SYSTEM AND METHOD FOR SLEEP MODE FOR A PUMPING SYSTEM

Description

FIELD

The present disclosure pertains to pumping systems, and more particularly to systems and methods for controlling a pumping system to cause a motor of a pump to enter a sleep mode in the absence of demand for liquid from the pumping system and to wake-up in response to a demand.

BACKGROUND

Liquid supply or pumping systems are generally controlled to supply a liquid at a substantially constant pressure even when demand for the liquid fluctuates. An example of such a pumping system is a system including a reservoir such as a well containing water which is pumped by a pump unit into one or more conduits that route the water to points of use such as faucets, sprinklers and/or appliances in a residence or business. The pump unit includes a pump driven by a motor which is powered by a motor drive, which may be a variable frequency drive.

When a faucet, sprinkler or appliance is turned on or demands water, water flows out of the system. To avoid a substantial pressure drop under such a demand, the motor drive increases the operating frequency of the motor to increase the speed of the pump and thereby maintain a substantially constant system pressure. In some instances, the demand on the system is zero or very low because no water is being used. Under such a zero-demand condition, continued operation of the pump, even at a very low speed, generates heat which may damage the pump, causes unnecessary wear on the pump, and wastes electricity. Some systems determine demand using a flow meter, which is typically more expensive than a pressure sensor and more susceptible to damage from contaminants in the water. Accordingly, there is a need for a system and/or method to reliably detect a zero-demand condition using a pressure sensor and cause the pump to stop operating (i.e., enter a sleep mode) until the demand increases.

SUMMARY

In one embodiment, the present disclosure provides a method of controlling a motor in a liquid system, comprising: controlling an operating frequency of the motor to cause a pump to maintain an actual pressure of liquid in the liquid system at or near a first pressure; determining whether a first timer has elapsed during the controlling step; responding to a determination that the first timer has elapsed by initiating a sleep mode determination, comprising: ramping the operating frequency to one of a low frequency or a high frequency; determining whether the actual pressure remains, for a duration of a second timer, one of above a second pressure which is less than the first pressure after ramping the operating frequency to the low frequency or below a third pressure which is greater than the first pressure after ramping the operating frequency to the high frequency; and responding to the actual pressure remaining, for the duration of the second timer, one of above the second pressure or below the third pressure by causing the motor to enter a sleep mode. In one aspect of this embodiment, the low frequency is a PID Lo Limit. In another aspect, the high frequency is a PID Hi Limit. Yet another aspect further comprises: determining whether, while the motor is in the sleep mode, the actual pressure one of drops below a fourth pressure which is less than the second pressure or increases above a fifth pressure which is greater than the third pressure; and responding to the actual pressure one of dropping below the fourth pressure or increasing above the fifth pressure by causing the motor to exit the sleep mode. In a variant of this aspect, determining whether the actual pressure drops below the third pressure includes computing a pressure error between the actual pressure and the fourth pressure and determining whether the pressure error is greater than zero. In another aspect of this embodiment, determining whether the actual pressure remains above the second pressure includes computing a pressure error between the actual pressure and the second pressure and determining whether the pressure error is greater than zero. In another aspect, the sleep mode determination further comprises responding to the actual pressure, during the second timer, one of dropping below the second pressure or increasing above the third pressure by exiting the sleep mode determination and returning to the controlling step. In another aspect, controlling the operating frequency of the motor includes controlling a variable frequency drive to vary power provided to the motor. In another aspect, the duration of the second timer is based upon the operating frequency of the motor when the first timer has elapsed. In a variant of this aspect, a range of the operating frequency extends from the low frequency to the high frequency, the range being divided into a plurality of zones, and the duration of the second timer is based upon which of the plurality zones the operating frequency of the motor falls when the first timer has elapsed.

According to another embodiment, the present disclosure provides a system for controlling an actual pressure of liquid in a liquid system, comprising: a motor drive including a controller and an inverter connected to the controller; a motor driven connected to the inverter; a pump connected to the motor, the pump being configured to deliver liquid to at least one conduit of the liquid system; and a pressure sensor configured to provide the controller measurements of an actual pressure of liquid in the at least one conduit; wherein the controller is configured to control an operating frequency of the motor in response to the actual pressure from the pressure sensor to cause the pump to maintain the actual pressure at or near a first pressure; and wherein the controller is further configured to respond to a first timer elapsing by initiating a sleep mode determination, comprising: ramping the operating frequency to a low frequency; determining whether the actual pressure remains above a second pressure which is less than the first pressure for a duration of a second timer; and responding to the actual pressure remaining above the second pressure for the duration of the second timer by causing the motor to enter a sleep mode. In one aspect of this embodiment, the low frequency is a PID Lo Limit. In another aspect, the controller is configured to: determine whether the actual pressure drops below a third pressure which is less than the second pressure while the motor is in the sleep mode; and respond to the actual pressure dropping below the third pressure by causing the motor to exit the sleep mode. In a variant of this aspect, the controller is configured to determine whether the actual pressure drops below the third pressure by computing a pressure error between the actual pressure and the third pressure and determining whether the pressure error is greater than zero. In another aspect, the controller is configured to determine whether the actual pressure remains above the second pressure by computing a pressure error between the actual pressure and the second pressure and determining whether the pressure error is greater than zero. In another aspect, the sleep mode determination further comprises responding to the actual pressure dropping below the second pressure during the second timer by exiting the sleep mode determination. In yet another aspect, the controller is configured to control the operating frequency of the motor by controlling the inverter to vary power provided to the motor. In another aspect, the duration of the second timer is based upon the operating frequency of the motor when the first timer has elapsed. In a variant of this aspect, a range of the operating frequency extends from the low frequency to a high frequency, the range being divided into a plurality of zones, and the duration of the second timer is based upon which of the plurality of zones the operating frequency of the motor falls when the first timer has elapsed.

