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Title:
SYSTEM AND METHOD FOR CONTROLLING FLUID FLOW
Document Type and Number:
WIPO Patent Application WO/2021/256916
Kind Code:
A2
Abstract:
The present invention relates to a system (100) for controlling fluid flow. The system (100) comprises a pump (102) and a controller (104) in communication with the pump (102). The controller (104) is configured to supply a drive signal to the pump (102) for providing a flow rate of the fluid through a fluid flow path for a predetermined duration (201), to receive a feedback signal outputted form the pump (102) after the predetermined duration (202), to obtain at least an electrical parameter data from the pump (102) after the predetermined duration (203), to determine at least one fluid flow path characteristic of the fluid flow path based on the received feedback signal and the obtained electrical parameter data (204), to determine a control signal based on the determined characteristic of the fluid flow path and a target fluid flow rate (205), and to output the control signal to the pump (102) for providing the target fluid flow rate (206). Further, the present invention relates to a method (200) of controlling fluid flow in the system (100).

Inventors:
SHIZUO OTAKI (MY)
LING NENG HUI KENNY JAMES (MY)
Application Number:
PCT/MY2021/050045
Publication Date:
December 23, 2021
Filing Date:
June 15, 2021
Export Citation:
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Assignee:
DAIKIN RES & DEVELOPMENT MALAYSIA SDN BHD (MY)
International Classes:
F04D13/06; F04D15/00; G05B11/28; G05B13/02; G05B15/02; G05D7/06
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Claims:
CLAIMS:

1. A system (100) for controlling fluid flow, the system (100) comprising: a pump (102) for pumping a fluid through a fluid flow path; and a controller (104) in connection with the pump (102) for controlling the operation of the pump (102), wherein the controller (104) is configured for: supplying a drive signal to the pump (102) for providing a fluid flow rate for a predetermined duration (201 ); receiving a feedback signal outputted from the pump (102) after the predetermined duration (202); obtaining at least an electrical parameter data from the pump (102) after the predetermined duration (203); determining at least one characteristic of the fluid flow path based on the received feedback signal and the obtained electrical parameter data (204); determining a control signal based on the determined characteristic of the fluid flow path and a target fluid flow rate (205); and outputting the control signal to the pump (102) for providing the target fluid flow rate (206).

2. The system (100) as claimed in claim 1, wherein the received feedback signal and the obtained electrical parameter data are used as input variables of an approximation function for determining a fluid flow rate calculation coefficient and a fluid flow rate calculation constant so as to determine the characteristic of the fluid flow path.

3. The system (100) as claimed in claim 2, wherein the approximation function for determining the fluid flow rate calculation coefficient is expressed as: a = p - qy ± rx where a denotes the fluid flow rate calculation coefficient; p is a regression constant; y denotes the received feedback signal; q is a regression coefficient associated with the received feedback signal; x denotes the obtained electrical parameter data; and r is a regression coefficient associated with the obtained electrical parameter data.

4. The system (100) as claimed in claim 2, wherein the approximation function for determining the fluid flow rate calculation constant is expressed as: b = —s + vy ± wx where b denotes the fluid flow rate calculation constant; s is a regression constant; y denotes the received feedback signal; v is a regression coefficient associated with the received feedback signal; x denotes the obtained electrical parameter data; and w is a regression coefficient associated with the obtained electrical parameter data

5. The system (100) as claimed in claim 2, wherein the approximation function is established by: obtaining a plurality of data under a plurality of predetermined operating conditions, wherein the plurality of data comprising a plurality of feedback signal data, a plurality of electrical parameter data, a plurality of fluid flow rate calculation coefficient data and a plurality of fluid flow rate calculation constant data; and performing a multiple regression analysis using the plurality of feedback signal data and the plurality of electrical parameter data as independent variables, and using the plurality of fluid flow rate calculation coefficient data and the plurality of fluid flow rate calculation constant data respectively as a dependent variable.

6. The system (100) as claimed in claim 5, wherein the multiple regression analysis is the method of least squares.

7. The system (100) as claimed in claim 5, wherein the plurality of data are obtained by a plurality of steps repeated by the controller (104) under each of the plurality of predetermined operating conditions, the plurality of steps comprising: supplying the drive signal to the pump (102) for providing the fluid flow rate for the predetermined duration, receiving the feedback signal outputted from the pump (102) after the predetermined duration as the feedback signal data, acquiring the electrical parameter data from the pump (102) after the predetermined duration, and measuring the fluid flow rate provided by the pump (102) via a sensor so as to determine the fluid flow rate calculation coefficient data and the fluid flow rate calculation constant data.

8. The system (100) as claimed in claim 7, wherein the fluid flow rate calculation coefficient data and the fluid flow rate calculation constant data are determined via a linear regression analysis using a plurality of the drive signals supplied to the pump (102) and a plurality of the fluid flow rates as measured by the sensor under each of the predetermined operating conditions.

