Model predictive control architecture for rotorcraft inverse simulation

A novel inverse simulation scheme is proposed for applications to rotorcraft dynamic models. The algorithm adopts an architecture that closely resembles that of a model predictive control scheme, where the controlled plant is represented by a high-order helicopter model. A fast solution of the inverse simulation step is obtained on the basis of a lower-order, simplified model. The resulting control action is then propagated forward in time using the more complex one. The algorithm compensates for discrepancies between the models by updating initial conditions for the inverse simulation step and introducing a simple guidance scheme in the definition of the tracked output variables. The proposed approach allows for the assessment of handling quality potential on the basis of the most sophisticated model, while keeping model complexity to a minimum for the computationally more demanding inverse simulation algorithm. The reported results, for an articulated blade, single main rotor helicopter model, demonstrate the validity of the approach

Development of a Generic Helicopter Mathematical Model for Application to Inverse Simulation. Internal Report No. 9216

This paper describes the development of a non-linear, generic mathematical model of a single main and tail rotor helicopter suitable for use in an inverse simulation. Multiblade representations of the main and tail rotors are used, each blade being assumed rigid and to have constant chord and profile. The flow around the blades is assumed to be steady and incompressible allowing two-dimensional aerodynamic theory to be applied in calculating the blade aerodynamic loads. Main rotor flapping is modelled by use of a centre-spring representation of the rotor disc. The fuselage, tailplane and fin aerodynamic forces and moments from were obtained from ”look-up” tables supplied by the Defence Research Agency (Bedford). The rotor model was derived using the computer algebra package, Mathematica that has allowed many of the terms normally disregarded for simplicity, to be retained. The derivation of the rotor model is dealt with in detail. Results are given for vehicle trim calculations and non-linear time responses to control input as well as some inverse simulations

Helicopter Inverse Simulation Incorporating an Individual Blade Rotor Model

No abstract available

On the Development of Multiple Manoeuvre Mission Sequences for Inverse Simulation. Internal Report No. 9802

As part of the continuing programme of work and collaboration between the Defence Evaluation and Research Agency (DERA) and Glasgow University (GU), the author was invited to attend the final phase of flight simulation trials entitled ‘TWINS’ at DERA, Bedford; using the Advanced Flight Simulator (AFS) large motion system. The precise nature and details of the five-day trial are given in [1] but the main thrust of the trial was essentially divided into two areas: 1. The simulation of American Design Standard (ADS) Mission Task Elements (MTEs) using a software image database of Coltishall airfield with the appropriate ADS-33 visual cues. 2. The simulation of a mission sequence based on the Haxton Down software image database which comprised fourteen individual tasks. The tasks were either based on ADS MTEs or Nap-of-the-earth (NOE) flight. A full description of the manoeuvre elements is given in Appendix A of [1]. The inverse simulation package HELINV at GU contains a library of manoeuvres based both on ADS MTEs and NOE flight. However, the manoeuvres are separate and individual and until recently it was not possible to run a simulation of combinations of two or more manoeuvres. A request was put forward to develop a method whereby it was possible to choose several elements (MTE or NOE) from the manoeuvre menu and piece them together to form what has been termed a ‘mini-mission sequence’ and then inverse simulate the mission as a whole. This report describes that development and presents the results from several simulated mission runs

The Estimation of Precision Pilot Model Parameters Using Inverse Simulation. Internal Report No. 9706

The practice of using mathematical models to simulate pilot behaviour in one-axis stabilisation tasks is a well known conventional simulation problem. In this report a system is developed whereby a mathematical model of a pilot is used as the controller of a rudimentary helicopter model. The main differences between this and other similar scenarios that have been found in the literature are that firstly, inverse simulation is used to provide results that are used as the forcing functions in the model of the pilot/helicopter system, and secondly a constrained optimisation routine is utilised to obtain values for the parameters within the pilot model itself. It will be shown that as the pilot is required to fly different manoeuvres, defined by standards set by the United States Army, or indeed if the severity of the set manoeuvres is varied, the pilot is required to adjust certain human parameters to fly the manoeuvre in a superlative manner. The report considers initially the pilot and helicopter models and subsequently analyses the system as a whole, illustrating how the pilot model can change depending on the circumstances

The Estimation of Helicopter Pilot Workload Using Inverse Simulation. Internal Report No. 9624