In still another embodiment, the present disclosure provides a non-transitory computer-readable medium with an executable program stored thereon for controlling a motor in a liquid system, wherein the program instructs a controller to perform the following steps: control an operating frequency of the motor to cause a pump to maintain an actual pressure of liquid in the liquid system at or near a first pressure for a first timer; and respond to a determination that the first timer has elapsed by initiating a sleep mode determination, comprising: ramping the operating frequency to a low frequency; determining whether the actual pressure remains above a second pressure which is less than the first pressure for a second timer; and responding to the actual pressure remaining above the second pressure for the second timer by causing the motor to enter a sleep mode. In one aspect of this embodiment, the low frequency is a PID Lo Limit. In another aspect, the program further instructs the controller to: determine whether the actual pressure drops below a third pressure which is less than the second pressure while the motor is in the sleep mode; and respond to the actual pressure dropping below the third pressure by causing the motor to exit the sleep mode. In a variant of this aspect, the controller determines whether the actual pressure drops below the third pressure by computing a pressure error between the actual pressure and the third pressure and determining whether the pressure error is greater than zero. In another aspect, the controller determines whether the actual pressure remains above the second pressure by computing a pressure error between the actual pressure and the second pressure and determining whether the pressure error is greater than zero. In yet another aspect, the sleep mode determination further comprises responding to the actual pressure dropping below the second pressure during the second timer by exiting the sleep mode determination.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other advantages and objects of this disclosure, and the manner of attaining them, will become more apparent, and the disclosure itself will be better understood, by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is conceptual diagram of a liquid system;

FIG. 2 is a conceptual diagram of the liquid system of FIG. 1 depicting components of a motor drive;

FIG. 3 is a simplified block diagram of the liquid system of FIG. 1;

FIG. 4 is a flow chart depicting a method according to the present disclosure of controlling a motor of the liquid system of FIG. 1;

FIG. 5 is a graphic depiction of actual pressure and motor operating frequency during an example execution of the method of FIG. 4; and

FIG. 6 is a diagram depicting motor operating frequency zones.

Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present disclosure, the drawings are not necessarily to scale, and certain features may be exaggerated or omitted in some of the drawings in order to better illustrate and explain the present disclosure.

DETAILED DESCRIPTION

Referring now to FIG. 1, a diagrammatic representation of a liquid supply system or liquid system 10 is shown. Example liquids include water, gasoline fuel, diesel fuel, petroleum, oil, sewage, and combinations of such liquids with gases and solids, such as water and coal-based methane gas. In the description below, the liquid is referred to as water 14 and the pump is described as a deep well pump. The teachings of the present disclosure, however, apply to a variety of different applications. The liquid system 10 comprises a reservoir 12 containing water 14 which is pumped by a pump unit 30 through a conduit 16, optionally via another reservoir 18, e.g., a pressure tank, to a conduit 20 of a closed system. The reservoir 12 may be an underground tank, a well casing, or any other reservoir containing water 14. A check valve 35 is positioned in the conduit 16 to prevent pressure from back-feeding into the reservoir 12. The submersible or immersive pump unit 30 includes a pump 36 driven by a motor 32 which is powered by a motor drive 100 via power conductors 34. The size of the reservoir 12, which is interposed between the pump unit 30 and a transducer or pressure sensor 22, affects the response of the system. In one example, the motor drive 100 is a variable frequency drive and the pump 36 is a centrifugal pump. The motor drive 100 may be referred to hereinafter as “the VFD”. The power conductors 34 may comprise two or more wires to provide single or three phase power to the motor 32. The teachings of the present disclosure may be used with various different types of motors 32, such as, but not limited to, three-phase induction motors, single-phase induction motors, single-phase induction motors with a start switch, and synchronous permanent magnet motors.

During operation of the system, the water 14 flows out of the conduit 20 when an outlet is opened. For example, the system may be a water system in a home, in which case water flows out of the conduit 20 when a faucet is opened or an irrigation system or an appliance is turned on. The liquid system 10 is configured to deliver water at a constant pressure to ensure, for example, that the heads of the irrigation system spray at a constant distance to provide even and predictable irrigation. Fluid characteristics including pressure may be monitored with the pressure sensor 22 disposed in the conduit 20 to generate a pressure signal use to maintain system pressure at or near a target or set point pressure. It should be understood that one or more pressure sensors 22 may be used to measure pressure and generate pressure signals corresponding to various locations in the liquid system 10. The pressure signal is provided via the line 24 connecting the pressure sensor 22 and the motor drive 100. An exemplary input device 60 is also shown. The input device 60 is provided to receive, from a user, input parameters such as set point pressures and operation schedules. The input device 60 may comprise a smart device wirelessly coupled to the motor drive 100. Example smart devices include computers, smart phones and tablets.

Although the embodiments are described with reference to liquids, particularly water, the invention is not so limited. Generally, the embodiments are applicable to any rotary fluid displacement machine driven by a motor with a variable speed drive, including a variable frequency drive. As used herein rotary fluid displacement machines include pumps, fans, ventilators, turbines, radial compressors and other machines having a rotating element provided to displace a fluid.