9. The system (100) as claimed in claim 8, wherein the fluid flow rate calculation coefficient data and the fluid flow rate calculation constant data are determined based on a relationship provided by the linear regression analysis, the relationship is defined as: i = ad-L + b where d-i denotes the drive signal supplied to the pump (102) f-i denotes the fluid flow rate measured by the sensor a denotes the fluid flow rate calculation coefficient; and b denotes the fluid flow rate calculation constant

10. The system (100) as claimed in claim 5, wherein each of the plurality of predetermined operating conditions is a combination of an electrical parameter applied to the pump (102) and a characteristic of the fluid flow path, and the operating conditions vary from each other.

11. The system (100) as claimed in claims 1 and 9, wherein the control signal is determined using a formula that is derived from the relationship, the formula is expressed as: where d2 denotes the control signal to be outputted to the pump (102) f2 denotes the target fluid flow rate a denotes the fluid flow rate calculation coefficient b denotes the fluid flow rate calculation constant

12. The system (100) as claimed in any of the preceding claims, wherein the drive signal is a pulse-width modulation signal with a predetermined duty cycle expressed in percentage.

13. The system (100) as claimed in any of the preceding claims, wherein the feedback signal is a pulse-width modulation signal measured in terms of duty cycle expressed in percentage.

14. The system (100) as claimed in any of the preceding claims, wherein the control signal is a pulse-width modulation signal measured in terms of duty cycle expressed in percentage. 15. The system (100) as claimed in any of the preceding claims, wherein the electrical parameter data comprises power amount used by the pump (102) or voltage applied to the pump (102).

16. The system (100) as claimed in any of the preceding claims, wherein the characteristic of the fluid flow path comprises flow resistance of the fluid flow path.

17. The system (100) as claimed in any of the preceding claims, wherein the system (100) is usable in any one or a combination of a water heating system, a water cooling system, and an air conditioning system

18. The system (100) as claimed in claim 17, wherein the system (100) is connectable to any one or a combination of the water heating system, the water cooling system, and the air conditioning system via the controller (104) for controlling the fluid flow at the target fluid flow rate.

19. The system (100) as claimed in claim 18, wherein the target fluid flow rate is determined by the controller (104) of the system (100) based on the heating performance of the water heating system, the cooling performance of the water cooling system, the cooling and heating performances of the air conditioning system, or any combination thereof.

20. A method (200) for controlling fluid flow in a system (100) comprising a pump (102) for pumping a fluid through a fluid flow path and a controller (104) in connection with the pump (102), the method (200) comprising: supplying, by the controller (104), a drive signal to the pump (102) for providing a fluid flow rate for a predetermined duration (201 ); receiving, by the controller (104), a feedback signal outputted from the pump (102) after the predetermined duration (202); obtaining, by the controller (104), at least an electrical parameter data from the pump (102) after the predetermined duration (203); determining, by the controller (104), at least one characteristic of the fluid flow path based on the received feedback signal and the obtained electrical parameter data (204); determining, by the controller (104), a control signal based on the determined characteristic of the fluid flow path and a target fluid flow rate (205); and outputting, by the controller (104), the control signal to the pump (102) for providing the target fluid flow rate (206).

Description:
SYSTEM AND METHOD FOR CONTROLLING FLUID FLOW

FIELD OF THE INVENTION

The present invention relates to a fluid flow control system, particularly a system of regulating the rate of a fluid flow through a fluid flow path without the need of a flow sensor and a method thereof.

BACKGROUND OF THE INVENTION

Pumps are used widely in industrial applications for several functions such as to provide cooling and lubrication services, to transfer fluids for processing, and to provide motive force in hydraulic systems. While in the commercial sector, pumps are used primarily in heating, ventilation, and air- conditioning (HVAC) systems to provide water for heat transfer. Pumps are also used to aid in the transport or transfer of the waste water of a catchment area.

Installation of a pump for an industrial application is often accompanied by multiple flow sensors for fluid flow measurement and management. The flow sensors are installed at various points in a pipeline system starting at pump output, and continuing downstream to ensure proper flow is maintained throughout the pipeline. Information from the flow sensors is used to regulate fluid flow rate of which pump produces, and to modulate flow control valves. Nevertheless, such flow sensors could be expensive with their relatively high accuracy. Installation of the flow sensors might introduce an additional pressure drop into the system, resulting in an increased pump energy consumption and a reduced energy efficiency. Further, the flow sensors are limited to a working range between a minimum and maximum readable flow at which they are configured to provide reliable flow rate measurements. Flow rates outside of the working range may be unreliable.

There are a number of examples in the prior art relating to a system for controlling a fluid flow rate in a pipeline system without the use of flow sensors. For example, US7795827B2 discloses a system used for controlling fluid flow without the use of any flow sensor. The microprocessor of the system is provided with an input signal in a form of pulse-width modulation (PWM) signal for controlling an operation of a pump. At the same time, a constant fluid flow control command is inputted into the microprocessor. The microprocessor will modulate the PWM signal which is outputted to a two-phase logic control circuit in order to perform a constant fluid flow operation. The PWM signal is calculated as a function value proportional to the speed and current of the motor and it is modulated accordingly to vary the speed of the motor of the pump. This system involves a number of components for controlling the operation of the pump, rendering the overall system configuration to be complicated. This is likely to increase the cost of making and implementing the system.

