial tests have shown that the manoeuvre sizing method led to feasible manoeuvres at multiple points of the flight envelope of a large civil transport aircraft. The manoeuvre capability to highlight desirable and undesirable handling qualities was also highlighted based on the initial findings for a couple of commercial large transport aircraft, a high aspect ratio wing and in-flight folding wingtip aircraft concepts. The relevance and applicability of the manoeuvre for multi-directional studies are discussed and compared against a more conventional offset landing manoeuvre. Finally, the potential use of the manoeuvre for different aircraft type and test flight is also suggested based on augmented reality technology.

Neural network-based nonlinear dynamic inversion control of variable-span morphing aircraft

A nonlinear command and stability augmentation system is designed based on feedback linearization for a morphing aircraft in the presence of different variable-span configurations. A variable-span morphing aircraft model is obtained by modifying a conventional aircraft model. Feed-forward neural networks are trained to learn the inverse dynamics in various morphing configurations and flight conditions. An attitude orientation system is designed to stabilize the airframe and track the commanded angular rates. Finally, an online adaptive mechanism is employed to compensate for inversion error. Even when the aircraft is changing the morphing configuration while maneuvering, the proposed design satisfies the desired handling quality specifications. Consequentially, the proposed design provides another degree of freedom to manipulate the morphing configuration, and therefore agility or fuel efficiency can be improved. Numerical simulation is performed to demonstrate the effectiveness of the proposed scheme.

Technological and physical properties of dry pressed red mud bodies containing chamotte

Each clay has its own distinct makeup, resulting in a different handling quality, color, temperature range and plasticity, or workability. The choice of clays is wide and you can also combine them which will increase the possibilities further. In this study, dry pressed red mud bodies containing chamotte were used for increasing mechanical properties. Five, 10, and 15 wt% chamottes were added to red mud bodies, separately. Prepared granules were dry pressed with suitable pressing pressure. Dry pressed granules were sintered at 900, 950, and 1000 °C for 2 h. Physical and technological properties were determined by measuring pore diameter, density, shrinkage, and water absorption. Structural characterization was carried out with XRD and scanning electron microscopy (SEM) studies. Vickers microhardness and bending strength test were done to determine mechanical properties. Optimum chamotte addition to red mud bodies and optimum sintering temperature with high mechanical properties were determined with this study. The best density, water absorption, firing shrinkage and bending strength values were obtained with RM15C sample sintered at 1000 °C as 2.94 g/cm3, 6.6%, 10.9%, and 107 MPa, respectively.

Efficient and Robust Inverse Simulation Techniques Using Pseudo-Spectral Integrator with Applications to Rotorcraft Aggressive Maneuver Analyses

This paper intends to propose new inverse simulation techniques to cope with the numerical stability and accuracy problems frequently encountered with the integration inverse simulation methods widely used today. To achieve this, the pseudo-spectral method is adopted as a time integrator of the aircraft motion equations. In addition, the quasi-Newton and fixed-point iterative methods are applied to solve the resultant nonlinear algebraic equations in an efficient manner. These algorithms are integrated into a moving horizon framework to guarantee fast numerical convergence. The proposed methods are applied to the analyses of rotorcraft aggressive maneuvers such as popup, pirouette, and depart/abort mission-task-elements defined in the rotorcraft handling qualities requirements, ADS-33E-PRF. Numerical properties of the proposed methods are thoroughly investigated to clarify the effect of the numbers of quadrature nodes and time-horizon segments, and the level of maneuver aggressiveness on the robustness and efficiency of the analyses. Numerical efficiency and robustness of the present method are identified using specially designed performance measures such as the number of iterations to obtain a converged solution, functional residuals at the final solutions, and the variation of the adaptive relaxation factor. The results show that the present approach can provide extremely fast solutions of the inverse simulation problems and presents strong robustness to the level of maneuver aggressiveness, long-term simulation, and solution control parameters. Therefore, it is worthwhile to use the present techniques as one of the inverse simulation methods.

Direct Yaw Moment Control for Enhancing Handling Quality of Lightweight Electric Vehicles with Large Load-To-Curb Weight Ratio

In this paper a vehicle dynamics control system is designed to compensate the change in vehicle handling dynamics of lightweight vehicles due to variation in loading conditions and the effectiveness of the proposed design is verified by simulations and an experimental study using a fixed-base driving simulator. Considering the electrification of future mobility, the target vehicle of this research is a lightweight vehicle equipped with in-wheel motors that can generate an additional direct yaw moment by transverse distribution of traction forces to control vehicle yawing as well as side slip motions. Previously, the change in vehicle handling dynamics for various loading conditions have been analyzed by using a linear two-wheel vehicle model in planar motion and a control law of the DYC system based on feed-forward of front steering angular velocity and feedback of vehicle yaw rate. The feed-forward controller is derived based on the model following control with approximation of the vehicle dynamics to 1st-order transfer function. To make the determination of the yaw rate feedback gain model-based and adaptable to various vehicle velocity conditions, this paper selects a method where the yaw rate feedback gain in the DYC system is determined in a way that the steady-state yaw rate gain of the controlled loaded vehicle matches the gain of the unloaded vehicle. The DYC system is simulated in a single lane change maneuver to confirm the improved responsiveness of the vehicle while simulations of a double-lane change maneuver with a driver steering model confirms the effectiveness of the DYC system to support tracking control. Finally, the effectiveness of the proposed DYC system is also verified in an experimental study with ten human drivers using a fix-based driving simulator.