FIG. 2 illustrates an embodiment of the motor drive 100 comprising a processing device, illustratively a controller 102, a rectifier 120 and an inverter 130. As shown, the controller 102 includes a CPU 104 configured to access a memory device 110 and execute processing instructions from a program module, exemplified by a program 112, based on data 114. Another example of a program module is shown as PID module 116. The PID module 116 may also be comprised in a hardware module communicatively coupled to the controller 102.

Techniques for generating motor voltages according to characteristics of a control signal are known in the art. In one example, a technique comprises storing values in a table corresponding to samples of an operating curve. The operating curve is typically a substantially straight line defining a volts-hertz relationship. When the speed control system determines a desired operating speed, such as for the pump 36, which defines an operating frequency, such as for the motor 32, the motor drive 100 looks up a voltage corresponding to the frequency. The motor drive 100 then generates a motor voltage based on the voltage and the frequency. In another example, a formula or a function embodying the operating curve characteristics is used by the controller 102 to generate the desired motor voltages.

The rectifier 120 is powered by a power source 40 and includes any rectification circuit well known in the art, e.g., a diode bridge, to convert three phase alternating-current (AC) voltage supplied by the power source 40 into direct-current (DC) voltage which it supplies, after smoothing, to the inverter 130. As is known in the art, the rectifier 120 includes a plurality of diodes connected in parallel which allow the positive portions of the three phase AC voltage to pass to the load. The inverter 130 receives DC power from the rectifier 120 through a conductor 122 and converts the DC power into an AC motor power. The power source 40 may comprise a single phase two-wire supply, a single phase three-wire supply, or a three-phase supply.

The CPU 104 receives inputs through an I/O interface 108 and outputs a control signal over a line 128 to the inverter 130. In one example, the control signal, e.g., a speed reference, is provided to a pulse-width-modulation (“PWM”) module having power switches and control logic which generates the appropriate gating signals for the power switches to convert the DC power supplied by the rectifier 120 to the AC motor voltage provided to the motor 32 via the conductors 132, 134 according to the control signal. One example of a PWM approach for controlling the inverter 130 is described in co-pending U.S. patent application No. 63/606,377, titled “SYSTEM AND METHOD FOR MODIFIED ACTIVE ZERO SPACE VECTOR PULSE WIDTH MODULATION,” filed on Dec. 5, 2023, the entire disclosure of which hereby being expressly incorporated herein by reference.

Current drawn by the motor 32 from the inverter 130 is sensed by a current sensor 123 and a current signal is provided by the current sensor 123 to the CPU 104 by the conductor 124. Motor voltage feedback can also be provided, for example through the conductor 126 connecting the inverter 130 and the controller 102. Motor voltages may also be generated with other known or later developed drive topologies programmed in accordance with embodiments of the present disclosure.

In a more general embodiment, the controller 102 comprises control logic operable to generate the control signal. The term “logic” as used herein includes software and/or firmware executing on one or more programmable processors, application-specific integrated circuits, field-programmable gate arrays, digital signal processors, hardwired logic, or combinations thereof. Therefore, in accordance with the embodiments of the present disclosure, various logic may be implemented in any appropriate fashion. A non-transitory machine-readable medium comprising logic can additionally be considered embodied within any tangible form of a computer-readable carrier, such as solid-state memory, magnetic disk, and optical disk containing an appropriate set of computer instructions and data structures that would cause a processor to carry out the techniques described herein. A non-transitory computer-readable medium, or memory, may include random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (e.g., EPROM, EEPROM, or Flash memory), or any other tangible medium capable of storing information.

Referring now to FIG. 3, a simplified version of the liquid system 10 according to the present disclosure is shown. The system 10 is essentially a control loop for ensuring that the pressurized liquid in the system 10 (i.e., the liquid contained in the conduit 20, which may represent a plurality of conduits having various output devices) remains at or near a particular target pressure. The valve 140 in FIG. 3 represents any and/or all of the outlets of the system 10, such as faucets or taps, toilets, sprinkler heads and appliances like washing machines, dishwashers, water heaters, water treatment systems, ice makers, refrigerators, evaporative coolers, etc. When the valve 140 is opened, the demand on the system 10 increases. The pressure of the liquid in the system 10 is sensed by the pressure sensor 22, which provides a pressure signal to the motor drive 100 as indicated above. The pressure signal represents the actual pressure (hereinafter, “P_A”) of the fluid in the system 10. The actual pressure P_A is compared to the target pressure (hereinafter, “P_T”), which is the pressure to which the controller 102 is driving the actual pressure P_A of the system 10 by varying the operating frequency of the motor 32 as is further described below. A comparator 142 of the controller 102 is shown as making the comparison between P_A and P_T, but any of a variety of other hardware and/or software approaches may be used.

The output of the comparator 142 is the difference between P_A and P_T, or the pressure error (hereinafter, “P_E”). Depending upon the magnitude and polarity of P_E, the controller 102 determines whether to increase or decrease in the operating frequency necessary for the motor 32 to change the speed of operation of the pump 36 to cause the actual pressure P_A to become closer to the target pressure P_T, thereby reducing the difference between the actual pressure P_A and the target pressure P_T.

