Showing papers on "Process variable published in 1993"

Flexible automation system for variable industrial processes

Abstract: A flexible automation system for variable industrial processes (e.g. for processes on an oil or gas conveyer platform) includes programmable controllers that are linked via bus subsystems to process variables that are assigned in digital or analog form. The bus subsystems have communication interfaces for retrieving process variables from the programmable controllers. A retrieval signal is assigned to each process variable in coded form.

Unbiased estimation in dynamic data reconciliation

Abstract: A computationally fast technique accurately estimates process variables when conditions are dynamic due to changes in steady states. The process variable estimators are unbiased and have known distributions. Thus, confidence intervals for true values of process variables are provided. The formulation of this technique was motivated by a recursive, dynamic data reconciliation technique that obtains very accurate estimators. These two techniques are compared in terms of computational speed and accuracy of estimators. The proposed technique is computationally faster, but not as accurate when variances of process measurements are large. However, the accuracy of the proposed estimators is shown to approach that of the recursive technique by iteratively recalculating estimates and when measurement variances decrease.

Adaptive process control system

Abstract: Adaptive process control system, where the control model (M) consists of several sub-models (M1, M2 to Mk) and the computed outputs ( pi 1, pi 2 to pi k) of the sub-models are passed to a neural network (8) which generates the process parameter to be pre-computed as the network output (yN) from the measured process parameter (y) is used to adapt the neural network parameters (NP). Where the influence of input values (xp) on the computed process parameter (y) cannot be described by modelling, these are entered directly into the neural network. The network parameters (NP) are adapted on-line after each process completion by evaluation of measured input values (x) and measured process parameters (y).

Filling of a complex-shaped mold with a viscoelastic polymer. Part I: The mathematical model

Abstract: A model for the filling stage of injection molding of viscoelastic thermoplastics in cavities of complex shape is presented. The model considers two-dimensional melt flow, with converging and diverging flow patterns induced by complex boundary shape and by the presence of an obstacle. The model is non-isothermal (with the melt loosing heat to the mold walls as it travels into the cavity) and handles a viscoelastic (following the White-Metzner model) material with properties that vary with temperature, shear rate, and pressure. The numerical method is based on finite differences, with boundary fitted curvilinear coordinates used in the mapping of the flow field (which has an arbitrary shape that evolves with time) into a time invariant rectangle. The numerical results reveal geometry-induced asymmetries in the flow and thermal fields as well as the effect of various process parameters on the pressure and temperature profiles in the cavity. The model admits variable cavity thickness, thus allowing for a treatment of the cavity thickness as a process parameter in the simulations.

Method of production and/or processing as well as winding an endless material of thermoplastic plastic with output of a quality signal as well as a takeup machine

Abstract: In such a process in which a quality signal Q is output as a function of a continuously measured process parameter, one selects a parameter of state of the forming package (33) as an indicative process parameter, one acquires same, a value derived therefrom, or the value varying with respect to time during the entire winding cycle of the formed packages (33), and one compares the values with a predetermined representative value or its tolerance range, so as to release a quality signal in the event of an undue deviation of the parameter of state or the derived value from the desired value. This [signal] may used to cause an alarm, to classify the production results of the continuously produced packages (33) and/or intervene in the process control, so as to counteract the detected deviations or tendencies to such deviations. To carry out the method, a suitable sensor winding head is described, which enables a continuous determination of the weight of packages (33) during the winding cycle.

An adaptive control optimization for circular sawing

Abstract: This paper describes a method of adaptive control optimization developed for circular sawing to produce a specified surface finish quality in a production environment. It is possible to develop the relationship between the workpiece feed-rate and acoustic emission (AE) count-rate, which is used for the automatic control of workpiece feed-rate, by a single cutting test. This is done for the workpiece immediately before operation by adaptive control optimization, with the workpiece feed-rate and AE count-rate chosen as control variable and process variable, respectively. A multiple-regression equation based on AE count-rate and specific gravity for softwoods is effective for adaptive control optimization of circular sawing in order to produce the required surface finish quality

Automatic process control and noise suppression

Abstract: A method for automatically controlling a nominal property value of a material in the process of making the material, The method includes the steps of providing a feedback model of the process and eliminating the influence of time delay on determining the nominal property value, A state observer is used to estimate at least one unmeasurable variable of the process as a function of at least one measurable variable of the process The above steps are combined to control the nominal property value as a function of a process variable that is both measurable and undelayed An actual feedback measurement containing a time delay can be used to correct for any errors that might exist in the feedback estimate

Interface controller for matching a process address field from a plurality of fields and generating a corresponding device address field

Abstract: An apparatus receives a query from a process controller containing a process variable address representing a storage location for a process variable in a network of field devices. A communication standard type and an unique field device address is associated with each field device. An associating section identifies a field device address and a communication standard type associated with each of a plurality of process variable addresses. An extracting section matches the stored process variable address with a process variable address in the associating section and extracts the associated field device address and the associated communication standard type from the associating section. A generating section generates a field device request containing the extracted associated field device address as a function of the extracted associated communication standard type. The field device request is conveyable over a communication line to address the storage location represented by the stored process variable address.

