Pilot Control Research Articles

Validation of mathematical models for helicopter flight simulators past, present and future challenges

AbstractAt the heart of a flight simulator resides the mathematical representation of aircraft behaviour in response to control inputs, atmospheric disturbances and system inputs including failures and malfunctions. While this mathematical model can never be wholly accurate, its fidelity, in comparison with real world behaviour, underpins the usefulness of the flight simulator. The present paper examines the state of the art achieved in validating mathematical models for helicopter simulators, addressing the strengths and weaknesses of the present European standard for the qualification of helicopter flight simulators, JAR FSTD-H (previously JAR-STD-1H/2H/3H). Essential questions are examined, such as: What is the required model fidelity to guarantee a simulation is sufficiently representative to be fit for purpose? Are the tolerances set in the current standards fine enough that they lead to only minor changes in handling qualities? What is an acceptable tuning process for the simulation? What is the effect of modelling fidelity on the overall pilot control strategy? What is the relationship between the settings of the simulator cueing environment and the behaviour of the pilot? What is the industrial experience on qualification of flight simulators that might usefully inform developments? Many of these questions were addressed in Europe in a previous GARTEUR Action Group (AG) HC/AG-12 the results of which are documented in this paper. Solutions are proposed for improving the current JAR-FSTD standard with respect to validation of mathematical models.

Influences of Simulator Motion System Characteristics on Pilot Control Behavior

Low-cost motion systems have been proposed for certain training tasks that would otherwise be performed on high-performance full-flight simulators. These systems usually have lower bandwidth and lower smoothness. The influence of these characteristics on pilot perception and control behavior is unknown and needs to be investigated. In this paper, this is done by simulating a model of a simulator with limited capabilities on a high-end simulator. The platform limitations, which consist of a platform filter, time delay, and noise characteristics, can then be removed one by one, and their effect on control behavior is studied in isolation. An experiment was conducted to identify pilot perception and control behavior in a closed-loop control task. The time delay and noise characteristics of the simulators did not have an effect. However, it was found that the bandwidth of the motion system had a significant effect on performance and control behavior. Results indicate that the motion cues were barely used at all in conditions with a low bandwidth, and that participants relied on the visual cues to generate lead to perform the control task.

Integration of Radar System with GPS-Based Traffic Alert and Collision Avoidance System (TCAS) for Approach Control Separation

The air traffic control system is a vast network of people and necessary navigational equipment that ensures the safe operation of commercial and private aircraft throughout the world. Air traffic controller service is responsible for area, approach and aerodrome control. Aircraft fatal accident data for commercial jet airplanes between 1959 and 2008 show that 36% of the accidents happen in the final approach and landing phase, possibly due to mechanical failure or human error resulting from poor communication between the pilot and air traffic controller. This paper presents an integration of a radar system with a GPS-based Traffic Alert and Collision Avoidance System (TCAS) for approach control separation between all instrument flight rules (IFR) flights and between IFR flights and visual flight rules (VFR) flights operated as controlled flights. The integration is simulated using MATLAB. Results of the simulation show that aircraft separation is easier and safer than relying only on an air traffic controller. We note, however, that the service of air traffic controllers is still required for successful aerodrome control.

Adverse weather diversion model DIVMET

Concept and first results are presented of a model development DIVMET for providing guidance for two-dimensional, horizontal navigation of an aircraft on an arbitrary prescribed flight level around or through adverse weather. In this paper we focus on thunderstorms but a later model development will allow for other weather hazards such as icing or volcanic ash. Adverse weather is represented as impermeable polygons on vertically staggered horizontal planes. The model concept maps the joint decision making process of pilot and air traffic controller into an algorithm, which encompasses (1) the recognition of thunderstorms within the pilot's field of view. The latter may consist either of the typical on-board weather radar display of varying range, or of the visible range determined by atmospheric conditions, or of the spatially unlimited “full view”. DIVMET then (2), in accordance with international flight rules, applies a minimum safety distance to any recognized adverse weather object, and (3) determines a reasonably short route not only around a single weather object but also through a whole field of them. Finally (4), DIVMET moves the aircraft purely kinematic along the previously determined diverted route ignoring so far any potential aircraft-aircraft conflicts. That movement may also be achieved by an externally coupled air traffic model which then also avoids the latter conflicts, accounts for aircraft performance and thus enables to study the combined effect of weather and traffic. Here we present the concept of the path finding through a storm field from a meteorological perspective and outline its potential applications.

