Patent Application
20170227943
The present invention relates to a method of optimizing the accuracy and precision of variables used in PID control units within the industrial field. The proportional-integral-derivative (PID) control function is used in the majority of the direct digital controllers throughout numerous industries. Utilizing the three step PID process allows systems to achieve optimum performance in a variety of applications. Current PID tuning methods are both complicated and time consuming, limiting industry capabilities to properly set PID tuning parameters in order to achieve optimum performance levels. Inefficient PID calculations result in lost time, less accurate results and ultimately reduced productivity and efficiency. Accordingly, an improved PID calculation method that is configured to alleviate inefficiencies and inconsistencies in PID tuning is desired.
In view of the foregoing disadvantages inherent in the known types of methods of optimizing the parameters used in digital controllers now present in the prior art, the present invention provides a method of optimizing PID controllers wherein the same can be utilized for providing convenience for the user when wishing to efficiently calculate accurate parameters for use in digital controllers. The present invention comprises a system and method for calculating optimum values to tune each proportional-integral-derivative (PID) control loop according to the intended use within a specific system and application.
The method for calculating optimized PID parameters includes the following steps: selecting a manufacturer, selecting a device, selecting the particular system, and selecting the desired application. In each of the steps the logic interacts with a database having various system applications parameters stored therein. Further, the system provides optional field values based on each manufacture's device PID algorithm and nomenclature, such as minimum output and maximum output, PID execution rate, percentage of stage capacity per design and the like. The PID parameter values are then calculated for optimum efficiency and performance.
Although the characteristic features of this invention will be particularly pointed out in the claims, the invention itself and manner in which it may be made and used may be better understood after a review of the following description, taken in connection with the accompanying drawings wherein like numeral annotations are provided throughout.
Reference is made herein to the attached drawings. Like reference numerals are used throughout the drawings to depict like or similar elements of the method for calculating optimum values using a proportional-integral-derivative (PID) control loop. The figures are intended for representative purposes only and should not be considered to be limiting in any respect.
As used herein, “logic” refers to (i) logic implemented as computer instructions and/or within one or more computer processes and/or (ii) logic implemented in electronic circuitry. As used herein, “computer-readable medium” excludes any transitory signals, but includes any non-transitory data storage circuitry, e.g. buffer cache, and queues, within transceivers of transitory signals. In the interest of economy, the present disclosure refers to “computer-readable medium,” “a processor,” “a database,” and so on. However, this should not be read as limiting in any way as the present disclosure contemplates embodiments of the present invention utilizing “one or more computer readable media,” “one or more processors,” “one or more databases,” and so on. Unless specifically limited to a single unit, “a” is intended to be equivalent to “one or more” throughout the present disclosure.”
According to some embodiments, the operations, techniques, and/or components described herein can be implemented as (i) a special-purpose computing device having specialized hardware and a logic hardwired into the computing device to persistently perform the disclosed operations and/or techniques or (ii) a logic that is implementable on an electronic device having a general purpose hardware processor to execute the logic and a computer-readable medium, e.g. a memory, wherein implementation of the logic by the processor on the electronic device provides the electronic device with the function of a special-purpose computing device.
Referring now to
The PID control unit is configured to run the PID control loop, as described below, while accessing stored information including optimum PID parameter from the database 110. The method for Calculating Optimum Values Using a Proportional-Integral-Derivative (PID) Control Loop may be executed on logic of any of the shown devices. In some embodiments, the database is stored locally relative to the logic, while in other embodiments the database may be accesses remotely.
Referring now to
As an example, the PID control unit 100 may be implemented to control the temperature of a room. First, a desired temperature, or set value 201, is determined. A sensor will measure the current temperature of the room and send that value to the PID control unit 100 as the process variable 203. The PID control unit 100 then compares the process value 203 to the set point 201 and subtracts the two variables, leaving the error value 204. The PID control unit 100 will then make various adjustments and output a control variable 202 to an air handling unit in order to minimize that error value. In the current example, the process 210 may involve activating a HVAC unit, with the control variable 202 determining if a cooling coil or heating coil may be activated to achieve the desired set point.