In the first instance this report describes the means by which inverse simulation can be used as a pilot workload estimation tool. An alternative approach to defining the mathematical model of the ADS-33 Rapid Side-step Mission Task Element (MTE) is presented and is used to drive various inverse simulation runs. Studies are conducted into three varying aggression side-step MTEs and the comparison of two dissimilar helicopter configurations based on the Westland Lynx, simulated using the same side-step. It is shown how the resulting time-histories and quickness charts can be utilised in pilot workload and handling qualities estimation. A third quickness parameter associated with the lateral cyclic stick displacements required to fly the side-step MTEs is introduced and is shown to be capable of discriminating between the pilot workload required for each side-step and vehicle configuration. The latter study in the report presents the preliminary findings on the effects of workload by firstly, introducing a Stability and Control Augmentation System and secondly investigating the effects of altering the value of the lateral cyclic actuator time constant

The Estimation of Helicopter Pilot Workload Using Inverse Simulation: Longitudinal Manoeuvre Analysis. Internal Report No. 9625

In the preceding report the concept of estimating pilot workload using inverse simulation was introduced. The report examined the ADS-33C defined Rapid Side-step Mission Task Element (MTE), and illustrated how various quickness parameters could be obtained from the lateral cyclic pitch and stick displacement time histories. These quickness parameters were plotted on charts and it was shown how the resulting plots could be used to discriminate between two dissimilar helicopter configurations, or identify which manoeuvres were more aggressive and would probably lead to a higher level of workload being placed upon the pilot. The intention of this report is to provide a supplementary study to the previous one by analysing another linear repositioning manoeuvre, the Rapid Acceleration / Deceleration or Quick-hop MTE. The longitudinal cyclic channel will be investigated in terms of pitch and stick displacement and the equivalent quickness parameters calculated and plotted on charts. A final study mirroring the previous one, on control system influence by the introduction of a Stability and Control Augmentation System, (SCAS) and the alteration of the longitudinal cyclic actuator constant will also be carried out

The Estimation of Helicopter Pilot Workload Using Inverse Simulation. Internal Report No. 9624

In the first instance this report describes the means by which inverse simulation can be used as a pilot workload estimation tool. An alternative approach to defining the mathematical model of the ADS-33 Rapid Side-step Mission Task Element (MTE) is presented and is used to drive various inverse simulation runs. Studies are conducted into three varying aggression side-step MTEs and the comparison of two dissimilar helicopter configurations based on the Westland Lynx, simulated using the same side-step. It is shown how the resulting time-histories and quickness charts can be utilised in pilot workload and handling qualities estimation. A third quickness parameter associated with the lateral cyclic stick displacements required to fly the side-step MTEs is introduced and is shown to be capable of discriminating between the pilot workload required for each side-step and vehicle configuration. The latter study in the report presents the preliminary findings on the effects of workload by firstly, introducing a Stability and Control Augmentation System and secondly investigating the effects of altering the value of the lateral cyclic actuator time constant

Mathematical Models of Three Slalom Types for Inverse Simulation. Internal Report No. 9716

In the absence of adequate data from flight trials, a request was put forward for the development of mathematical models of various configurations of slalom manoeuvres. The models were to be based on the existing manoeuvres as flown by United States Army, specified in ADS-33D, the Defence Evaluation and Research Agency (DERA), Bedford and the German Aerospace Research Establishment (DLR), the definitions of which have been stated previously by the DERA. This report describes the development of the manoeuvres and their utilisation within the inverse simulation package HELINV, at Glasgow University. It will be shown that data acquired from the inverse simulations of these manoeuvres can be used in workload calculations using software developed by Glasgow Caledonian University, and this process in itself will verify or disprove the validity of the manoeuvres that have been developed. Although there is potentially no real substitute for genuine data obtained from actual flight trials, it is hoped that these slalom simulations will prove to be a useful tool when used in conjunction with the inverse simulation, workload estimation metrics and handling qualities software

The principles and practical application of helicopter inverse simulation

Inverse simulation is a technique whereby the control actions required for a modelled vehicle to fly a specified manoeuvre can be established. In this paper the general concepts of inverse simulation are introduced, and an algorithm designed specifically to achieve inverse simulation of a single main and tail rotor helicopter is presented. An important element of an inverse simulation is the design of the input functions i.e. manoeuvre definitions, and the methods used are also detailed. A helicopter mathematical model is also discussed along with the validation and verification of the inverse simulation. Finally, the applicability of the method is demonstrated by illustration of its use in two flight dynamics studies