US9605680B2 discloses another system used for controlling fluid flow and adjusting thereof towards a constant flow rate. The prior art does not involve direct sensing of the pressure or flow rate of a fluid but it takes parameters associated with pump operation as an indication of pump performance. One example of the pump parameter is input power and it is used to determine fluid pressure and/or flow rate. However, the input power may not always accurately determine the flow rate of the fluid.

Accordingly, it can be seen in the prior art documents that there exists a need to provide an improved system or technique for controlling fluid flow via a pump which overcomes the aforesaid problems and shortcomings.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a system for controlling fluid flow without involving a flow sensor as well as a complicated system configuration, thereby reducing the components used and hence saving cost of production. A further objective of the present invention is to provide a system for controlling fluid flow that enables a pump to be responsive to a change in characteristic of a fluid flow path, a target fluid flow rate to be achieved or both so as to vary its operation accordingly.

It is a further objective of the present invention to provide a system for controlling fluid flow that automatically regulates or maintains a flow rate of the fluid according to at least one characteristic of a fluid flow path, a target fluid flow to be achieved or both, thereby reducing unnecessary waste of power consumption for pump operation.

Another objective of the present invention is to provide a system for controlling fluid flow through a fluid flow path that utilizes an easily obtainable input to control the operation of a pump for providing a target fluid flow rate. The input is preferably a pulse-width modulation signal having a duty cycle that is adjustable based on at least one characteristic of the fluid flow path, the target fluid flow rate or both.

Accordingly, these objectives shall be achieved by following the teachings of the present invention. The present invention relates to a system for controlling fluid flow. The system comprises a pump for pumping a fluid through a fluid flow path and a controller in connection with the pump for controlling the operation of the pump. The controller is configured for supplying a drive signal to the pump for providing a fluid flow rate for a predetermined duration, receiving a feedback signal outputted from the pump after the predetermined duration, obtaining at least an electrical parameter data from the pump after the predetermined duration, determining at least one characteristic of the fluid flow path based on the received feedback signal and the obtained electrical parameter data, determining a control signal based on the determined characteristic of the fluid flow path and a target fluid flow rate, and outputting the control signal to the pump for providing the target fluid flow rate. It is preferred that the received feedback signal and the obtained electrical parameter data are used as input variables of an approximation function for determining a fluid flow rate calculation coefficient and a fluid flow rate calculation constant so as to determine the characteristic of the fluid flow path. The approximation function for determining the fluid flow rate calculation coefficient is expressed as: a = p - qy ± rx where a denotes the fluid flow rate calculation coefficient; p is a regression constant; y denotes the received feedback signal; q is a regression coefficient associated with the received feedback signal; x denotes the obtained electrical parameter data; and r is a regression coefficient associated with the obtained electrical parameter data

While, the approximation function for determining the fluid flow rate calculation constant is expressed as: b = —s + vy ± wx where b denotes the fluid flow rate calculation constant; s is a regression constant; y denotes the received feedback signal; v is a regression coefficient associated with the received feedback signal; x denotes the obtained electrical parameter data; and w is a regression coefficient associated with the obtained electrical parameter data

It is preferred that the approximation function for determining the fluid flow rate calculation coefficient and the fluid flow rate calculation constant are established by obtaining a plurality of data under a plurality of predetermined operating conditions, wherein the plurality of data comprising a plurality of feedback signal data, a plurality of electrical parameter data, a plurality of fluid flow rate calculation coefficient data and a plurality of fluid flow rate calculation constant data, and performing a multiple regression analysis using the plurality of received feedback signal data and the plurality of electrical parameter data as independent variables, and using the plurality of fluid flow rate calculation coefficient data and the plurality of fluid flow rate calculation constant data respectively as a dependent variable. In particular, the multiple regression analysis is the method of least squares.

Further, the plurality of data are obtained by a plurality of steps repeated by the controller under each of the plurality of predetermined operating conditions. The plurality of steps comprise supplying the drive signal to the pump for providing the fluid flow rate for the predetermined duration, receiving the feedback signal outputted from the pump after the predetermined duration as the feedback signal data, acquiring the electrical parameter data from the pump after the predetermined duration, and measuring the fluid flow rate provided by the pump via a sensor so as to determine the fluid flow rate calculation coefficient data and the fluid flow rate calculation constant data. The fluid flow rate calculation coefficient data and the fluid flow rate calculation constant data are preferably determined via a linear regression analysis using a plurality of the drive signals supplied to the pump and a plurality of the fluid flow rates as measured by the sensor under each of the predetermined operating conditions.

