Showing papers by "Saab AB published in 2000"

System and method for avoidance of collision between vehicles

Abstract: A system and a method for avoidance of collision between vehicles, wherein a possible avoidance manoeuvre trajectory (Tr1, Tr2) for the respective vehicle is calculated and compared with the avoidance manoeuvre trajectories calculated for the other vehicles for controlling whether the avoidance manoeuvre trajectory of the vehicle in every moment during its calculated lapse is located at a stipulated minimum distance (d) from the avoidance manoeuvre trajectories of the other vehicles. A warning is presented to a person manoeuvring the vehicle and/or the vehicle is made to follow an avoidance manoeuvre trajectory previously calculated and stored for the vehicle if the comparison shows that the avoidance manoeuvre trajectory (Tr1, Tr2) of a vehicle in any moment during its calculated lapse is located at a distance from the avoidance manoeuvre trajectories of any of the other vehicles that is smaller than the stipulated minimum distance (d).

Equivalent Damage and Residual Strength for Impact Damaged Composite Structures

Abstract: Determining structural durability and damage tolerance of aircraft-composite structures is an important task, not only in the design process but also when the aircraft is in operational use. There ...

Redundant system for the indication of heading and attitude in an aircraft

Abstract: A method and an arrangement for synthetically calculating redundant attitude and redundant heading by means of existing data in an aircraft. In one embodiment the heading of the aircraft is available and in another embodiment the heading is calculated from a magnetic heading sensor. When the heading is available (redundant heading) attitude is calculated by weighting together the signals from and angular rate gyros (2) in the aircraft's flight control system, information from air data (altitude, speed, angle of attack) as well as information about heading (redundant heading). When the heading is not available, attitude and heading are calculated in one embodiment with the aid of Kalman filters (11, 22) by weighting together the signals from the angular rate gyros in the aircraft's control system, information from air data (altitude, speed, angle of attack and sideslip angle) as well as information from a magnetic heading detector existing in the aircraft.

Method and guidance system for guiding a missile

Abstract: The present invention relates to a method and an arrangement for guiding a missile. In accordance with the prior art, the angle position of a target (9) when the missile (3) is expected to reach the target is predicted on the basis of the angular velocity determined in a preceding time period. In order to improve the strike accuracy, the operator, in a second subsequent time period, tracks the actual position of the missile in relation to the predicted angle position of the target. If a deviation is observed, a correction command is transmitted to the missile in order to correct the missile trajectory. For this purpose, a communications link is provided to transmit the correction command given by the operator.

An outlet device for a jet engine

Abstract: An outlet device for a jet engine (2) includes an outlet channel (3), which has an upstream end (3') for being connected to the jet engine and a downstream end (3'') and which defines a main flow direction (a) for a jet from the jet engine. The outlet channel has in the proximity of the downstream end an elongated shape, seen in a section across the flow direction, and includes at least two outlet portions (4, 5, 6), which are separated from each other, for a respective outlet flow of said jet. A first outlet portion (5, 6) includes means for controlling the outlet direction of the outlet flow in a first plane and a second outlet portion (4) includes means for controlling the outlet direction of the outlet flow in a second plane, which forms an angle to the first plane. An aircraft may include such an outlet device.

Manufacturing of components for valve mechanisms for internal combustion engines

Abstract: A method for fabricating components such as rocker arms (4), cam followers (3) or cams for valve mechanisms for combustion engines, in which a billet of an MMC material (Metal Matrix Composite) containing 10-70 % ceramic material by volume in the form of particles or fibers is extruded into a bar (1, 2) having the cross-sectional profile of the final component (3, 4), and where separate billets for the respective components (3, 4) are obtained by cross-cutting the bar (1, 2) by means of cutting via high-speed machining, HSM.

A tool, a machine tool, and a method of cutting

Abstract: The invention refers to a tool (1), a machine tool, and a method for cutting machining of a workpiece. The tool includes a mounting portion (5) for mounting of the tool in the machine tool, a tool shaft (7), which has a first inner end (7'), connected to the mounting portion (5), a longitudinal centre axis (a), which extends through the mounting portion and the tool shaft, and a main cutting edge (9) on the tool shaft. The main cutting edge (9) has an extension in an axial direction along an imaginary envelope surface, which is concentric to the centre axis (a) and located radially outside an outer periphery surface of the tool shaft (7). The main cutting edge (9) is arranged to permit cutting engagement with said workpiece when the tool is rotated around the longitudinal centre axis.