A method for controlling the actual pressure P_A of the system 10 (via control of the operating frequency of the motor 32) which implements a sleep mode feature and a wake-up feature according to the teachings of the present disclosure is depicted in FIG. 4. Initially, the motor drive 100 responds to a start command provided via some type of input such as an ON/OFF switch, a digital input, an analog input, application of power, etc. In response to the start command, the controller 102 ramps the operating frequency of the motor 32 up to a relatively low frequency, such as a PID Lo Limit, which causes the motor 32 and the pump 36 to begin operating. After this initial activation operation, the motor drive 100 begins the method described below.

The method 200 begins at step 202 where the controller 102 sets the target pressure P_T for the system 10. In normal operation, the target pressure P_T is a set point pressure (hereinafter, “P_SP”) determined by the controller 102 or input by a user via, for example, the input device 60. In certain embodiments, P_SP is approximately 60 PSI. The controller 102 determines the difference between the set point pressure P_SP and the actual pressure P_A as measured by the pressure sensor 22 at step 204. This difference is the pressure error P_E determined by the comparator 142 as described above. At step 206, the controller 102 determines whether the pressure error P_E is greater than a positive threshold pressure (hereinafter, “+TP”). In certain embodiments, +TP is approximately 1% of the set point pressure, P_SP. If P_E is sufficiently large to exceed +TP (i.e., the actual pressure P_A is above 101% of the set point pressure P_SP, for example), then the controller 102 reduces the operating frequency of the motor 32 at step 208. By reducing the operating frequency of the motor 32, the speed of the pump 36 is also reduced, thereby causing the actual pressure P_A to decrease toward the target pressure P_T.

Then, the controller 102 increments a first timer at step 210 and determines whether the first timer has elapsed at step 212. The first timer represents the time between sleep mode determinations as is further described below. In other words, the controller 102 periodically determines whether to cause the motor 32 to enter a sleep mode when the first timer has elapsed as is further described below. In certain embodiments, the first timer is within a range of approximately 5 seconds to approximately 120 seconds. In one particular embodiment, the first timer is approximately 10 seconds. If the first timer has not elapsed, then the controller 102 returns to step 204 to again determine the pressure error P_E.

If, on the other hand, at step 206 the pressure error P_E is not greater than +TP, then the controller 102 determines whether the pressure error P_E is less than a negative threshold pressure, (hereinafter, “−TP”), at step 214. In certain embodiments, −TP is approximately −1% of the set point pressure, P_SP. If P_E is sufficiently negative to be less than −TP (i.e., the actual pressure P_A is below 99% of the set point pressure P_SP, for example), then the controller 102 increases the operating frequency of the motor 32 at step 216. By increasing the operating frequency of the motor 32, the speed of the pump 36 is also increased, thereby causing the actual pressure P_A to increase toward the target pressure P_T. Then, the controller 102 increments the first timer at step 210 and determines whether the first timer has elapsed at step 212. If the first timer has not elapsed, then the controller 102 returns to step 204 to again determine the pressure error P_E. Also, if the pressure error P_E is not less than −TP at step 214, then the controller 102 increments the first timer at step 210, determines whether the first timer has elapsed at step 212, and if not, returns to step 204 where the pressure error P_E is again determined.

If at step 212 the controller 102 determines that the first timer has elapsed, then the controller 102 resets the first timer to zero at step 218 and initiates a sleep mode determination. At step 220, the controller 102 ramps the operating frequency of the motor 32 down to a low frequency, such as the PID Lo Limit, which causes the motor 32 and the pump 36 to slow substantially. In certain applications, the PID Lo Limit is an operating frequency of approximately 30 Hertz. The controller 102 also sets the target pressure equal to a low pressure such as a DIP pressure, (hereinafter, “P_DIP”), which is a pressure below the set point pressure, P_SP, at step 222. As further explained below, the DIP pressure P_DIP is the pressure below which the actual pressure P_A must fall (or “dip”) during the sleep mode determination to avoid the motor 32 entering the sleep mode. In certain applications, P_DIP is approximately 56 PSI. At step 224, the controller 102 determines the pressure error P_E in the manner described above with reference to step 204, but at step 224 the target pressure is P_DIP. At step 226 the controller 102 determines whether the pressure error P_E is greater than zero. In other words, the controller 102 determines whether the actual pressure P_A remains above the target pressure P_DIP such that P_A is greater than P_DIP and the difference, P_E, is positive or greater than zero. If the pressure error P_E is not greater than zero at step 226 (i.e., the actual pressure P_A has dropped below the target pressure P_DIP indicating that demand on the system 10 exists and the frequency of the motor 32 and speed of the pump 36 need to be increased), then the controller 102 returns to step 202 where the target pressure P_T is again set to the higher set point pressure P_SP. As such, the sleep mode determination is terminated when, after the operating frequency of the motor 32 is dropped to the PID Lo Limit, the actual pressure P_A drops below the target pressure P_DIP before a second timer (or sleep delay) has elapsed.

