Flight Motion Simulator Research Articles

Consideration of the problem of motion cueing along angular degrees of freedom on flight simulators

The object of research is motion cueing along angular degrees of freedom on flight simulators of non-maneuvering aircraft. One of the most problematic places is lack of statement and effective solution of the problem to ensure high-quality motion cues along angular degrees of freedom on flight simulators, which would correspond to motion cues along angular degrees of freedom in real flight with the same control actions. In the course of the research, on the basis of the peculiarities of human movement perception, a set of characteristic attributes of perception of motion cues is determined: character, direction, duration, intensity and time of motion perception (according to Gibson’s perception theory). Based on the system approach principles, the mathematical formulation of the solution to the problem of motion cueing along angular degrees of freedom on flight simulators of non-maneuvering aircraft is used. Such approach made it possible, taking into account the existing constructive resource of flight simulator motion system, to bring as close as possible motion cueing along angular degrees of freedom on flight simulators of non-maneuvering aircraft to motion cues along angular degrees of freedom in real flight with the same control actions. Due to this the character and direction of motion cues fully correspond to the real motion cues, the difference between the perception time of motion cues on airplane and simulator is minimal and meets the current requirements. The duration and intensity of the motion cue perception on simulator are proportional duration and intensity of motion cue perception on airplane. Such approach significantly improves the quality of training and retraining of pilots on flight simulators. Implementation of the developed problem formulation on aircraft simulators, in particular on An-74TK-200, showed its high efficiency. In the future, the proposed approach can be used on flight simulators of aircraft developed in Ukraine and modernization of operated flight simulators.

Robust model reference tracking control for high‐order descriptor linear systems subject to parameter uncertainties

AbstractThis paper investigates the robust model reference tracking control problem for high‐order descriptor linear systems (HODLS) subject to norm‐bounded parameter uncertainties. The problem is divided into two subproblems: a robust proportional plus derivative state feedback stabilization (RPPDSFS) problem and a robust feed‐forward compensation (RFFC) problem. In the presence of uncertainties, by using the controller consisting of RPPDSFS part and RFFC part, all the signals of the closed‐loop system are bounded. The latter is equivalent to seeking three coefficient matrices such that a series of linear matrix equations are satisfied, and simultaneously the effect caused by uncertainties is minimized. Based on the right coprime factorization, the RFFC problem is further converted into a minimization problem with a quadratic performance index and some linear constraints. Thereafter, a linear matrix equation that determines the optimal solution is achieved. The restrictive condition that the coefficient matrix of the augmented reference system is non‐defective is relaxed, which reduces the conservativeness. A numerical example and the application of a three‐axis dynamic flight motion simulator manifest the effectiveness and the practicability of the proposed algorithm.

Optimizing the utilization of structural resources of flight simulator motion systems

The object of the study is a six degrees-of-freedom motion system of the synergistic type of a flight simulator. The latter is the main technical means for training pilots and means of research and development of aircraft. The task of optimal utilization of its structural resources was solved, which provides an opportunity to improve the quality of motion cueing. The result is the developed method, which ensures optimal use of structural resources of motion systems of flight simulators. This is explained, first of all, by the use of the developed simplified operator for converting the movements of jacks into the movement of a motion system along individual degrees of freedom on the basis of quadratic approximation. Given this, it became possible to describe the coordinates of the centers of the axes of rotation of the motion system by cubic spline functions. Secondly, the solution of the task of estimating the structural resources of the motion system along linear degrees of freedom on the basis of the developed criterion was carried out by an effective modified method of the deformed polyhedron. This method combines the random search method in the first steps of the search and the gradient method in determining the global extremum. Thirdly, the problem of determining the dependence of the coordinates of the pitch and yaw axes along the pitch angle was stated and solved. Owing to the optimal utilization of the structural resources of motion systems, the coordinates of the axis of their rotation along pitch are as close as possible to the coordinate of the axis of the aircraft. Thus, the quality of motion cueing on the flight simulator is significantly increased and it is possible to use motion systems with shorter lengths of jacks, and therefore, to reduce the cost of their manufacture and operation

MATHEMATICAL MODEL OF STABLE EQUILIBRIUM OPERATION OF THE FLIGHT SIMULATOR BASED ON THE STEWART PLATFORM

This paper analyses the available mathematical models of flight simulators based on the Stewart platform. It was found that there is no model that describes the conditions for stable dynamic equilibrium operation of the Stewart platform as a function of a number of important motion parameters. In this context, a new physical model is proposed based on classical models of theoretical mechanics using the d’Alembert formalism, the concept of stable equilibrium of a mechanical system. This model mathematically separates the stable equilibrium of the flight simulator motion system from the general uniformly accelerated motion. The systems of equations obtained in the framework of the model connect the physical and geometrical parameters of the Stewart platform and make it possible to determine the reactions in the upper hinges of the platform support, the limit values of the position angles in the space of the base of the support of the Stewart platform, under which the condition of stable equilibrium operation of the Stewart platform is satisfied. The proposed physical model and the analytical relations obtained on its basis are of great practical importance: the operator controlling the operation of the Stewart platform-based flight simulator can control the range of parameters during training so as not to bring the flight simulator out of stable equilibrium.