Synthetic attitude and heading reference for Saab Gripen

Abstract: In future versions of Saab Gripen, the mechanical artificial horizon will be replaced by a computer calculated attitude and heading, independent of the inertial navigation system (INS). The system uses data from sensors already existing in the aircraft, which are easily available in a highly integrated, 4th generation combat aircraft such as the Gripen. The sensor information used is a three-axis magnetic detector, true airspeed, angle of attack, barometric altitude, flight control rate gyros and load factor. The sensor data is fused together in an extended Kalman filter (EKF). Each sensor by itself is of relatively poor quality. For instance, the accuracy of the rate gyros is in the order of degrees per second, rather than degrees per hour as is the case in gyros dedicated for navigation use. However, when all data are combined, they provide an attitude and heading estimate with sufficient quality for its purpose; to cross-monitor the INS, and to serve as a backup in case the INS fails or data can not be displayed. The system is called synthetic attitude and heading reference system (SAHRS), and is a Saab patent. A similar system is developed and operational in the Saab Viggen.

Saab NINS/NILS-an autonomons landing system for Gripen

Abstract: This paper presents a new approach for integrated landing systems. Applicable avionics platforms are military aircraft, helicopters, and unmanned aerial vehicles. In this paper we focus on the introduction of NILS (new integrated landing system) in the Saab fourth generation fighter JAS39 Gripen. NILS is based on an integrated navigation system (NINS) which is covered in the paper as well. The landing system in older generations of aircraft is usually designed by combination of different equipment. In the fourth generation aircraft the same functionality is solved in software implemented in the aircraft system computers. Typical applications of Saab NINS are accurate random route navigation (RNAV) under instrument flight rules, inputs to the auto-pilot, ground collision avoidance system (GCAS), terrain following, landing system and weapon initialization. Future applications are inputs to head-up or head-down display synthetic terrain presentation, mid-air collision avoidance system (MCAS) and passive target ranging.

Use of Cognitive Walkthrough for Evaluation of Cockpit Design

Abstract: This paper outlines the use of cognitive walkthrough for design and evaluation of an airplane cockpit. Designers need methods that can help predicting the outcome of proposed design features at an early stage of design and later during design alterations and updating. Since the design of a military aircraft may take 10-15 years, it is important to develop evaluation methods other than user testing. This report proposes the use of Cognitive Walkthrough (CW) to evaluate the Pilot-Cockpit Interface.

Bearing reinforcement in light metal housing

Abstract: Bearing reinforcement for a shaft (3) mounted in bearings in a cast light-metal housing (1, 2) such as an engine block or a gearbox housing, in which an insert (5) that forms a bearing seat for the shaft (3) is made of an MMC material, i.e. a metal matrix composite, and in which the base material of the MMC material consists of the same metal as the metal that comprises the principal component in the light-metal housing, wherein the MMC material of the insert (5) is reinforced with 10-70 % ceramic material by volume in the form of particles or fibers. The invention also describes a method for fabricating inserts (5) in which they are formed into a bar having the same cross-section as the radial cross-section of the insert, whereupon separate inserts are cross-cut from the bar by means of high-speed machining or water cutting.

Method and device for the presentation of objects in surrounding space

Abstract: The invention relates to a method and device for displaying, in a way that is easy for an operator, such as a pilot in an aircraft, to grasp and understand, the direction to objects (A, B) in the surrounding space. In accordance with the invention the object is projected onto a projection surface (3) comprised of the envelope surface of a conical solid of revolution, where the operator is somewhere vertically (h) on the axis of rotation (2) about which the envelope surface (3) is created. Thereafter, the operator observes, on a display surface (I) such as a viewing screen, a plan view from above of the conical envelope surface, where the horizontal direction (c, d) to the objects, and each object's height (a, b) compared to one's own height (h), represented by a circular curve (6), are easily read.