On the other hand, if at step 226 the pressure error PE remains above zero (i.e., P_A has not dropped below P_DIP, indicating zero or very low demand), then the second timer is incremented at step 228. In certain embodiments, the second timer is within a range of approximately zero seconds to approximately 3,000 seconds. In one particular embodiment, the second timer is approximately 6 seconds. Then, the controller 102 determines at step 230 whether the second timer has elapsed. If not, then the controller 102 returns to step 224 to again compute P_E and to step 226 to determine whether P_E is greater than zero as described above. If P_E remains greater than zero, the loop including steps 224, 226, 228 and 230 is repeated. In this manner, the controller 102 continues to determine whether the actual pressure P_A remains above the target pressure P_DIP for the entire period of time represented by the second timer. If the controller 102 determines that the second timer has elapsed at step 230, then the actual pressure P_A will have remained above the target pressure P_DIP for the duration of the second timer (because there is zero or very low demand on the system 10), and the controller 102 causes the motor 32 to enter the sleep mode at step 232. The sleep mode is characterized by the controller 102 causing the operating frequency of the motor 32 to reach zero. In other words, the controller 102 disables or shuts down the motor 32, thereby preventing excessive heat and wear and unnecessary power consumption.

After the controller 102 causes the motor 32 to enter the sleep mode, the controller 102 resets the second timer at step 234, and begins a wake-up determination. As part of the wake-up determination, the controller 102 sets the target pressure P_T to a wake-up pressure (hereinafter, “P_WU”), which is a pressure below the DIP pressure P_DIP. In certain applications, P_WU is approximately 55 PSI. Next the controller 102 begins monitoring the pressure error P_E to determine whether the actual pressure P_A drops below the wake-up pressure P_WU. More specifically, at step 238 the controller 102 computes P_E as the actual pressure P_A minus the wake-up pressure P_WU. At step 240, the controller 102 determines whether P_E is greater than zero. If P_E is greater than zero, then the actual pressure P_A remains higher than the wake-up pressure P_WU, indicating that the system 10 remains in a zero-demand condition and the motor 32 may remain in sleep mode. If that is the case, then the controller 102 returns to step 238 to again compute P_E. The controller 102 repeats steps 238 and 240 as long as the actual pressure P_A does not drop below the wake-up pressure P_WU. On the other hand, if at step 240 the controller 102 determines that P_E is not greater than zero (i.e., P_A has dropped below P_WU, indicating there is demand on the system 10), then the controller 102 ramps the operating frequency of the motor 32 to a PID Lo Limit at step 242 and returns to step 202, thereby exiting the sleep mode and returning to normal operation with the target pressure P_T set to the set point pressure P_SP. If necessary, the controller 102 continues ramping the operating frequency of the motor 32 in the manner described above to a PID Hi Limit, which in certain embodiments is approximately 60 Hertz. In certain embodiments, the controller 102 cannot change the operating frequency of the motor 32 beyond the PID Hi Limit (or the PID Lo Limit). It should be understood that any time the motor drive 100 receives a stop command, the controller 102 stops the motor 32.

The controller 102 then continues normal operation until the first timer has elapsed and another sleep mode determination is initiated as described above. As should be apparent from the foregoing, in certain embodiments the steps executed during normal operation are steps 202, 204, 206, 208, 210, 212, 214, 216 and 218, the steps executed in the sleep mode determination are steps 220, 222, 224, 226, 228, 230, 232 and 234, and the steps executed in the wake-up determination are steps 236, 238, 240, and 242. As should be apparent to a person of ordinary skill in the art, certain steps of the method 200 described above may be combined, divided into multiple sub-steps, or performed in a sequence that is different from that shown in FIG. 4.

Referring now to FIG. 5, an example set of pressure and frequency measurements are provided to illustrate the various actions described above with reference to the method 200. More specifically, the actual pressure P_A is shown as measured by the pressure sensor 22 depicted in FIGS. 1-3, and an operating frequency 302 of the motor 32 is shown as controlled by the controller 102. In the upper part of FIG. 5, the status 304 of the system (i.e., run mode or sleep mode) and the level of demand 306 on the system 10 in this example is indicated as is further described below. As shown, the actual pressure P_A begins at a low pressure before the motor drive 100 is activated. At a time indicated by the vertical dashed line 308, the controller 102 is activated and begins ramping up the operating frequency 302 of the motor 32. At point 310, the operating frequency 302 reaches the PID Lo Limit, and the controller 102 begins incrementing the first timer (step 210 of FIG. 4). Correspondingly, at point 312 the actual pressure P_A begins to increase as the operating speed of the pump 36 increases. As is shown, during the initial period of time (i.e., between the vertical dashed line 308 and the vertical dashed line 314), the demand 306 for water from the system 10 is assumed to be high. As such, the controller 102 ramps the operating frequency 302 of the motor 32 rapidly from the PID Lo Limit at point 310 to the PID Hi Limit at point 316. The actual pressure P_A therefore increases rapidly as well. At point 316 the operating frequency 302 of the motor 32 is clamped at the PID Hi Limit. Eventually, at point 318 of the actual pressure P_A, the pump 36 causes the actual pressure P_A to increase sufficiently to exceed the set point pressure P_SP.

When the controller 102 determines at step 206 of FIG. 4 that the actual pressure P_A exceeds the set point pressure P_SP by more than the positive threshold pressure +TP, the controller 102 decreases the operating frequency 302 of the motor 32 (step 208 of FIG. 4) to reduce the actual pressure P_A toward the set point pressure P_SP as described above. This occurs at point 320 of the operating frequency 302. During normal operation, the controller 102 adjusts the operating frequency 302 to maintain the actual pressure P_A between the positive threshold pressure +TP and the negative threshold pressure −TP, above and below the set point pressure P_SP as described above. Under a high demand condition 306, this normal operation is depicted in the period of time from the vertical dashed line 322 and the vertical dashed line 314.

