Flow control device and method for a direct current water pump

Abstract

The application relates to the technical field of water pump flow control, in particular to a flow control device and method of a direct-current water pump, which comprises a current sampling unit, a voltage amplification unit and a control unit connected in sequence, wherein the current sampling unit is used for sampling the working current of the direct-current water pump and converting the working current into a first voltage signal; the voltage amplification unit is used for amplifying the first voltage signal to obtain a second voltage signal which can be collected by the control unit; the control unit is used for obtaining the working state corresponding to the direct-current water pump according to the second voltage signal, and obtaining the estimated flow according to the working state; and the estimated flow is used for adjusting a PWM signal through PID control to control the flow of the direct-current water pump; thus, the current signal flowing through the water pump is detected and converted into a voltage signal, and the water flow is estimated through a software algorithm, so that the water pump flow control is realized, and the product miniaturization design is promoted while the cost is saved.

Description

Technical Field

[0001] This invention relates to the field of water pump flow control technology, and in particular to a flow control device for a DC water pump and a flow control method for a DC water pump. Background Technology

[0002] In related technologies, flow meter components are an important detection component for water output control. Different flow rates of water generate different pulse frequencies after passing through the flow meter component. The flow meter can accurately detect the water flow rate, and most of the industry adopts this solution. However, flow meters are expensive and must be connected in series in the water circuit. The component is large in size and occupies a lot of space, which is difficult to meet the requirements in the small space of household water purifiers. Summary of the Invention

[0003] The present invention aims to at least partially solve one of the technical problems in the aforementioned technologies. Therefore, one object of the present invention is to provide a flow control device for a DC water pump, which achieves flow control by detecting the current signal flowing through the water pump, converting it into a voltage signal, and estimating the water volume through a software algorithm, thereby saving costs and promoting product miniaturization.

[0004] The second objective of this invention is to provide a flow control method for a DC water pump.

[0005] To achieve the above objectives, a first aspect of the present invention provides a flow control device for a DC water pump, comprising a current sampling unit, a voltage amplification unit, and a control unit connected in sequence. The current sampling unit samples the operating current of the DC water pump and converts it into a first voltage signal. The voltage amplification unit amplifies the first voltage signal to obtain a second voltage signal that the control unit can acquire. The control unit obtains the corresponding operating state of the DC water pump based on the second voltage signal, estimates the flow rate based on the operating state, and adjusts the PWM signal using PID control based on the estimated flow rate to control the flow rate of the DC water pump. Thus, by detecting the current signal flowing through the water pump and converting it into a voltage signal, and estimating the water volume using a software algorithm, water pump flow control is achieved, thereby saving costs and promoting product miniaturization.

[0006] In addition, the flow control device for a DC water pump according to the above embodiments of the present invention may also have the following additional technical features: Optionally, the operating state of the DC water pump is obtained based on the second voltage signal, including: The operating current of the DC water pump is obtained based on the second voltage signal, and the operating state of the DC water pump is obtained based on the operating current.

[0007] Optionally, the operating state of the DC water pump is determined based on the operating current, including: if the operating current is less than 20mA, the operating state of the DC water pump is determined to be an unloaded state; if the operating current is 40-100mA, the operating state of the DC water pump is determined to be a normal pumping state; if the operating current is 120mA-140mA, the operating state of the DC water pump is determined to be a water circuit blockage state; if the operating current is greater than 150mA, the operating state of the DC water pump is determined to be a pump stall state.

[0008] Optionally, obtaining the estimated flow rate based on the operating state includes: if the operating state is an unloaded state or a pump stalled state, the estimated flow rate is 0; if the operating state is a normal pumping state, the corresponding output power is obtained based on the second voltage signal, and the estimated flow rate corresponding to the output power is obtained based on a pre-calibrated relationship between the output power and the flow rate curve; if the operating state is a water circuit blockage state, the corresponding output power is obtained based on the second voltage signal, and the estimated flow rate corresponding to the output power is obtained based on a pre-calibrated relationship between the output power and the flow rate curve, and then multiplied by a correction factor.

[0009] Optionally, adjusting the PWM signal through PID control based on the estimated flow rate includes: if the operating state is an unloaded state, a normal pumping state, or a water circuit blockage state, calculating the difference between the estimated flow rate and the preset target flow rate to obtain the flow deviation, and outputting the corresponding PWM signal based on the flow deviation; if the operating state is a pump stall state, cutting off the PWM signal output.