Three types of adjustments are made by the PID control unit 100 to minimize the error value: proportional 214, integral 212 and derivative 210. Proportional 214 adjustments multiply the error value by a predetermined constant. This can either be a positive or negative number depending on the current control variable and the desired set point. The integral adjustment 212 takes into account the magnitude of the error along with the duration of that error. Finally, the derivate adjustment 210 calculates the rate of change of the error value. The control variable 202 is affected by all three adjustments to achieve the desired set 201 point in most efficient manner.
Referring now to
Similarly,
Referring now to
After retrieving these saved settings from the database, the user may be presented with the option of modifying any of the original parameters 450 such as the manufacturer, device, or system units used. This would allow the user to start the method from the beginning using new parameters as a base starting point 410. Additionally, a user may amend the system or application to be used 460. If no further adjustments are desired, the final optimum PID parameters are calculated 470.
Referring now to
In addition to the system and application values, there are a number of optional fields 515 that a user may choose to adjust. These may vary depending on the manufacturer and device selected. Examples of these optional fields may include a PID minimum and maximum output, bias percentage set point and PID deadband. Subtracting the PID maximum output from the PID minimum span will be set the PID span. System application design comments 517 may be displayed as well as a quick reference to each design specifications, offering additional information and useful comments.
The various additional variables may include, but are not limited to, span as float, PID as a single or individual, proportional as gain or band, integral and derivative time as none or seconds or minutes or repeat per minute, gain limit value, select deadband as none or half weight or full weight, PID execution time as preset, adjustable. All manufacturer device forms use the same predefined database for the system applications.
When all of the desired variables have been entered, the user may select a button to calculate the optimum PID parameters, which are then displayed in the selected system units. These calculated PID parameters may then be used in the PID control loop to optimum efficiency. A user can adjust the variables after having calculated the PID parameters, but such a change will clear the calculated PID parameters and require a recalculation thereof.
The following is an incomplete listing of variables that may be included within the database and their respective equations:
PID execution rate=PID execution time seconds
Bias=((Span)(Bias %))+(Min Span)
Bias multiplier=(ABS(Bias Constant−Bias %))+Bias Constant
Select deadband as none, half or full and stages enabled as true or false.
Deadband none=0
Deadband half stage=(Design)(DB capacity per stage)(DB half)
Deadband half modulating=(Design)(DB percentage design)
Deadband full stage=(Design)(DB capacity per stage)
Deadband full Modulating=(Design)(DB percentage design)(DB full)
PID as single, individual and Proportional as gain, band and PID control as P, I, PI, PID
Proportional gain=((span/design)(100%−deadtime %)(bias multiplier)),
Proportional band=(100/((span/design)(100%−deadtime %)(bias multiplier)),
Individual Integral gain=((span/design)(100%−deadtime %)(bias multiplier)(IND I gain)),
Individual Integral time seconds=((time constant)(IND I time))
Individual Integral time minutes=(((time constant)(IND I time))/60)
Individual Integral time repeats/minute=(1/(((time constant)(IND I time))/60))
Individual Derivative Gain=0
Individual Derivative Time=0
Proportional/Controller gain=((span/design)(100%−deadtime %)(bias multiplier)),
Proportional band=(100/((span/design)(100%−deadtime %)(bias multiplier)),
Single Integral time seconds=((time constant)(SIN I time))
Single Integral time minutes=(((time constant)(SIN I time))/60)
Single Integral time repeats/minute=(1/(((time constant)(SIN I time))/60))
Single Derivative time=0
The forgoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiment was chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated.
It is therefore submitted that the instant invention has been shown and described in various embodiments. It is recognized, however, that departures may be made within the scope of the invention and that obvious modifications will occur to a person skilled in the art. With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.
Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
This application claims the benefit of U.S. Provisional Application No. 62/291,637 filed on Feb. 5, 2016. The above identified patent application is herein incorporated by reference in its entirety to provide continuity of disclosure.
| Number | Date | Country | |
|---|---|---|---|
| 62291637 | Feb 2016 | US |
