Showing papers on "Process variable published in 1986"

Method of digital process variable transmitter calibration and a process variable transmitter system utilizing the same

Abstract: A method of digital process variable transmitter calibration includes the steps of sensing the process variable (PV) to produce an analog output which is converted to a digital signal representation. The digital signal is corrected by a microprocessor using a characterization equation previously individually developed during a manufacturing testing of the process variable transmitter over a predetermined range of environmental stimuli to ascrtain the coefficients for a polynomial in the form of PV=Ao =A1 P+A2 +. . . Ai Pi. Thus, the digital computer produces a process variable representation as a modified digital output. Subsequently, the digital output from the computer is converted to a conventional 4-20 mA analog signal for use as a process control signal. The process variable transmitter apparatus utilizing the aforesaid method includes means for receiving an output from a process variable sensor, an analog-to-digital converter for converting the received output from the sensor to a digital representation, a digital computer, a non-volatile memory for storing an individualized correction equation determined during the manufacturing testing of the transmitter and a digital-to-analog converter for converting the computer output to an analog control signal.

Method and apparatus for process control

Abstract: A method and apparatus are provided for producing a control signal by digital computation for controlling an element affecting a process. The process is described by a sequence of activities, and the onset of each activity is marked by a predetermined change of a process parameter. An event detector is provided for detecting the occurrence of predetermined changes of process parameters in response to data included within event detector data blocks. The event detector data blocks include data defining the desired response to the detection of a predetermined change of a process parameter. The control signal is produced in accordance with a selected predetermined algorithm using data included in algorithm data blocks. A first event detector data block and a first algorithm data block are selected defining a first predetermined change of a process parameter and a first algorithm. Upon detection of the first predetermined change, of a process parameter, a second predetermined change of a process parameter is selected in accordance with data included within the first selected event detector data block and a second algorithm data block is selected defining a second algorithm.

Process variable effects on sheet metal quality

Abstract: A system for major classification of sheet metal forming process variables is established. Subsequently five major sheet forming process variables — blank size, blank location, binder force, material thickness and lubrication — were selected for investigation. The effects of these variables on panel quality were quantified by determining panel strain state and buckle severity.

Method for manufacturing mineral fibers

Abstract: A method for manufacturing mineral fibers comprises controlling the bushing temperature to maintain molten glass throughput from a bushing at a constant, calculating the viscosity of the molten glass from the bushing temperature and the temperature of a glass delivery means, and modifying a process parameter in response to the calculated viscosity.

Using Counts to Monitor a Process Mean

Abstract: A procedure for controlling a process mean to a target midway between two specified values is presented. It is assumed that the process variable has a normal distribution with unknown mean and variance, and that the data consists solely of counts of the..

Simple, low‐cost planar flow casting machine for rapid solidification processing

Abstract: The design, fabrication, and operation of a relatively simple low‐cost planar flow casting (PFC) machine optimized for small‐batch processing were investigated by the Bureau of Mines. Several design features found beneficial to PFC process operation include: a ground nozzle stopper to retain the alloy charge during melting; a remote, large‐volume pressure vessel connected to the crucible gas system to reduce temperature‐induced pressure fluctuations; and the use of a nested induction coil that allows both the melt charge and the crucible reservoir to be located close to the cooling wheel. The results of several PFC process runs are provided showing typical values of the cooling wheel surface velocity, crucible ejection pressure, and crucible nozzle clearance gap. Examination of the rapidly solidified, Fe‐based ribbons for thickness, dimensional uniformity, and atomic structure indicated that good quality glassy ribbon could be produced with proper selection of the controllable process variables. In addition, single‐variable linear regression analysis was used to determined the effect of each process variable on the resulting ribbon thickness.

Automatic adjusting method of control constant

Abstract: PURPOSE:To adjust a control constant to an optimum value and to allow process variables on the lower side of a control system to respond with excellent stability and promptness by identifying the transmission function of a controlled system in the control system and that of the controlled system on the lower side of the control system and allowing the transmission function from a target value of a controlled variable to a process variable, whose response control is required, on the lower side of the control system to coincide with the transmission function of a reference model showing an ideal response characteristic CONSTITUTION:A control operation device is provided with the second controlled system (process) 6 on the lower side of the control system, the second identifying operation part 7 which identifies the transmission function of the second controlled system in accordance with a controlled variable signal ys(t) and a process variable signal xs(t), and the second detector 8 which detects a process variable x(t) to output the process variable signal xs(t) The first and the second controlled systems are approximated by self-regression moving average models, and G1(s) and G2(s) are identified in accordance with time series signals vs(t),ys(t), and xs(t) before and after them A control constant operation part 4 obtains the transmission function from a target value rs(t) or y(t) to the process variable x(t) and obtains the optimum control constant on a basis of an operation formula so that this transmission function coincides with a transmission function Gm(sigma, s) of the reference model showing the ideal response characteristic, and the control constant of a control operation device 2 is corrected Thus, the control constant by which the process variable in the lower side of the control system responds ideally is obtained easily without feeding back this process variable to the control system

Recursive estimation of the continuous-time process parameters

Abstract: The problem of continuous-time process parameter identification is considered. Filtered input-output process signals are used to create a linear differential equation governed by the same continuous-time process parameters. The estimation scheme is implemented by sampling the filtered signals and using a recursive least squares algorithm (RLS). The choice of filter leads to different parameter convergence properties. Conditions for parameter convergence are established in terms of frequency content of the input signal. The convergence rate is also analysed and an upper bound on the parameter error norm is given. The relation between choice of filter, sampling time selection and quality of the estimates is discussed and exemplified with simulation examples.