[0010] Optionally, the current sampling unit includes a sampling resistor to convert the operating current of the DC water pump into a first voltage signal through the sampling resistor.

[0011] Optionally, the voltage amplification unit includes two operational amplifiers to amplify the first voltage signal.

[0012] To achieve the above objectives, a second aspect of the present invention provides a flow control method for a DC water pump, applied to the aforementioned flow control device for the DC water pump. The control method includes the following steps: acquiring the operating current of the DC water pump and converting it into a first voltage signal; amplifying the first voltage signal to obtain a second voltage signal; obtaining the operating state of the DC water pump based on the second voltage signal, and obtaining an estimated flow rate based on the operating state; and adjusting a PWM signal through PID control based on the estimated flow rate to control the flow rate of the DC water pump. Attached Figure Description

[0013] Figure 1 This is a block diagram of a flow control device for a DC water pump according to an embodiment of the present invention; Figure 2 A schematic diagram of the circuit principle of a flow control device for a DC water pump according to an embodiment of the present invention; Figure 3 This is a schematic flowchart of a flow control method for a DC water pump according to an embodiment of the present invention. Detailed Implementation

[0014] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0015] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0016] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0017] refer to Figure 1 As shown, the flow control device for a DC water pump in this embodiment of the invention includes a current sampling unit 10, a voltage amplification unit 20, and a control unit 30.

[0018] The current sampling unit 10 is used to sample the operating current of the DC water pump and convert it into a first voltage signal; the voltage amplification unit 20 is used to amplify the first voltage signal to obtain a second voltage signal that can be collected by the control unit; the control unit 30 is used to obtain the corresponding operating state of the DC water pump according to the second voltage signal, and to obtain the estimated flow rate according to the operating state; and to adjust the PWM signal through PID control according to the estimated flow rate to control the flow rate of the DC water pump.

[0019] It should be noted that the output power of the DC water pump directly determines the water flow rate of the control system. Due to the need for miniaturization in the hardware system design, this application cannot add a flow meter to accurately detect the water flow rate. To calculate the water output in this application, this application focuses on the detection and control of the water pump's output power. It detects the current signal flowing through the water pump, converts it into a voltage signal, amplifies it through an integrated operational amplifier circuit, and sends the data to a microprocessor for acquisition. The water output is then estimated using a software algorithm, thereby achieving flow control. The hardware principle is as follows: Figure 2 As shown, the current sampling unit 10 includes a sampling resistor R22 to convert the operating current of the DC water pump into a first voltage signal through the sampling resistor R22; the voltage amplification unit 20 includes a two-stage operational amplifier U5 to amplify the first voltage signal through the two-stage operational amplifier U5.

[0020] As one embodiment, obtaining the operating state of the DC water pump based on the second voltage signal includes: obtaining the operating current of the DC water pump based on the second voltage signal, and obtaining the operating state of the DC water pump based on the operating current.

[0021] As an example, the operating state of the DC water pump is determined based on the operating current, including: if the operating current is less than 20mA, the operating state of the DC water pump is determined to be no-load; if the operating current is 40-100mA, the operating state of the DC water pump is determined to be normal pumping; if the operating current is 120mA-140mA, the operating state of the DC water pump is determined to be water circuit blockage; if the operating current is greater than 150mA, the operating state of the DC water pump is determined to be pump stall.

[0022] In other words, the selected DC water pump is rated for a maximum output of 24V / 3W. The measured operating current of the DC water pump under various operating conditions is as follows: Under no-load conditions, the operating current of the DC water pump is <20mA; During normal water pumping, the operating current of a DC water pump is 40-100mA. When the water path is blocked, the DC water pump will output close to full power, with an actual measurement of approximately 120mA-140mA. When the water pump is stalled, the operating current of the DC water pump is >150mA.

[0023] As one embodiment, the estimated flow rate is obtained based on the operating state, including: if the operating state is no-load or pump stall, the estimated flow rate is 0; if the operating state is normal pumping, the corresponding output power is obtained based on the second voltage signal, and the estimated flow rate corresponding to the output power is obtained based on the pre-calibrated relationship between output power and flow rate curves; if the operating state is water circuit blockage, the corresponding output power is obtained based on the second voltage signal, and the estimated flow rate corresponding to the output power is obtained based on the pre-calibrated relationship between output power and flow rate curves, and then multiplied by a correction factor.