It is further preferred that the fluid flow rate calculation coefficient data and the fluid flow rate calculation constant data are determined based on a relationship provided by the linear regression analysis. The relationship is defined as: i = ad- L + b where di denotes the drive signal supplied to the pump f-i denotes the fluid flow rate measured by the sensor a denotes the fluid flow rate calculation coefficient; and b denotes the fluid flow rate calculation constant It is preferred that each of the plurality of predetermined operating conditions is a combination of an electrical parameter applied to the pump and a characteristic of the fluid flow path, and the operating conditions vary from each other. It is preferred that the control signal is determined based on a formula that is derived from the relationship provided by the linear regression analysis. The formula is expressed as where d 2 denotes the control signal to be outputted to the pump f 2 denotes the target fluid flow rate a denotes the fluid flow rate calculation coefficient b denotes the fluid flow rate calculation constant

Preferably, the drive signal is a pulse-width modulation signal with a predetermined duty cycle expressed in percentage. The feedback signal and the control signal are also pulse-width modulation signal measured in terms of duty cycle expressed in percentage.

Preferably, the electrical parameter data comprises power amount used by the pump or voltage applied to the pump.

Preferably, the fluid flow path characteristic comprises flow resistance of the fluid flow path. In a preferred embodiment of the present invention, the system is usable in any one or a combination of a water heating system, a water cooling system, and an air conditioning system. The system is preferably connectable to any one or a combination of the water heating system, the water cooling system, and the air conditioning system via the controller (104) for controlling the fluid flow at the target fluid flow rate. The target fluid flow rate is preferably determined by the controller based on the heating performance of the water heating system, the cooling performance of the water cooling system, the cooling and heating performances of the air conditioning system or any combination thereof.

According to another aspect of the present invention, there is provided a method for controlling fluid flow in a system comprising a pump for pumping a fluid through a fluid flow path and a controller in connection with the pump. The method comprises supplying a drive signal by the controller to the pump for providing a fluid flow rate for a predetermined duration, receiving a feedback signal outputted from the pump by the controller after the predetermined duration, obtaining at least an electrical parameter data from the pump by the controller after the predetermined duration, determining at least one characteristic of the fluid flow path by the controller based on the received feedback signal and the obtained electrical parameter data, determining a control signal by the controller based on the determined characteristic of the fluid flow path and a target fluid flow rate, and outputting the control signal by the controller to the pump for providing the target fluid flow rate.

BRIEF DESCIRPTION OF THE ACCOMPANYING DRAWINGS

The features of the invention will be readily understood and appreciated from the following detailed description when read in conjunction with the accompanying drawings of the preferred embodiment of the present invention, in which:

Figure 1 illustrates a system for controlling fluid flow according to a preferred embodiment of the present invention. Figure 2 is a flow chart illustrating steps executed by a controller of a system for controlling fluid flow according to a preferred embodiment of the present invention.

Figure 3 is a scatter plot illustrating an exemplary relationship between drive signals supplied to a pump and fluid flow rates as measured by a flow sensor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the present invention is described herein by way of example using embodiments and illustrative drawings, those skilled in the art will recognize that the invention is not limited to the embodiments of drawing or drawings described, and are not intended to represent the scale of the various components. Further, some components that may form a part of the invention may not be illustrated in certain figures, for ease of illustration, and such omissions do not limit the embodiments outlined in any way. It should be understood that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the scope of the present invention as defined by the appended claim. As used throughout this description, the word "may" is used in a permissive sense (i.e. meaning having the potential to), rather than the mandatory sense, (i.e. meaning must). Further, the words "a" or "an" mean "at least one” and the word “plurality” means “more than one” unless otherwise mentioned. Furthermore, the terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Language such as "including," "comprising," "having," "containing," or "involving," and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited, and is not intended to exclude other components, integers or steps. Any discussion of documents, materials, devices, and the like is included in the specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention.

The present invention is described hereinafter by various embodiments with reference to the accompanying drawings, wherein reference numerals used in the accompanying drawings correspond to the like elements throughout the description. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiment set forth herein. Rather, the embodiment is provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art.

The present invention relates to a system (100) for controlling fluid flow. The system (100) is preferably configured to regulate or maintain a flow rate of the fluid that flows through a fluid flow path. Figure 1 shows a preferred embodiment of the present invention. The system (100) comprises a pump (102) for pumping a fluid through the fluid flow path and a controller (104) in connection with the pump (102). The fluid to be pumped is preferably a liquid, more preferably but not limited to, water or any water-based fluids.

In the preferred embodiment of the present invention, the pump (102) is a centrifugal pump having at least an impeller extending radially from a central axis for exerting a force towards the fluid flowing through the fluid flow path, a motor for driving the impeller to move and a shaft for connecting the impeller and the motor. The impeller preferably comprises one or multiple vanes extending outwardly from the hub of the impeller. The impeller is configured to rotate so to create a centrifugal force that imparts velocity on the fluid, causing the fluid to move rapidly from the center of the impeller, along the vanes, and exit from the outermost diameter of the impeller. It is not limited to the centrifugal pump, other motor-operated pumps may also be applicable within the scope of the present invention. In the preferred embodiment of the present invention, the impeller is driven by a drive force provided by the motor that is connected to the impeller via the shaft. The motor is configured to provide the drive force in a form of rotational force to rotate the impeller. The motor is preferably but not limited to, a permanent magnet motor, more preferably, a permanent magnet synchronous driving motor. In the permanent magnet synchronous driving motor, permanent magnets are embedded in a rotor to create a constant magnet field, while a stator carries windings connected to a modulated AC supply to produce a rotating magnetic field. The magnetic poles of the rotor will lock onto the rotating magnetic field via magnetic attraction between the opposing poles and follow the movement of the rotating magnetic field during operation.

