摘要:

ABSTRACTThe expanding role of the helicopter in the battlefield environment has burdened the pilot with missions of greater complexity and risk with a concomitant increase in pilot workload. Navigation of the helicopter is an essential supportive element to the prime mission and has until recent years been a significant contribution to the workload. Technological advances in navigational electronics such as Doppler navigation radar, computers, integrated avionic control and display systems, etc., now can provide automated navigation with vital benefits in cost, size, weight and power which permit incorporation of these advances into the helicopter. Cost reductions are particularly important since helicopters are used in large quantities in modern military forces. Multi‐sensor navigation systems already available and in use in helicopters are discussed followed by a review of the system trade‐offs and considerations leading to new systems that use more advanced digital electronic techniques to achieve the goals of reduced pilot workload, improved performance at minimum size, weight, and cost. The beneficial impact of ongoing technological advances in improving the operating capabilities of future avionics systems is indica

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1983.tb00820.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1983.tb00821.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe operation of a NAVSTAR GPS multiplex receiver is defined in this paper as processor‐controlled time‐sharing of a single channel of receiver hardware in a manner that permits continuous (in a sampled data sense) digital phase‐locked loop tracking of four GPS transmitters while simultaneously reading the 50‐Hz navigation message data from the same four transmitters. The operational and performance characteristics are described for a proven advanced NAVSTAR GPS digital multiplex receiver front‐end design that time‐shares one code generator and one carrier synthesizer in accordance with this definition.Multiplexing has been demonstrated with this advanced single‐channel receiver front‐end in a manner that creates up to eight pseudochannels. The receiver can also be operated at a reduced number of pseudochannels in binary multiples of 4, 2, or 1. The eight pseudochannels provide simultaneous tracking of four GPS transmitters in P‐code of both the L1and L2signals. In addition, the space vehicle (SV) 50‐Hz navigation message data are read continuously from all four GPS transmitters. The eight pseudochannels emulate a multichannel set that is virtually free of interchannel bias and interchannel phase drift error since all GPS signals of the same frequency travel the same hardware path.Sixteen observables are continuously available: four L1code phases, four L2code phases, four L1carrier doppler phases, and four L2carrier doppler phases. These measurements are captured directly as a by‐product of the nearly instantaneous phase presetting and the digital synthesis of the numerically controlled code and carrier tracking loops. From these raw measurements, the usual GPS receiver pseudoranges, delta pseudoranges, and their L1/L2differences can be derived. Quantization noise is negligible since the raw measurements are of such ultrahigh resolution (2−16P‐chip code phase and 2−16cycle carrier doppler phase).The receiver error characteristics are described and actual tracking error plots for 16 simultaneous observables from four re

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1983.tb00822.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThis paper describes a capability for simulating significant aspects of the imagery available from an idealized “fan‐beam” radar. The object is two‐fold. First, it is to evaluate the utility of such imagery in assessing the progress of an aircraft along postulated final approach paths, and secondly, to determine if the sensed imagery from a horizontally scanned fan‐beam radar can be enhanced by implementing a second, vertically scanned fan‐beam radar and combining the two images.Mathematical algorithms necessary to perform the simulations are derived and a Vax 11/780 computer is utilized to implement them. Plots are drawn for various aircraft positions and attitudes utilizing discrete points delineating Los Angeles International airport runways 7L and 7R. The simulated visual scene is presented with the radar sensed imagery for comparison purposes.The simulation is performed in two parts. Part I contains the horizontally scanned Fan‐beam Radar Imagery (FRI) and shows that while the radar imagery presents an accurate lateral view, it lacks vertical information. Thus, while yaw is apparent, pitch and roll information, as well as vertical path deviations, are not apparent. It is concluded that such imagery is inadequate to provide critical aircraft position and attitude information, especially in the vertical dimension.Part II adds a vertically scanned fan‐beam radar to the horizontally scanned fan‐beam radar so that combined FRI can be evaluated. The simulation shows that this technique produces an accurate view in both the lateral and vertical direction. In fact, the visual view and radar view are practically identical. Thus, yaw, pitch, and roll information, as well as progress in both the horizontal and vertical planes, are apparent. It is concluded that such combined imagery can provide critical aircraft position and att

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1983.tb00823.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTFormulations of Kalman filters are presented which are capable of aligning one strapdown inertial sensor assembly with another by estimating the misalignment angle between them. One formulation treats the case of a fixed misalignment. Another treats the case of a dynamic misalignment, caused, say, by bending of the common supporting body. Measurements can be made by gyros only, or by gyros plus accelerometers. Filters which estimate inertial sensor error parameters are also discussed.

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1983.tb00824.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe High Speed Rocket Sled Test Track at Holloman AFB, New Mexico is a precision, highly‐instrumented facility which has found extensive use in the quantitative error evaluation of state‐of‐the‐art guidance systems. The sleds, containing the guidance system tested and extensive monitoring instrumentation, are subjected to a positive and negative acceleration profile tailored to both simulate missile environment and maximize separability of test system errors. While thrust is provided by rocket engines, deceleration has traditionally been accomplished by water brake: a sledborne scoop which disperses water from a channel between the two rails.With the evolution of high speed flight computers has come a trend toward real time guidance system error compensation. This has resulted in enhanced visibility of errors such as high order nonlinearities and effects due to erroneous compensation. The isolation of system errors is so strongly a function of the sled acceleration profile which drives those errors that the success of a specific profile to aid error separation can be simulated prior to actual testing. This was shown for the case of an anticipated sled test project which was to involve high (>50 g) accelerations and was expected to propagate unusually highly‐correlated errors: the result was that no level of water brake deceleration provided the velocity change necessary for error separation. Thus the reverse velocity sled concept was proposed and analyzed in 1979. This technique uses a reverse thruster to provide a sled brake of desired magnitude and time duration, the optimal retro thrust resulting in a considerable reverse sled velocity. This sled is presently under design and construction and is to be thoroughly tested in calendar year 1982.The aerodynamics of the reverse velocity sled being built are such that the sled will return to the launch point. This factor leads to new dimensions in this test concept. Firstly, start and stop points can be measured to extreme accuracy, because of their proximity, permitting excellent determination of non‐cancelling errors such as asymmetries and even‐powered nonlinearities. Secondly, traversal of the Test Track in two directions decouples Track survey errors from test guidance system errors. Thus, if the test system performance conforms to a deterministic model, then the test system can be used to help identify, and then remove, many errors in the Track reference itself.This paper reviews the efforts accomplished to date, including an analysis of the above‐mentioned benefits of sled return to t

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1983.tb00825.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1983.tb00826.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1983.tb00827.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY