IBM (Portugal)

Under certain conditions, the orbit estimated by a Kalman filter has errors that are much greater than predicted by theory. This phenomenon is called divergence, and renders the operation of the Kalman filter unsatisfactory. This paper investigates the control of divergence in a Kalman filter used for autonomous navigation in a low earth orbit. The system studied utilizes stellar-referenced angle sightings to a sequence of known terrestrial landmarks. A Kalman filter is used to compute differential corrections to spacecraft position, spacecraft velocity, and landmark location. A variety of filter modifications for the control of divergence was investigated. These included the Schmidt-Pines analytical modification and an empirical modification based upon Pines' machine noise treatment. Several simplified approximations to the theoretically optimum analytical modifications were also investigated. The principal numerical results are presented in graphs of the magnitude of the error in estimated position and velocity vs time for sixteen orbits. These graphs compare actual position and velocity errors with the theoretical estimates furnished by the trace of the position and velocity covariance matrices. Numerical results indicate that a properly modified filter achieves a steady-state operating level.

A prerequisite for the best equipment to suit a particular requirement is a thorough knowledge of the economics, selection, application, and performance of component parts. Other factors that affect equipment reliability — engineering costs, rating of component parts, customer losses — are discussed along with a working formula for determining the cost of a part.

THE Lincoln Laboratory and International Business Machines Corporation (IBM) have, during the past 3 years, worked out the design for a new digital computer which is the central component of a large-scale real-time system. In this system, data from many sources are fed automatically into the computer where they are processed under programmed control. A complete compilation of the real-time situation is made by the computer and presented to operators by means of a special display system. The computer automatically generates control commands for the external environment in response to corrections and command information fed into it by the operators.

This paper describes a method for the accurate computation of the operating characteristics of elecromagnets, such as used in relays and other electromechanical devices. The dynamic solution involves the use of techniques applicable to digital computers. The evaluation of the computer solutions offers a means of obtaining the optimum magnet design for a given device. The method eliminates the need for building successive models for testing and evaluation.

A NUMBER of bistable configurations are known which use vacuum tubes and transistors. Each of these requires two active elements and has two stable states. Binary coded decimal counters having ten stable states and using eight active elements, can be made with these devices. Point contact transistors, tetrodes and gas tubes (by virtue of internal positive feedback) exhibit bistability with a single active element. A scale of ten counters can be made with these devices with the use of four active elements. In general, either the speed of response of the reliability is inferior to that obtainable with counters using two active elements per trigger. This paper will consider a method of multistable operation which requires only two active elements, theoretically, for any number of statically stable states. These stable states are achieved by using two active elements in a conventional trigger arrangement. The feedback in the circuit is controlled by a nonlinear load which determines whether the net positive feedback makes the circuit stable or unstable. Thus it is possible to divide the operating range of the trigger into a number of alternately stable and unstable regions.