Kabushiki Kaisha Toshiba

Tokyo Shibaura Denki Kabushiki Kaisha

Kazuo Hiroi

Kojiro Ito

Kenji Kojima

Yoshiyuki Yamamoto

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&gt;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&gt;1.

Digital PID control apparatus

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. The system includes dead time compensation unit, connected to the controller, including a system model unit having a system transfer function approximative to the transfer function of the process system and a model unit having a model transfer function resulting from eliminating the dead time term element from the system transfer function, for outputting a compensation output signal to compensate the dead time, and gain adjustment unit, connected to the dead time compensation means, for adjusting a gain of the system model unit to the process system gain according to the variation in the process system gain of the process system.

Process control system

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 disturbance obtained upon a predetermined adjustment, on the basis of the addition result and the first approximation signal, and multiplying the gain correction ratio signal by the controlled variable to perform gain correction of the control loop, and an apparatus implementing the method.

Method and apparatus for controlling a process having a control loop

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 0.54, these values are variable in the range of 2 to 4 and the range of 0 to 1, respectively, depending on a first-order delay time T and a dead time L of the object. By setting .alpha. and .beta. in this way, the gain of the filter can be set at 1 at steady state and more than 1 at the transition state, so that both set point values following characteristic and disturbance suppression characteristics are improved.

Process control apparatus

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.

Two degrees of freedom type control system

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. The main control unit includes a suppressing unit for suppressing fluctuation of the control amount value produced by the external disturbance, an adjusting unit for adjusting a proportional gain of the suppressing unit, derivative time of the suppressing unit, and the control amount value to the given target value, a proportional gain revision coefficient unit for setting a plurality of given proportional gain revision coefficients, and a coefficient selecting unit for selecting the given proportional gain revision coefficient from among the plurality of given proportional gain revision coefficients.

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.

Two degree of freedom controller

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 the change rate. The first portion includes an output unit for the first calculation output, and a stopping unit for selectively stopping the output of the first calculation output. When the judgment portion determines that the manipulative variable is deviated, it supplies a signal to the stopping unit, and stops the summing operation by the summing portion.

Controlling apparatus utilized in process instrumentation system

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.

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.

Digital control system

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.

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.

Process control having improved combination of feedforward feedback

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.

Process controller having an adjustment system with two degrees of

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.

Feedforward feedback control having predictive disturbance compensation

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. The feedforward control model comprises a gain memory for memorizing storing the FF model gain correction signal from the feedforward control model gain adaptive unit and an operational means for receiving a correction signal from the gain memory and a disturbance signal to compute and output a disturbance compensation signal. The process control apparatus further includes a FF model gain adaptive mechanism for controlling the supply to the gain memory of the FF model gain correction signal by confirming that the process is in a steady state, and for controlling as well the additive synthesis of the disturbance compensation signal to the feedback control signal when the difference between the disturbance compensation signal and the manipulated quantity exceeds a prescribed value.

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Tokyo, Japan

Kazuo Hiroi