Design of Hardware-in-the-loop Simulation System for Image-guided Missiles

This paper introduces a design method of a hardware-in-the-loop simulation system applied to a certain type of image-guided missile. By studying the characteristics of a certain type of image-guided missile, the working principle of the image-guidance system is analyzed, the mathematical simulation scheme and the hardware-in-the-loop simulation scheme are designed, and the working mechanism of RTX is analyzed. Established a real-time hardware-in-the-loop simulation system based on RTX+Windows, analyzed the delay of the simulation computer, the simulated launch control computer, the flight motion simulator and the image simulator, and finally integrated the flight data and missed target amount of the hardware-in-the-loop simulation test, and obtained the hardware-in-the-loop simulation system meets the requirements.

Modeling, control and experimental investigation of horizontal hydraulic flight motion simulator

Modeling, control and experimental investigation of horizontal hydraulic flight motion simulator

FEA based opto-mechanisms design and thermal analysis of a dynamic SFS with an ultra-long exit pupil distance

The dynamic star field simulator (SFS) reproduces the actual operating conditions for the star tracker (STR) to assess its performance along with the flight motion simulator (FMS) in the hard-ware-in-the-loop (HWIL) simulation. The exit pupil distance of a traditional SFS is extremely short, which limits its application to large FMSs. To project the liquid crystal on silicon (LCoS) output to the STR entrance pupil, a 1250 mm ultra-long exit pupil distance SFS, operating in the broad waveband of 450–900 nm, is designed and implemented. In this study, the opto-mechanisms design and thermal analysis of the SFS are evaluated. The detailed design for key assemblies is specifically addressed to suppress negative heat effects. From the finite element analysis (FEA) results under different thermal conditions, the Zernike coefficients of 16 deformed optical surfaces in the projection module are solved using singular value decomposition (SVD), and the temperature adaptability is verified using a ray-tracing software. The preliminary SFS assessment confirms the simplicity of manufacture and excellent performance. The closed-loop opto-mechanisms design significantly improves the SFS reliability and enhances its suitability for large FMS use.

An Experimental Study on Outer Frame Position Control of Hydraulic Flight Motion Simulator With Model Compensation

The hydraulic flight motion simulator (HFMS) is the key equipment for the hardware-in-the-loop simulation in the field of aerospace and has been widely used on occasions requiring high maneuverability and large power. However, three mismatched uncertainties, including nonlinear friction torque, unbalanced gravity torque, and unknown inertia, bring some certain difficulties for receiving the high-precision outer frame position control of the HFMS. In this article, first, by means of an ingenious experimental design, the coupled friction torque and gravity torque were identified separately. Subsequently, through combining the established mathematical model and identification results, an adaptive robust controller with model compensation was investigated in which adaptive controller is not only used to estimate unknown system parameters but also able to online correct identified parameters, and the robust controller is able to guarantee the stability of the whole system. Additionally, the zero bias of the servo valve was also introduced to assist controller implementation. Finally, experimental results show that by using the method of torque identification to improve the model accuracy, the burden of parameter adaptation and robust items can be effectively alleviated, and the high-precision outer frame position control of HFMS can be realized.

DESIGNING AN EVOLUTIONARY OPTIMAL WASHOUT FILTER BASED ON GENETIC ALGORITHM

This paper aims to design a reliable filter that can transform the actual motion of a flight simulator maneuver into a logical and understandable movement for its workspace. Motion cueing algorithms are used in scaling maneuvers to improve the user’s perception of real-world motion. As a unique algorithm, the washout-filter algorithm reduces the real motions where the user cannot understand the difference between the actual and simulated maneuvers. To design a proper washout filter, first, apply the inner ear model where humans can feel the motion to design a proper filter. The Otolith and semicircular systems were represented by two parts in this model. Second, an evolutionary theory based on a genetic algorithm is used to design a structure that minimizes human perception error and workspace boundaries. The issue is determining the coefficients in the model in order to create a high-performance flight simulator. The filtering algorithm, based upon the human vestibular model, compares human perception with flight simulator motion knowledge. The findings demonstrate an objective function that minimizes user perception error, and the flight simulator motion range can prepare a reliable washout filter for motion cueing.

