Novel Approach to Rotorcraft Simulation Fidelity Enhancement and Assessment

Lead Research Organisation: Liverpool John Moores University
Department Name: School of Engineering

Abstract

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.
 
Description In previous work at the University of Liverpool (UoL), a frequency domain renovation technique based on SID was developed to improve the fidelity of a FLIGHTLAB Bell 412 (F-B412) simulation model, and the identified model was compared with FLIGHT TEST data over a range of forward flight conditions. The flight test data are from trials conducted on the National Research Council's (NRC) ASRA Bell 412. A group of candidate SID derivatives (having a high impact on the fidelity 'cost-function' metrics) were used to improve the off-axis and cross-coupling response of the model. Although efficient in improving the fidelity of a simulation model, this tuning approach does not necessarily reveal the physics responsible for these modelling discrepancies. This work continues in Liverpool's awarded Rotorcraft test Simulator Fidelity (RSF) project aimed at developing a physics-based toolset for fidelity enhancement. As part of the RSF project, a new approach to SID in the time-domain is being developed and will be presented in this paper. We refer to this method as Additive System-IDentification (ASID), with the model parameters identified sequentially based on their contribution to the local dynamic response of the system, i.e. over a defined time range. One or more candidate parameters in a proposed model structure are identified using the primary response characteristic of the rotorcraft; others are then identified in a sequential manner. The initial studies have been conducted on both the nonlinear F-B412 response and flight test data for roll dynamics, using an equation-error process, to illustrate the effectiveness of the ASID approach, and to develop guidelines for the process. The results are very encouraging and outperforms that classical Stepwise Regression method.
Exploitation Route they can access the results and approach through the related publications
Sectors Aerospace, Defence and Marine,Transport
 
Description We used a technique called System Identification to find and fix issues with a simulation model of a Bell 412 helicopter created by Liverpool's FLIGHTLAB. We compared the simulation model with real-life measurements from the National Research Council's Advanced Systems Research Aircraft in Canada. After making improvements to the simulation model, we found that it matched well with the real-life measurements, particularly in terms of how the helicopter moves during flight. In addition to improving the simulation model, we also developed a new way to identify how different parts of the helicopter affect its movement during flight. This new approach helped us better understand how the helicopter behaves during larger maneuvers and allowed us to explore nonlinearities attributed to phenomena such as maneuver wake distortion and skew effects. Our work has been used by companies like Vertical Aerospace and Leonardo Helicopters to improve their understanding of flight dynamics. Vertical Aerospace is interested in applying our new heuristic approach to understand the flight dynamics of their newly developed X4 aircraft. Leonardo Helicopters has also used our methodology to analyze physical sources of deficiency relating to their models.
Sector Aerospace, Defence and Marine,Transport
Impact Types Policy & public services
 
Description Certification by Simulation for Rotorcraft Flight Aspects
Geographic Reach Europe 
Policy Influence Type Contribution to a national consultation/review
Impact The ROtorcraft Certification by Simulation (RoCS) project aims to explore the possibilities, limitations, and guidelines for best practices for the application of flight simulation to demonstrate compliance to the airworthiness regulations related to helicopters and tiltrotors. The results of the awarded project will be directly integrated in to the RoCS to improve the fidelity of a simulation aircraft model, and then to improve the fidelity of the overall simulation environment. The research sees the opportunity within RoCS for the European rotorcraft community to take the lead in the development of new standards for certification using simulation. The European Union Aviation Safety Agency (EASA), the aerospace safety policy maker in Europe, is also a project partner and they are of great interest in using these research outcomes for upgrading existing aircraft certification and compliance guidelines, e.g., CS29 to increase the safety.
 
Description D3.5RoCs
Geographic Reach Multiple continents/international 
Policy Influence Type Contribution to new or Improved professional practice
Impact The new guideline provides support to early adopters of Rotorcraft Certification by Simulation, including those who have considerable experience and expertise in the use of modelling and simulation in support of design and development. It is dedicated to helping the industry to accomplish fast certification with reduced risk and cost. The guideline is developed under the supervision of EASA and will be released as a general guideline for the European aerospace industry to partly replace the flight test hours by simulation. It also will be refereed in the other parts of the world since it is frontier research in aircraft modelling and simulation.
 
