Development of a Generic Time-to-Contact Pilot Guidance Model

The time-to-contact ττ theory posits that purposeful actions can be conducted by coupling the actor’s motion onto the so-called ττ guides generated internally by their central nervous system. Although significant advances have been made in the application of ττ for flight control purposes, little research has been conducted to investigate how pilots are able to adapt their ττ-guidance strategy to different aircraft dynamics, or how a ττ-guide-based pilot–aircraft model might be used to represent control behavior. This paper reports on the development of such a model to characterize the adaptation of pilot guidance to variations in aircraft dynamics using data obtained from a clinical pilot-in-the-loop flight simulation experiment. The results indicate that pilots tend to maintain a constant coupling between the dynamic system’s motion and the ττ guide across a range of different configuration parameters. Simultaneously, the pilot modulates the guidance maneuver period to adapt to these different aircraft dynamics that result in changes in workload. Modeling the complete pilot stabilization and guidance function as a regulator plus inverter yields good comparative results between the pilot–aircraft model and simulator trajectory data, and it supports the hypothesis that the following ττ-based guidance strategies suppress an aircraft’s natural dynamics

A Virtual Engineering Approach to the Ship-Helicopter Dynamic Interface; a decade of modelling and simulation research at The University of Liverpool

This paper reviews some of the research that has been carried out at the University of Liverpool where the Flight Science and Technology Research Group has developed its Heliflight-R full-motion research simulator to create a simulation environment for the launch and recovery of maritime helicopters to ships. HELIFLIGHT-R has been used to conduct flight trials to produce simulated Ship-Helicopter Operating Limits (SHOLs). This virtual engineering approach has led to a much greater understanding of how the dynamic interface between the ship and the helicopter contributes to the pilot's workload and the aircraft's handling qualities and will inform the conduct of future real-world SHOL trials. The paper also describes how modelling and simulation has been applied to the design of a ship's superstructure to improve the aerodynamic flow field in which the helicopter has to operate. The superstructure aerodynamics also affects the placement of the ship's anemometers and the dispersion of the ship's hot exhaust gases, both of which affect the operational envelope of the helicopter, and both of which can be investigated through simulation

A Role for Virtual Engineering in Engineering Skills Development

The paper will address how the Problem-Based-Learning (PBL) approach developed at Liverpool for undergraduate and graduate students has been extended to the continued professional development (CPD) of practising engineers. As the complexity of engineering systems grows, engineers increasingly need to be able to use a range of tools to undertake synthesis and analysis, address affordability goals, and reduce risk as they work in the various phases of the engineering life-cycle. To assist engineers operate successfully within this product life-cycle, there have been significant developments in modelling and simulation tools. Integrating these tools in a Virtual Engineering (VE) environment allows engineers to examine potentially conflicting requirements within the different phases of the life-cycle, to develop a co-ordinated approach to requirements capture and product design through to identifying costly problems that might occur later in the development and operations phases. Technical skills development to use these tools is critical in this process. This paper presents the experiences, learning outcomes and lessons gleaned in the development and implementation of bespoke rotorcraft engineering training programmes at The University of Liverpool. The programmes were designed using a Problem Based Learning (PBL) framework where knowledge and skills are gained through solving problems. Four cases studies are presented in the paper, demonstrating how this PBL/VE approach has been used effectively in training programmes. Consideration is given to the future use of VE tools, together with some challenges for their successful application

Virtual Engineering in Skills Acquisition and Development in the Career of the Rotorcraft Engineer

As the complexity of engineering systems grows, engineers increasingly need to be able to use a range of tools in order to reduce the costs, and associated risks, as they work in the various phases of the engineering life-cycle. In order to help engineers operate successfully within this product lifecycle, there have been significant developments in modelling simulation tools. Integrating these tools in a Virtual Engineering (VE) environment allows engineers to examine the potentially conflicting requirements of the different phases of the life-cycle, to develop a co-ordinated approach to requirements capture and product design through to identifying potential costly problems that could occur later in the development and operations phases. Technical skills development to use these tools is key to this process. This paper presents the experiences, learning outcomes and lessons learned in the development and implementation of bespoke rotorcraft engineering training programmes. The programmes were designed using a Problem Based Learning (PBL) framework where knowledge and skills are gained through solving problems. Four cases studies are presented in the paper, demonstrating how this PBL/VE approach can be used in the training programmes. Consideration of the future use of VE tools is provided together with future challenges for their successful application

Progress in the development of unified fidelity metrics for rotorcraft flight simulators

Flight simulators are integral to the design/development, testing/qualification, training and research communities and their utilisation is expanding rapidly. The quantification of simulation fidelity underpins the confidence required for the use of flight simulation in design, to reduce real life testing, and to provide a safe environment for pilot training. Whilst regulatory simulator standards exist and new standards are in development, previous research has shown that current standards do not provide a fully quantitative approach for assessing simulation fidelity, even in a research environment. This paper reports progress on developments of the HELFLIGHT-R flight simulator at the University of Liverpool, and its subsequent use in a research project (Lifting Standards) aimed at creating new predicted and perceived measures of simulator fidelity, derived from handling qualities engineering. Results from flight tests on the National Research Council (Canada) Bell 412 ASRA research aircraft and HELIFLIGHT-R piloted simulation trials are presented to show the strong connection between handling qualities engineering and fidelity assessment. The issue of (pilot) perceived fidelity is examined and the development of new metrics discussed. Copyright (c) 2010 by the American Helicopter Society International, Inc. All rights reserved

