Showing papers on "Process variable published in 1992"

Model predictive controller

Abstract: A model predictive controller for a process control system which includes a real-time executive sequencer and an interactive modeler The interactive modeler includes both a process model and an independent disturbance model The process model represents the dynamic behavior of the physical process, while the disturbance model represents current and future deviations from the process model The interactive modeler estimates current process states from the process model and input data received from the executive sequencer The executive sequencer then projects a set of future process parameter values, which are sought to be controlled, over a predetermined control horizon The interactive modeler then solves a set of equations as to how the physical process will react to control changes in order to determine an optimized set of control changes As a result, the process control system will be able to accurately track a predetermined set-point profile in the most effective and cost efficient manner

An enhanced Taguchi method for optimizing SMT processes

Abstract: Taguchi quality control method is a cost-effective experimental design technique for characterizing the optimal operating parameters for a manufacturing process. Most previous applications of the Taguchi method have been concerned with the optimization of a single-response process and a large amount of satisfactory implementation results have been published. However, for multi-response cases, an effective and user-friendly technique is still lacking. The multi-response technique presented in this paper modifies the traditional Taguchi method by adopting an empirical loss function to sum up the impact of each process variable. Compared with previous methods, this technique is distinguished in two aspects: (1) it theoretically optimizes the single-response case in a more accurate way; (2) it can optimize multi-response processes involving discrete and continuous data types. Considering a surface mount technology (SMT) process for a VGA card (a typical multi-response process involving six variables and nine responses), experiments applying the proposed technique were conducted and showed satisfactory results. The yield rate for the SMT process improved from 88% to 98%.

Method and apparatus for obtaining process characteristics in a self-tuning controller

Abstract: The characteristics of the field process system controlled by a self tuning controller are obtained by analyzing the open loop response of the process variable to a step applied at the controller's control output. A first-order system response with pure time delay is used to approximate a higher-order field process system's actual response. The overall deadtime and time constant of the first-order approximation are determined. The maximum slope of the process variable response to the step is stored along with an assigned time of its occurrence and an assigned process variable. The stored information is used to approximate the overall deadtime. In one embodiment the stored information is assumed to be the data obtained from a second-order response having a 10:1 time constant ratio and is used to find the assumed second-order time constants which are used to find the first-order time constant. In a second embodiment the first order time constant is determined by using a convergence point falling within a predetermined range between the actual response data and the first-order approximation. The step is not applied to the control output until the process variable has reached the initial steady state condition and the calculation of slope ceases when the process variable response reaches the final steady state condition. Alternative techniques are disclosed for determining the steady state condition.

Dynamic modelling of material and process parameter effects on self-propagating high-temperature synthesis of titanium carbide ceramics

Abstract: A dynamic, finite-difference model evaluation of titanium carbide (TiC) ceramic processing by self-propagation high-temperature synthesis (SHS) has revealed that material and process parameters have a significant influence on SHS reaction propagation kinetics. Examination of the effects of Ti∶C stoichiometry variations and the presence of pre-reacted TiC diluents in the initial (Ti+C) reactant powder mix indicates that off-stoichiometric ratios and dilution additions tend to lower SHS reaction velocities. Increasing compact preheat temperatures, lowering powder particle sizes and raising compact packing densities, on the other hand, cause a significant increase in this reaction variable. Model results are supported by experimental studies on dilution, stoichiometry and preheat temperature effects on SHS velocity, and other literature data on packing density and particle size effects on this parameter. Simulations also suggest that effects of these initial conditions are due to their influence on adiabatic reaction temperatures and heat transfer patterns produced during the process. Critical selection of initial material and process conditions thus appears to be of vital importance during SHS processing of TiC ceramics.

Quality control using multi-process performance analysis

Abstract: A new graphical tool, called a multi-process performance analysis chart, can be used in a quality control method for analyzing the performance of a group of processes in a multi-process environment. The method achieves at least three objectives. One, the method is useful for aggregating on one chart the overall status of a group of processes. Departures of process mean values from target values are readily interpreted from the chart as are process variabilities and process capability indices. Estimates of the expected fallout of a process parameter with respect to its tolerance are also readily generated. Two, the method allows for prioritizing quality improvement efforts in complex operations, which may comprise many processes. And three, the method allows for quantifying improvements resulting from reductions in the departures of process means from target values and from reductions in process variabilities.