Interlaminar stresses in composite notched and unnotched laminates

Abstract: The purpose of this paper is to determine the interlaminar stress distribution at curved and straight free edges for quasi-isotropic and zero-dominated laminates. The interlaminar stresses are calculated using a three-dimensional finite-element code with error control. For straight free edges the results are compared to existing semi-analytical methods. Another objective with this investigation is to evaluate a quadratic failure criterion for prediction of initial load for delamination and the most likely position for the delamination. In this paper it is found, for quasi-isotropic stacking sequences, that it is not possible to tailor a stacking sequence so that σ z becomes compressive near hole boundaries or at straight free edges. On the contrary both tensile and compressive stresses appear in a periodic manner through the thickness. It can also be concluded that interlaminar stresses exhibit a thickness effect for repeating bundles. The singularity of the interlaminar components is concentrated to a narrow region, approximately 1-2 fibre diameters in thickness and radial direction. Since the interlaminar stresses are so localised, a continuum approach will not provide useful solutions in this area. Consequently the material cannot be treated as homogeneous in this region, instead the heterogeneous nature within each ply should be modelled. The smallest element size in the present analysis for the refined mesh is less than 1 μm, i.e., far less than a fibre diameter. Utilising a quadratic failure criterion, for the studied quasi-isotropic laminates, in conjunction with obtained FE-results, it is shown that global strain to initiate delamination does not depend on the stacking sequence, but so does the number of possible initiation points. For quasi-isotropic layups with a circular cut-out, initiation of delaminations occurs at approximately the same global strain, 0.25%. For unnotched zero-dominated layups initiation and fracture strain are almost the same, i.e., ∼1.2%. The investigation also shows that the number of ±45°/0° or ±45°/90° alterations should be kept at a minimum to minimise the interlaminar stresses and possible damage initiation points. It is likely that the primary cause for delamination initiation for notched plates are the high interlaminar shear stresses and not the normal stresses. Finally it is demonstrated that available semi-analytical methods do not correctly describe the interlaminar stress distribution.

Track-to-track association in decentralized tracking systems with feedback

Abstract: In air combat, information advantage over the opponent is vital for the success of the operation. For that reason, modern fighter aircraft have extensive sensor suites to track other objects. In order to form a unified picture of the vicinity; all sensor information is fused. Since system modularity and high computational performance are key issues in the application, a decentralized tracking approach, where the information from the decentralized trackers is fused in a central node, is preferable. Furthermore, in order to improve the sensor tracking performance, it is often desired to feed back information to the sensors from the central node. In this paper, track-to-track association in such a decentralized tracking system with feedback is addressed. The central fusion node has to associate the sensor tracks to each other to be able to fuse them. In a system without feedback, the track-to-track association algorithm bases its conclusions on the assumption that the estimation errors of the tracks from different local trackers are not correlated. However, when information is fed back to the local trackers, this assumption is not valid, since the sensor tracks then consist of common information. System configurations that deal with this problem are proposed and tested in a fighter aircraft application. One approach is to extract the uncorrelated information from the sensor data and use that in the association process. Another approach is to keep parallel trackers in the sensors that only contain the local sensor information. Both approaches produce sensor tracks that contain the same information as the sensor tracks in a system without feedback. Also, a track-to-track association algorithm that recursively uses information from multiple time steps is proposed. The use of multiple time step data separates it from conventional track-to-track association algorithms that mostly use only current information. The result is an algorithm that improves the performance and gives a more stable solution.

Standby attitude estimation

Abstract: In most military aircraft an inertial navigation system (INS) is the main source for attitude and heading data. Aircraft attitude and heading are important quantities, and in the case of a failure in the INS, backup values are needed. We here present how these can be calculated using other sensors in the aircraft. In order to determine attitude and heading with respect to a reference coordinate system, the same quantities in both the aircraft body coordinates as well as in the reference coordinate system are needed. These can then be used to determine the rotation from reference to body coordinates and thus the attitude and heading of the aircraft. We show how data from various sensors in the Saab Gripen aircraft, can be used to generate quantities exhibiting such relations. These relations are analyzed using recorded flight data. Using vector relations the QUEST algorithm yields a least squares fit of the quaternion of rotation from reference to body coordinates. We show here an alternative and simpler approach to such an algorithm in quaternion space. The REQUEST algorithm is an extension to the QUEST algorithm that processes measurements recursively. In the REQUEST algorithm angular velocities can also be used between measurements to update the quaternion of rotation. We extend our alternate approach in a similar way, but we also solve the case were additional states besides the quaternion rotation are introduced. The angular velocities used in a system of this type are often of poor quality, and states representing e.g. bias can thus be introduced.