Cross-platform validation for a model of a low-cost Stewart platform

Low-cost motion systems have been proposed for certain training tasks that would otherwise be performed on high-performance full flight simulators. These systems have shorter stroke actuators, lower bandwidth, and higher motion noise. The influence of these characteristics on pilot perception and control behavior is unknown, and needs to be investigated. A possible approach to this would be to simulate a platform with limited capabilities with a high-end platform, and then remove the platform limitations one by one. The effects of these platform limitations on pilot behavior can then be investigated in isolation. In this paper, a model of a low-cost simulator was validated for simulation on a high-performance simulator. A dynamic model of the MPI Stewart platform was analyzed and compared with measurements of the baseline simulator response. Measurements for validation of the implementation of the model on the SIMONA Research Simulator showed that the dynamics of the MPI Stewart platform could be represented well in terms of dynamic range, time delay, and noise characteristics. The implementation of the model of the MPI Stewart platform will be used in experiments on the effects of these characteristics on pilot control behavior.

Simulation on an Experimental System for the Dynamic Characteristics of Safety Valves with High Pressure and Large Flow Rate

Safety valves play very important role in protecting the safety of hydraulic support in coal mine. However, its development is greatly limited by the corresponding test bench for the dynamic experiment. In this paper, an experimental system for testing the dynamic performance of the safety valve with rated pressure up to 50MPa and rated flow rate up to 2000L/min, is introduced. Based on AMEsim software, modeling and simulation on the designed system is carried out. Some parameters of the system are also analyzed and their influences to the tested valve’s dynamic performance are obtained by simulation. It is found that the designed system, which adopting the combination of a piston and a plunger cylindersas well as accumulators, can fulfill the demands of the relevant standard. Among all the investigated factors, both the volume and pre-charged gas pressure of the accumulators have optimum values matching with the other parameters of the system. The stroke of the plunger cylinder, the rated flow rates of the cartridge valve and its pilot control valve, are required to be higher than a certain value to avoid negative effects on the dynamic performance of the tested valve. The research presented in this paper is helpful to the design of the test system.

Aerodynamic Loading Characteristics of a Model-Scale Helicopter in a Ship's Airwake

Experiments have been conducted in a water tunnel using a specially designed Airwake Dynamometer (AirDyn) to characterize the aerodynamic loading of a helicopter immersed in the airwake of a generic frigate ship. The AirDyn is a 1:54 model-scale helicopter based on a Merlin AW-101, with a six-component force balance mounted inside the fuselage and a simplified spinning main rotor. The AirDyn has been used to measure the unsteady forces and moments imposed by the ship airwake at fixed locations along the flight path of a landing maneuver for a headwind and a 45 wind-angle. A region of ‘thrust-deficit’ in the headwind and a ‘pressure-wall’ in the 45 wind-angle were identified as ‘time-averaged’ loading characteristics caused by spatial velocity gradients in the airwake. The unsteady loading on the AirDyn in the headwind was compared with the 45 case in terms of the severity of the airwake disturbances and the stages of the landing maneuver at which they are significant. The causes of the observed AirDyn loading characteristics have been explained using unsteady Computational Fluid Dynamics analysis of the ship airwakes. The implications of the AirDyn aerodynamic loading characteristics for pilot workload and control input strategies during a real landing are discussed.