At the time corresponding to the vertical dashed line 314 in FIG. 5, the demand 306 on the system 10 is assumed to be lower. When the demand 306 drops, the current operating frequency 302 of the motor 32 (and the speed of the pump 36) is higher than necessary, and the actual pressure P_A increases beginning at point 324 to pressures above the set point pressure P_SP. As explained above, when the actual pressure P_A is greater than the set point pressure P_SP by an amount greater than the positive pressure threshold +TP, the controller 102 decreases the operating frequency 302 of the motor 32 to lower the actual pressure P_A. This begins at point 326 of the operating frequency 302 and ends at point 328 which corresponds to point 330 of the actual pressure P_A where the actual pressure P_A drops below the set point pressure P_SP. For a period of time thereafter, the controller 102 varies the operating frequency 302 to maintain the actual pressure P_A at or near the set point pressure P_SP. During this time, the controller 102 continues to increment the first timer described above at step 210 of FIG. 4. When the first timer elapses (as determined at step 212 of FIG. 4), the controller 102 initiates a sleep mode determination as described above. In FIG. 5, the first timer expires at the vertical dashed line 332. Thus, the period of time corresponding to the first timer begins at the point 310 and ends at the vertical dashed line 332.

Upon expiration of the first timer (at point 334 of the operating frequency 302), the controller 102 ramps the operating frequency 302 of the motor 32 down to the PID Lo Limit as shown by the segment 336 (step 220 of FIG. 4). As shown by the segment 338 of the actual pressure P_A, in this example the actual pressure P_A drops as the operating frequency 302 decreases because there is a demand 306 (i.e., lower demand) on the system 10 for water. At point 340, the actual pressure P_A falls below the DIP pressure P_DIP, which the controller 102 had previously set as the target pressure P_T at step 222 of FIG. 4. When the actual pressure P_A falls below P_DIP, the pressure error P_E determined at step 224 of FIG. 4 is less than zero (i.e., the determination at step 226 of FIG. 4 is “N”). Thus, the controller 102 terminates the sleep mode determination and again sets the target pressure P_T to P_SP at step 202 of FIG. 4. The controller 102 also begins incrementing the first timer. As shown by the segment 342, the controller 102 ramps the operating frequency 302 up until the actual pressure P_A reaches P_SP (point 344), and then adjusts the operating frequency 302 to maintain the actual pressure P_A at or near P_SP in the manner described above.

In this example, at a time corresponding to the point 346, the demand 306 changes from a lower demand to zero demand (i.e., all outlets of the system 10 are closed). At a time corresponding to the point 348 of the operating frequency 302, the first timer again elapses as determined at step 212 of FIG. 4. It should be understood that in FIG. 5 the period of time corresponding to the first timer for the second sleep mode determination (i.e., from the point 340 to the point 348) is not to scale. The period of time corresponding to the first timer for the second sleep mode determination is actually the same as the period of time corresponding to the first timer for the above-described first sleep mode determination (i.e., from the point 310 to the vertical dashed line 332).

The controller 102 again initiates a sleep mode determination at the point 348 and ramps the operating frequency 302 to the PID Lo Limit (step 220 of FIG. 4) as indicated by the segment 350. This time, because there is zero demand 306 on the system 10, the decrease in the operating frequency 302 of the motor 32 (and the corresponding decrease in the speed of the pump 36) does not cause the actual pressure P_A to drop. Accordingly, P_E remains greater than zero as determined at step 226 of FIG. 4 until the second timer elapses as determined at step 230 of FIG. 4. The second timer corresponds to the period of time labelled 352 in FIG. 5. Thus, the controller 102 causes the motor 32 to enter the sleep mode (step 232 of FIG. 4) and, at a time corresponding to the vertical dashed line 354, ramps the operating frequency 302 to zero as indicated by the segment 356. The sleep mode is indicated on the status graph 304 of FIG. 4.

As explained above, when the controller 102 causes the motor 32 to enter the sleep mode, the controller 102 begins a wake-up determination by resetting the second timer (step 234 of FIG. 4), setting the target pressure P_T to a wake-up pressure P_WU (step 236 of FIG. 4) and monitoring the actual pressure P_A to determine whether it drops below P_WU (steps 238 and 240 of FIG. 4). As indicated by the point 358 of the demand 306 in FIG. 5, in this example while the motor 32 is in sleep mode the demand 306 changes from none to high. Because the motor 32 is off, the increase in demand 306 causes the actual pressure P_A to decrease beginning at the point 360. Eventually, at point 362, the actual pressure P_A drops below the wake-up pressure P_WU. As a result, the controller 102 determines at step 240 of FIG. 4 that the pressure error P_E is not greater than zero (i.e., the actual pressure P_A is less than the target pressure P_T, which has been set to P_WU). Accordingly, the controller 102 ramps the operating frequency 302 to the PID Hi Limit (step 242 of FIG. 4) and exits the sleep mode, returning to normal operation beginning at step 202 of FIG. 4 where the target pressure P_T is again set to the set point pressure P_SP. The ramp up of the operating frequency 302 is indicated by the segment 364 in FIG. 5.

In this example, the controller 102 continues to operate the motor 32 at the PID Hi Limit for a period of time (indicated by the segment 366) until the actual pressure P_A exceeds the set point pressure P_SP as indicated by the point 368. The controller 102 then varies the operating frequency 302 of the motor 32 to maintain the actual pressure P_A at or near the set point pressure P_SP as described above.

