Design and Evaluation of Flight Control Systems

1974 ◽  
Vol 188 (1) ◽  
pp. 89-96
Author(s):  
F. R. Gill
Keyword(s):  
Control Systems ◽  
Flight Control ◽  
Optimization Technique ◽  
Gain Control ◽  
Linear Control ◽  
Control Policies ◽  
Transport Aircraft ◽  
Variable Gain ◽  
Performance Requirements ◽  
Glide Path

Studies at the Royal Aircraft Establishment are aimed at the in-flight demonstration of improved control systems and policies in a fighter-attack and/or a transport aircraft. The systems being flight evaluated at the present time employ conventional linear-control policies, the design being based on a parameter-optimization technique. Two important modes are discussed briefly in the paper: a pitch-rate manoeuvre-demand system for the fighter-attack aircraft and an ILS glide path and flare system for the transport aircraft. The design studies of these and other modes have yielded quantitative data on conflicts between different performance requirements which cannot be avoided when linear-control policies are used. Studies are being made therefore to replace linear control by variable-gain policies in selected parts of the control system in order to reduce the extent of these conflicts. The reasons for and principles of the variable-gain control policies are outlined in the paper; in addition certain system improvements are discussed (e.g. trim problems) which result from the application of these non-linear control policies.

Airworthiness aspects of new technologies: Interaction between aircraft structural dynamics and control systems

1998 ◽  
Vol 212 (5) ◽  
pp. 309-317 ◽  
Author(s):  
M Hockenhull
Keyword(s):  
Control Systems ◽  
Structural Dynamics ◽  
Flight Control ◽  
Closed Loop ◽  
New Technologies ◽  
Loop Control ◽  
Transport Aircraft ◽  
Control Load ◽  
Dynamics And Control ◽  
And Control

The application of electrical flight control systems to civil transport aircraft has directed attention to the need for improved airworthiness regulation. In this paper, the scope and interpretation of a new FAR/JAR Part 25 regulation in preparation is discussed, applicable to aircraft that have closed-loop control systems for flight control, load alleviation or stability augmentation, and have the potential to interact with the aircraft's structural dynamics.

scholarly journals A model-based design methodology for flight control systems: Global 7500 pitch control case study

2021 ◽  
pp. 095441002110247
Author(s):  
Jonathan Liscouët
Keyword(s):  
Control Systems ◽  
Flight Control ◽  
High Performance ◽  
Design Methodology ◽  
Aircraft Design ◽  
Preliminary Design ◽  
Design Phase ◽  
Performance Requirements ◽  
Design Challenge

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.

Video-Enhanced Microscopy--Better Visibility of Plant Cell Structures

1982 ◽  
Vol 40 ◽  
pp. 182-185
Author(s):  
N.S. Allen ◽  
R.D. Allen
Keyword(s):  
Diffraction Pattern ◽  
Theoretical Basis ◽  
Numerical Aperture ◽  
Gain Control ◽  
Control Unit ◽  
Camera Control ◽  
Variable Gain ◽  
Contrast Method ◽  
Fine Detail ◽  
Cell Structures

Various methods of video-enhanced microscopy combine TV cameras with light microscopes creating images with improved resolution, contrast and visibility of fine detail, which can be recorded rapidly and relatively inexpensively. The AVEC (Allen Video-enhanced Contrast) method avoids polarizing rectifiers, since the microscope is operated at retardations of λ/9- λ/4, where no anomaly is seen in the Airy diffraction pattern. The iris diaphram is opened fully to match the numerical aperture of the condenser to that of the objective. Under these conditions, no image can be realized either by eye or photographically. Yet the image becomes visible using the Hamamatsu C-1000-01 binary camera, if the camera control unit is equipped with variable gain control and an offset knob (which sets a clamp voltage of a D.C. restoration circuit). The theoretical basis for these improvements has been described.

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