Apparatus for and method of controlling a process

Abstract: A process control apparatus for use in a control system includes a controller (40) for coupling to a process in a closed loop of the control system and for controlling a process variable having predetermined set point and measured values. A deviation signal is generated by comparing the set point and measured values to generate a deviation signal and the controller (40) is responsive to the deviation signal to control at least one operating parameter of the process to reduce the deviation signal. An identification section (60) is provided which is responsive to the deviation signal and which provides a measured value of at least one characteristic of the closed loop response of the control system from the deviation signal by integrating the deviation signal with time. A design section (80) is coupled to the output of the identification section (60) and compares the measured characteristic value with at least one predetermined desired characteristic value representing a desired closed loop response of the control system. The controller (40) is adjustable when the difference between the measured and desired characteristic values is greater than a predetermined amount such that the closed loop response of the control system moves towards a desired closed loop response.

Yield improvement in SMT production by integrated process monitoring and testing

Abstract: Almost 30-50% of fabrication costs in electronics production are caused by testing and repair operations. A strategy for yield improvement requires strong dedication to causal relationships and specification of process and product quality. Critical process parameters and their causal effects on product quality must be analyzed. Once critical process parameters are addressed, control strategies can be developed to assure high first pass yields. An overview of ongoing work that has been performed to establish a surface mount technology (SMT) production line with closed loop quality control via direct process monitoring capabilities and integrated inspection operations is given. For different inspection tasks, 3-D laser and X-ray inspection is applied. Process parameter as well as test and inspection results are gathered online. Thus, interrelationships between process steps beginning from material inspection, solder paste application, components placement, reflow soldering and final inspection can be analyzed. >

Process control of regulated system, e.g. rolling system

Abstract: In a method of carrying out a process in a regulated system, the system is pre-adjusted by a selected process parameter (yv) calculated from a mathematical model (M) in a computer supplied with input values (xM). The novelty is that, in order to calculate the process parameter (yv), the computed result (yM) of the model (M) is combined with the network response (yN) of a neural network (8) fed with at least some of the input values (xN). After the end of the process, the deviation between the calculated process parameter (yv) and the measured process parameter is used for adaptation of alterable network parameters of the neural network to reduce the deviation. Also claimed is an appts. for carrying out the above method.

Method of controlling the temperature of moulds for plastics processing

Abstract: In conventional methods of temperature control, an adaptation of the temperature conditions to the process parameters at any one moment is not possible, and it is not possible to compensate for disturbances in the injection-moulding process nor the unfavourable position of cooling surfaces with respect to the mould contour in the case of complicated moulds. Taking these disadvantages as a starting point, the object was to provide a method which, while taking into account the parameters of the injection-moulding operation at any given moment, including disturbances of the process which occur, ensures adequately good adaptation of the average mould temperature to a set temperature, to be predetermined, with simultaneously self-adjusting control, and which operates without additional energy. As a solution, it is proposed that the temperature-controlling process is separated into two phases, an initial phase and a steady-state operating phase, with different temperature-controlling conditions in each case, the initial phase being ended after the predetermined set mould temperature is reached or exceeded for the first time, and the average mould temperature being measured continuously throughout the entire cycle at a precisely defined location and a surge of coolant which takes into consideration the temperature control in the previous cycles being introduced at the point in time Z2, which is fixed by a signal of the machine sequence control at a time close to the injection operation, in order ... in the time period of greatest temperature difference between injected melt and ... Original abstract incomplete.

Process variable measuring and display device and portable power supply

Abstract: This invention relates to the field of process variable measuring and display devices and portable power supplies for process variable display devices. This invention can be used to measure and display any process variable, including pressure, temperature, volume, and flow rate. Specifically, this invention relates to an electronic process variable measuring device electronically coupled to a battery powered process variable display device which displays both a bar graph trend indication of the process variable and a digital display of the process variable. In a preferred embodiment, the process variable display device is totally self-contained, including the battery operated power supply.

Self tuning process control system

Abstract: The closed loop control of a process variable is effected depending on the deviation of the measured value of that variable from a set value with the closed loop response being adjusted when at least one characteristic of the closed loop response, obtained by integrating the deviation, differs from a desired level by more than a set amount. The closed loop system response is therefore made to approach a desired response. The deviation can be multiplied by a plurality of weighting functions prior to integration with the weighted integrals being used to determine the characteristics of the control system.