The Need for Increased Fidelity in Flight Training Devices to address the ‘Rotorcraft Loss of Control Inflight’ problem

This paper examines the trends in rotorcraft accident statistics, particularly regarding Loss of Control In-flight accidents (LOC-I), with the aim of stimulating interest in new research relevant to this area. Despite recent safety initiatives, LOC-I rotorcraft accidents have been identified as a significant and growing contribution to accident rates. The fixed-wing commercial airline community faced a similar situation starting in the late 1990s and, through a coordinated international effort, developed a new training program to help reduce accident rates. Lessons learned from the fixed-wing work are presented to highlight the need for improved rotorcraft modeling tools to reduce rotorcraft accidents through higher-quality, simulator-based training programs. The findings from previous and ongoing rotorcraft modeling and simulation research are presented, and areas for further research are identified. A proposal is made in the paper for a workshop to bring together the key rotorcraft stakeholders to develop future steps in tackling rotorcraft LOC-I accidents

Rotorcraft modeling renovation for improved fidelity

Copyright © 2019 by the Vertical Flight Society. All rights reserved. The research reported in this paper examines both established and new system identification techniques for rotorcraft flight-model renovation. Flight behavior models based on legacy aircraft are often the starting point for a new design and the fidelity, or model accuracy, can be validated when data are gathered in early flight testing of the new prototype. As data flow in, so flight models can be improved in fidelity, eventually supporting certification, provided the correct physics are embodied. System identification has become an established method for enhancing fidelity and suggesting causal relationships between flight and flight-model mismatches and missing physics. The objectives of our investigation include extending current system identification methods to address nonlinear model structures, and establishing appropriate approximations to the complex rotorcraft aeromechanics required to enhance fidelity, including maneuver wake distortion effects. The research is focused on renovation using Liverpool’s FLIGHTLAB Bell 412 simulation model based on data gathered on the National Research Council’s Advanced Systems Research Aircraft. We build on earlier work using frequency-domain methods, ideally suited to linear model structures and flight conditions sufficiently stable to allow control sweep data to be gathered. For hover and low-speed flight, strong nonlinearities caused by rotor-wake effects and significant deviations from the trim conditions, require a different approach and the paper shows how a new time-domain approach enables model structures and the parameters to be identified incrementally

Vibration reduction for vision systems on board unmanned aerial vehicles using a neuro-fuzzy controller

In this paper, an intelligent control approach based on neuro-fuzzy systems performance is presented, with the objective of counteracting the vibrations that affect the low-cost vision platform onboard an unmanned aerial system of rotating nature. A scaled dynamical model of a helicopter is used to simulate vibrations on its fuselage. The impact of these vibrations on the low-cost vision system will be assessed and an intelligent control approach will be derived in order to reduce its detrimental influence. Different trials that consider a neuro-fuzzy approach as a fundamental part of an intelligent semi-active control strategy have been carried out. Satisfactory results have been achieved compared to those obtained by means of vibration reduction passive techniques

Fidelity enhancement of a rotorcraft simulation model through system identification

High fidelity modelling and simulation are prerequisites for ensuring confidence in decision making during aircraft design and development, including performance and handling qualities, control law developments, aircraft dynamic loads analysis, and the creation of a realistic simulation environment. The techniques of system identification provide a systematic framework for ‘enhancing’ a physics–based simulation model derived from first principles and aircraft design data. In this paper we adopt a frequency domain approach for model enhancement and fidelity improvement of a baseline FLIGHTLAB Bell 412 helicopter model developed at the University of Liverpool. Predictability tests are based on responses to multi–step control inputs. The techniques have been used to generate one, three, and six degree-of-freedom linear models, and their derivatives and predictability are compared to evaluate and augment the fidelity of the FLIGHTLAB model. The enhancement process thus involves augmenting the simulation model based on the identified parameters. The results are reported within the context of the rotorcraft simulation fidelity project, Lifting Standards, involving collaboration with the Flight Research Laboratory (NRC, Ottawa), supported with flight testing on the ASRA research helicopter

Investigation of rotorcraft-pilot couplings under flight-path constraint below the minimum-power speed

In some situations, closed loop control by the pilot can result in the combined pilot-aircraft system becoming marginally stable or even unstable. This can happen whether the pilot is controlling attitude or flight path. In this paper, an investigation into helicopter stability under flight-path constraint below the minimum-power speed is reported. The work provides a theoretical basis for flight path handling qualities criteria particularly for flight on the, so-called, back-side of the power curve. The research uses the theory of weakly coupled systems by partitioning the helicopter longitudinal dynamics to investigate three interacting subsystems – classically the surge mode, the phugoid mode and the heave mode. Under certain conditions, strong control of flight path or vertical speed is shown to drive the aircraft-pilot system unstable and a conflict is shown to exist between feedback gain values to guarantee stability of both the surge and the flight path motions. This conflict constitutes a potential source of adverse rotorcraft-pilot couplings. The problems are exacerbated in cases when the use of collective control is restricted. The phenomenon is explored in both ground based simulation and flight test to provide a verification of the theor