Description Certification by Simulation for Rotorcraft Flight Aspects
Amount € 3,000,000 (EUR)
Funding ID H2020-CS2-CFP08-2018-01 
Organisation European Commission H2020 
Sector Public
Country Belgium
Start 05/2019 
End 04/2022
 
Description IES\R3\193110 - International Exchanges 2019 Round 3
Amount £6,000 (GBP)
Funding ID IES\R3\193110 - International Exchanges 2019 Round 3 
Organisation Johns Hopkins University 
Sector Academic/University
Country United States
Start 05/2020 
End 03/2022
 
Title A New Heuristic Approach to Rotorcraft System Identification 
Description The new approach identifies the parameters of the flight model in an additive manner, based on their contribution to the local dynamic response of the system. This is in contrast to conventional approaches where parameter values are identified to minimize errors over an entire manoeuvre. In these early investigations, low-order rigid-body linear models have been identified and show good agreement with flight test data. The approach is extended to explore nonlinearities attributed to manoeuvre wake distortion and skew effects that emerge during larger manoeuvres. 
Type Of Material Improvements to research infrastructure 
Year Produced 2022 
Provided To Others? Yes  
Impact The research presents a robust tool for the academic community to conduct system identification based on physical information. It not only facilitates the capture of the physical system with a high degree of fidelity but also engenders the design of a control system with superior performance. In addition, the industry can leverage this innovative tool to reliably assess the trim, stability, and responses of a novel model and discern the outcomes from a physical standpoint. The tool is particularly salient in illuminating the intricacies arising from aerodynamic couplings and interference effects. Furthermore, the information derived from this approach can be utilized to prepare a model and enhance its fidelity, thereby serving as a potent mechanism for training and certification. 
URL https://doi.org/10.4050/JAHS.68.022005
 
Title Helicopter handling qualities: a study in pilot control compensation 
Description This study presents a novel metric that utilizes time-varying frequency-domain exposure to investigate the relationship between a pilot's subjective assessment, measured control activity, and task performance. By combining results from subjective and objective metrics for a range of mission task elements, compensation boundaries are proposed to predict and verify subjective assessments obtained using the Cooper-Harper Handling Qualities Rating scale. 
Type Of Material Improvements to research infrastructure 
Year Produced 2022 
Provided To Others? Yes  
Impact These findings contribute to a deeper understanding of the complex interplay between pilot perceptions, control activity, and task performance, and have implications for the design and evaluation of aircraft systems. 
URL https://doi.org/10.1017/aer.2021.87
 
Title Rotorcraft Lateral-Directional Oscillations: The Anatomy of a Nuisance Mode 
Description High fidelity rotorcraft flight simulation relies on the availability of a quality flight model that further demands a good level of understanding of the complexities arising from aerodynamic couplings and interference effects. One such example is the difficulty in prediction of the characteristics of the rotorcraft lateral-directional oscillation (LDO) mode in simulation. Achieving an acceptable level of the damping of this mode is a design challenge requiring simulation models with sufficient fidelity that reveal sources of destabilizing effects. This method is focused on using System Identification to highlight such fidelity issues using Liverpool's FLIGHTLAB Bell 412 simulation model and in-flight LDO measurements from the National Research Council's (Canada) Advanced Systems Research Aircraft. The simulation model was renovated to improve the fidelity of the model. 
Type Of Material Technology assay or reagent 
Year Produced 2020 
Provided To Others? No  
Impact The results show a close match between the identified models and flight test for the LDO mode frequency and damping. Comparison of identified stability and control derivatives with those predicted by the simulation model highlight areas of good and poor fidelity. 
 
Title Rotorcraft Simulation Fidelity Enhancement through Augmented Rotor Inflow 
Description The rotorcraft is a complex dynamical system that demands specialist modelling skills, and a high level of understanding of the aeromechanics arising from the main rotor wake and aerodynamic couplings. One such example is the difficulty predicting off-axis responses, particularly in hover and low-speed flight, associated with induced velocity variation through the rotor disk resulting from the rotor wake distortions. Various approaches have been developed to deal with this phenomenon but usually demand prerequisites of high levels of expertise and profound aerodynamic knowledge. The new and feasible approach aims to capture this wake distortion through an augmented inflow model. The proposed inflow model is coupled with a nonlinear simulation using the FLIGHTLAB simulation environment, and comparisons are made between the simulation results and flight test data from the National Research Council of Canada's Advanced System Research Aircraft in hover and low speed. 
Type Of Material Technology assay or reagent 
Year Produced 2020 
Provided To Others? No  
Impact Results show a good correlation of the proposed nonlinear model structure, demonstrated by its capability to closely match the time responses to multi-step control inputs from flight test. The results reported are part of ongoing research at Liverpool into rotorcraft simulation fidelity. 
 
