Aircraft Landing System Research Articles

Gear walk instability studies using flexible multibody dynamics simulation methods in SIMPACK

In a variety of mechanical systems friction induced vibrations are a major concern. The aircraft landing gear is by nature a complex multidegree-of-freedom dynamic system. It may encounter various vibration modes which can be induced by brake frictional characteristics and design features. These brake induced oscillations can lead to very high loads in the landing gear and brake structure which may result in passenger discomfort and sometimes in component failure. Along with the serious fore and aft oscillations of a landing gear, often referred to as gear walk, chatter, squeal, shimmy and other vibrations in aircraft landing systems are not only annoying and disconcerting but can also affect the stability of the plane during take-off, landing, and rolling. In this paper, simulation of such an unstable and complex phenomenon during aircraft ground maneuvers is done to detect vibrations in aircraft landing gear. A commercial multibody simulation tool SIMPACK is used for this purpose. The article is based on work done in co-operation between DLR and Liebherr Aerospace.

RGPS - Based Automatic Landing System for Light and Commuter Aircraft

The report is devoted to the design problems of Navigation, Guidance and Flight Control of the Light and Commuter Aircraft in the landing mode using Local Area Augmentation Systems, based on the relative GPS. The integrated strapdown Inertial Navigation and Global Positioning System is used for the solution of guidance problems and robust flight control system is used for the Aircraft stabilization in landing mode. Problems of design of robust control autopilot with structured uncertainty of aircraft parameters are consider.

Hybrid knowledge bases

Deductive databases that interact with, and are accessed by, reasoning agents in the real world (such as logic controllers in automated manufacturing, weapons guidance systems, aircraft landing systems, land-vehicle maneuvering systems, and air-traffic control systems) must have the ability to deal with multiple modes of reasoning. Specifically, the types of reasoning we are concerned with include, among others, reasoning about time, reasoning about quantitative relationships that may be expressed in the form of differential equations or optimization problems, and reasoning about numeric modes of uncertainty about the domain which the database seeks to describe. Such databases may need to handle diverse forms of data structures, and frequently they may require use of the assumption-based nonmonotonic representation of knowledge. A hybrid knowledge base is a theoretical framework capturing all the above modes of reasoning. The theory tightly unifies the constraint logic programming scheme of Jaffar and Lassez (1987), the generalized annotated logic programming theory of Kifer and Subrahmanian (1989), and the stable model semantics of Gelfond and Lifschitz (1988). New techniques are introduced which extend both the work on annotated logic programming and the stable model semantics.

Stabilization of an inverted pendulum by a high-speed fuzzy logic controller hardware system

A high-speed fuzzy controller hardware system employing Min-Max operations is presented. It has fifteen control rule boards and one defuzzifier. Grades of membership are represented with 0 V ∼ 5 V corresponding to 0.0 ∼ 1.0. This fuzzy controller facilitates approximate reasoning at 1 000 000 FIPS (fuzzy inferences per second) and is able to be used for various purposes by programming on each control rule board. It handles fuzzy linguistic information of the form NL (negative large), NM (negative medium), NS (negative small), ZR (approximately zero), PS (positive small), PM (positive medium), PL (positive large) and NG (negation). This fuzzy controller hardware system makes an inverted pendulum stand on a vehicle by using seven control rules. Two pendulums (5 mm diameter, 15 cm length, 3.5 g weight; respectively 10 mm, 50 cm, and 50 g) can be stabilized by the same rule set. It is much easier to produce control rules than to solve the nonlinear differential equations representing the dynamics of an inverted pendulum. This fuzzy controller hardware system can be applied to attitude control of a space booster rocket and satellite, an automatic aircraft landing system, pattern recognition, stabilization of nuclear fuel rods in a reactor, an intelligent sensor, and many other applications which need swift approximate reasoning.

Aircraft Automatic Landing Systems Using GPS

abstractThis paper is based on a presentation made at the IAIN International Navigation Congress held in Sydney, Australia, in February 1988.The global positioning system (GPS) offers a new opportunity for the automation of aircraft landing systems. The position and velocity measurements provided by a state-of-the-art GPS receiver using the C/A code and working in a normal or differential mode (D-GPS) and aided by one or two ground-based PseudoLites (PLS), may be able to satisfy the landing accuracy requirements of the FA A.This paper describes the design and simulation of an aircraft automatic landing system. Aircraft position and velocity are assumed to be measured using a (carrier-tracking) GPS receiver. The hypothesized capability is based on measurements taken at Stanford and elsewhere, using the Trimble 4000SX, five-channel receiver in an integrated-doppler-aiding mode. For some of the autopilot designs, either ground-based GPS transmitters (pseudolites) or a radar altimeter have also been incorporated.Included in the landing simulations are wind shears and a gust model, creating realistic landing situations. The performances of the lateral and vertical displacements are presented with their 1σ r.m.s. estimation errors during the glide-slope and flare phases. Included are different wind conditions, GPS configurations and controllers. The results are compared with the FAA requirements for various categories of automatic landing systems.

Equipment, Materials and Services

An important new development in the calibration of aircraft landing systems and navigational aids has been announced by McAlpine Aviation.

