Fast-time Simulation Research Articles

ILLIADS: a fast timing and reliability simulator for digital MOS circuits

The authors introduce ILLIADS as a fast MOS timing and reliability simulator for very large digital MOS circuits. The use of the proposed general circuit primitive not only provides better accuracy but also significantly reduces the simulation time. The use of an analytic solution embedded in the simulation engine improves both the simulation speed and the accuracy. Postponing the waveform approximation process provides better waveform approximation even for non-fully-switching waveforms and glitches. The channel length modulation effect is captured accurately in fast timing simulation with only 10% of speedup tradeoff. It is also shown that ILLIADS manifests the charge sharing problem. The modified PWCTC algorithm, PWCTC-W, which handles circuits with feedback, is introduced and shown to be superior to the dynamic-windowing scheme. It also does not manifest the window-growing problem and is insensitive to the level of strongly concerned component (SCC) hierarchy. The use of this algorithm keeps the speedup of ILLIADS over SPICE for circuits with feedbacks at the same level as that for combinational circuits.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

水域施設における船舶操船の安全性評価方法に関する研究

In this paper, a systematic approach to assess maneuvering safety of ships in harbors and narrow channels is reported. At first, the sequence of safety assessment is discussed. Combining fast-time simulation and real-time simulation with CGI system, the safety assessment works can be systematically achieved. The deviation from the planed trajectory, which comes from many factors such as wind, current, can be estimated by use of fast-time simulation that controlling model is fixed. The estimated deviation from the standard can be used as a measure of maneuvering safety, and it will be helpful to set scenarios of real-time simulations. Real-time simulations are carried out for assessing maneuvering safety including human factors. By applying fast-time simulation's control model to real-time simulation's trajectory, and comparing with the both deviation, it is also possible to grasp hidden risk of maneuvering. The examples of safety assessment are finally reported and the effectiveness of the procedure mentioned above is shown.

Analytic transient solution of general MOS circuit primitives

The exact analytic transient solution is presented for a general MOS circuit primitive. In the circuit primitive, I-V characteristics of transistors are modeled by quadratic equations and node voltages by piecewise-linear waveforms. The proposed MOS circuit primitive, of which an inverter is a special case, is shown to be more suitable for switch level and fast timing simulations than the commonly used inverter. For circuit simulation of medium-size digital circuits containing a few hundred transistors, the application of this analytic solution has resulted in two to three orders of speed improvement over the conventional circuit simulator. The speed improvement factor is expected to grow with the circuit size. It is also shown that the exact transient solution of a macromodel which models the charge sharing can be obtained in the same way.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The billiard algorithm and KS entropy

There is known to be a close relation between the Kolmogorov-Sinai entropy (sum of the positive Lyapunov exponents) of an ergodic dynamical system and the algorithmic complexity of encoding trajectories of the system with respect to some partition. The authors explicitly gives an encoding which demonstrates this relation for the square Sinai billiard. The encoding depends on the fact that the collision criterion for the billiard is an example of rational approximants. The method may be used to achieve very fast simulation times for the system.

Compiling gate RC models into a top level simulation model for rough timing analysis of VLSI circuits

For aiding hardware compilers in selecting appropriately timed hardware components, for fast timing simulation, and for high level timing model generation, a timing analysis method is developed. This method uses simple RC models with the property that they can recursively be linked to form models for modules consisting of smaller modules. Only the timing parameters of the outer module are significant for delay calculation of the primary outputs. In this paper the linkable models, recursive linking procedure and timing analysis applications based on these models will be described.

Ship Auto-navigation Fuzzy Expert System (SAFES)

The growing demand for automation in ship navigation and for various assessments of harbors and waterways lends increasing importance to so-called fast-time simulation techniques and to ship simulator experiments that include man-in-the-loop simulation. The authors present an automatic navigation system known as SAFES that they have developed combining fuzzy theory and an expert-system, and that is applicable to the automation of ship navigation and to the modeling of the navigator in fast-time simulation. SAFES can treat various ship operations in both open seas and restricted waterways, as well as scenarios involving multiship encounters. It is pointed out that the expert system approach is essential for dealing with the complexities of the navigator's decision-making process, which cannot easily be handled in a sequential programming style such as one using FORTRAN. Each function of the navigator's orders and the helmsman's behavior can, however, also be represented by a non-fuzzy description. But once a general-purpose fuzzy controller/reasoner is prepared that passes one fuzzy output from two fuzzy inputs, almost all functions can be easily handled by fuzzy control/reasoning because most functions of human operation are originally characterized by only fuzzy descriptions.

A Fast-Timing Simulator for Digital MOS Circuits

An efficient and accurate algorithm has been developed for predicting the timing waveforms of general MOS transistor circuits. The algorithm uses a switch-level simulation technique to determine the steady-state conditions, a forward prediction method to predict the transient time between two adjacent voltage levels, a simplified timing simulation technique to correct this delay, and novel approaches for controlling the voltage step automatically. The simulation is further speeded up by the use of a table lookup model to calculate the transistor current and macromodels to evaluate certain circuit structures. This algorithm has been implemented as a new simulation mode, called fast timing, in the MOTIS3 multilevel mixed-mode simulator. Many production chips have been verified, and the results show that the fast-timing simulation can be three orders of magnitude faster than a conventional circuit analysis program such as SPICE, one order of magnitude faster than the MOTIS3 timing simulation, and only five times slower than the MOTIS3 unit-delay, switch-level evaluator. The delay accuracy of the new simulator is within 5 percent of the timing simulation.

