Nonlinear Adaptive Control of a Synchronous Machine

A nonlinear adaptive controller for a load-commutated brushless dc machine that allows the machine to develop high torque over a wide range of operating conditions, while satisfying voltage and current constraints on both stator and field circuits, is presented. The approach taken is fundamentally different from past work in that a nonlinear control is formulated from the steady-state model of the synchronous machine. Adaptive algorithms are presented for both the unknown load and motor cases.     

Limitations of radiometer performance in spherically invariantnoise

The radiometer is a common method for detection of unknown signals in noise. Most analyses of radiometer performance are based on assumptions of stationary Gaussian noise with known marginal statistics. In this note, we use a spherically invariant noise model to derive simple expressions for radiometer performance degradation in noise variance uncertainty. Numerical examples are provided to show that channel uncertainty imposes a substantial penalty in detection performance     

A directed search for extraterrestrial laser signals

This paper analyzes the technical feasibility of interstellar communication at infrared frequencies, both in its own right and in comparison with communication at radio frequencies. The analysis considers both the practical and fundamental limits affecting communication over interstellar distances and concludes that for specified transmitter and receiver locations communications at infrared and radio frequencies can be equally effective. On this basis a search for extraterrestrial signals at infrared wavelengths is equally as valid as any planned microwave effort. Work is now in progress to adapt a 10 micrometers heterodyne spectrometer to search for CO2 laser signals from 200 nearby stars.     

Adaptive field-oriented control of an IM using predictive control

A novel adaptive control algorithm for the field-oriented control of a CSI-fed induction machine is presented. It includes an adaptive flux model for determining the position and magnitude of the rotor field vector, which avoids the need to obtain the orientation and magnitude of the flux for purposes of feedback. This online estimation of field vector requires the measurements of stator voltage and rotor speed. The algorithm has been tested by simulating the machine using a digital computer. The controller perform well, and the machine parameters are estimated with reasonable accuracy. The controller has a self-adjusting mechanism and adjusts itself to any variation of machine parameters during operation. It can be applied to any machine and requires no tuning. The scheme is being tested on a machine inverter setup controlled by a microcomputer     

Adaptive Control of a Current-Fed Induction Motor

An adaptive nonlinear control system is presented for a currentsource inverter-fed induction motor. The approach to the control problem is fundamentally different to previous work in that it uses the steady-state model to formulate a nonlinear control which directly controls the shaft speed. The controller is adaptive, so neither load nor machine parameters need to be specified, although in practice the latter would always be known since they are required for the current-source inverter design.     

Torque, Speed, and Position Control of Induction Machines Using the DQ Model

New nonlinear controllers for torque, speed, and shaft position of inverter fed induction machines are developed. The controllers are novel because they are based on the full DQ model of the machine and hence account for the nonlinear characteristics of induction machines. In addition, a multivariable control algorithm based on the DQ model is considered. Simulation results for the single input controllers are presented.     

Adaptive on-line flux estimation in field-oriented control of an IM

An adaptive technique for the online estimation of the rotor field vector to use as a feedback for the field-oriented control of an induction machine (IM) is described. This method makes use of the stator voltage and rotor speed measurements. It uses the least square estimation technique for identifying the machine parameters to be used in the estimation of the field vector. The position and magnitude of the flux vector are identified during the normal operation of the machine by applying some special constraints to the forcing function. This constraint is applied only for a short duration to make some measurements, and the machine performance is not affected. Extensive simulation of the system has been carried out, and the results are presented