Finite-element model and feasibility study of thin strip continuous casting of steel

Abstract: The thermal feasibility of a newly proposed thin strip continuous casting process was investigated by using an extended finite-element model. The investigation is presented as a case study of how such a process can be modeled. Details of the thermal model are given, including the boundary-layer phase change technique developed for modeling the solidification process. Bonding of solidified melt to clad was investigated on a near-microscopic scale, using microsecond time steps to track the thermal shock of initial molten metal/clad contact. This casting process would provide a product with two quality surfaces at substantial energy savings over conventional full-thickness cast/rolled sheet production by using thin cold-rolled feedstock as a cladding. The candidate material used for study was ANSI-1020 carbon steel. Modeling parameter variations identified the melt-to-solid(clad) ratio of the product as the most important modeling and process parameter, with thermal feasibility demonstrated for values of thi...

Furnace pressure control device in converter waste gas treatment device

Abstract: PURPOSE:To improve the rate of recovering waste gas and to stabilize an operation by providing a means for discriminating the adequateness and inadequateness of control parameters, etc. and making changeable the control parameter of a furnace pressure control means in accordance with the result of the discrimination. CONSTITUTION:The titled furnace pressure control device consists of a furnace pressure detecting means 12, the furnace pressure control means 14 which compares the furnace pressure detected by said means and a set value and outputs the control signal corresponding to the deviation therebetween, a flow rate control means 15 which controls the flow rate of the waste gas generated from the inside of a furnace 1 in accordance with the signal therefrom and the discriminating means 16. The means 16 discriminates the adequateness and inadequateness of the control parameter at certain point of the time of the means 14 in accordance with the control output from the means 14 and the furnace pressure. The control parameter of the control means is so changed as to be adaptive to the process parameter at the point of said time in accordance with the result of the discrimination.

Abnormality diagnosis system of process

Abstract: PURPOSE:To study early a fundamental factor that produced the operation variance by obtaining a stability coefficient from the measured value of each process variable and displaying these coefficients in the form of a pattern. CONSTITUTION:When either one of process variables reaches an alarm level, a CPU22 produces an alarm. At the same time, the CPU22 calculates the stability coefficients before 1, 2 and 3 minutes from the alarm produced point for each process variable and displays these coefficients in the order of larger absolute value and in the form of a pattern on a CRT display device 25. Further, a fault state of each instrument is displayed on a CRT display device 25. Then the CPU22 calculates the stability coefficient of each process variable every time the countermeasure enable time, e.g., 1min elapses, and absolute value of the stability coefficient is displayed in the display device 25 as pattern in order from large value at each point of time.

Manufacturing method of diaphragm for speaker

Abstract: PURPOSE:To obtain a TiN (titannitride) layer with high elastic ratio at a surface by processing, with high temperature and high pressure, a titanium foil and a titanium alloy foil molded to a dome-shaped diaphragm shape, in a nitrogen gas atmosphere beforehand. CONSTITUTION:This material using a titanium alloy foil is molded to a dome-shaped diaphragm shape beforehand. Next, a surface at a titanium diaphragm is cleaned with an ultrasonic wave by fleon solution and an oily dust, etc., which are stuck at the surface, are removed. After that, after a diaphragm for a speaker is set into a high temperature high pressure processing device, a cover is closed and the inside of the device is evacuated, the inside of the device is replaced by a special pressure nitrogen gas and next, a special high pressure nitrogen gas is filled and a temperature up is executed. After preservation is executed by a special high temperature for a special time, temperature descends and pressure decreases and a processed body is removed. A process parameter of high temperature and high pressure processing by the method is shown in a figure. As shown in the figure by processing of the method, TiN (titannitride) layers 2 and 3 of a special thickness are formed at the surface of the titanium diaphragm 1, and a diaphragm with very high surface hardness and high elasticity can be obtained.

Optimum control system

Abstract: PURPOSE:To make always a stable control of good quick responsiveness possible by providing an identifying operation part which identifies a process parameter and a parameter operation part which obtains an optimum control parameter on a basis of the identified parameter. CONSTITUTION:A process variable (x) from a process 1 is inputted to an optimum control device 4 and the optimum control operation is executed, and a calculation result U is inputted to a plant to execute the control. Meanwhile, an identifying operation part 2 of the process calculates a process parameter Pp in accordance with an identifying signal Z outputted from the process 1 to detect the variation of the process characteristic. The calculated process parameter Pp is sent to an optimum control parameter operation part 3, and an optimum control parameter Pc is operated by a prescribed operation there and is given to the optimum control device 4. Thus, the optimum control parameter which is not unstable even in the severest conditions of control and is weakened unnecessarily is obtained in accordance with the variation of the process parameter.

The basic process unit

Abstract: A process control system comprises a process involved in a controlled system and a process controller. Functions of the entire process control system are described in this chapter. The basic process unit which integrates all essential process and process control functions is identified as the basic building block of the process control system, both for its vertical and horizontal integration. The most critical parameter of the functioning of the basic process unit is its data processing ability. Therefore the different functions of the basic process unit controller are considered separately. The necessary data processing functions of the controller are established and analysed as based on available data processing time. The timing relations and informational features of process input/output devices are also given because they limit the functional and informational characteristics of the basic process unit and therefore the entire process control system.