On–off motion of a hydraulic free-piston engine

The current paper presents the on–off characteristics of a compression ignition single-piston hydraulic free-piston engine. A pilot control circuit and a control method for on–off control of the engine are introduced. Detailed piston motion under on–off control of the engine is investigated. The results indicate that the piston on–off motion of 1 cycle can be divided into a pilot phase and a wave phase. The piston motion in the pilot phase is determined by the flow capacity of the frequency control valve. The piston acceleration during the accelerated compression process peaks in the pilot phase. The wave phase consists of a rebound stage, a decaying stage and a creep stage. The rebound stage determines the initial conditions of the other two stages and affects the piston frequency control. The control method proposed is immune from the bottom-dead-centre cycle variation. A high piston frequency results in a better engine fuel economy.

Ship-Helicopter Operating Limits Prediction Using Piloted Flight Simulation and Time-Accurate Airwakes

This paper gives an overview of the ship―helicopter dynamic interface simulation facility at the University of Liverpool, with an emphasis on recent improvements made through the inclusion of unsteady computational fluid dynamics (CFD) ship airwake data. A FLIGHTLAB model of an SH-60B Seahawk helicopter has been flown in a full motion base simulator to the deck of a Type 23 frigate and a Wave class auxiliary oiler, under the influence of unsteady airwakes derived from CFD. Pilot workload ratings have been obtained for the deck landing task, using both the Bedford workload rating scale and the deck interface pilot effort scale, from which fully simulated ship―helicopter operating limits have been derived. Analysis of pilot ratings, comments, and control inputs has also enabled both subjective and objective assessments of workloads at various wind-over-deck conditions, highlighting the dominant aerodynamic airwake features which contribute to the difficulty of the landing task. Having access to the underlying CFD data allows the aircraft handling qualities and pilot workload to be correlated with the aerodynamic characteristics of the airwake and identification of the geometric features of the ship that cause them.

Gnatho-Postural Treatment in an Air Force Pilot

Due to the stresses of flight, air force pilots are more likely to experience oral parafunctions such as bruxism when compared to the general population. Further, their craniocervical mandibular system is subjected to particular stresses in the course of their duties. The aim of this study was to analyze an air force pilot who was undergoing gnatho-postural treatment in order to protect the masticatory system and achieve better occlusal balance. A 32-yr-old pilot from the Italian Air Force national aerobatic team P.A.N. Frecce Tricolori was chosen from the pilots analyzed and treated at the Istituto Medico Legale A. Mosso. A resin stabilization splint was designed for the pilot's lower arch, allowing for the unobstructed excursive glides of the mandible in the protrusive position, and laterality and occlusal balance in the centric position. The clinical gnatho-postural treatment involving a functional diagnostic instrument used on Italian Air Force pilots protects the masticatory system from dental abrasion and, in this particular case, seemed to improve the pilot's posture control system as analyzed by the stabilometric platform.

The uptick rule and stock returns: an analysis of Regulation SHO on the NYSE

This article investigates the impact of short sale constraints on stock returns in a powerful setting in which the uptick rule on the New York Stock Exchange (NYSE) was suspended for a given set of stocks (pilot stocks) by the Securities and Exchange Commission (SEC) in 2005. Comparing future stock returns for pilot stocks and control stocks, I show that the suspension of the uptick rule on average mitigates stock overvaluation by 3.5% of the stock value during a 1-year time period. This effect is profound in stocks with no options, small stocks, and value stocks. Findings in this article are consistent with Miller's (1977) overpricing hypothesis and suggest that removing the uptick rule help improve market efficiency by bringing stock prices closer to their fundamental values.

