Abstract: In the digital PID (P:proportional, I:integral, D:derivative) control apparatus of the present invention, in which a deviation is obtained from a controlling amount of an object to be controlled, and a target value, a velocity type PI control operation is carried out on the deviation, a velocity type D control operation is carried out on the deviation or the controlling amount, these velocity type control operation outputs are synthesized, and then converted into a position type manipulation signal, and this signal is supplied to the object to be controlled, the derivation processing unit includes the judgment unit for judging whether K=2.multidot..DELTA.t/(.DELTA.t+2.eta..multidot.TD).ltoreq.1, or K>1 by using a control operation period .DELTA.t, a derivative time TD and a derivative gain 1/.eta., and the operation unit which carries out a lagged derivative operation by a bilinear transfer method when K.ltoreq.1, or carries out an exact derivative operation when K>1.

Abstract: A system for controlling a process system with a process system gain and dead time of which its transfer function includes a gain term element corresponding to the process system gain and a dead time term element corresponding to the dead time, subject to an external disturbance, by adjusting a control variable output by the process system to a target value according to a manipulated variable output by a controller performing at least proportional and integral control operations based on a deviation between the control variable and the target value.

Abstract: A method of controlling a process having a control loop using feedback control, including inputting a set point for controlling the process and a controlled variable from the process to calculate a deviation between the set point and the controlled variable, performing one of PI and PID adjustment calculation to make the set point coincide with the controlled variable from the process to output a velocity-type adjustment calculating signal as a manipulated signal to the process, inputting the manipulated signal and outputting a first approximation signal in accordance with a characteristic of an approximated control system, receiving a disturbance signal to be added to the process and outputting a second approximation signal approximated to disturbance characteristic, adding the second approximation signal and the velocity-type adjustment calculation signal and outputting the result, calculating a gain correction ratio signal in accordance with a change in gain of the controller system and a change in disturb

Abstract: A set point value SV(s) and a process value PV(s) are supplied to a deviation arithmetic operation circuit, and thereby a deviation E(s) is obtained. The deviation E(s) is input to a control arithmetic operation circuit, and at least a PI control arithmetic operation is executed to obtain a manipulative value MV(s) such that the deviation E(s) is set at zero. An disturbance D(s) is added to the manipulative value MV(s) and the result of the addition is supplied to the object to be controlled. A process value filter having a lead/lag time proportional to an integral time T.sub.I of the PI control arithmetic operation is inserted in a feedback line of the process value PV(s) to the deviation arithmetic operation circuit. The transfer function of the filter is (1+.alpha..multidot..beta..multidot.T.sub.I .multidot.s)/(1+.beta..multidot.T.sub.I .multidot.s). Although the optimal values of coefficients .alpha. and .beta. are 2.5 and 0.

Abstract: A system for controlling a process system subject to an external disturbance by adjusting a process variable output by the process system to a given target variable. The system includes a target variable filter unit for generating a computed target variable to perform a compensation control operation, a deviation operating unit for computing a deviation between the process variable and the computed target variable, a main control unit for performing at least proportional and integral control operations on the computed deviation between the process variable and the computed target variable to suppress fluctuation of the process variable produced by the external disturbance, and a target variable control unit for changing an input into the deviation operation unit from the computed target variable to the given target variable only when the deviation between the given target variable and the computed target variable computed by the target variable filter unit is less than a predetermined value.

Abstract: A control system is provided for controlling a process system subject to an external disturbance by adjusting the value of a control amount output from the process system to a given target value. The system includes a target value generating unit for generating a given target value, and a main control unit receiving the target value and the control amount value for performing control operations to suppress fluctuation of the control amount value produced by the external disturbance and to adjust the control amount value to the given target value.

Abstract: A PI type 2DOF controller comprises setpoint filter for receiving a setpoint value, and outputting a control setpoint value, the setpoint filter having a transfer function which follows the setpoint value, and is expressed by the following formula: ##EQU1## where T.sub.I : an integral time, S: a Laplace operator, .alpha.: a constant which can be set between 0 and 1, and .beta.: a constant which can be set between 0 and about 10, deviation-calculating portion for calculating a deviation between the control setpoint value and a control value fed back from a controlled system, control operation portion for receiving the deviation, executing at least a PI (P: proportional, I: integral) control operation, and outputting a manipulative variable, and applying portion for applying the manipulative variable to the controlled system.

Abstract: A controlling apparatus comprises a portion for calculating a deviation between a process variable from a controlled system and a target value, a first portion for receiving the deviation and executing a velocity-type I controlling calculation to obtain a first calculation output, a second portion for receiving the deviation and executing a velocity-type P or PD controlling calculation to obtain a second calculation output, a summing portion for summing the first and second calculation outputs to obtain a velocity-type manipulative variable, a conversion portion for converting the velocity-type manipulative variable into a positional manipulative variable, a portion for limiting a magnitude of the positional manipulative variable between upper and lower limits, and limiting a change rate of the positional manipulative variable within a predetermined change rate, and a judgment portion for judging whether or not the positional manipulative variable is deviated from at least one of upper and lower limits and th

Abstract: A two degree of freedom PID controller which includes a setpoint filter for performing a derivative operation on a process disturbance signal in accordance with a setpoint value and a control value of a controlled system, thereby outputting a setpoint signal, a PI-control operation device for determining a deviation between the setpoint signal and the control value, and performing a PI-control operation on the deviation, thereby outputting a manipulative signal, and an adder for adding the process disturbance signal to the manipulative signal output by the PI-control operation device, thus obtaining a sum signal, and for supplying the sum signal to the controlled system.