[0024] It should be noted that for detecting the output power of the DC water pump, this application uses a 0.2Ω / 0.25W / 1206 packaged sampling resistor. The operating current of the resistor will not exceed 0.4A (due to pump motor stall), meaning the maximum power consumption of the sampling resistor will not exceed 0.032W, which is far less than the rated power of the sampling resistor itself. The pump's operating current flows through the 0.2Ω / 0.25W / 1206 sampling resistor, converting it into a small signal voltage. This voltage is then amplified by a two-stage operational amplifier circuit to a voltage signal of 11×11=121 times, which is then sampled and processed by the microprocessor. This signal is then converted into the actual output power of the DC water pump. The voltage across the sampling resistor and the voltage output to the microprocessor are calculated as follows: When the microprocessor detects that the voltage flowing through the water pump is below 484mV, it can be considered that the water pump is running dry, as calculated below: Sampling resistor: Ui(max) = 20 × 0.2 = 4mV Op-amp output: Uo(max)=4×11×11=484mV When the microprocessor detects that the voltage flowing through the water pump is between 968mV and 2.42V, the water pump can be considered to be pumping water normally. The calculation is as follows: Sampling resistors: Ui(min) = 40 × 0.2 = 8mV Ui(max) = 100 × 0.2 = 20mV Op-amp output: Uo(min)=8×11×11=968mV Uo(max)=20×11×11=2.42V When the microprocessor detects that the voltage flowing through the water pump is between 2.904V and 3.388V, the system's water circuit can be considered blocked, as calculated below: Sampling resistors: Ui(min) = 120 × 0.2 = 24 mV Ui(max) = 140 × 0.2 = 28 mV Op-amp output: Uo(min)=24×11×11=2.904V Uo(max)=28×11×11=3.388V When the microprocessor detects that the voltage flowing through the water pump is higher than 3.63V, the water pump is considered to be stalled, as calculated below: Sampling resistor: Ui(min) = 150 × 0.2 = 30mV Op-amp output: Uo(min)=30×11×11=3.63V As an example, the PWM signal is adjusted by PID control based on the estimated flow rate, including: if the working state is no-load state, normal pumping state, or water circuit blockage state, the difference between the estimated flow rate and the preset target flow rate is calculated to obtain the flow deviation, and the corresponding PWM signal is output according to the flow deviation; if the working state is pump stall state, the PWM signal output is cut off.

[0025] It should be noted that the equivalent resistance of a DC water pump is constant. To control the output power of a DC water pump, it can only be achieved by controlling the pump's operating voltage (or current). This application calculates the pulse width of the PWM wave based on a PID control algorithm to adjust the operating voltage of the DC water pump, thereby achieving the adjustment of the pump's output power.

[0026] As a specific example, assume the target flow rate is set to 1.5L / min (suitable for typical water output requirements of a household water purifier); pump parameters: 24V / 3W DC water pump, rated speed 3000RPM; PID parameters: proportional coefficient Kp=0.8, integral coefficient Ki=0.2, derivative coefficient Kd=0.1; PWM range: 0-100% (corresponding to output voltage 0-24V).

[0027] (a) Normal pumping conditions (current 40-100mA) 1. Power detection and flow estimation: Assuming the current sampling voltage is 1.694V, calculate the current in reverse:

[0028] Calculate the output power:

[0029] According to the calibration curve Estimate the flow rate:

[0030] 2. Flow deviation calculation

[0031] 3. PID Calculation and PWM Output PID controller output calculation:

[0032] Assume that in the first calculation, the integral and differential terms are both zero:

[0033] Convert to PWM duty cycle:

[0034] If the current duty cycle is 50%, adjust it to 79.76%, which corresponds to a voltage of approximately 19.14V.

[0035] (ii) No-load condition (current <20mA) 1. Status recognition The sampling voltage is 0.3V, and the current is calculated in reverse:

[0036] Determined to be in an unloaded state, the flow rate is directly estimated. .

[0037] 2. Flow deviation and control

[0038] PID output:

[0039] The PWM duty cycle is adjusted as follows:

[0040] Since the maximum value of PWM is 100%, the system directly outputs a 100% duty cycle (24V) and issues a no-load alarm.

[0041] (III) Waterway blockage (current 120-140mA) 1. Power detection and flow estimation The sampling voltage is 3.146V, and the current is calculated in reverse:

[0042] Calculate the output power:

[0043] Estimate flow rate based on calibration curve:

[0044] Due to waterway blockage, the actual flow rate is far lower than the estimated value and needs to be multiplied by a correction factor of 0.4.

[0045] 2. Flow deviation and control

[0046] PID output:

[0047] The PWM duty cycle is adjusted as follows:

[0048] The system outputs 100% duty cycle and triggers a blockage alarm, suggesting that the filter element be replaced.