Allocation of Communications to Reduce Mental Workload

As the United States Department of Defense continues to increase the number of Remotely Piloted Aircraft (RPA) operations overseas, improved Human Systems Integration becomes increasingly important. Manpower limitations have motivated the investigation of Multiple Aircraft Control (MAC) configurations where a single pilot controls multiple RPAs simultaneously. Previous research has indicated that frequent, unpredictable, and oftentimes overwhelming, volumes of communication events can produce unmanageable levels of system induced workload for MAC pilots. Existing human computer interface design includes both visual information with typed responses, which conflict with numerous other visual tasks the pilot performs, and auditory information that is provided through multiple audio devices with speech response. This paper extends previous discrete event workload models of pilot activities flying multiple aircraft. Specifically, we examine statically reallocating communication modality with the goal to reduce and minimize the overall pilot cognitive workload. The analysis investigates the impact of various communication reallocations on predicted pilot workload, measured by the percent of time workload is over a saturation threshold.

Evaluation on novel architecture for harmonizing manual and automatic flight controls under atmospheric turbulence

Pilot uncertainty in aircraft response under automatic flight control has triggered aircraft accidents/incidents in the past. This uncertainty compels a pilot to disengage autopilot and switch to manual control. However, the decision to disengage autopilot and when to do it can be difficult: especially if there is not enough time to monitor the cockpit displays, for instance while countering atmospheric turbulence. Against this background, we proposed the “human as a control module” architecture for harmonizing pilot and autopilot controls. The architecture blends pilot maneuver with autopilot control instead of switching between them when simultaneous inputs are given to the aircraft. By automatically adjusting pilot and autopilot control inputs, the architecture avoids overlaps of both control authorities and helps to circumvent the effect of conflicting actions. This paper applies the architecture to the situations of past aircraft incidents which had been caused by the transfer from autopilot control to pilot maneuver after encountering atmospheric turbulence. The effectiveness of the architecture is evaluated via simulation study for the specific incident examples. Furthermore, this paper extends the architecture with an Extended Kalman Filter (EKF) based observer and evaluates its robustness under errors in wind estimation.

What should the government do regarding health policy-making to develop community health care in Shanghai?

What should the government do regarding health policy-making to develop community health care in Shanghai?

Modeling Wide-Frequency-Range Pilot Equalization for Control of Aircraft Pitch Dynamics

In continuous manual control tasks, human controllers adapt their control strategy to the dynamics of the controlled element. This compensation for the controlled-element dynamics is performed around the pilot–vehicle system crossover frequency, in order to obtain satisfactory performance of the combined pilot–vehicle system, but is also seen to extend to frequencies well above crossover. For a controlled element representing the linearized pitch dynamics of a small conventional jet aircraft, an extension to the models for pilot equalization described in the literature was found to be needed for the modeling of the adopted pilot equalization dynamics over a wide frequency range. Measured pilot describing functions revealed that pilots use a combination of low-frequency lag and high-frequency lead equalization to compensate for the characteristics of these typical aircraft pitch dynamics around the short-period mode. An additional high-frequency lead term in the pilot equalization transfer function was found to allow for the modeling of these adopted equalization dynamics over a wide frequency range, thereby also yielding a significant increase in the percentage of measured control inputs that is explained by the pilot model. Furthermore, for this controlled element the extended model for the equalization dynamics was found to be important for the interpretation of the changes in pilot control behavior that occur due to the presence of physical motion feedback.

Prediction of icing effects on the lateral/directional stability and control of light airplanes

The accumulation of ice on an airplane in flight is one of the leading contributing factors to general aviation accidents, and to date only relatively sophisticated methods based on detailed empirical data and flight data exist for its analysis. This paper develops a methodology and simulation tool for a preliminary yet accurate evaluation of airplane dynamical response and stability and control characteristics due to icing. It uses only basic mass properties, configuration, and propulsion data, together with known icing data obtained for similar configurations. Existing icing data for a light airplane is suitably modified and applied to a non-real-time, six degree-of-freedom simulation model of a different but similar light airplane, developed from empirical data and Data Compendium methods. The component build-up method is used to implement icing effects on the wing alone, horizontal tail alone, and various unequal distributions of combined wing and horizontal tail icing as well as ice accretion on only one half of the wing. Results presented in the paper are limited to the roll axis and yaw axis maneuvers with various levels and distributions of ice accretion show that the methodology captures the basic detrimental effects of ice accretion on roll and yaw response and lateral stability, in addition to the sensitivity of pilot control response.