Advanced flow simulation methods in aircraft design

Abstract: The compressible Navier‐Stokes equations are solved numerically for turbulent transonic aerospace applications on parallel computers. An Explicit Algebraic Reynolds Stress Model (EARSM) models the turbulence. Expressing the EARSM as an extension of an eddy‐viscosity model makes the implementation straightforward in a flow solver with existing two‐equation eddy‐viscosity models. The k−ω transport equations are used as a platform for the model. The EARSM approach significantly improves the shock position for transonic flow over wings without substantial increase in computational cost. Industrial use of advanced flow modelling requires a short turn‐around time of computations. This is enabled through the use of parallel computers. To achieve good parallel performance the computational load has to be evenly distributed between the processors of the parallel computer. A heuristic algorithm is described for distributing and splitting the blocks of a structured multiblock grid for a good static load balance. Speed‐up results are presented for turbulent flow around a wing on a number of parallel platforms.

Arrangement for charging energy in an energy-storing arrangement such as an ignition capacitor

Abstract: The present invention provides an arrangement for charging energy in an energy-storing arrangement such as an ignition capacitor in electronic ignition systems. To reduce the risk of malfunction, direct-current-controlled breakers controlled by environmental conditions, normally occurring on the primary side of a transformer (4) in series with the primary winding (5) have been replaced by a frequency divider (2) controlled by environmental conditions. This frequency divider divides down a signal supplied by a signal generator (1) to a pulse train with a lower frequency which controls a breaker (7) connected in series with the primary winding (5) of the transformer.

Surface coated motor component and process for producing it

Abstract: An engine component made of a metal matrix material (MMC), wherein at least one of the tolerance-critical surfaces of the engine component is coated with a metallic layer that is easier to work by machining than the metal matrix material itself For example, the interior hollow surfaces of a connecting rod are thus coated with bronze or a corresponding tribologically functional metal The invention also provides a method for coating the component with the metallic layer, and in particular a method wherein the component is pre-machined from a raw billet of MMC by means of high-speed machining, HSM

A method and a device for signal processing

Abstract: Through a method for signal processing a number of samples are taken from a signal in digital state and Discrete Fourier Transformations having a restricted word length are applied on the samples, a mean value of the results of these transformations is calculated, the calculated mean value is compared with a known ideal value for a result of a said transformation of said signal without any systematical error emanation from a restricted word length, and in connection with subsequent Discrete Fourier Transformations having a restricted word length of signals a correction is made depending upon the deviation between said mean value and the ideal value established by said comparison.

Method and device for the alignment of a weapon with a weapon simulator mounted on the weapon

Abstract: The present invention relates to an alignment device and method for alignment of a weapon (2) with a weapon simulator (1) mounted on the weapon. The weapon is provided with a sight (3) oriented along a sighting axis (8). The weapon simulator is equipped with a first device arranged to emit an electromagnetic simulator beam (4) exiting along a simulator axis (5). The device and method are characterized in that a second device is arranged to generate an alignment beam (6) along an alignment axis (7), wherein the angle between the simulator axis and the alignment axis (7) is fixed and known. Further, a reflection device is arranged to reflect the alignment beam (6) into the sight, and means of adjustment are arranged to collectively guide the alignment axis (7) and the simulator axis (5) during the alignment of the simulator axis (5) with the sight (3) so that the said axes during the alignment maintain the fixed relative angular relationship. This makes it possible for a firer to easily align the simulator axis to the sighting axis with the aid of the means of adjustment while looking through the sight.

A device for preventing leakage of electromagnetic radiation

Abstract: The invention concerns a device for preventing leakage of electromagnetic radiation between a first (10) and a second (12) part. The first (10) and the second (12) parts are shaped to be arranged against each other such that a first gap (20) is formed between them. Furthermore, the first (10) and the second (12) parts are shaped to engage each other such that at least a second gap (30) is formed between them. The second gap (30) defines a second plane (32) which forms an angle (34) with the first plane (22) which is defined by the first gap (20). Furthermore, the second gap (30) has an extension such that it intersects the first plane (32). The second plane (32) also has an extension in a leakage direction (24) which is defined by the first gap (20).