In the preferred embodiment of the present invention, the pump (102) includes a variable speed drive that could control the operating speed and torque of the motor by varying the motor’s input frequency and voltage supplied. The variable speed drive generally works by converting an alternating current (AC) power supply with fixed frequency and fixed voltage into direct current (DC) power supply via an integrated rectifier, and then inverting the converted DC power supply into a simulated pulse-width modulation (PWM) sinusoidal AC output via integrated power electronics. The PWM output is provided with continuously variable frequency and voltage that are used to drive the motor. It is not necessary to install the variable speed drive in the pump (102). The variable speed drive could be possibly installed in the controller (104) but the variable speed drive will remain its connection to the motor that is accommodated within the pump (102).

In the preferred embodiment of the present invention, the controller (104) is provided for controlling the operation of the pump (102) to regulate the fluid flow rate. The controller (104) comprises a plurality of components to accomplish various functions. The plurality of components could be integrated in the controller (104), or, they could be externally connected to the controller (104). Preferably, the controller (104) comprises a micro-processor that could store a set of instructions. The set of instructions could be executed by the controller (104) with aid of the micro-processor for controlling the operation of the pump (102).

With reference to Figure 2, the controller (104) is configured to execute a set of instructions for regulating the operation of the pump (102) so that the pump (102) is driven to achieve a target fluid flow rate and maintain thereof without the aid of any flow sensor. The controller (104) will start off with supplying a drive signal to the pump (102) at step 201 so that the pump (102) provides a fluid flow rate for a predetermined duration. Preferably, the drive signal is a pulse-width modulation signal (PWM) with a predetermined duty cycle which is preferably expressed in percentage. In the preferred embodiment of the present invention, the drive signal with the predetermined duty cycle is continuously provided by the controller (104) to the pump (102) during the predetermined duration so that the pump (102) is driven to produce the maximum fluid flow rate for the predetermined duration.

After the pump (102) is driven to produce the maximum fluid flow rate for the predetermined duration according to the preferred embodiment of the present invention, the controller (104) is then configured to receive a corresponding feedback signal outputted from the pump (102) at step 202. The feedback signal is preferably a pulse-width modulation signal. In the preferred embodiment of the present invention, the controller (104) is configured to measure the duty cycle of the feedback signal that is preferably expressed in percentage upon receiving the feedback signal outputted from the pump (102).

At the same time of step 202, the controller (104) is configured to obtain at least an electrical parameter data from the pump (102) at step 203 after the pump (102) is driven to produce the fluid flow rate for the predetermined duration. Preferably, the controller (104) is in connection with a means for sensing or determining one or more electrical parameters of the pump (102). The electrical parameters may include voltage applied to the pump (102), current drawn by the pump (102), power factor of the pump (102) and power amount used by the pump (102). More preferably, the controller (104) is configured to obtain the electrical parameter data from the motor that is accommodated in the pump (102). In the preferred embodiment of the present invention, the controller (104) is connected to one or more sensors to sense and determine at least one electrical parameter of the pump (102) so as to obtain data thereof. The electrical parameter data preferably comprises power amount used by the pump (102) or voltage applied to the pump (102).

Upon receiving the feedback signal and obtaining the electrical parameter data from the pump (102) after the predetermined duration, the controller (104) will then determine at least one characteristic of the fluid flow path based on the received feedback signal and the obtained electrical parameter data at step 204. In the preferred embodiment, the received feedback signal and the obtained electrical parameter data are used as input variables of an approximation function for determining a fluid flow rate calculation coefficient and a fluid flow rate calculation constant in order to determine the characteristic of the fluid flow path. The fluid flow rate calculation coefficient and the fluid flow rate calculation constant may serve as quantitative indication of the characteristic of the fluid flow path. They may vary according to inherent properties of the fluid flow path. In one of the exemplary embodiments, the characteristic of the fluid flow path may vary according to the configuration of a pipeline network. Preferably, the characteristic of the fluid flow path is, but not limited to, flow resistance of the fluid flow path.

In the preferred embodiment of the present invention, the approximation functions for determining the fluid flow rate calculation coefficient and the fluid flow rate calculation constant are established by obtaining a plurality of data under a plurality of predetermined operating conditions in which the plurality of data comprises a plurality of feedback signal data, a plurality of electrical parameter data, a plurality of fluid flow rate calculation coefficient data and a plurality of fluid flow rate calculation constant data; and performing a multiple regression analysis using the plurality of feedback signal data and the plurality of electrical parameter data as independent variables, and using the plurality of fluid flow rate calculation coefficient data and the plurality of fluid flow rate calculation constant data respectively as a dependent variable. More preferably, the multiple regression analysis is the method of least squares. The method of least squares is generally a mathematical regression analysis that determines a definite relationship between two or more variables via combining a set of measurements to derive estimates of one or more parameters that specify a curve or a line that best fits the data. The line of best fit is fitted through a set of data points across a scatter plot with the minimal sum of deviations squared from the given set of the data so as to provide the best approximation of the given set of the data. Each point of data represents the relationship between one or more known independent variables and an unknown dependent variable.

