Alan M. Schneider

Observability of Relative Navigation Using Range-Only Measurements

A simulation tool is described which is capable of determining the observability of various fleet configurations and maneuvers in a relative navigation environment. The motion of the relative grid established by the navigation controller is explicitly modeled as a function of the errors in his dead-reckoning sensors. The simulation uses centralized, optimal processing of an extended Kalman filter. Results show observability on a good geometry, with some degradation in performance when dead-reckoning sensor errors change rapidly.

A computer program for 24-hour electric utility load forecasting

A computerized statistical model is described which makes twenty-four hourly forecasts of the total load supplied by an electric utility company. Weather forecasts are included in the load-forecasting process. The root-mean-square hourly forecasting error was less than 2% of the typical daily peak load in three weeks of testing.

A Kalman filter for an integrated Doppler/GPS navigation system

A Kalman filter has been designed to integrate a Doppler radar navigation system with a GPS (global positioning system) system. The filter uses eight states for flights over land, and ten over water. Simulation data shows navigation errors of 1 m or less on each axis under good operating conditions. The performance is equivalent in position error to the standard standalone GPS filter in straight and level flight, and superior in maneuvering flight under dynamic conditions. The filter implementation was also designed to provide additional improvement in the performance of a Doppler navigation system. The results demonstrate that this capability was achieved.<<ETX>>

Elasticity of demand for gasoline since the 1973 oil embargo

The magnitude E of the price elasticity of gasoline was found to be E = 0.2054(1 − savings due to unemployment and voluntary conservation (per cent of forcast sales)4.78 ± 0.0378 within 95% confidence limits. This results holds over a two-year period following the Arab oil embargo in which real prices rose as much as 30%. No discernable change in elasticity was observed over the two-year period. Savings in gasoline consumption due to unemployment and voluntary conservation are almost certainly less than 4.78% of forecast sales. Voluntary conservation may well be closer to 0% than to 4.78%. The methodology of the study was to fit a Box-Jenkins2 time series model to 13 years of gasoline sales prior to the embargo, and to use this model to predict what sales would have been had no change in price or other conditions occurred.

A new tax on gasoline: estimating its effect on consumption.

Based on extrapolation of a recent estimate of the elasticity of demand for gasoline, it is concluded that a tax of 5 cents per gallon per year over the period 1979 to 1988 can be expected to produce significant reductions in gasoline consumption, contrary to widely expressed opinions.

Fundamentals of higher-order s-to-z mapping functions and their application to digital signal processing

Abstract The principal advantage of using higher-order mapping functions is increased accuracy in digitizing linear, time-invariant, continous-time filters for real-time applications. A family of higher-order numerical integration formulas and their corresponding s-to-z mapping functions are presented. Two of the main problems are stability and handling discontinuous inputs. The stability question is resolved by analyzing the stability regions of the mapping functions. Sources of error in the accuracy of the output of digitized filters relative to their continuous-time counterparts are explored. Techniques for digitizing continuous-time filters, using the mapping functions, are developed for reducing different sources of error, including error resulting from discontinuous inputs. Performance improvement of digital filters derived from higher-order s-to-z mapping functions, as compared to those derived from linear mapping functions, is demonstrated through the use of examples. Analysis to demonstrate improvement is carried out in both the time and frequency domains.

Modeling the lines at the gas stations

A simulation model of the gasoline delivery system demonstrates the panic and formation of long lines at service stations. The dynamics of this process are similar to those observed in Southern California in the Spring of 1979.

MIT system dynamics articles available

Would you please pass the word on to readers that papers presented at the MIT summer course in system dynamics (described in my newsletter in the August issue, page 62), are obtainable at Xerox cost from System Dynamics Librarian, Massachusetts Institute of Technology E40-253, Cambridge, Massachusetts 02139. The two sets of Xerox study notes, costing

Simulation and Error Analysis of a Manual Rendezvous System

9.75 each, will also be available--hopefully, within

Rendezvous Navigation and Guidance Using a Hand-Held Self-Powered Digital Computer

Abstract A system for navigation, guidance, and control of a spacecraft to rendezvous with an orbiting target, based entirely on observations by handheld, unpowered instruments, and computations done entirely by hand, has been developed. This paper describes results of an interactive simulation of this system through a selected set of rendezvous missions, demonstrating feasibility in the presence of realistic errors. The simulation is carried out by a trained operator, the “astronaut,” working in conversational mode with a desk-size digital computer. The computer represents the environment, and the operator represents the astronauts decision-making process. Plots are given showing the increase in fuel and in a composite fuel-time cost as a function of the magnitude of the principal error sources, namely: model error due to separation range, model error due to eccentricity of the reference orbit, control errors in direction and magnitude of burn vectors, and measurement error. Results of a manual computation error study are also presented. It is shown that the manual rendezvous system is strongly convergent, so that the real penalty of errors is not failure to rendezvous, but rather, using more fuel and/or time than would otherwise have been necessary.