Method and apparatus for drying coated webs

Abstract: /OF THE DISCLOSURE: A method and apparatus for drying a continuously moving web carrying a liquid, wherein the web is passed through a dryer in which the web is exposed to a recirculating flow of heated drying gas. Exhaust gas is diverted and discharged from the recirculating gas flow at a flow rate which is variable between maximum and minimum levels, and makeup gas is added to the recirculating gas flow at a flow rate which is 4180 variable between maximum and minimum levels. A process variable is sensed and compared to selected set point. A first of the aforesaid flow rates is adjusted to maintain the process variable at the selected set point, and a second of the aforesaid flow rates is adjusted in response to adjustments to the first flow rate in order to insure that the first flow rate remains between its maximum and minimum levels.

Statistical process control for continous forest products manufacturing operations

Abstract: Statistical process control (SPC) techniques developed for discrete manufacturing industries, such as auto and electronic assembly, are not applicable in continuous forest products operations including paper, waferboard or particleboard manufacture. These manufacturing processes generate data streams that exhibit serial correlation, that is, the present value of the specific process parameter is dependent on the previous value of that parameter. In this research effort, SPC techniques based on time series and exponentially weighted moving average techniques were applied to process data from a fiberboard manufacturing operation.

Temperature-compensated logarithmic detector having a wide dynamic range

Abstract: An IF amplifier/log detector with a modular architecture includes a plurality of voltage amplifiers, a plurality of rectifiers, a plurality of voltage-to-current converters and a current summing circuit. Each amplifier has a first differential transistor pair driven by a first current proportional to the temperature to fix the gain. Each converter includes a second differential transistor pair driven by a current proportional to the temperature and inversely proportional to a process parameter, and a third differential transistor pair driven by a third current inversely proportional to the process parameter. In this manner a circuit having improved performance with variations in temperature and process parameters is obtained.

Method and apparatus for setting variable to desired value

Abstract: A variable under operator control is set to a desired value by taking a pause when the value of the variable has been modified such that it would surpass the desired value. Upon meeting the desired value, the value of the variable is set to the desired value for the duration of a pause period, during which the value of the variable remains fixed regardless of further attempts to modify the variable. Therefore, even if the operator is careless, the variable does not pass over the desired values. The variable may represent a voltage or current, or the position of a cursor.

Adjusting process parameter dependent on changing operating state - estimating value of changing parameter and simultaneously calculating max. error incurred

Abstract: An adaptive control method is based on a microcomputer (2) connected to a processor (4) assigned to the process (6) which typically can be an electrical power generator. The microcomputer system has a status detector (8) a parameter identification unit (10), processors (12,16), a memory (14) and a regulating parameter stage (18). The system is continuously monitored to determine the controlled error and also the change in system parameters, e.g. rotor resistance. The operating condition is modified based upon a combination of both effects. Each error is used to determine a weighing factor for the correction process. ADVANTAGE - Improved real-time adaptive control.

Process variable measuring and display device

Abstract: This invention relates to the field of process variable measuring and 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 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.

Updating optimal value of adjustment parameter during welding - by using each adjustment value to modify optimal value as process proceeds

Abstract: Method of constantly adjusting the regulating parameter during a welding process in which a process parameter is measured and compared with an optimal parameter value and any deviation from this value is used to adjust the process. This regulating parameter value is then fed to a storage unit and used to modify the optimal parameter value by means of the formula Fmu.i = Falti (Po-P) where Fmu is the actual parameter. Falt is the old parameter, Po is the reference value of the control signal, P is the actual control signal and i is the index of current wave. The new optimal value is then used in the succeeding process to determine the regulating value. USE/ADVANTAGE - Esp. spot resistance welding. The regulation of the welding process can be carried out independent of the complexity of the whole system in a simple manner.

Rotary substrate treatment apparatus

Abstract: PURPOSE:To reduce the labor required when new substrate treatment procedure is formed. CONSTITUTION:When a processing step (heat treatment step) for setting a process parameter (variable parameter) is indicated, a parameter setting screen for urging the setting of all of the process parameters related to the heat treatment step is displayed. When the parameter values of all of process parameters (heat treatment temp., a heat treatment time, heat treatment-related non- treatment time, a heat treatment-related treatment time, substrate temp. promising correction quantity) to be set are inputted by an input key, the data input of the heat treatment step is completed. Thereafter, new substrate treatment procedure for the setting input of the parameter values of process parameters and the reading of an initial parameter is formed with respect to the remaining treatment step in the same way to be stored.

Injection-molding control device with control variable learning function

Abstract: PURPOSE: To permit execution of corrective learning between injection molding cycles in a short process by providing an open-loop control means, a closed-loop control means and a settling target value correcting means. CONSTITUTION: The present settling target value determined by a segment pointer 360 and a profile table 350 is inputted to either a non-inversion input 368 of a closed-loop control device 352 or an input 366 of an open-loop control device 354. Using an open-loop reference value, the open-loop control device 354 coverts it into the present set target value and makes this an open-loop valve control voltage. A learning block 353 receives a value of the process variable of the pressure or the rate of a ram according to a control function and, receiving a trigger from the segment pointer 360 at the time of the end of each segment, corrects an open-loop settling target value so that a difference between the process variable value and the open-loop settling target value be decreased. According to this constitution, corrective learning can be executed even between injection molding cycles in a short process such as an injection process.