Preferably, the approximation function for determining the fluid flow rate calculation coefficient is expressed as: a = p — qy ± rx where a denotes the fluid flow rate calculation coefficient; p is a regression constant; y denotes the received feedback signal; q is a regression coefficient associated with the received feedback signal; x denotes the obtained electrical parameter data; and r is a regression coefficient associated with the obtained electrical parameter.

Preferably, the approximation function for determining the fluid flow rate calculation constant is expressed as: b = —s + vy ± wx where b denotes the fluid flow rate calculation constant; s is a regression constant; y denotes the received feedback signal; v is a regression coefficient associated with the received feedback signal; x denotes the obtained electrical parameter data; and w is a regression coefficient associated with the obtained electrical parameter.

In the preferred embodiment of the present invention, the plurality of data are preferably obtained by a plurality of steps repeated by the controller (104) under each of the predetermined operating conditions. The plurality of steps include supplying the drive signal to the pump (102) for providing the fluid flow rate for the predetermined duration, receiving the corresponding feedback signal outputted from the pump (102) after the predetermined duration as the feedback signal data, acquiring the electrical parameter data from the pump (102) after the predetermined duration, and measuring the fluid flow rate provided by the pump (102) using a sensor so as to determine the fluid flow rate calculation coefficient data and the fluid flow rate calculation constant data. In particular, the duty cycle of the feedback signal is measured upon receiving the feedback signal from the pump (102). The plurality of data are collected and used for plotting a scatter plot so as to determine and establish the aforementioned approximation functions when performing the multiple regression analysis. The regression coefficients and constants of the approximation functions can be determined via the method of least squares.

In the preferred embodiment of the present invention, the fluid flow rate calculation coefficient data and the fluid flow rate calculation constant data are determined via a linear regression analysis using a plurality of the drive signals supplied to the pump (102) and a plurality of the corresponding fluid flow rates as measured by the sensor under each of the predetermined operating conditions. The plurality of the drive signals are varied by the controller (104) to have a plurality of duty cycles different from each other. The plurality of the drive signals with different duty cycles and the measured fluid flow rates corresponding to the drive signals are taken as variable data to be plotted on a scatter plot so as to determine a line of best fit and equation thereof. The equation of the line of best fit depicts a relationship between the drive signal supplied to the pump (102) and the fluid flow rate measured by the sensor and the relationship is defined as: i = ad- L + b where d-i denotes the drive signal supplied to the pump (102); f-i denotes the fluid flow rate measured by the sensor; a denotes the fluid flow rate calculation coefficient; and b denotes the fluid flow rate calculation constant. The fluid flow rate calculation coefficient can be determined by computing gradient or slope of the line of best fit using ratio of the change in height to the change in horizontal distance between any two distinct points on the line of best fit; while the fluid flow rate calculation constant can be determined by computing intercept of the line of best fit along the vertical axis.

In a further embodiment of the present invention, the feedback signal data and the electrical parameter data used for establishing the approximation functions are derived from the predetermined operating condition where the supplied drive signal is having a duty cycle equivalent to that of the drive signal in step 201. Preferably, the supplied drive signal comprises a duty cycle that could drive the pump (102) to produce the maximum fluid flow rate.

In the preferred embodiment of the present invention, each of the plurality of predetermined operating conditions is a combination of an electrical parameter applied to the pump (102) and a characteristic of the fluid flow path, and the operating conditions vary from each other. In particular, the electrical parameter applied to the pump (102) preferably comprises voltage applied to the pump (102); while the characteristic of the fluid flow path preferably comprises flow resistance of the fluid flow path. The flow resistance of the fluid flow path can be varied by varying an opening degree of a valve in the fluid flow path in order to simulate a plurality of actual conditions that may happen on the fluid flow path, for instance, where there is a built-up clog along the fluid flow path. The flow resistance of the fluid flow path can be also varied to imitate different pipe dimension and length, and also presence of pipe fittings installed in a pipeline.

Upon determining the characteristic of the fluid flow path at step 204, the controller (104) will proceed to determine a control signal to be outputted to the pump (102) based on a target fluid flow rate required to be achieved by the system (100) at step 205. The control signal is outputted by the controller (104) from time to time in order to adjust the fluid flow rate to be provided by the pump (102). Thus, the system (100) could react promptly when there is any change happened to the target fluid flow rate. The control signal is determined by the controller (104) using a formula that is expressed as: where d 2 denotes the control signal to be outputted to the pump (102); f 2 denotes the target fluid flow rate; a denotes the fluid flow rate calculation coefficient; and b denotes the fluid flow rate calculation constant. Preferably, the control signal is a pulse-width modulation signal having a duty cycle which is adjustable based on the characteristic of the fluid flow path or/and the target fluid flow rate. The formula is preferably derived from the aforementioned relationship between the drive signal supplied to the pump (102) and the fluid flow rates as measured by the sensor. The control signal is eventually outputted by the controller (104) to drive the pump (102) for providing the target fluid flow rate at step 206.