Title Rotorcraft fidelity enhancement using 'additive' system identification 
Description In previous work at the University of Liverpool, a frequency domain renovation technique based on system identification (SID) was developed to improve the fidelity of a FLIGHTLAB Bell 412 (F-B412) simulation model, and the identified model was compared with FT data over a range of forward flight conditions. A group of candidate SID derivatives (having a high impact on the fidelity cost-function metrics) were used to improve the off-axis and cross-coupling response of the model. Although efficient in improving the fidelity of a simulation model, this tuning approach does not necessarily reveal the physics responsible for these modelling discrepancies. This work continues in the recently awarded Rotorcraft Simulator Fidelity (RSF) project10 aimed at developing a physics-based toolset for fidelity enhancement. As part of the RSF project, a new approach to SID in the time-domain is being developed and will be presented in this paper. We refer to this method as Additive System-IDentification (ASID), with the model parameters identified sequentially based on their contribution to the local dynamic response of the system, i.e. over a defined time range. One or more candidate parameters in a proposed model structure are identified using the primary response characteristic of the rotorcraft; others are then identified in a sequential manner. 
Type Of Material Improvements to research infrastructure 
Year Produced 2019 
Provided To Others? No  
Impact An initial study has been conducted for nonlinear roll dynamics, using an equation-error process. The results have shown that the new approach is superior than the classical Stepwise Regression approach for identifying the speed related derivatives. 
 
Title FLIGHTLAB Bell412 model 
Description A fully nonlinear and complex mathematical model has been developed for Bell412 aircraft in the FLIGHTLAB environment. The model has been validated against the real flight test data at Hover and 95 knots. All results show that the developed model has reached high fidelity. The model is also suitable for real time flight simulation. 
Type Of Material Computer model/algorithm 
Year Produced 2019 
Provided To Others? No  
Impact 1.) The high fidelity of the developed model guarantees the continuous research. 2.) Good results from this model lead to higher impact on the on-going NATO STO AVT-296 RTG3 and increase the position of UK as a key player in the rotorcraft field. 3.) Good research conducted on this qualified model makes it possible contributing more to RoCs project. The related results are more appropriate for being used the source and reference information for EASA to update the current aircraft Certification and Compliance design guidelines. 
 
Title FT1 
Description We conducted the first sortie flight test on May and September 2019 and gathered an amount of data at hover and 90knots. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
Impact This database can help to understand better the Dull-roll oscillation, that is one of key handling qualities index. In addition, the database can be used to build a high fidelity rotorcraft simulation model that can improve safety. 
 
Description AIRBUS Helicopters (Germany) 
Organisation Airbus Group
Department Airbus Helicopters
Country France 
Sector Private 
PI Contribution Airbus Helicopters has accumulated amounts of datasets that are crucial to building a high-fidelity aeroelastic rotor system to study the load problem during the transition phase. My research team will analyze these data using system identification technique developed from this EPSRC project. My team tend to develop a novel toolset to monitor the health of a rotor blade using SysID through investigation of its aeroelastic behaviour.
Collaborator Contribution The collaboration was only founded one month ago and therefore this is no contributions made yet. Airbus Helicopters will provide datasets that are crucial to building a high-fidelity aeroelastic rotor system. Moreover, they will provide the supervision of the PhD joined in this project.
Impact We submitted an EPSRC Doctoral Training Partnership (DTP) Application in Feburay 2022 and now we are waiting for the outcomes.
Start Year 2022
 
Description Collaboration with National Research Council of Canada 
Organisation National Research Council of Canada
Department Aerodynamics Laboratory
Country Canada 
Sector Public 
PI Contribution not suitable
Collaborator Contribution National Research Council of Canada's provides their Bell 412 Advanced Systems Research Aircraft for conducting flight test for the awarded research. These flight test data are one of factors guaranteeing the successful delivery of this project.
Impact So far we conducted the 1st flight test in October 2018 on the Bell 412 helicopter and the 2nd flight test has been scheduled and will occur June 2019.
Start Year 2018
 