Robust Terminal Sliding Mode Control on SE(3) for Gough–Stewart Flight Simulator Motion Platform with Payload Uncertainty

This work proposes a robust terminal sliding mode control scheme on Lie group space SE(3) for Gough–Stewart flight simulator motion systems with payload uncertainty. A complete dynamic model with geometric mechanical structures and a computer dynamic model built in the MATLAB/Simulink package are briefly presented. The robust control strategy on the Lie group SE(3) is applied at the workspace level to counteract the effects of imperfect compensation due to model simplification and payload uncertainty in flight simulator application. With exponential coordinates for configuration error and adjoint operator on Lie algebra se(3), the robust control strategy is designed to guarantee almost global finite-time convergence over state space through the Lyapunov stability theory. Finally, a describing function and a step acceleration response to characterize the performance of a flight simulator motion base are employed to compare the robustness performance of the proposed controller on SE(3) with the conventional terminal sliding mode controller on Cartesian space. The comparison experimental results verify that the proposed controller on SE(3) provides better robustness than the conventional controller on Cartesian space, which means higher bandwidth in two degrees of freedom and faster response with smaller tracking error in six degrees of freedom.

6DOF nonlinear control loading system for a large transport aircraft simulator

PurposeFlight simulators are one of the noticeable breakthroughs in aerospace engineering. One of the main compartments of flight simulators is its control loading system (CLS). The CLS functions as a generator of virtual aerodynamic control-loads over control columns of a simulator. This paper aims to present the design of a high-fidelity six six degrees of freedom (6DOF) nonlinear CLS for the Boeing-747 aircraft simulator.Design/methodology/approachAn introduction to CLS for flight motion simulators are first recapitulated. Afterward, the commanding devices are explained through schematics available in an engineering sense. This paper then presents in detail, the active control loading strategy and hardware design for the CLS, while also introducing the aerodynamic model structure. The satisfactory computer numerical simulations are presented before the paper ends up in concluding remarks.FindingsThe multiple input multiple output (MIMO) 6DOF nonlinear CLS for Boeing-747 flight simulator has been successfully developed. The outcome of computer simulations in real-time verifies practicality of the design strategy. The research presented in this paper could be a simple roadmap for prototyping high-fidelity 6DOF nonlinear CLS for flight motion simulators.Originality/valueThe available control architecture and hardware technologies cannot enable a high-fidelity load realization in a CLS. The existing research has not yet presented a 6DOF nonlinear MIMO CLS architecture along with the underlying controller setup for a high-fidelity load realization. In this paper, the design of a high-fidelity 6DOF nonlinear MIMO CLS for flight simulator of a large transport aircraft has been accomplished.

Experimental validation of a practical nonlinear control method for hydraulic flight motion simulator

The hydraulic flight motion simulator (HFMS), as a key equipment for hardware-in-the-loop (HWIL) simulation in the field of aerospace, is required to have the ability to accurately simulate the aircraft attitude in the laboratory. However, three model uncertainties including nonlinear friction torque, unbalanced gravity torque and time-varying inertia existing in the outer frame of the HFMS at the same time become a main obstacle to achieving its high-precision position control effect. In this paper, according to identification results of friction torque and gravity torque from experiments, combining with simulation result of time-varying inertia of the outer frame from virtual prototype, a disturbance-observer-based nonlinear robust controller with the model compensation was designed on the basis of the mathematical model. Here, since the model compensation has eliminated the main mismatched uncertainties, dual disturbance observers are only necessary to suppress unmodeled mismatched uncertainties and matched uncertainties. Furthermore, the zero bias of the servo valve was also considered to help controller implementation. Finally, the effectiveness and the practicability of the proposed control method were validated by comparative experiments, which demonstrates that the proposed control method is promising and can be applied in the high-precision position control for the HFMS.

Benchmarking cEEGrid and Solid Gel-Based Electrodes to Classify Inattentional Deafness in a Flight Simulator.