In a further embodiment of the present invention, the system (100) is usable in any one or combination of a water heating system, a water cooling system and an air conditioning system. The system (100) is also applicable in any other systems that require regulation of fluid flow or a constant fluid flow rate. More preferably, the system (100) is connectable to any one or a combination of the water heating system, the water cooling system, and the air conditioning system via the controller (104) for controlling the fluid flow at the target fluid flow rate. The target fluid flow rate is preferably determined by the controller (104) based on the heating performance of the water heating system, the cooling performance of the water cooling system, the cooling and heating performances of the air conditioning system, or any combination thereof. More preferably, the controller (104) is configured to determine the target fluid flow rate according to the heating capacity of the water heating system, the cooling capacity of the water cooling system, the cooling and heating capacity of the air conditioning system, or any combination thereof.

In one of the exemplary embodiment of the present invention, the system (100) is preferably connectable to a water heating system in combination with an air conditioning system to constitute a heat recovery system. The water heating system works in connection with the air conditioning system via a heat exchanging means for performing heat transfer between water in the water heating system and refrigerant in the air conditioning system. Under certain circumstances, the controller (104) of the system (100) will adjust the target fluid flow rate in order to maintain the heating capacity of the water heating system and the cooling capacity of the air conditioning system.

With regard to the method (200) for controlling fluid flow in the system (100), the steps have been primarily described and illustrated in the preceding paragraphs. Referring to Figure 2, the method (200) preferably comprises supplying, by the controller (104), a drive signal to the pump (102) for providing a rate of a fluid flow through a fluid flow path for a predetermined duration (201 ), receiving, by the controller (104), a feedback signal outputted from the pump (102) after the predetermined duration (202), obtaining, by the controller (104), at least an electrical parameter data from the pump (102) after the predetermined duration (203), determining, by the controller (104), at least one characteristic of the fluid flow path based on the received feedback signal and the obtained electrical parameter data (204), determining, by the controller (104), a control signal based on the determined characteristic of the fluid flow path and a target fluid flow rate (205), and outputting, by the controller (104), the control signal to the pump (102) for producing the target fluid flow rate (206).

Hereinafter, examples of the present invention will be provided for more detailed explanation. The advantages of the present invention may be more readily understood and put into practical effect from these examples. However, it is to be understood that the following examples are not intended to limit the scope of the present invention in any way. Examples

Example 1

Establishing Approximation Functions for Determining Fluid Flow Rate Calculation Coefficient and Fluid Flow Rate Calculation Constant

To establish the approximation functions for determining the fluid flow rate calculation coefficient and the fluid flow rate calculation constant, a plurality of data were obtained under a plurality of predetermined operating conditions. The plurality of operating conditions were provided by creating different flow resistance in the fluid flow path, altering voltage applied to the pump (102) and varying duty cycle of the drive signal comprised of pulse-width modulation (PWM) signal for each of the predetermined operating conditions. The resulted data were collected including the feedback signal data and the electrical parameter data, and tabulated in Table 1. Then, a scatter plot was created as shown in Figure 3 by taking a plurality of the drive signals with varying duty cycles and a plurality of the measured fluid flow rates under each of the predetermined operating conditions as variable data to determine the fluid flow rate calculation coefficient data and the fluid flow rate calculation constant data. In this particular example, the feedback signal data and the electrical parameter data used for establishing the approximation functions were obtained under the predetermined operating condition in which the duty cycle of the drive signal was set to drive the pump (102) to produce the maximum fluid flow rate. Further, the fluid flow rate calculation coefficient data and the fluid flow rate calculation constant data were determined for each of the predetermined operating conditions and the results were tabulated in Table 2.

The approximation functions for determining the fluid flow rate calculation coefficient and the fluid flow rate calculation constant based on the received feedback signal and the power amount used by the pump (102) were established via the method of least squares according to the data in Table 3 which is summarized from Tables 1 and 2. The approximation functions are expressed as: a = 0.1678886 - 0.0103199y - 0.002806x where a denotes the fluid flow rate calculation coefficient; y denotes the received feedback signal and x denotes the power amount used by the pump (102) b = -16.21279 + 0.920425y + 0.27831x where b denotes the fluid flow rate calculation constant; y denotes the received feedback signal and x denotes the power amount used by the pump (102).