Prediction of pilot induced oscillations

An important problem in the design of flight-control systems for aircraft under piloted control is the determination of handling qualities and pilot-induced oscillations (PIO) tendencies when significant nonlinearities exist in the vehicle description. The paper presents a method to detect possible pilot-induced oscillations of Category II (with rate and position limiting), a phenomenon usually due to a misadaptation between the pilot and the aircraft response during some tasks in which tight closed loop control of the aircraft is required from the pilot. For the analysis of Pilot in the Loop Oscillations an approach, based on robust stability analysis of a system subject to uncertain parameters, is proposed. In this analysis the nonlinear elements are substituted by linear uncertain parameters. This approach assumes that PIO are characterized by a limit cycle behavior.

Rapport management in air traffic control in Malaysian aviation discourse

Oral communication is documented as the weakest link in air traffic control interactions and one of the primary causes of aviation accidents and incidents. The language of air traffic control communication is characterised by the use of prescribed phraseologies, and when these are missing, plain language becomes a dominant feature. During plain language use mitigation is recorded as a feature of communication and described as an attribute of communication in crews classified as high in safety performance. The present study departs from this observation and seeks to examine the linguistic features for rapport management in air traffic control in non-routine situations in the Malaysian context. Managing the pilot–controller relationship is categorised as one of the dominant communicative functions in air traffic control and a category that is associated with the use of politeness markers. An examination of the language functions in this category and their associated forms vis-à-vis features of politeness are considered useful for training in air traffic communication. Pragmatics is used in this study as the approach to discourse analysis and Spencer-Oatey’s (2000b) understanding of politeness as ‘rapport management’ is employed as the framework for data analysis. The study draws on both audio-recordings of radiotelephony communication in role-play situations involving expert Malaysian controllers taking on roles as pilot and controller, as well as transcripts of real-life radiotelephony communication between Malaysian controllers and international pilots. The findings show that the interactions are primarily oriented to rapport-maintenance. The linguistic devices for rapport management include justifications, terms of address, conventionally polite expressions such as ‘please’, modals, and conditional language use. Rapport management is shown to help foster shared mindfulness and team thinking between controllers and pilots.

Multiple use of an industrial‐distributed control system in control engineering education

AbstractThe paper demonstrates how a four‐tank laboratory process equipped with a modern distributed control system (DCS) is used in different control engineering laboratories for the undergraduate and graduate levels. This includes the utilization of commercial tools for DCS engineering as well as the design and commissioning of traditional and advanced control solutions. Using the same pilot plant and control system in different modules lowers the costs, allows the reutilization of results and enables an efficient laboratory organization. It also supports the process of learning the inner context of different process control related subjects. © 2011 Wiley Periodicals, Inc. Comput Appl Eng Educ 21: 313–321, 2013

Identification of Multimodal Pilot Models Using Ramp Target and Multisine Disturbance Signals

This paper investigates the extent to which target forcing functions consisting of multiple ramplike or steplike changes in target attitude can be used for identification of multimodal pilot models. The main question addressed is whether such signals provide enough excitation of the pilot-vehicle system to allow for reliable estimation of pilot model parameters from measured pilot control data. The compensatory control task from a previous human-in-the-loop experiment performed in a moving base flight simulator is used to define a typical multimodal pilot model identification problem. Using simulations of this control task, where different multisine and ramp target forcing function signals are used to excite the pilot-vehicle system (in addition to a multisine disturbance signal), the accuracy and consistency of pilot model estimation results are evaluated. It is found that both the bias and variance of the pilot model parameter estimates decrease with increasing ramp signal steepness. If the steepnesses of the ramps in the target signals are higher than 3 deg /s, estimation results are found to be more accurate than those obtained using a quasi-random target forcing function. This indicates that reliable pilot model identification results can be obtained using such ramp target forcing function signals.