Aircraft Separation Assurance: Systems Design

One of the major concerns in the operation of an air traffic system is the maintenance of adequate separation between aircraft. The assurance of an ‘acceptably low’ risk of collision is a crucial element in the system design. A number of factors need to be assessed in this process. What is the navigational performance of the aircraft in the system ? What are the possibilities for radar surveillance ? Are procedural arrangements together with position reporting a suitable mechanism? What difference would be made by collision avoidance or warning systems? Given that any combination of these or other factors has an implication on the minimum separation between aircraft, the level of safety ‘assured’ has to be balanced against the costs of the various alternatives which may present themselves.In planning for change the implications of new operating practices or devices have to be assessed carefully. For most changes the process is one of evolution rather than revolution, although collision avoidance devices may have more of the latter's characteristics. Even for ‘revolutionary’ changes it may be possible to model the new system. Thus the existing situation is studied and its characteristics observed, then there are hypotheses of the ways in which the change alters the mechanisms in the system and finally the likely effects on system performance through mathematical and computer (often fast-time simulation) modelling.

Evaluation of Airfield Performance by Simulation

Through the application of computerized simulation techniques, the future operation of a proposed airport can be evaluated prior to construction. TAMS developed and used a fast-time computer simulation to evaluate the performance of the proposed Dallas-Fort Worth Regional Airport. This simulation traces each aircraft operation between arrival and departure, including runway, taxiway, and gate selection and occupancy under various operating conditions. Output of the program provides total travel time and cost per aircraft type and by airline, delay times and location, facility utilization frequencies, and a computer-generated motion picture showing aircraft ground movements.

Ergonomic research in the German travelling mail services Part 2: Results of ergonomic research in railway mail vans

The travelling mail office clerks are shown, by medical examination and sociopsychological questionnaire, to be a very homogeneous naturally self-selected group with a low average age. The analysis of tasks shows a disadvantageous distribution of some main tasks over the work shift. Energy expenditure and cardio-vascular strain above physiological endurance limits occur mainly with the tasks of loading, handling and emptying mail bags. Environmental factors are mainly within acceptable standards. Fast-time simulation studies show that proposals can be made for organisation work (by job rotation) and selection of TMO clerks based on their individual working capacity.

Analysis of pilot warning indicator performance in terminal area traffic.

Three pilot warning indicator concepts for collision hazard avoidance are analyzed using computer fast-time simulation. A hazard measure is defined based on a 1/2-g maximum horizontal acceleration, a maximum climb or dive angle of 10 deg for each aircraft, and a 20-sec warning time, through escape completion. The traffic model is based on flight tracks recorded in the Atlanta terminal area over an 11 hr period during August 1967. The basic PWI concept studied alarms on range to flashing beacons mounted on intruder aircraft as a function of relative azimuth and elevation. The alarm-hazard epoch ratio is about 17/1 to maintain the missed-alarm rate below 10%. Beacon vignetting or range-rate discrimination are shown to reduce the false-alarm rate by about 75%.

Application of fast-time simulation techniques to the study of ATC systems.

Abstract This paper reviews the techniques open to the study of air traffic control systems and, in particular, the feasibility of fast-time simulation methods. The peculiarities of an ATC system and the difficulties of representing it by a logical element are discussed. A description is, nevertheless, given on the progress which has been made in the development of the so-called ‘ Ground ’ model, a fast-time simulation which, although still in its infancy, is expected to evolve very soon into an efficient tool for the study and comparison of various ATC systems and organisations.

Near ideal digital predictive compensation

The problem of realizing a near ideal predictor for use in compensation of error sampled linear systems is considered and a solution using fast-time simulation is proposed. Prediction theory is extended to include the near ideal predictor and analytical results are presented. A comparison is made between ideal and near ideal prediction as applied to the compensation of example systems. Near ideal predictive compensation is compared with conventional compensation; their combination provides a new and versatile approach to compensation. Errors in the fast-time simulation model are considered, and it appears that the fundamental advantages of using near ideal predictive compensation are retained even when the model is inexact. The ability of this new technique to provide, in effect, a zero without a pole in the z plane offers unique advantages in the compensation of systems containing a time delay.

The Minicomputer Approach to Predictive Compensation

The theory concerning the use of fast-time simulation to realize a near-ideal predictor for sampled control systems is discussed, and an evaluation is presented of its use as a method of compensation. A comparison is made between near-ideal predictive compensation and conventional compensation. When the approaches are combined they form a new and versatile approach to compensation.

Determining if Sonar Contact Can be Maintained

ASW effectiveness is strongly dependent on whether sonar contact can be maintained long enough for a attack to be accomplished. Proper design and use of weapons systems both depend upon the probable duration of contact maintenance. A number of stochastic models of propagation and detection variability are considered. A method is described of fast-time tactical simulation which makes use of such models to evaluate the overall effectiveness of the sonar/weapon system combination.

Analytical methods of research into terminal area air traffic operations

The application of mathematical models of various suboperations in the terminal area, and the use of fast time simulation on a digital computer to study the operation of a complete terminal area traffic control system, are briefly demonstrated. Mathematical models are used to analyze the capacity of race track holding patterns, the laddering operation, and the instrument landing system (ILS) funnel with time separations at the gate. The results of a fast time simulation on an IBM 7094, for an advanced method of providing sequencing and spacing for a single ILS runway are given. The landing system demonstrates a capacity of 32 landings/hr, along with runway availability for 20 takeoffs.

Queueing Theory in Fast Time Simulation of Air Traffic Control

the use of queueing theory in understanding certain Air Traffic Control problems is discussed. Two primary areas of application are given as: (a) Providing a theoretical comparison for experimental (simulation) results; (b) Obtaining solutions to certain small scale problems not justifying a simulation study. A brief introduction on the general theory is given, followed by a presentation of certain developments found in the literature applicable to Air Traffic Control, and especially as an analytical counterpart to Fast-Time Simulation. Two examples illustrate applications.