Description EASA 
Organisation European Aviation Safety Agency
Country Germany 
Sector Public 
PI Contribution We work together to generate the guideline in support of certification is expected to commence well in advance of the certification campaign, and ideally should grow with the development of the different prototypes of a new aircraft in order to program well in advance the tests required to validate the FSM and include these in the development plans of a new aircraft. We applied the knowledge and skills from the EPSRC funded project to enhance this collaboration.
Collaborator Contribution EASA provided the necessary guidance and supports from the regulator's point of view.
Impact We are working together to generate the guideline in support of certification is expected to commence well in advance of the certification campaign, and ideally should grow with the development of the different prototypes of a new aircraft in order to program well in advance the tests required to validate the FSM and include these in the development plans of a new aircraft. We applied the knowledge and skills from the EPSRC funded project to enhance this collaboration. This guideline will be issued by EASA soon, possibly in the middle of this year.
Start Year 2020
 
Description Johns Hopkins University 
Organisation Johns Hopkins University
Country United States 
Sector Academic/University 
PI Contribution The team will analyse, model and predict upcoming motor events, investigate control laws, and develop new algorithms to control flying robots. This can be broken down into two parts. Firstly, we will analyse bat trajectory and echolocation data and seek to provide powerful explanations as to how the animal's path planning and manoeuvring strategies are achieved. Specifically, we will investigate what kinds of guidance mechanisms and control variables are implemented to achieve rapid and agile manoeuvres while maintaining safe margins. Secondly, our research will establish a theoretical guidance framework for biologically inspired flight robotics in cluttered and dark environments.
Collaborator Contribution The team will use the empirical data collected and shared from experiments took place in a specialized multimedia facility at Johns Hopkins University (JHU) in which free-flying echolocating bats engaged in obstacle avoidance, target interception and landing tasks.Professor Moss will come to visit the LJMU at a certain stage for guiding the progress of the proposed research.
Impact The project has been affected and delayed by Covid. This collaboration is multi-disciplinary and covers the fields of Biology, Aeronautics, and Drones,
Start Year 2020
 
Description leonardo helicopters 
Organisation Leonardo S.p.A.
Country Italy 
Sector Private 
PI Contribution We will use the methodology developed in the EPSRC funded RSF project to improve the AW109 FLIGHTLAB model provided by Leonardo S.p.A.
Collaborator Contribution Leonardo S.p.A. will provide AW109 FLIGHTLAB model and full sets of flight data for usage.
Impact not yet
Start Year 2019
 
Title ASID 
Description The new approach identifies flight model parameters 'additively', based on their contribution to the local dynamic response of the system, in contrast with conventional approaches where parameter values are identified to minimize errors over a whole manoeuvre. In these early investigations, identified low-order rigid-body linear models show good comparison with flight test data. The approach is extended to explore nonlinearities attributed to so-called manoeuvre wake distortion and skew effects emerging in larger manoeuvres. 
Type Of Technology New/Improved Technique/Technology 
Year Produced 2022 
Impact The research provides a powerful tool for academia to conduct system identification based on physical information. This not only can capture the physical system at a high level of fidelity but also lead to the design of a control system with better performance. The industry can use this new tool to reliably access the trim, stability, and responses of a new model and interpret the results from the physical point of view. It can lead to a good level of understanding of the complexities arising from aerodynamic couplings and interference effects Moreover, the information extracted from this approach can be used to prepare a model and improve its fidelity to serve the purpose of training and certification. 
URL https://doi.org/10.4050/JAHS.68.022005
 
Title Rotorcraft Lateral-Directional Oscillations: The Anatomy of a Nuisance Mode 
Description High fidelity rotorcraft flight simulation relies on the availability of a quality flight model that further demands a good level of understanding of the complexities arising from aerodynamic couplings and interference effects. One such example is the difficulty in prediction of the characteristics of the rotorcraft lateral-directional oscillation (LDO) mode in simulation. Achieving an acceptable level of the damping of this mode is a design challenge requiring simulation models with sufficient fidelity that reveal sources of destabilizing effects. This method is focused on using System Identification to highlight such fidelity issues using Liverpool's FLIGHTLAB Bell 412 simulation model and in-flight LDO measurements from the National Research Council's (Canada) Advanced Systems Research Aircraft. The simulation model was renovated to improve the fidelity of the model. 
Type Of Technology New/Improved Technique/Technology 
Year Produced 2020 
Open Source License? Yes  
Impact The results show a close match between the identified models and flight test for the LDO mode frequency and damping. Comparison of identified stability and control derivatives with those predicted by the simulation model highlight areas of good and poor fidelity. 
 