Transfer from experiments in the laboratory to real-life tasks is challenging due notably to the inability to reproduce the complexity of multitasking dynamic everyday life situations in a standardized lab condition and to the bulkiness and invasiveness of recording systems preventing participants from moving freely and disturbing the environment. In this study, we used a motion flight simulator to induce inattentional deafness to auditory alarms, a cognitive difficulty arising in complex environments. In addition, we assessed the possibility of two low-density EEG systems a solid gel-based electrode Enobio (Neuroelectrics, Barcelona, Spain) and a gel-based cEEGrid (TMSi, Oldenzaal, Netherlands) to record and classify brain activity associated with inattentional deafness (misses vs. hits to odd sounds) with a small pool of expert participants. In addition to inducing inattentional deafness (missing auditory alarms) at much higher rates than with usual lab tasks (34.7% compared to the usual 5%), we observed typical inattentional deafness-related activity in the time domain but also in the frequency and time-frequency domains with both systems. Finally, a classifier based on Riemannian Geometry principles allowed us to obtain more than 70% of single-trial classification accuracy for both mobile EEG, and up to 71.5% for the cEEGrid (TMSi, Oldenzaal, Netherlands). These results open promising avenues toward detecting cognitive failures in real-life situations, such as real flight.

High dynamic output feedback robust control of hydraulic flight motion simulator using a novel cascaded extended state observer

High dynamic tracking performance is a key technical index of hydraulic flight motion simulator (HFMS). However, the strong nonlinearities, various model uncertainties and measurement noise in hydraulic actuation systems limit the high dynamic performance improvement. In this paper, the outer axis frame of a HFMS is taken as a case study and its nonlinear dynamic model with consideration of strong nonlinearities, matched and mismatched uncertainties is established. A novel cascaded extended state observer (ESO) is proposed to estimate the unavailable system states to avoid the adverse effect of measurement noise on control performance. Meanwhile, the designed cascaded ESO also produces estimates of matched and mismatched uncertainties. Then, an output feedback robust controller (OFRC) is proposed by integrating the cascaded ESO with a robust integral of the sign of the error (RISE) feedback based on the backstepping framework. The proposed controller achieves compensation of both matched and mismatched model uncertainties in an output feedback form. Theoretical analysis indicates that the proposed OFRC ensures the boundedness of all closed-loop system signals in the presence of matched and mismatched time-varying model uncertainties. Excellent asymptotic tracking performance can also be obtained when the model uncertainties are time-invariant. Comparative experimental results show that the proposed OFRC achieves significant performance improvement compared with the extensively employed PI control with velocity feedforward (VFPI).

MV-22B Short Takeoff and Minimum Run-On Landing Tests Aboard Nimitz-Class Ships

Tiltrotor aircraft ship suitability and envelope expansion testing aboard a U.S. Navy aircraft carrier is discussed. The purpose was to validate and expand day/night vertical launch and recovery wind envelopes, and the development of short takeoff and minimum run-on landing wind envelopes. The preparation phase incorporated a six-degree-of-freedom motion flight simulator to evaluate flight dynamics prior to on-shore testing using V-22 developmental and production aircraft. The short takeoff and minimum run-on landing testing totaled 12.3 flight hours with 33 takeoffs and 32 landings. The gross weights ranged from 51,000 to 57,000 lb with of relative wind from 0 to 45 kt. The test pilots provided assessments of handling and flying qualities throughout the maneuvers using the deck interface pilot effort scale. Predictability tests were required to determine the pilot’s ability to land within the defined touchdown zone and speeds for safely stopping within the braking zone. The results show the integrated nature of shipboard flight testing and the process of combining pilot workload ratings, control strategies, and aerodynamic analyses to field a needed capability.

A parametric approach of partial eigenstructure assignment for high-order linear systems via proportional plus derivative state feedback

<abstract><p>In this paper, a partial eigenstructure assignment problem for the high-order linear time-invariant (LTI) systems via proportional plus derivative (PD) state feedback is considered. By partitioning the open-loop system into two parts (the altered part and the unchanged part) and utilizing the solutions to the high-order generalized Sylvester equation (HGSE), complete parametric expressions of the feedback gain matrices of the closed-loop system are established. Meanwhile, a group of arbitrary parameters representing the degrees of freedom of the proposed method is provided and optimized to satisfy the stability of the system and robustness criteria. Finally, a numerical example and a three-axis dynamic flight motion simulator system example with the simulation results are offered to illustrate the effectiveness and superiority of the proposed method.</p></abstract>

Piloted Flight Simulation of Helicopter Recovery to the Queen Elizabeth Class Aircraft Carrier

This Paper describes how flight simulation has been used to investigate helicopter recovery operations to the deck of HMS Queen Elizabeth, the United Kingdom’s new aircraft carrier. A helicopter flight simulation environment has been developed in which the unsteady airflow over the ship has been created using full-scale computational fluid dynamics. A six-degree-of-freedom motion flight simulator has been used to conduct real-time piloted deck landings where a helicopter flight dynamics model representative of a Sikorsky SH-60B Seahawk helicopter was recovered to the designated rotorcraft landing spots toward the stern of the ship. A test pilot was instructed to land the helicopter and to give workload ratings for the difficulty of the task when flying in relative winds from Ahead, and 45 deg and 90 deg from starboard. The workload ratings, along with the corresponding pilot control activity and helicopter positional accuracy, are discussed in relation to the airflow to which the helicopter was subjected. The Paper demonstrates how flight simulation could be used to support flight trials and helicopter clearance activities but also notes that real-world trials data are needed to compare with the simulations before the techniques can be beneficially deployed.