Process controlling method and process controller, and method for controlling size in mask region

Abstract: PURPOSE: To provide a process controller which decides the quality of a measured process parameter and continuously drives a production process to obtain an optimum product. CONSTITUTION: The quality of the process parameter value is measured based on the function of the parameter value which is kept positive and monotonous in a range secured by a parameter, has a single peak with the desirable parameter value and is separated and reduced to be exact from the desirable parameter value. A processor 114 is controlled based on the quality function of the parameter observation 112, so that an optimum product is obtained.

Nature control method for petrochemical product

Abstract: PURPOSE:To easily obtain gasoline at target octane number by immediately estimating the exact octane number even when the target value of the octane number is changed or the kind or quantity of charge oil is changed. CONSTITUTION:A basic model is prepared by analyzing the operation result data of a process and the test value analysis data of a product nature at a neural network (203). Next, the pattern of the operation data of the process to be inputted to the basic model is compared with the pattern of the normal operation data (206), and the operation data of the abnormal pattern are excluded. Afterwards, the operation data of the process are inputted to the basic model, and the estimated value of the product nature is calculated. Further, difference between this estimated value and the target value is calculated and when the difference is within an allowable range, a control signal corresponding to the difference is outputted to this process. When the difference exceeds the allowable range, a process parameter is changed, the estimated value of the product nature is calculated again, and difference from the target value is calculated.

Method of controlling a multi-output physical process

Abstract: Disclosed is a method of controlling a multi-output physical process with a vertically distributed process controller having interrupt data transfer. The process controller includes a host digital computer operating in a multi-tasking environment digital computer, and having a plurality of communications ports. Each of the communications ports is associated with a microprocessor and memory. According to the disclosed invention a process control application program is running in the digital computer, while the sensing and digitizing of at least one of the process physical outputs is being carried out in conjunction with one of the communications ports. The digitized output of the physical process is stored in the memory and an interrupt request is generated by the communications port corresponding to the process physical output. The host digital computer services an interrupt routine to input the contents of the communications port memory means to the digital computer. After inputting the value of the variable, the process control task or thread resumes its process control application with a new value of the physical process variable. This new value is then used to generate a process control output corresponding to the newly inputted process physical output. This new output is transmitted from the digital computer as an input to an effector of the controlled physical process.

Rolling process control method

Abstract: FIELD: regulation of hot and/or cold rolling processes SUBSTANCE: method involves setting rolling program for rolling process control system, with program involving data on initial and final sizes, material characteristics, rolling temperatures etc Control system has units for controlling predetermined values of subordinate, preferably free, individual devices for regulating variable functional parameters of separate stands of rolling mill, for instance, rolling force, rotational speed, roll position etc Method further involves conducting calculations by model equation on the basis of prepared and statistically processed, process variable measured values; adapting parameters to actual parameters and determining predetermined values of regulators In case changes in rolling process requirements occur, particularly, when manual mode is changed for automatic mode, or when final thickness and/or temperature are varied, adaptation of parameters is effectuated, with set values used prior to changes in requirements, being employed as basis for adaptation EFFECT: increased efficiency and improved quality of rolled products 3 cl, 2 dwg

Method and deformation device for measuring and recording process parameters during the deformation of the workpiece.

Abstract: The invention relates to a method and a device for measuring and recording process parameters during the deformation of a workpiece and/or for controlling the deformation of workpieces as a function of at least one measured process parameter. According to the invention, provision is made that during the deformation of workpieces occurring in steps or cycles, the start of the measured value detection of the process parameters is selected as a function of a change, of at least one parameter value, which is characteristic of the respective deformation cycles (or steps) and that this start of the measured value detection given by the selected parameter change is also used in all the subsequent deformation cycles (or steps) of at least the same deformation sample as the start of the detection of the parameters in these deformation cycles.

The effect of process parameter variation on polysilicon temperature transducer characteristics

Abstract: Polysilicon layers for application in temperature sensors have been investigated. Hence the characteristics of polysilicon resistors as a function of process parameter variation have been studied. Continuing our previous work, the effect of annealing temperature and time on the thermal behaviour of polysilicon layers is shown in this paper. Also a pre-annealing step preceding the implantation of the dopant has been included in our experiments and the results of this investigation are discussed. It is then shown how layer thickness affects the temperature characteristics of polysilicon meanders. Finally, the characteristics of the temperature transducer of our developed multifunctional sensor are described.