A method of combining Kahnan filtering and minimax filtering is proposed and demonstrated in an application to phase-locked loop design. Kalman filtering suffers from a lack of robustness to departures from the assumed noise statistics. Minimax filtering, however, has the drawback of ignoring the engineer's (admittedly incomplete) knowledge of the noise statistics. It is shown in this paper that hybrid Kalman/minimax filtering can provide the “best of both worlds” . Phase-locked loop filter design is used in this paper to demonstrate an application of hybrid estimation.

Different approaches to parameter identification for a triaxial shaker system are examined. One approach uses an output error formulation of a cost function, which is then minimized using a standard algorithm. Two other approaches use a cost function defined through an input error formulation. The cost function is minimized through, alternately, a standard function minimization algorithm and a linearized least-squares algorithm. For the case of fewer measurements than degrees of freedom, a generalized technique for reconstructing the states is proposed. This technique does not make any assumptions regarding the absence of external forces on unmeasured degrees of freedom. The three approaches to parameter identification are compared for two different systems.

Computer modeling and simulation has been a successful tool in the design of complex control systems. This paper discusses a computer simulation that is being developed to evaluate a controller for a triaxial shaker system. The shaker system has eight inputs and six outputs. Frequency response data from testing of the actual system has been used to identify parameters for the model

The problem of robust phase-locked loop design has attracted attention for many years, particularly since the advent of the global positioning system. This paper proposes and demonstrates the use of a fuzzy PLL to estimate the time-varying phase of a sinusoidal signal. It is shown via simulation results that fuzzy PLL's offer performance comparable to analytically derived PLL's (e.g. Kalman filters and H/sub /spl infin estimators) when the phase exhibits high dynamics and high noise. The fuzzy PLL rules are optimized using a gradient descent method and a genetic algorithm.< >

The optimal interpolative (OI) classification network is extended to include fault tolerance and make the network more robust to the loss of a neuron. The OI net has the characteristic that the training data are fit with no more neurons than necessary. Fault tolerance further reduces the number of neurons generated during the learning procedure while maintaining the generalization capabilities of the network. The learning algorithm for the fault-tolerant OI net is presented in a recursive formal, allowing for relatively short training times. A simulated fault-tolerant OI net is tested on a navigation satellite selection problem

The application of neural networks to optimal satellite subset selection for navigation use is discussed. The methods presented in this paper are general enough to be applicable regardless of how many satellite signals are being processed by the receiver. The optimal satellite subset is chosen by minimizing a quantity known as Geometric Dilution of Precision (GDOP), which is given by the trace of the inverse of the measurement matrix. An artificial neural network learns the functional relationships between the entries of a measurement matrix and the eigenvalues of its inverse, and thus generates GDOP without inverting a matrix. Simulation results are given, and the computational benefit of neural network-based satellite selection is discussed.

The complexity of the design of a Global Positioning System (GPS) user segment, as well as the performance demanded of the components, depends on user requirements such as total navigation accuracy. Other factors, for instance the expected satellite/vehicle geometry or the accuracy of an accompanying inertial navigation system can also affect the user segment design. Models of GPS measurements are used to predict user segment performance at various levels. Design curves are developed which illustrate the relationship between user requirements, the user segment design, and component performance.

This paper presents the results of an investigation of the application of the Global Positioning System (GPS) to real-time integrated missile navigation. We present quantifiable measures of navigation accuracy as a function of GPS user segment parameters. These user segment parameters include antenna phase response accuracy, single versus dual frequency, and Kalman filter structure and size. We also formulate some new phase-locked loop (PLL) filter designs for application in GPS receivers, and demonstrate their superiority over more conventional filters.< >

The problem of robust phase-locked loop (PLL) design has attracted attention for many years, particularly since the advent of the Global Positioning System. This paper proposes and demonstrates the use of a fuzzy PLL to estimate the time-varying phase of a sinusoidal signal. It is shown via simulation results that fuzzy PLLs offer performance comparable to analytically derived PLLs (e.g., Kalman filters and H/sub /spl infin estimators) when the phase exhibits high dynamics and high noise. The fuzzy PLL rules are optimized using a gradient descent method and a genetic algorithm.<>