In an alternative embodiment, the second timer is dependent upon the current operating frequency of the motor 32. If the current operating frequency is low (e.g., close to the PID Lo Limit), then it is more likely that there is zero or very low demand 306, and the second timer may be relatively short. If the current operating frequency is high (e.g., close to the PID Hi Limit), then it is more likely that there is demand 306, and the second timer may be relatively long. In this embodiment, step 220 of FIG. 4 is replaced with a step that records the active operating frequency (“F_A”) of the motor 32. The second timer of step 230 is then based on F_A. The operating frequencies between the PID Lo Limit and the PID Hi Limit may be divided into zones, each zone corresponding to a different duration for the second timer as described below.

FIG. 6 depicts various operating frequencies F_A of the motor 32 as determined by the controller 102 ranging from the PID Lo Limit at the low end and the PID Hi Limit at the high end. Zone A (or a sleep ready zone) is between the PID Lo Limit and F1 and represents a range of operating frequencies likely to correspond to zero or very low demand 306 such that a short second timer may be used to cause the controller 102 to more quickly put the motor 32 in the sleep mode. In one embodiment, the frequency F1 is equal to the PID Lo Limit plus 0.5 Hertz. In embodiments where the PID Lo Limit is 30 Hertz, F1=30.5 Hertz. Thus, at the modified step 220 of FIG. 4, when the controller 102 determines that F_A falls within Zone A (i.e., is greater than or equal to the PID Lo Limit and less than or equal to F1), the controller 102 will use a short duration second timer. In certain embodiments, the second timer corresponding to Zone A is one second.

Zone B of FIG. 6 (a high sleep chance zone) is between F1 and F2. In certain embodiments, F2 is equal to 0.25 times the difference between the PID Hi Limit and the PID Lo Limit, plus the PID Lo Limit. In embodiments where the PID Lo Limit is 30 Hertz and the PID Hi Limit is 60 Hertz, F2=0.25*(PID Hi Limit−PID Lo Limit)+PID Lo Limit (or 0.25*(60−30)+30), which equals 37.5 Hertz. Thus, at the modified step 220 of FIG. 4, when the controller 102 determines that F_A falls within Zone B, the controller 102 will use a second timer that is longer in duration than the second timer corresponding to Zone A. In certain embodiments, the second timer corresponding to Zone B is ten seconds.

Zone C of FIG. 6 (a medium sleep chance zone) is between F2 and F3. In certain embodiments, F3 is equal to 0.5 times the difference between the PID Hi Limit and the PID Lo Limit, plus the PID Lo Limit. In embodiments where the PID Lo Limit is 30 Hertz and the PID Hi Limit is 60 Hertz, F3=0.5*(PID Hi Limit−PID Lo Limit)+PID Lo Limit (or 0.5*(60−30)+30), which equals 45 Hertz. Thus, at the modified step 220 of FIG. 4, when the controller 102 determines that F_A falls within Zone C, the controller 102 will use a second timer that is longer in duration than the second timer corresponding to Zone B. In certain embodiments, the second timer corresponding to Zone C is 2.5 times the second timer corresponding to Zone B, or 25 seconds.

Zone D of FIG. 6 (a low sleep chance zone) is between F3 and F4. In certain embodiments, F4 is equal to the PID Hi Limit minus 1 Hertz. In embodiments where the PID Hi Limit is 60 Hertz, F4 is equal to 59 Hertz. Thus, at the modified step 220 of FIG. 4, when the controller 102 determines that F_A falls within Zone D, the controller 102 will use a second timer that is longer in duration than the second timer corresponding to Zone C. In certain embodiments, the second timer corresponding to Zone D is 4 times the second timer corresponding to Zone B, or 40 seconds.

Zone E of FIG. 6 (a no sleep zone) is between F4 and the PID Hi Limit. Thus, in embodiments where the PID Hi Limit is 60 Hertz, if at the modified step 220 of FIG. 4 the controller 102 determines that F_A is greater than (or equal to) 59 Hertz and less than (or equal to) 60 Hertz, the controller 102 will not perform a sleep mode determination and returns to step 202 of FIG. 4.

In the manner described above, the time that the actual pressure P_A must remain greater than the target pressure of P_DIP (i.e., the second timer) is not a fixed interval but rather is dependent upon the zone of the operating frequency of the motor 32 (and thus, the demand 306 on the system) at the time the sleep mode determination is initiated. It should be understood that in further alternative embodiments, the second timer may be a continuous function of the operating frequency of the motor 32.

It should also be understood that while the systems and methods described above are implemented with a pressure sensor 22 that detects the pressure of the liquid in the conduit 20 (i.e., a Direct PID regulation with sleep mode), the principles of the present disclosure may also be applied to a system with Inverse PID regulation with sleep mode. In such a system, the pressure of the liquid in the reservoir 12 is monitored and used in the sleep mode determination. The pressure of the liquid in the reservoir 12 may be measured by a pressure sensor positioned at or near the bottom of the reservoir 12 such that the level of the water 14 in the reservoir 12 affects the pressure. When the controller 102 increases the operating frequency of the motor 32, the level of the water 14 in the reservoir 12 lowers, which decreases the pressure sensed by the sensor at or near the bottom of the reservoir 12. Conversely, when the controller 102 decreases the operating frequency of the motor 32, the reservoir 12 refills, raising the level of the water 14 and increasing the pressure sensed by the sensor at or near the bottom of the reservoir 12. In such an Inverse PID system, the concepts of the present disclosure may readily be applied to provide sleep mode control by simply inverting the above-described pressures and operating frequencies.

