Further Developments to the HFM Toolbox

Abstract

The Hardware in the Loop Facility Model (HFM) is an engineering-level simulation model of a generic Hardware in the Loop (HWIL) simulation system. In fact, it could be viewed as a simulation of a simulation. In the past, the model has been used to study the influence of hardware limitations on experimental outcomes of a HWIL simulation and has been instrumental in facilitating the calculation of error bounds on those outcomes. However, to modify inputs to the simulation and vary HWIL scenarios required intimate and detailed knowledge of the code. Addressing this shortcoming has led to the development of an integrated and automated, user-friendly software package known as the HFM toolbox. The development has also supported enhancements to some of the original capabilities of the HFM code. This toolbox integrates the above-mentioned HFM simulation model with supporting graphical user interface (GUI) and visualization/plotting routines. The HFM toolbox allows the user to quickly test and study the performance of various HWIL scenarios and hardware configurations within a virtual environment. In this regard, the package can be quite useful in providing the customer with confidence and valuable insight concerning the prospective HWIL project prior to any hardware commitment. Some useful applications of the software include concept development and virtual demonstration of desired HWIL configurations, pre-planning of HWIL trials, 6DOF integration and verification of axes systems, testing synthetic line of sight and forcing function algorithms, performance predictions of the virtual unit and the assessment of error budgets due to hardware misalignment, latency and parallax effects. In this paper, the HFM toolbox is described and demonstrated by way of some typical examples. I. Introduction The HWIL Facility Model (HFM) is an engineering-level simulation model of a generic Hardware in the Loop (HWIL) simulation system. The model has been implemented in FORTRAN and is based on a generic air-to-air scenario in which the launcher and target are represented by three degrees of freedom (3DOF) equations of motion while the missile motion is described by a full 6DOF set of equations. The software allows the user and potential customer of a HWIL facility to run virtual trials on their guidance unit prior to committing to actual hardware in the real facility and the associated preparation and integration effort. This capability to rehearse the planned HWIL simulations in an appropriately configured virtual facility benefits the HWIL program in two ways; it serves to increase customer confidence in the program and provides a means for assessing and mitigating program risk. Other capabilities and uses of the software package include performance prediction of the virtual unit under different configurations and identification of limitations of the real facility, design and validation of appropriate variable window algorithms to compensate for scene generator and/or motion table limitations arising from specific customer requirements, verification of axes systems and their accompanying transformations and the assessment of error budgets due to hardware misalignment, latency and parallax effects. A detailed description of the mathematical models underpinning the HFM software engine has been covered in various DSTO reports 1-4 and AIAA conference papers. 5,6 The purpose of this paper is to provide a brief outline of how these models are implemented in HFM and then to describe the software enhancements to the HFM engine that allow for greater flexibility, user-friendliness and automation in its use, particularly during scenario set-up. These software enhancements have been realized in three ways. Firstly, additional FORTRAN code was written to upgrade