Table 1 Collection of a plurality of data including a plurality of feedback signal data, a plurality of electrical parameter data and a plurality of fluid flow rates measured by the flow sensor under the plurality of predetermined operating conditions

Table 2 Fluid flow rate calculation coefficient data (a) and fluid flow rate calculation constant data (b) determined for each predetermined operating condition

Table 3 Fluid flow rate calculation coefficient data (a), fluid flow rate calculation constant data (b), feedback signal data in terms of PWM and electrical parameter data comprised of power amount used by the pump (102) for each predetermined operating condition

On the other hand, the approximation functions for determining the fluid flow rate calculation coefficient and the fluid flow rate calculation constant based on the received feedback signal and the voltage applied to the pump (102) were also established via the method of least squares according to the data in Table 4 which is summarized from Tables 1 and 2. The approximation functions are expressed as: a = 0.0068236 - 0.016038y + 0.0002559x where a denotes the fluid flow rate calculation coefficient; y denotes the received feedback signal and x denotes the voltage applied to the pump (102) b = -0.5051892 + 1.482857y - 0.0240422x where b denotes the fluid flow rate calculation constant; y denotes the received feedback signal and x denotes the voltage applied to the pump (102). Table 4 Fluid flow rate calculation coefficient data (a), fluid flow rate calculation constant data (b), feedback signal data in terms of PWM and electrical parameter data comprised of applied voltage measurement for each predetermined operating condition Example 2

Evaluation of Effectiveness of System (100) for Controlling Fluid Flow

Effectiveness of the system (100) of the present invention was evaluated in view of the conventional practices that employ a flow sensor for controlling water flow rate. With reference to Example 1, the controller (104) was configured to supply a plurality of drive signals with different duty cycles (as shown in Table 1) to the pump (102) in order to determine the effectiveness of the system (100). The plurality of drive signals with different duty cycles were used to estimate and determine the fluid flow rate to be provided by the system (100) using the aforementioned relationship that is defined as: i = ad- L + b where d-i denotes the drive signal supplied to the pump (102); denotes the fluid flow rate measured by the sensor; a denotes the fluid flow rate calculation coefficient; and b denotes the fluid flow rate calculation constant. In this case, represents the fluid flow rate to be provided by the system (100). The fluid flow rate calculation coefficient and the fluid flow rate calculation constant were derived based on the received feedback signal and the electrical parameter data as provided in Table 1 using the approximation functions as established in Example 1. The computed fluid flow rates to be provided by the system (100) were tabulated and compared with the fluid flow rates measured by the flow sensor. The results were shown in Tables 5 and 6.

The result in Table 5 shows that the mean difference between the fluid flow rates measured by the flow sensor and the fluid flow rates determined by the system (100) based on the received feedback signals and the power amount used by the pump (102) is 0.001 I/m. While, the result in Table 6 shows that the mean difference between the fluid flow rates measured by the flow sensor and the fluid flow rates determined by the system (100) based on the received feedback signals and the voltage applied to the pump (102) is 0.0921 I/m.

Table 5 Comparison between the fluid flow rates measured by the flow sensor and the fluid flow rates determined by the system (100) based on the received feedback signals and the power amount used by the pump (102) under a plurality of operating conditions. (A: valve opening degree and voltage (V) applied to the pump (102); B: drive signal (PWM, %); C: power amount (W) used by the pump (102); D: received feedback signal (PWM, %); E: fluid flow rate (I/m) measured by the flow sensor; F: fluid flow rate calculation coefficient; G: fluid flow rate calculation constant; H: fluid flow rate (I/m) determined by the system (100); I: difference between the fluid flow rate measured by the flow sensor and the fluid flow rate determined by the system (100))

Table 6 Comparison between the fluid flow rates measured by the flow sensor and the fluid flow rates determined by the system (100) based on the received feedback signals and the voltage applied to the pump (102) under a plurality of operating conditions. (A: valve opening degree and voltage (V) applied to the pump (102); B: drive signal (PWM, %); C: received feedback signal (PWM, %); D: fluid flow rate (I/m) measured by the flow sensor; E: fluid flow rate calculation coefficient; F: fluid flow rate calculation constant; G: fluid flow rate (I/m) determined by the system (100); H: difference between the fluid flow rate measured by the flow sensor and the fluid flow rate determined by the system (100))

It can be seen from the description above that the system (100) of the present invention provides a number of advantages over the conventional system for controlling fluid flow. The system (100) is capable of controlling a flow rate of a fluid flowing through a fluid flow path without the need of measuring the fluid flow rate using a flow sensor. The controller (104) of the system (100) is configured to be responsive to the pump (102) operation and control thereof from time to time. This not only eliminates the use of the flow sensor but also reduces power used by the operation, eventually saving the overall cost involved. Further, the system (100) of the present invention does not require a complex configuration as the other prior arts.

The exemplary implementation described above is illustrated with specific configuration, figures and other characteristics, but the scope of the invention also includes other possible configuration, figures and characteristics. For example, the configuration of the controller (104) could be modified to adapt to any appropriate particular combination of various parts of the system (100).

Various modifications to these embodiments are apparent to those skilled in the art from the description and the accompanying drawings. The principles associated with the various embodiments described herein may be applied to other embodiments. Therefore, the description is not intended to be limited to the embodiments shown along with the accompanying drawings but is to be providing broadest scope of consistent with the principles and the novel features disclosed or suggested herein. Accordingly, the invention is anticipated to hold on to all other such alternatives, modifications, and variations that fall within the scope of the present invention and appended claims.