Modified proportional integral derivative controller
AssigneeSti Co., Ltd.
InventorsFlavio Tondolo, Roberto Valoti
Life of this patent
Estimating the term…
Abstract
A method and device for controlling a process variable based upon a set point is disclosed. A process variable is measured, and a proportional term is assigned to a manipulated variable that is based upon a product of a proportional gain coefficient and an error magnitude between the process variable and the set point. An integral term is added to the manipulated variable under a first set of conditions, and a derivative term is added to the manipulated variable under a second set of conditions different from the first set of conditions. The sum of the proportional term, the integral term, and the derivative term is output, resulting in the process variable being responsively adjusted thereto.
Claims23
A method for controlling a process variable based upon a set point, the method comprising:
- measuring the process variable;
- assigning a proportional term to a manipulated variable, the proportional term being a product of a proportional gain coefficient and an error magnitude of a difference between the set point and the process variable at a given time instance;
- adding an integral term to the manipulated variable under a first set of conditions, the integral term being a product of an integral gain coefficient and a sum of a predefined number of error magnitudes over a time interval;
- adding a derivative term to the manipulated variable under a second set of conditions different from the first set of conditions, the derivative term being a product of a derivative gain coefficient and the rate of change of the error magnitudes over the time interval;
- and
- generating a controller output of the manipulated variable, the process variable being responsively adjusted to the generated controller output.
A controller device for an actuator of a control valve, the actuator including an input port and an output port, the device comprising:
- a set point input receptive to a signal representative of a set point value;
- an actuator position feedback connectible to the output port of the actuator and receptive to a process variable value;
- an actuator drive output connectible to the input port of the actuator, an output corresponding to the manipulated variable value being generated therefrom;
- a proportional module, a proportional term being generated thereby;
- an integral module, an integral term having a non-zero value under a first set of conditions being generated thereby;
- a derivative module, a derivative term having a non-zero value under a second set of conditions different from the first set of conditions being generated thereby;
- and
- an adder module, the manipulated value being generated thereby from a sum of the proportional term, the integral term, and the derivative term.
An article of manufacture comprising a program storage medium readable by a data processing device, the medium including a tangible embodiment of one or more programs of instructions executable by the data processing device to perform a method for controlling a process variable based upon a defined set point, the method comprising:
- measuring the process variable;
- assigning a proportional term to a manipulated variable, the proportional term being a product of a proportional gain coefficient and an error magnitude of a difference between the set point and the process variable at a given time instance;
- adding an integral term to the manipulated variable under a first set of conditions, the integral term being a product of an integral gain coefficient and a sum of a predefined number of error magnitudes over a time interval;
- adding a derivative term to the manipulated variable under a second set of conditions, the derivative term being a product of a derivative gain coefficient and the rate of change of the error magnitudes over the time interval;
- and
- generating a controller output of the manipulated variable, the process variable being responsively adjusted to the generated controller output.
Dependencies are inferred from the claim text.