Abstract
This article introduces an original model-based design methodology addressing a high-performance aircraft design challenge: conflicting performance requirements. The case study of the Global 7500 elevator actuation system also provides in-depth insight into the complex design process of today’s fly-by-wire flight control systems. The methodology presented here redefines the aircraft manufacturer’s involvement in the design process of the systems, implementing analysis and iteration capabilities early in system development. To this end, it introduces a novel modeling approach for analyzing loaded rate requirements by simulating closed-loop performance with a generic nonlinear second-order state filter, including the main performance limitations without requiring a preliminary design definition. In this way, it provides means to mature the system requirements and addresses requirement conflicts upfront. Then, a simulation-based preliminary sizing and performance assessment validates the candidate design concept. It also secures the preliminary design phase by implementing advanced design uncertainties and involving interfacing systems and disciplines early in the process. The redefined methodology identified directly that the problem’s root cause was a conflict between stability and control and flutter protection requirements. It also indicated that the first sizing driver is the response time required under a specific failure case. These findings lead to an optimal elevator actuator design compliant with matured performance requirements. Thus, the methodology resolved a design challenge blocking the Global 7500 aircraft development and prevented redesign occurrences later during the detailed design phase. In this way, it directly contributed to the successful development of the Global 7500 and its optimal operational performance. This methodology applies to future aircraft design challenges, and the technical insight provides valuable lessons learned for high-performance T-tail business jets.
Highlights
As the flight control system is the interface of all the critical aircraft systems and disciplines, its design process is highly complex and requires intensive aircraft-level iterations during the system and equipment definition and integration
We focus on the equipment specific to the system under study: the elevator actuator
The integration aims to validate the proposed design at the aircraft level and approve the continuation of the actuator preliminary design, but it can lead to a large design
Summary
The advantage of such an analysis is that it can be done conveniently with a spreadsheet It considers all the critical design phenomena driving the actuator performance (hydraulic power supply, servo valve characteristics, fluidic losses, mechanical friction, and external load) except the fluid compressibility and the controller roll-off occurring when converging to the commanded position. The objective here is to allow the aircraft manufacturer to analyze the requirements in a dynamic approximation and capture all the sizing drivers To this end, a novel modeling approach bridging the performance requirements and the actuation dynamics without a preliminary design definition is proposed. The resulting requirement model reproduces the loaded rate performance of a closed-loop actuation system in both the normal mode and failure case, including the main nonlinearities limiting the performance and without requiring the preliminary design of an actuator, its kinematics, and controller. It does not replace the design expertise
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