Any directional references used with respect to any of the figures, such as right or left, up or down, or top or bottom, are intended for convenience of description, and do not limit the present disclosure or any of its components to any particular positional or spatial orientation. Additionally, any reference to rotation in a clockwise direction or a counter-clockwise direction is simply illustrative. Any such rotation may be implemented in the reverse direction as that described herein.

Although the foregoing text sets forth a detailed description of embodiments of the disclosure, it should be understood that the legal scope of the invention is defined by the words of the claims set forth at the end of this patent and equivalents. The detailed description is to be construed as exemplary only and does not describe every possible embodiment. Numerous alternative embodiments may be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims.

The following additional considerations apply to the foregoing description. Throughout this specification, plural instances may implement components, operations, or structures described as a single instance. Although individual operations of one or more methods are illustrated and described as separate operations, one or more of the individual operations may be performed concurrently, and nothing requires that the operations be performed in the order illustrated. Structures and functionality presented as separate components in example configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements fall within the scope of the subject matter herein.

In various embodiments, a hardware module may be implemented mechanically or electronically. For example, a hardware module may comprise dedicated circuitry or logic that is permanently configured (e.g., as a special-purpose processor, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC)) to perform certain operations. A hardware module may also comprise programmable logic or circuitry (e.g., as encompassed within a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. It will be appreciated that the decision to implement a hardware module mechanically, in dedicated and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.

Accordingly, the term “hardware module” should be understood to encompass a tangible entity, be that an entity that is physically constructed, permanently configured (e.g., hardwired), or temporarily configured (e.g., programmed) to operate in a certain manner or to perform certain operations described herein. Considering embodiments in which hardware modules are temporarily configured (e.g., programmed), each of the hardware modules need not be configured or instantiated at any one instance in time. For example, where the hardware modules comprise a general-purpose processor configured using software, the general-purpose processor may be configured as respective different hardware modules at different times. Software may accordingly configure a processor, for example, to constitute a particular hardware module at one instance of time and to constitute a different hardware module at a different instance of time.

Hardware modules may provide information to, and receive information from, other hardware modules. Accordingly, the described hardware modules may be regarded as being communicatively coupled. Where multiple of such hardware modules exist contemporaneously, communications may be achieved through signal transmission (e.g., over appropriate circuits and buses) that connect the hardware modules. In embodiments in which multiple hardware modules are configured or instantiated at various times, communications between such hardware modules may be achieved, for example, through the storage and retrieval of information in memory structures to which the multiple hardware modules have access. For example, one hardware module may perform an operation and store the output of that operation in a memory device to which it is communicatively coupled. A further hardware module may then, at a later time, access the memory device to retrieve and process the stored output. Hardware modules may also initiate communications with input or output devices, and may operate on a resource (e.g., a collection of information).

The various operations of example methods described herein may be performed, at least partially, by one or more processors that are temporarily configured (e.g., by software) or permanently configured to perform the relevant operations. Whether temporarily or permanently configured, such processors may constitute processor-implemented modules that operate to perform one or more operations or functions. The modules referred to herein may, in some example embodiments, comprise processor-implemented modules.

Similarly, the methods or routines described herein may be at least partially processor-implemented. For example, at least some of the operations of a method may be performed by one or more processors or processor-implemented hardware modules. The performance of certain of the operations may be distributed among the one or more processors, not only residing within a single machine, but deployed across a number of machines. In some example embodiments, the processor or processors may be located in a single location (e.g., within a home environment, an office environment or as a server farm), while in other embodiments the processors may be distributed across a number of locations.

The performance of certain of the operations may be distributed among the one or more processors, not only residing within a single machine, but deployed across a number of machines. In some example embodiments, the one or more processors or processor-implemented modules may be located in a single device or geographic location (e.g., within a home environment, an office environment, or a server farm). In other example embodiments, the one or more processors or processor-implemented modules may be distributed across a number of devices or geographic locations.

Unless specifically stated otherwise, use herein of words such as “processing,” “computing,” “calculating,” “determining,” “presenting,” “displaying,” or the like may refer to actions or processes of a machine (e.g., a computer) that manipulates or transforms data represented as physical (e.g., electronic, magnetic, or optical) quantities within one or more memories (e.g., volatile memory, non-volatile memory, or a combination thereof), registers, or other machine components that receive, store, transmit, or display information.

As used herein any reference to “one embodiment” or “an embodiment” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.

Some embodiments may be described using the expression “coupled” and “connected” along with their derivatives. For example, some embodiments may be described using the term “coupled” to indicate that two or more elements are in direct physical or electrical contact. The term “coupled,” however, may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. The embodiments are not limited in this context.

Additionally, some embodiments may be described using the expression “communicatively coupled,” which may mean (a) integrated into a single housing, (b) coupled using wires, or (c) coupled wirelessly (i.e., passing data/commands back and forth wirelessly) in various embodiments.

As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

In addition, use of the “a” or “an” are employed to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of the description. This description, and the claims that follow, should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

The patent claims at the end of this patent application are not intended to be construed under 35 U.S.C. § 112(f) unless traditional means-plus-function language is expressly recited, such as “means for” or “step for” language being explicitly recited in the claim(s).