Abstract: A method of determining the degree z of a hyperbolic non-linear characteristic, of a process that is controlled by application of a manipulated variable signal thereto for varying a first characteristic thereof, and that generates a controlled variable signal representative of that first characteristic by applying a first pulse to the process by stepping the manipulated variable signal and observing the resultant maximum change in the controlled variable and then applying a second pulse to the process by stepping the manipulated variable in the opposite direction and observing the maximum change in the controlled variable, and using the ratio of the two maxima to determine the non-linear characteristic and make appropriate compensation in the controller.

Abstract: A self-tuning deadtime controller for adaptively adjusting one or several controller parameters during process control activities. The controller tunes, for example, the controller deadtime and the proportional band to optimize deadtime controller performance. The high performance of a deadtime controller is maintained even though the controller is incorrectly pretuned or if the process is subject to loads which change its characteristics.

Abstract: The invention provides improved methods and apparatus for determining characteristics of a process--such as primary and second time constants, dead-time, and gain--by applying a doublet pulse to the process and measuring its response. By way of example, in one aspect of the invention, there is provided a method for generating a signal, .tau..sub.1, representing an estimate of a primary time constant of a non-self-regulating process, in accord with the mathematical expression .tau..sub.1 =(.delta.m.tau..sub.a.sup.2)/A.sup.+ is a factor representing the time-wise integration of the controlled variable during the period when the doublet pulse is being applied .delta.m is a factor representing an amount by which the manipulated variable is incremented, and .tau..sub.a represents the time period over which the controlled variable signal changes from its original value by a predetermined amount.

Abstract: An adaptive PID.tau..sub.d controller has a proportional derivative section that generates an error signal representing an error in the control signal, particularly, as a function of (i) a time rate of change of the controlled variable signal and (ii) a difference between the controlled variable signal and a predetermined setpoint. A summation element sums that error signal with a time-delayed integral signal to generate a summation signal. That summation signal, in turn, is filtered by the aforementioned adaptive noise filter to generate a manipulated variable signal, which is selectively applied to the process by an output section. A feedback element processes the manipulated variable signal to generate the time-delayed integral signal, referred to above. That processing includes time-delaying the manipulated variable signal an mount substantially equal to the deadtime of the process, .tau..sub.

Abstract: An improved system for tuning process control equipment applies a load change of amplitude .delta.q to the process to effect a change in it and, therefore, in the controlled variable. Monitoring the response of the controller to that change, the system identifies an observed overshoot, OVS.sub.o, in the manipulated variable signal. From that overshoot signal and a predetermined theoretical overshoot signal, OVS.sub..tau., the system generates an optimum gain, K.sub.opt, as a function of the mathematical expression K.sub.opt =K*(1+OVS.sub..tau.)/(1+OVS.sub.o), where K is the current gain of the automatic control subsection, OVS.sub.o is the observed overshoot, and OVS.sub..tau. is the predetermined overshoot.

Abstract: A process controller may incorporate statistical computations of the variance in the controlled variable. Statistical measures may then be used to offset the controller set point to maintain the controlled variable distribution in an acceptable specification zone. The statistical measures may be made automatically and continuously thereby obviating human intervention, while producing high quality, though statistically variable, process output. The statistical measures may be calculated specifically or generated by a weighted integration method.

Abstract: Control of multiple distillation columns for producing anhydrous alcohol suitable for blending with gasoline to produce gasohol. The distillation process involves production of a first-stage distillate containing a predetermined amount of water, followed by azeotropic distillation in the presence of a hydrocarbon entrainer to strip the distillate of its water content, leaving anhydrous alcohol as a bottom product. Tight controls are present during first-stage distillate production to hold its proof at an optimum value derived at through material balance calculations to minimize energy consumption for the overall system. Control over the dehydrating stage is accomplished by a combination of ratio control to regulate and maintain the proper proportion of the entrainer and temperature control to regulate within the column the actual inventory of entrainer.

Abstract: Control of multiple distillation columns for producing anhydrous alcohol suitable for blending with gasoline to produce gasohol. The distillation process involves production of a first-stage distillate containing a predetermined amount of water, followed by azeotropic distillation in the presence of a hydrocarbon entrainer to strip the distillate of its water content, leaving anhydrous alcohol as a bottom product. Tight controls are present during first-stage distillate production to hold its proof at an optimum value derived at through material balance calculations to minimize energy consumption for the overall system. Control over the dehydrating stage is accomplished by a combination of ratio control to regulate and maintain the proper proportion of the entrainer and temperature control to regulate within the column the actual inventory of entrainer.

Abstract: A method and apparatus for controlling the operation of a distillation column which utilizes cost factors to achieve the best economical production of a product within acceptable purity limits while maintaining the column at maximum operating capacity. The control is based on a series of priorities in which each of the following control signals is selectively used in turn to modify the control the heat-input to the column; cost factors applying to the column, cost factors applying to the several columns in the system, the purity of the product, the operating pressure limit of the column and, for lighter products, the rate of fluid velocity through the column. For heavier products, the rate of fluid velocity through the column is used independently of the heat-input control to restrict the flow of overhead product to the condenser to increase the back pressure on the column.