Boots – shoes – and leggings
Patent
1996-05-15
1998-06-09
Trammell, James P.
Boots, shoes, and leggings
364153, 364185, 364581, G06F 1760
Patent
active
057645370
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/US93/11303 filed Nov. 19, 1993.
BACKGROUND OF THE INVENTION
The present invention generally relates to a method and an apparatus for detecting the freezing or failure of a sensing process and assembly in a controlled apparatus and process. The sensing process and assembly comprises a sensor which generates a sensor output signal which is further converted to a process signal by the sensing process and assembly, and the sensor within the sensing process and assembly is subjected to (continuous) transient variations due to process noise in the controlled apparatus and process.
In the case of process control, noise signals can either be produced in the controlled apparatus and process (to which measurements are applied) as process noise or in the measurement method (which is implemented using an extended sensing process and assembly) as measurement noise. In this connection the term "noise" is used to signify all forms of interference. It is usually not possible to identify the source of noise in a signal through the use of conventional analytical techniques on the time discrete signals themselves. Usually, noise will demonstrate an oscillatory or vibrational characteristic when a series of discrete signals is analyzed as a function of time; usually, the overall oscillatory pattern can be resolved into a set of sine waves having characteristic frequencies.
Process noise is produced from transient variations in the controlled apparatus and process itself in the regions proximate to the location of the measuring sensor. There are a variety of factors that can contribute to such variations in the controlled apparatus and process itself such as the presence of entrained gas bubbles in liquid, local variations in a liquid density as in the case of agitated oil/water mixtures, local variations in liquid temperature, turbulence, or the like.
Measurement noise is produced in each stage of the sensing process and assembly. The measurement noise is usually a function of the quality of the sensing process and assembly.
Current methods used to measure process variables such as temperature, pressure, and flow inherently yield signals which incorporate both process noise and measurement noise in their magnitude. Hence, using a process signal corrupted by noise is a long-standing problem of process control engineers. Measurement noise is normally the less significant component in the total amount of noise present in a given signal when compared to the process noise component, and the measurement noise can be reduced further by corresponding measures such as grounding of the electrical circuitry or the like. The following discussion will, therefore, focus on the process noise component and presume that the influence of the measurement noise component is essentially negligible in the application of the present invention.
In a controlled apparatus and process where a control unit or set of control units assists in the operation of a complicated machine such as a nuclear power station, automobile, turbine, chemical manufacturing process, or the like, various parameters of the process being controlled are monitored to determine the status of the process at any point in time. To this end, sensors and transducers are used to generate sensor output signals which represent the values of various attributes (such as temperature, pressure, flow rate, rpm., or vessel level) characteristic of the controlled apparatus and process.
A sensor is a device which is constructed to respond to a given event, occurrence, or state and to produce an accordingly predetermined sensor output signal representing the aforementioned state, occurrence, or event as an analog or digital signal (or, in a more virtual sense, as a numeric or Boolean quantity). The term "sensor" can also include, as a further component, a device which might be designated as an interactive measuring device which is in physical contact with the controlled apparatus and process (a transducer), and this general device will be hereinafter considere
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patent: 5394744 (1995-03-01), James et al.
patent: 5504473 (1996-04-01), Ceci et al.
patent: 5514968 (1996-05-01), Spanjers
H. V. Panossian, V. R. Kemp, "Real-time fault detection of the space shuttle main engine", Proceedings of the 30.sup.th IEEE Conference on Decision and Control, vol. 3/3, Dec. 1991, Brighton GB, pp. 2609-2610.
Gagne Ronald
Walter Hilger A.
Schultz Dale H.
The Dow Chemical Company
Trammell James P.
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