Abstract: A digital controller comprising a deviation calculator, a positional P-controlling calculation device, a velocity-type I-controlling calculation device, a signal converter, and an adder unit. The deviation calculator for subtracts a process variable of an object from a set point variable, to obtain a deviation. The positional P-controlling calculation device performs positional P-calculation on the deviation obtained by the deviation calculator. The velocity-type I-controlling calculation device performs velocity-type I-calculation on the deviation. The signal-converting device converts the velocity-type I-calculation output of the velocity-type I-controlling algorithm device, into a positional I-signal. The adder unit adds the positional I-signal obtained by the signal-converting device and the positional P-calculation output obtained by the positional P-controlling algorithm device, thereby obtaining a manipulative variable. The manipulative variable value is supplied to the object to control the object.

Abstract: A system for controlling a process system subject to an external disturbance by adjusting a value of a control amount outputted by the process system to a given target value. The system includes a difference computing unit for computing a difference between the control amount value and the given target value, a main control unit for performing at least proportional and integral control operations from a choice of proportional, integral and differential control operations based on control constants including proportional gain, integration time, and derivation time adjusted to a first given state that suppresses fluctuation of the control amount produced by external disturbance, and a compensation control unit for performing a compensation control operation to equivalently adjust the control constants of the main control unit to second given state that tracks target value variation.

Abstract: A process controller includes a change fetch circuit for fetching a change in feedforward controlled variable due to a variation in load, and an auto-tuning control circuit for performing auto-tuning for mis-matching of the feedforward control, in accordance with a compensation variable obtained by multiplying a ratio of an adjusted output signal of a feedback control system corrected by the feedforward control to the feedforward controlled variable, with the change in feedforward controlled variable, to determine an optimal next feedforward controlled variable.

Abstract: A process controller comprises a deviation calculating device for calculating the deviation between a control value obtained from a controlled object and a set value for the control value, and a first operation device for performing at least one of proportional, integral and differential operations with respect to the deviation from the deviation calculating device based on control parameters adjusted in a characteristic state for optimally restricting variation due to a disturbance. The first operation device outputs an adjusting signal based on the at least one of proportional, integral and differential operations. The process controller further comprises a second calculating device for correcting the control parameters to parameter values in a characteristic state for optimally following change in the set value.

Abstract: In a method and a system for process control comprising in combination a feed-back control in which a manipulated variable is determined in accordance with a deviation of a controlled variable with reference to a target value and a feed-forward control in which a disturbance is detected and a disturbance compensation is determined and used in determining the manipulated variable to counteract the effect of the disturbance, when the control is in a steady state, disturbance compensation is adjusted in such a manner that the difference between the disturbance compensation and the manipulated variable is reduced.

Abstract: A process control apparatus according to the present invention comprises a feed back control system for outputting a feedback control signal which is computed by comparing and adjusting a set value and a process variable, and a feedforward control system for outputting a disturbance compensation signal by detecting and compensating for the disturbance based on a feedforward control model. The gain of the feedback control signal is corrected in response to the magnitude of the disturbance variations by a gain scheduling unit, and the gain of the feedforward control model is controlled by supplying a correction signal which compares and equalizes, at a feedforward control model gain adaptive unit, the disturbance compensation signal and the manipulated variable obtained by adding the disturbance compensation signal and the feedback signal that is gain-corrected by the gain scheduling unit.

Abstract: A mixture control apparatus controls a flow rate of a second fluid to be mixed with a first fluid so as to prepare a third fluid having a predetermined concentration. A set point variable of the flow rate of the second fluid is calculated in accordance with the flow rate of the third fluid so as to improve controllabilty of the apparatus. A gain correction circuit calculates a gain correction quantity using the flow rate of the third fluid. A feed forward circuit calculates a feed forward control component. A feedback circuit calculates a feedback control component. The set point variable of the flow rate of the second fluid is calculated in accordance with the feed forward control component and the feedback control component. The flow rate of the second fluid is controlled to coincide with this set point variable.

Abstract: A method and system of process control comprising in combination a feed-back control in which a deviation of a controlled variable with reference to a target value is applied to a velocity type controller and a manipulated variable is determined in accordance with the output of the controller and a feed-forward control in which a disturbance is detected and a disturbance compensation is determined and added in determining the manipulated variable to counteract the effect of the disturbance. A static compensation component and a dynamic compensation component of the disturbance compensation are separately determined in accordance with the detected disturbance, and the static compensation component is converted to a velocity type signal, and added to the output of the controller to obtain a first sum. The first sum is converted to a position type signal, and added to the dynamic compensation component to obtain a second sum, in accordance with which the manipulated variable is determined.

Abstract: Oxygen content in the exhaust gas of a combustion system is controlled such that the actually detected value of the oxygen content is compared with a set value which is varied in accordance with the combustion load of the system. A value theoretically adapted to control an air-fuel mixing ratio is calculated from the combustion load and the result of the comparison, and the flow rates of air and fuel supplied to the combustion system are controlled according to this value.