AVID OAV

Organic Air Vehicle

AVID LLC has developed a multidisciplinary optimization code (AVID OAV) for the design and analysis of ducted fan VTOL UAVs such as the iSTAR and Kestrel vehicles. The objective of this effort is to acquire a design synthesis capability for the nation that includes the ducted fan VTOL UAV in the design space in a manner that will enable objective requirements and technology development decisions. The tool brings together the design lessons that have been learned through the DARPA OAV Phase I and Phase II and MAV ACTD programs. It will allow the concepts to be manipulated and scaled. The customers’ desires can be evaluated through an accurate simulation of the vehicle performance. Design characteristics, payload requirements, mission requirements and operational concepts can be developed based on the results from the design optimization code.

Figure 1. Disciplinary Elements of AVID OAV

AVID OAV has evolved from the original design codes developed by Honeywell/AeroVironment and Allied Aerospace/MicroCraft during Phase I of the DARPA OAV Program. AVID LLC brings to these codes the advanced aircraft design methodologies and legacy codes of the NASA and Aerospace industry sponsored ACSYNT Institute. In addition the founders of the ACSYNT Institute are also among the founders of AVID LLC.

A major portion of AVID LLC’s effort is to create a design tool that is centered on parametric 3-dimensional modeling. The performance of the vehicle is predicted from the design characteristics, which can then be modified through a parametric optimization methodology or through a sensitivity and trade study tool. AVID LLC is setting out to provide an improved design capability to the UAV community by providing a conceptual design program that acts at a complex level to include payload, power and integration issues, but with a usable interface. Many detail design considerations important for small UAV’s, such as avionics components, batteries, power supplies, etc., are brought forward to the conceptual design stage by AVID OAV models. This promotes rapid, accurate, fine-tuning of designs at concept time.

Multidisciplinary design optimization requires a balanced discipline analysis that can accurately predict system performance, as depicted in Figure 1. AVID LLC is adapting and creating advanced design and analysis algorithms, verifying them through validation with test results, and combining them through an object-oriented, standards-based software system.

Figure 2. Sample 3D Geometry Model

Standards-based methods have been employed throughout the code development process. AVID OAV is designed, coded and maintained using Rational Rose and Clearcase Computer Aided Software Engineering tools. The code is written in Object-Oriented C++ and uses the OpenGL graphics standard and Object-oriented GUI builder, Qt. As a result, the same code is implemented on PC Linux, Mac OS X (Unix) and Windows platforms. AVID LLC will act as an open-source code provider to the government and government contractors. For customers, this means accessibility, versatility, maintainability, and reusability.

The primary technical enhancements to AVID OAV have been in the areas of geometric modeling, aerodynamics, weight & balance, propulsion & power, mission performance, and user interface. Complex geometric concepts can now be modeled in the code, as seen in Figure 2. A database of parametric components is available, and the user can easily generate new components and libraries to incorporate into their concept. Each geometric component of this model has weight, volume, power and aerodynamic characteristics that are used in the calculation of the performance. The weights of these components are not only summed, but the moments of inertia, CG’s, and balance information are computed as the design is developed in the anticipation of computing flight dynamic performance. Aerodynamic methods have been developed to accurately predict and account for the lift and drag of this arbitrary geometry. The electrical components can be combined on circuits that operate at different voltages to precisely predict the power consumption of the UAV and this power then can be either provided through a motor and generator or by sizing batteries to meet the power requirements. The virtual OAV is then flown on the design mission to combine all of the disciplinary performance toward addressing the user’s requirements. By selection of design variables, constraints and objectives, the user can then find the best vehicle to meet a task.

Plans for the expansion of AVID OAV include the development of more disciplines and greater depth of analysis in current disciplines, such as propulsion modeling. A simplified, rapid, CFD analysis with semi-automated mesh generation from AVID OAV models will enhance the aerodynamic analyses. As the vehicle size increases, the structural design criteria begin to change. Incorporating a simplified stress analysis will increase the confidence in scaling between vehicle classes, and blur the boundaries by enabling trade-studies to show where technologies have their highest impact. Including simple maneuvers will enable the systems to be designed to dynamic performance requirements such as gust response. As noise is one of the critical FCS concerns for the OAV, a noise model with directional propagation will be developed to enable noise/performance tradeoff studies. Plans are to develop a process based cost model for the airframe combined with a component cost model for other components.