Process for annealing metal work pieces in a hydrogen-enriched protective atmosphere in a continuous furnace.

Abstract: of EP0379104The invention relates to a process for annealing metal work pieces in a protective hydrogen gas in a furnace, wherein, to reduce the amount of protective gas required and as an additional process parameter, gas with a higher density than hydrogen is blown into the leakage openings of the continuous furnace, for example and in particular at the inlet (11) and outlet (4) of the furnace and is thus mixed with the protective gas situated there, whereas in the rest of the continuous furnace the hydrogen-enriched protective atmosphere is maintained in accordance with the heat treatment to be carried out.

Control process with temporally cyclically controlled determination of manipulated variables in accordance with a fuzzy logic

Abstract: A control process with temporally cyclically controlled determination of manipulated variables in accordance with a fuzzy logic improves the control process by providing an improved reaction to changes to the input variable. In the control process of the invention, a fictitious, probable input variable of the next following cycle is determined. This probable input value is considered in the determination of the manipulated variable. In this way, account is taken of a probable development of the input variable and appropriate action is taken in advance on the manipulated variable. The consideration of an extrapolated future, fictitious input variable value is possible, since control loops with fuzzy controllers are not inclined to show a resonance behavior between control variable and manipulated variable, as is usual with conventional controlled systems.

Method and device for in-temperature regulation of a heating system and control unit for carrying out the process.

Abstract: of EP0565853In a method for controlling the feed temperature in a heating system, in which method the actual value of the feed temperature of the heating system is compared with the desired value of the feed temperature of the heating system and the difference, representing the system deviation, between the desired value and actual value of the feed temperature of the heating system is converted into an actuating signal for a mixing valve (4), when the actuating signal for the mixing valve (4) is generated account is taken of the rate of change, detected by means of a derivative-action element (17), of at least one temperature variable in the heat carrier circuit. The temperature variable can be the feed temperature of the heating system and/or the boiler temperature. In the case of a rising temperature variable, the actuating signal is corrected in the closing direction, and in the case of a falling temperature there is a correction in the opening direction. The absolute magnitude of the rate of change in this case determines the absolute value of the correction. The method disclosed improves the control response. Also described is a heating controller (11) for carrying out the method.

Computer-integrated manufacturing system

Abstract: PURPOSE: To model a manufacturing process and to obtain a system including monitoring, control, and optimization by sequentially controlling adjustment of control variables and optimization of the manufacturing process by a first to a third networks CONSTITUTION: The manufacturing system is modeled, controlled, and optimized through three interacting networks (A-C net) constituting a layered structure of process All manufacturing processes are samely processed from a simple process step up to a complete factory via a manufacturing zone and a production line to simplify the calculation Namely, a net represents a manufacturing process where a node represents a process and a side represents a product flow This models job application, which is controlled and optimized with respect to its process parameter and target specification In a net B, the node shows a control operation and the side shows a process control to specify the flow of a control parameter In a net C, the node shows a target (manufacturing specification) adjusting operation and the side shows a process optimization to specify flow of the target specification

Optimal control of a steel strip rinsing process

Abstract: Deals with optimal control of a steel strip rinsing process. The rinsing process is a dynamic nonlinear process. Modelling and identification of the process is based on a priori knowledge about the process and measured data from the process. Some parts of the process wear out. In the model, the worn parts are modelled explicitly and estimated on-line by an extended Kalman filter. The process is influenced by changing production variables, which are measurable but not controllable. The process is also influenced by disturbances. The optimal controller is based on a mathematical model of the process which includes on-line estimation of unknown parameters. The model is expressed in a discrete state space form, which makes the model suitable for optimal control. The physical limits of the process consist of the limits of the control signal. The optimal control signal is achieved by minimization of a quadratic loss function. >

Real-time statistic process monitoring apparatus

Abstract: PURPOSE: To identify noteworthy process parameter of a production process having a plurality of parameters by utilizing a computer. CONSTITUTION: In order to appropriately discriminate parameters related to the production of nonconformable products, the productivity deterioration of conformable products, or the deterioration of other production efficiencies without largely increasing the human labor in a production process having a plurality of parameters, a process monitoring device 10 is constituted of a real-time statistic analyzer 24 which analyzes a selected process variable related to a production process by conducting one to a plurality of statistic analyses, a terminal 30 which displays a process variable when the variable is deviated from one of a plurality of reference values, a means which discriminates all processes which cause the deviation of the variable from the reference values, and a means which displays the statistic history of the discriminated process variable while the operation of the production process and real-time statistic analysis are made freely continuable.

