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Spacecraft control systems with computer command redundant jets for linear and angular pulses, relating configuration design to level-of- redundancy and task dimension
System combines two concepts - triple modular redundancy (TMR) and spares (replacement system) redundancy. System has triplicated active unit core with associated bank of specifically arranged standby spare units. Curves plotted from characteristic equation show hybrid system is more reliable than conventional TMR systems.
Redundant functional element, together with basic elements of system, constitutes a redundant system with primary and backup capability for performing particular functions with increased reliability. Methodology is applicable to design of a verification system for hypothetical complex communication system.
Methods for ascertaining dimensional redundancies in mathematical functions related to electronic phenomena and for removal of redundancies are presented. Two computer programs, one to determine a complete B-matrix and the other to optimize the matrix, are discussed. Three subroutines are analyzed.
A description of a mathematical model reference system is presented which provides redundancy management for an electrohydraulic servoactuator. The mathematical model includes a compensation network that calculates reference parameter perturbations induced by external disturbance forces. This is accomplished by using the measured pressure differential data taken from the physical system. This technique was experimentally verified by tests performed using the H-1 engine thrust vector control system for Saturn IB. The results of these tests are included in this report. It was concluded that this technique improves the tracking accuracy of the model reference system to the extent that redundancy management of electrohydraulic servosystems may be performed using this method.
The use of the handbook is discussed and the design progress is reviewed. A description of the problem is presented, and examples are given to illustrate the necessity for redundancy verification, along with the types of situations to which it is typically applied. Reusable space vehicles, such as the space shuttle, are recognized as being significant in the development of the automated redundancy verification problem.
This analysis considers the optimum allocation of redundancy in a system of serially connected subsystems in which each subsystem is of the k-out-of-n type. Redundancy is optimally allocated when: (1) reliability is maximized for given costs; or (2) costs are minimized for given reliability. Several techniques are presented for achieving optimum allocation and their relative merits are discussed. Approximate solutions in closed form were attainable only for the special case of series-parallel systems and the efficacy of these approximations is discussed.
Interfacing of the redundant display and keyboard subsystem with the triple redundant computer system is defined according to space shuttle design. The study is performed in three phases: (1) TRCS configuration and characteristics identification; (2) display and keyboard subsystem configuration and characteristics identification, and (3) interface approach definition.
This paper suggests guidelines for the utilization of low-redundancy convolutional codes with emphasis on providing a quick look capability (no decoding) and a moderate amount of coding gain. The performance and implementation complexity of threshold, Viterbi, and sequential decoding when used with low-redundancy, systematic, convolutional codes is discussed. An extensive list of optimum, short constraint length codes is found for use with Viterbi decoding, and several good, long constraint length codes are found for use with sequential decoding.
This paper presents a design method for optimal redundancy management for nonlinear systems with application to highly maneuvering aircraft. The approach taken is based on selecting the failure states to be covered by the system design and constructing a cost function that represents the cost of making an incorrect decision. The decision logic which minimizes the cost requires a bank of extended Kalman filters running in parallel. This produces a severe computational requirement. To reduce this requirement, a suboptimal logic is developed based on using a nonlinear single-stage prediction algorithm in the filters with filter gains and decision logic selected using steady-state results obtained from a linearization of the vehicle and sensor dynamics. The design process is then applied to designing a redundancy management system for the F8-C aircraft. Results indicate that the system is superior in failure detection to a system using the same structure but using a linear single-stage prediction algorithm in the filters.
Knowledge of the statistical characteristics of natural telemetry information is important for the development of principles and methods of reduction of redundancy of telemetry messages as well as planning of on-board information compression devices. An evaluation was made to determine these characteristics for the telemetry information of the Luna-9 and Luna-13 automatic lunar probe, to allow estimation of the redundancy of the information. Histograms as well as numerical characteristics were used.
This paper presents a description of redundancy techniques employed in the design of fault-tolerant computers, and a discussion of the effects of functional requirements, technology constraints, and cost considerations which enter into the choice of these techniques. The STAR computer, developed at the Jet Propulsion Laboratory for long-duration planetary spacecraft missions, is discussed along with several later fault-tolerant computer designs. The class of computers described in this paper employs dynamic redundancy, i.e., the machine is divided into a set of submodules, each with standby spares; a special hard core monitor unit detects and diagnoses faults, and effects automated recovery by replacing failed parts.
The constraint of requiring airplanes to have inherent aerodynamic stability can be removed by using active control systems. The resulting airplane requires control system reliability approaching that of the basic airframe. Redundant control actuators can be used to achieve the required reliability, but create mechanization and operational problems. Of numerous candidate systems, two different approaches to solving the problems associated with redundant actuators which appear the most likely to be used in advanced airplane control systems are described.
It is shown that it is possible to make a change of variables in a Lagrangian in such a way that the number of variables is increased. The Euler-Lagrange equations in the redundant variables are obtained in the standard way (without the use of Lagrange multipliers). These equations are not independent but they are all valid and consistent. In some cases they are simpler than if the minimum number of variables are used. The redundant variables are supposed to be related to each other by several constraints (not necessarily holonomic), but these constraints are not used in the derivation of the equations of motion. The method is illustrated with the well known Kustaanheimo-Stiefel regularization. Some interesting applications to perturbation theory are also described.
A highly fault tolerant digital computer system has been configured based on extensive experience with flight proven, redundant digital flight control systems. The feasibility of minimizing hardware complexity is shown while maintaining high levels of fault tolerance. The emerging hardware design combines reconfiguration concepts with conventional hardware redundancy techniques and special operational software to provide dual fail operate performance with a basic triplex system. The design provides high reliability and flight safety, enhances maintainability, and reduces life cycle cost while offering improved performance for future aircraft.
Report describes application of order statistics to analysis of failure modes in redundant systems. Report provides detailed mathematical discussion of approach, accompanied by graphs and equations. Techniques are relevant to process that demand high reliability, such as manufacture of dangerous chemicals. It also includes discussion of quad-redundant system.
Circuit arrangements for flip-flops, counters, and clock drivers in redundant systems ensure that control is synchronously transferred to surviving components when failure occurs. In addition to original application to spacecraft systems, redundant circuits have terrestrial uses in power generators, solar-energy converters, computers, vehicle controllers, and other systems demanding high reliability.
In this paper we present a reliable technique for failure detection and identification (FDI) for dual redundant flight control sensors aboard the NASA F-8 digital fly-by-wire (DFBW) aircraft, and we discuss the successful application of the technique to identifying failures injected on test flight telemetry data. The technique exploits the analytic redundancy which exists as relationships among variables being measured by dissimilar instruments. With straightforward modification the technique may be extended to provide failure monitoring of a single remaining sensor after the identified failure of its companion sensor.