Title Rotorcraft Simulation Fidelity Enhancement through Augmented Rotor Inflow 
Description The rotorcraft is a complex dynamical system that demands specialist modelling skills, and a high level of understanding of the aeromechanics arising from the main rotor wake and aerodynamic couplings. One such example is the difficulty predicting off-axis responses, particularly in hover and low-speed flight, associated with induced velocity variation through the rotor disk resulting from the rotor wake distortions. Various approaches have been developed to deal with this phenomenon but usually demand prerequisites of high levels of expertise and profound aerodynamic knowledge. The new and feasible approach aims to capture this wake distortion through an augmented inflow model. The proposed inflow model is coupled with a nonlinear simulation using the FLIGHTLAB simulation environment, and comparisons are made between the simulation results and flight test data from the National Research Council of Canada's Advanced System Research Aircraft in hover and low speed. 
Type Of Technology New/Improved Technique/Technology 
Year Produced 2020 
Open Source License? Yes  
Impact Results show a good correlation of the proposed nonlinear model structure, demonstrated by its capability to closely match the time responses to multi-step control inputs from flight test. The results reported are part of ongoing research at Liverpool into rotorcraft simulation fidelity. 
 
Description ERtalk 2021 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Around 100 international academic and senior industrial players attended my talk on using simulation for certification. I presented a system identification based approach to improve the fidelity of a simulation model. The aududices showed great interest and triggered quite a few questions.
Year(s) Of Engagement Activity 2021
URL https://www.youtube.com/watch?v=OO3wU-bB7kw&t=497s
 
Description MSc System Identificaiton Module 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact 27 postgraduate students attended the Introduction on System Identification. The lectures triggered a lot of interesting questions and discussions in this field. A few students commented that they will use this technique in some industrial areas such as verification and validation of the quality of an aircraft.
Year(s) Of Engagement Activity 2021,2022
 
Description NATO STO AVT-296 RTG activity 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact The research is directly contributing to a NATO STO AVT-296 RTG3 entitled "Rotorcraft Flight Simulation Model Fidelity Improvement and Assessment" led by the US Army Aviation Development Directorate. This AVT consists of the key players of rotorcraft research in the world, e.g., US Army, Sikorsky Aircraft Corporation, DLR etc. The work of this awarded project has attracted significant interest of the partners.
Year(s) Of Engagement Activity 2018,2020
 
Description NATO-AVT Panel 296 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact The Applied Vehicle Technology (AVT) Panel of the NATO Science and Technology Organization (STO) has recently engaged a Research Task Group on the topic of rotorcraft flight simulation model fidelity. This group aimed to explore a comprehensive set of methods for flight mechanics simulation fidelity enhancement, including training simulation applications. Particular effort was also directed to the metrics used for simulation fidelity model assessment as suitable for the final intent of the model.
Year(s) Of Engagement Activity 2018,2020,2021
 
Description Verification & Validation: Metrics for the Qualification of Simulation Quality 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact an Exploratory Group under the GARTEUR Group of Responsables Helicopter (GoR-HC) with the aim to define metrics for the qualification of the quality of rotorcraft simulations, as a contribution to the Verification and Validation (V&V) process of numerical codes.
The Exploratory Group will therefore consider the following activities to be performed within the timescale appropriate to an Action Group programme:
1. to review the current status of methods and metrics that may already exist to qualify a simulation quality;
2. to make a list of relevant information (physical quantities) that would be well suited for the qualification of simulation quality in the field of rotorcraft (belonging to different disciplines);
3. to consider how a Garteur activity could be linked to CleanSky proposal (under evaluation) on Certification by Simulation of Rotorcraft;
4. to apply the methodologies to the physical quantities and comparisons for which data already exist;
5. to propose metrics that could define the quality of such comparisons;
6. to cost a proposal for the work, showing partner workshare and financial (manpower and other costs) contributions.
Year(s) Of Engagement Activity 2019