Method for automatically tuning pid parameter

Abstract: PURPOSE:To present the transfer function of a controlled system and to finally unnecessitate the addition of test signals by a learning function in the case of changing parameters by adaptive operations CONSTITUTION:While containing a PID loop defining a P (proportion) operation, I (integration) operation and D (differentiation) operation as the basic elements of control operations, this method is equipped with a process parameter calculation part 12 and a PID parameter calculating mechanism to decide the parameters of the respective PID operations based on calculated process parameters, and the process parameter calculation part 12 is composed of a transfer function tuning part to tune the transfer functions of processes by observing the responded waveforms of a control system when stepwise inputs are impressed to the control system, and a gain scheduling part to describe relation between various environmental parameters and process parameters, selects one of the process parameters outputted from both parts, and calculates the respective parameters of the PID operations

Laser interferometry studies of polymeric membrane formation

Abstract: The various processes by which polymeric membranes are formed all involve the solidification of an initially homogenous liquid phase. In order to validate a predictive model for these formation processed, it is necessary to make real-time noninvasive measurements of important process parameters. Although techniques have been described recently for the acquisition of mass and temperature data, no procedures have been reported for the measurement of instantaneous film thickness even though this is a particularly critical process variable. In response to this need, the authors have developed a novel laser interferometry technique which permits changes as small as 0.2 microns in film thickness to be measured. Utilizing this technique, real-time film thickness data for the cellulose acetate-acetone-water system have been obtained and compared with the dry-cast process model developed by the authors` group. It has been found that the experimental results and the model predictions are in good agreement. The theoretical basis for interference measurements, the experimental considerations in the utilization of a laser light source and the general applicability of the experimental technique also will be discussed.

Statistical process control method of air separation process

Abstract: PURPOSE: To improve the efficiency in an air separation process by utilizing history data for each of a plurality of process variables in a manufacturing process, and by combining statistical technique with existing control/monitor one for use CONSTITUTION: Supply air 401 passing through a filter 402 is compressed by a compressor 404, water, CO2 , HC, and the like are cleaned by a cleaner 406, and cooling is made by a heat exchanger 408 for introducing to a high-pressure column 410 of a double purification column plant In this case, vapor 411 containing high nitrogen and vapor 416 containing high oxygen are guided to a top condenser 417 of a separation column The vapor 411 is condensed by a main condenser 412, one portion of the generated liquid 414 is guided to the high-pressure column 410 and the remaining portion is guided to a low- pressure column 413 for separating into a constituent that is rich in nitrogen and a constituent that is rich in oxygen before being collected At this time, a large number of process data values are collected for each related process variable from an air separation process, and statistical technique is combined with control/monitor one for controlling the process

Measuring system to determine air mass flow.

Abstract: of EP0411518A measuring system, in particular for motor vehicles, for determining the air mass flow with an ohmic resistor which can be subjected to an air stream and heated by means of electric heating source, a characteristic variable which represents the heating process serving as measuring variable for the air mass flow, is characterised according to the invention by the fact that the resistance variable of the resistor is at least largely independent of temperature, that a first measuring element which detects the momentary operating temperature of the resistor is assigned to the resistor, that a first temperature variable of the first measuring element together with a second temperature variable of a second measuring element which detects the momentary temperature of the air stream passes to the heat source as an operating input variable, that the heat source controls the heating current for the resistor which is to be heated up to a largely, essentially constant excess temperature as a function of the difference between the temperature variables and that the variable and/or the average switch-on duration of the heating current serves as a measuring variable for the air stream. Such a measuring device makes complicated adjustment processes for temperature compensation superfluous and permits the sensors to be directly interchangeable. The heating processes of the resistor can take place continuously or with switching.

Nonlinear adaptive control of a continuous fermentation process

Abstract: In this paper, an application of discrete time adaptive control of nonlinear systems is proposed for the control of a continuous flow fermentation process. The process is described by a time varying non linear model obtained from mass balance considerations, where the key process parameter is considered as time varying parameter. A discrete time model is derived and the parameters estimation is carried out using discrete indirect parameters estimation. An adaptive control law is then obtained combining linearising control law with this indirect parameter estimator. The controller is applied to a pilot scale fermentation system with satisfactory results.

An approach for relating model parameter variabilities to process fluctuations

Abstract: An approach which attempts to identify the key processing disturbances which cause MOSFET model parametric variations and correlations is presented. This technique employs the same statistical model parametric information used in statistical circuit design to isolate the key process variable fluctuations which cause circuit performance changes. This methodology, which links model parameters and circuit performance to process quantities, is of benefit to both design engineers and process engineers alike.