Engineering topics
Publications and source records attributed to Phillips, C. L..
This paper considers digital controllers (filters) operating in floating-point arithmetic in either open-loop or closed-loop systems. A quantization error analysis technique is developed, and is implemented by a digital computer program that is based on a digital simulation of the system. The program can be integrated into existing digital simulations of a system.
In this paper a technique is developed for choosing programing forms and bit configurations for digital filters that minimize the quantization errors. The technique applies to digital filters operating in fixed-point arithmetic in either open-loop or closed-loop systems, and is implemented by a digital computer program that is based on a digital simulation of the system. As an output the program gives the programing form required for minimum quantization errors, the total bit configuration required in the filter, and the location of the binary decimal point at each quantizer within the filter.
The results are reported of research into the effects on system operation of signal quantization in a digital control system. The investigation considered digital controllers (filters) operating in floating-point arithmetic in either open-loop or closed-loop systems. An error analysis technique is developed, and is implemented by a digital computer program that is based on a digital simulation of the system. As an output the program gives the programing form required for minimum system quantization errors (either maximum of rms errors), and the maximum and rms errors that appear in the system output for a given bit configuration. The program can be integrated into existing digital simulations of a system.
The existence of quantizer-induced limit cycles in digital control systems is a well-known phenomenon. This paper reports the results of an investigation into the discrete describing function technique which is applicable not only to the quantizer nonlinearity but also to any nonlinearity in an otherwise linear discrete system. First a general expression is developed for the discrete describing function that is applicable to any nonlinearity. The describing function is then obtained for the quantizer nonlinearity. Finally, the use of the discrete describing function is illustrated by an example of a digital control system.
It is shown that an otherwise stable digital control system can be made unstable by signal quantization when the controller operates on floating-point arithmetic. Sufficient conditions of instability are determined, and an example of loss of stability is treated when only one quantizer is operated.
Signal quantization induced low amplitude oscillations in digital control systems, discussing relationship to digital controller programming form
Accuracy requirements determination method for digital controller coefficients, discussing bits needed
Generation and application of sensitivity coefficients
Upper bound on system errors caused by quantization in multirate digital control system
Bits quantity required to represent coefficient within digital controller with high sampling rate
Digital controller bits number determination to meet nominal controller coefficients accuracy requirements
Upper bound determination for errors due to signal quantization in multirate digital control system through state variable or z transform formulations
Linear ordinary differential equation systems first order output sensitivity coefficients generation and application to second order cross sensitivities
Taylor series expansion used in correcting quantized digital coefficient errors in hybrid feedback control system
Coefficient quantization in digital continuous time process controllers, applying results to nominal transfer function approximation
Correction coefficients for time response of hybrid control systems with digital feedback elements containing quantized coefficients
Time response deviation correction in hybrid computer control systems with digital feedback elements containing quantized coefficients
Simultaneous generation of sensitivity functions for linear automatic control system with known characteristic differential equation