Development of Cueing Algorithm Based on “Closed-Loop” Control for Flight Simulator Motion System

The classical washout algorithm had fixed gains and manually constructed filters, so that it led to poor adaptability. Furthermore, it lost the sustained acceleration cues of high- and mid-frequency in cross-over (tilt-coordination) channel, and the acceleration of cross-over frequency was also limited by angular velocity limiter, so the false cues in flight simulation process were clearly perceived by pilots. The paper studied the characteristics of the classical washout algorithm and flight simulator motion platform, tried to redesign the source of cross-over acceleration channel and translation acceleration channel, and transferred the part of cross-over acceleration that was unsimulated sustained acceleration to translation acceleration channel. Comparisons were mainly made between classical washout algorithm and revised algorithm in a longitudinal/pitch direction. The evaluation was based on the implementation of human vestibular perception system. The results demonstrated that the revised algorithm could significantly reduce the phase lag, and improved the spikes tracking performance. Furthermore, sensory angular velocity and the error of sensory acceleration were strictly controlled within the threshold of human perception system, and the displacement was a little broader than the classical washout algorithm. Therefore, it was proved that the new algorithm could diminish the filters parameters and heighten the self-adaptability for the washout algorithm. In addition, the magnitude of false cues was remarkably reduced during flight simulator, and the workspace utilization of the motion platform was developed by “closed-loop” control system.

Motion Fidelity Requirements for Helicopter-Ship Operations in Maritime Rotorcraft Flight Simulators

The research presented in this paper is part of a longer-term project to develop overall fidelity requirements for simulated helicopter shipboard operations to inform and support first-of-class flight trials. The paper reports the results of motion cueing assessment and optimization research, conducted in a six-degree-of-freedom motion flight simulator, to develop simulator motion drive laws capable of providing high-fidelity motion cueing for simulated shipboard operations. To do this, a novel objective technique, vestibular motion perception error (VMPE), has been developed. The technique was used to optimize the motion cues for simulated helicopter landings on a naval single-spot destroyer at different wind and sea-state conditions. New simulator motion tuning sets were derived offline and then tested experimentally to compare the objective VMPE predictions with subjective assessments from a test pilot. Results show the influence of different motion cues, airwake conditions, and ship motion states on the pilot’s overall perception of self-motion, control strategy, task performance, and workload. It was found that high-fidelity motion cueing becomes more desirable for the pilot at higher wind conditions and sea states, for which an “Optimized” motion setting was obtained using the new technique. Moreover, the use of an “Optimized” motion setting generated by the VMPE methodology resulted in reduced pilot workload, leading to improved simulated maritime helicopter operational capability. The technique provides a rational methodology for motion tuning, which could be applied in training and engineering simulators.

Inattentional deafness to auditory alarms: Inter-individual differences, electrophysiological signature and single trial classification

Inattentional deafness can have deleterious consequences in complex real-life situations (e.g. healthcare, aviation) leading to miss critical auditory signals. Such failure of auditory attention is thought to rely on top-down biasing mechanisms at the central executive level. A complementary approach to account for this phenomenon is to consider the existence of visual dominance over hearing that could be implemented via direct visual-to-auditory pathways. To investigate this phenomenon, thirteen aircraft pilots, equipped with a 32-channel EEG system, faced a low and high workload scenarii along with an auditory oddball task in a motion flight simulator. Prior to the flying task, the pilots were screened to assess their working memory span and visual dominance susceptibility. The behavioral results disclosed that the volunteers missed 57.7% of the auditory alarms in the difficult condition. Among all evaluated capabilities, only the visual dominance index was predictive of the miss rate in the difficult scenario. These findings provide behavioral evidences that other early cross-modal competitive process than top down modulation process could account for inattentional deafness. The electrophysiological analyses showed that the miss over the hit alarms led to a significant amplitude reduction of early perceptual (N100) and late attentional (P3a and P3b) event-related potentials components. Eventually, we implemented an EEG-based processing pipeline to perform single-trial classification of inattentional deafness. The results indicate that this processing chain could be used in an ecological setting as it led to 72.2% mean accuracy to discriminate missed from hit auditory alarms.