A method of combining Kalman filtering and minimax filtering is proposed and demonstrated in an application to phase-locked loop design. Kalman filtering suffers from a lack of robustness to departures from the assumed noise statistics. But minimax filtering has the drawback of ignoring the engineer's (admittedly incomplete) knowledge of the noise statistics. It is shown in this paper that hybrid Kalman/minimax filtering can provide the best of both worlds. Phase-locked loop filter design is used in this paper to demonstrate an application of hybrid estimation.

A trajectory reference system based on the Global Positioning System (GPS) can be used instead of conventional radars during missile flight tests. The high quality of the GPS-based trajectory reference makes it useful for evaluating the performance of the missiles' inertial measurement units. Such a system was installed and flight tested on two recently launched ballistic missiles. The GPS hardware configuration used on these flights is described. A Kalman filter approach is used to estimate individual inertial measurement unit errors based on the GPS range and delta range data. The ability of the GPS-based system to identify inertial measurement unit errors is compared to that of radar; the GPS is found to provide superior estimates.

This paper uses Lyapunov stability theory to analyze the stability properties of digital phase lock loops (DPLLs). As is the case with most stability analyses, this paper deals with the noisefree case. While practical analysis and simulation of a real system must include some noise model, a prerequisite for such analysis is the knowledge or assumption of the system's stability. The stability conditions derived in this paper are the same as those obtained elsewhere. The purpose of this paper is to expose Lyapunov theory as a viable option for DPLL design and analysis.< >

There is much interest in integrated navigation us- ing the Global Positioning System and Inertial Mea- surement Units (accelerometers and gyroscopes). The results reported in this paper quantify integrated nav- igation performance as a function of GPS receiver de- sign parameters. The specific application considered is missile navigation.

There is much interest in integrated navigation using the global positioning system and inertial measurement units (accelerometers and gyroscopes). The results reported in this paper quantify integrated navigation performance as a function of GPS receiver design parameters. The specific application considered is missile navigation

The purpose of this paper is to discuss the use of modeling and simulation in the design and analysis of a hydraulic rail car stabilization control system. The simulated models have been verified by comparing the simulation results with engineering test data. The simulation was used as a tool to understand the causes of different anomalies observed during system hardware testing, defining solutions to test anomalies, and improving overall system performance.

As new applications for the use of the Global Positioning System (GPS) on aerospace vehicles emerge, more attention is being paid to the design of the user segment, which comprises the hardware and software employed by the user to obtain navigation information from GPS. The complexity of the design of the user segment, as well as the performance demanded of the components (such as the antenna), depends on user requirements such as total navigation accuracy. Other factors, for instance the expected satellite/vehicle geometry or the accuracy of an accompanying inertial navigation system, can also affect the user segment design. The interaction between these effects, the user requirements, and the user segment design is studied. Design curves are developed which allow quick trade studies to be performed.

The high quality of a GPS-based trajectory reference makes it useful for evaluating the performance of a missile's Inertial Navigation System (INS) during a missile flight test. The complexity of the design of the GPS user segment depends on flight test objectives and factors such as the expected satellite/vehicle geometry. Design curves are developed which illustrate the relationship between flight test objectives, the GPS user segment design, and such factors as antenna performance.

The optimal interpolative (OI) classification network is extended to include fault tolerance and make the network more robust to the loss of a neuron. The OI Net has the characteristic that the training data are fit with no more neurons than necessary. Fault tolerance further reduces the number of neurons generated during the learning procedure while maintaining the generalization capabilities of the network. The learning algorithm for the fault tolerant OI Net is presented in a recursive format, allowing for relatively short training times. A simulated fault tolerant OI Net is tested on a navigation satellite selective problem.< >