Observers as Noise Filters in an Automatic Aircraft Landing System

Observers as Noise Filters in an Automatic Aircraft Landing System

Introduction into the Subject of the Workshop

Publisher Summary This chapter discusses a few techniques and strategies to prevent dangers to in control computer systems that may occur as a result of errors and failures. It discusses the basis for systems acceptance, approval, and licensing. When computer control is applied to safety-related technical processes such as railway systems, aircraft landing systems, nuclear power stations, chemical reactors, elevators, and cranes, faults in the computer system may cause hazards to human life. Considering the causes of possible hardware or software faults, three different categories may be distinguished: (1) hardware faults as a result of physical or chemical failure mechanisms, (2) hardware design errors and software errors as a result of human failure mechanisms, and (3) software faults as a result of sporadic hardware failures. This effect is known as software poisoning. There are two basic strategies to avoid possible dangers induced by computer hardware or software faults: (1) to eliminate the failure mechanisms and to aim at a perfect system without faults and (2) to use a non-perfect system and to apply special means to prevent the failure mechanisms from causing any danger.

Aerospace and military: Progress in space structure research, aircraft landing systems, integrated optics, and digital communications

Progress in space structure research, aircraft landing systems, integrated optics, and digital communications is outlined.

Avionics: Microwave landing systems: As MLS technology enters its third decade, competing approaches contend for standardization at the international level

The author discusses various aircraft landing systems including the Time Reference Scanning Beam (TRSB) and the Doppler MLS.

Coefficient plane models for tracking system design

A traditional method of designing the ‘fine control’ mode of tracking systems is via the Bode plot relating system output to system error. This approach has a major disadvantage in failing to yield estimates of the system dynamic performance other than on an empirical basis which is somewhat unreliable. The paper shows how coefficient plane models may be used to solve this problem. Radar tracker and aircraft landing systems are used to illustrate the integrated coefficient plane-Bode plot approach.

International decisions on aircraft landing systems to be taken in 1976?

International decisions on aircraft landing systems to be taken in 1976?

Generalised Neustadt algorithm for minimum time control of linear systems with norm constraints on the controls

The problem of transferring a linear system between two closed sets in minimum time, when the control constraints can be formulated in terms of a norm on the control space, is treated. An algorithm for determining the optimal control is presented that is a significant improvement on current methods based on solving a sequence of minimum-effort problems. As an illustration, a 4th-order aircraft-landing system is considered.

Quasi-optimum design of an aircraft landing control system

Quasi-optimum control law for aircraft landing control system design based on Friedland technique, evaluating effectiveness by computer simulation

Quasi-optimum design of an aircraft landing control system

Quasi-optimum design of an aircraft landing control system

Synthesis of feedback controls using optimization theory--An example

This paper illustrates the use of optimization theory in the synthesis of a linear time-varying feedback control by carrying out the design of an aircraft landing system. The optimization method employed is the Parametric Expansion Method. A number of different controls are synthesized by selecting different functional forms for the weighting factors appearing in the error index formulated from the performance requirements. These controls are compared by presenting the landing trajectories of the aircraft.

Radio guidance elements of the B.L.E.U. automatic landing system for aircraft

The object of this paper is to describe the radio aids which form part of the B.L.E.U. automatic landing system and only a brief description is given of the system itself. The internationally accepted i.l.s. is used as guidance during the approach phase, and reasons are given why this cannot be used to complete the landing. Two new aids are therefore introduced for the landing phase, magnetic leader cable for azimuth guidance and an f.m. radio altimeter for height guidance. These equipments are described in turn in some detail. Finally there is a discussion on the two main problems to be solved in introducing the system to civil aviation, namely ensuring the extremely high safety level required and finding a guidance system whose ground elements will, at the same time as satisfying the accuracy requirements, be completely acceptable to the installing authorities.

Discussion on “Radio guidance elements of the B.L.E.U. automatic landing system for aircraft”

Discussion on “Radio guidance elements of the B.L.E.U. automatic landing system for aircraft”

The practical realization of final-value systems with limiting constraints

In certain applications, the desired function of a control system is to control some variable accurately only at one instant of time. Examples of this can be found in homing missile guidance systems or aircraft landing systems. In the latter case, it is desired to have the vertical component of velocity be small at the instant of touchdown. Complicating features of such systems are the constraints imposed by physical limitations, such as the limited vertical acceleration capability of airplanes, and the noise or inaccuracy of measurements of the controlled variable. The optimum configuration for such systems has been derived, and this form can be used as the basis for the design of actual systems. The theoretical derivation of the optimum system idealized the actual situation, and a number of problems must be considered when the physical system is designed. Such problems as the closed-loop realization, the number of measurements of the system response, and the manner in which these measurements are utilized are discussed in this paper.

Some Considerations Concerning Nuclear Radiations for Application to Aeronautical Navigational Aids

A brief introduction to nuclear radiation physics and particularly gamma radiation is followed by a discussion of methods of measuring emitter to detector distance. Consideration is given to statistical accuracy of range measurements as well as to an example of a possible aircraft landing system.