[0049] (iv) Stalled rotor state (current > 150mA) 1. Status recognition The sampling voltage is 3.8V, and the current is calculated in reverse:

[0050] Determined to be in a stalled state, direct estimation .

[0051] 2. Security Protection Mechanism The system immediately cuts off the PWM output (duty cycle 0%) and issues a stall alarm to prevent the motor from burning out. At this time, flow deviation calculation is meaningless, and the protection action is executed first.

[0052] In summary, the flow control device for a DC water pump proposed in this application estimates the water output by detecting the current signal flowing through the water pump and converting it into a voltage signal, thereby achieving flow control. Specifically, the output power of the water pump is controlled by PWM, and the operating current of the water pump is detected and incorporated into the PID control algorithm to fine-tune the PWM output in order to find an adaptive PWM duty cycle, thereby accurately controlling the water output.

[0053] Figure 3 This is a schematic flowchart of a flow control method for a DC water pump according to an embodiment of the present invention. Figure 3 As shown, the flow control method includes the following steps: S101 acquires the operating current of the DC water pump and converts it into a first voltage signal.

[0054] S102, amplify the first voltage signal to obtain the second voltage signal.

[0055] S103: Obtain the corresponding operating state of the DC water pump based on the second voltage signal, and obtain the estimated flow rate based on the operating state.

[0056] S104, based on the estimated flow rate, adjusts the PWM signal through PID control to control the flow rate of the DC water pump.

[0057] In summary, this application eliminates the need for an additional flow sensor. Flow control is achieved by detecting the pump's output power and estimating the water volume using a software algorithm. The hardware detection circuit converts the pump's current signal into a voltage signal, amplifies it, and sends it to the microprocessor for acquisition. The software algorithm estimates the flow rate based on the acquired data and adjusts the PWM pulse width using PID control to control the pump's power. Specifically, the PID control algorithm implements closed-loop flow control, comparing the estimated flow rate with the set target flow rate, calculating and outputting the PWM pulse width adjustment signal, and dynamically adjusting the output power by changing the pump's operating voltage (current), thus stabilizing the actual flow rate at the target value.

[0058] It should be noted that the foregoing explanation of the embodiment of the flow control device for a DC water pump also applies to the flow control method for a DC water pump in this embodiment, and will not be repeated here.

[0059] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0060] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0061] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0062] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0063] It should be noted that any reference signs placed between parentheses in the claims should not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The invention can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0064] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0065] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

[0066] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0067] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0068] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0069] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0070] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A flow control device for a DC water pump, characterized in that, It includes a current sampling unit, a voltage amplification unit, and a control unit connected in sequence, wherein, The current sampling unit is used to sample the operating current of the DC water pump and convert it into a first voltage signal; The voltage amplification unit is used to amplify the first voltage signal to obtain a second voltage signal that can be acquired by the control unit; The control unit is used to obtain the operating state of the DC water pump based on the second voltage signal, and to obtain an estimated flow rate based on the operating state; And based on the estimated flow rate, the PWM signal is adjusted by PID control to control the flow rate of the DC water pump.

2. The flow control device for a DC water pump as described in claim 1, characterized in that, The operating state of the DC water pump is obtained based on the second voltage signal, including: The operating current of the DC water pump is obtained based on the second voltage signal, and the operating state of the DC water pump is obtained based on the operating current.

3. The flow control device for a DC water pump as described in claim 2, characterized in that, The operating state of the DC water pump is obtained based on the operating current, including: If the operating current is less than 20mA, then the operating state of the DC water pump is determined to be no-load state. If the operating current is 40-100mA, then the operating state of the DC water pump is determined to be the normal pumping state. If the operating current is 120mA-140mA, then the operating state of the DC water pump is determined to be a water circuit blockage state. If the operating current is greater than 150mA, then the operating state of the DC water pump is determined to be the pump stall state.

4. The flow control device for a DC water pump as described in claim 3, characterized in that, The estimated flow rate is obtained based on the described operating status, including: If the operating state is no-load or pump stall, the estimated flow rate is 0. If the working state is the normal pumping state, the corresponding output power is obtained according to the second voltage signal, and the estimated flow rate corresponding to the output power is obtained according to the pre-calibrated relationship between the output power and the flow rate curve. If the working state is a water circuit blockage state, the corresponding output power is obtained according to the second voltage signal, and the estimated flow rate corresponding to the output power is obtained according to the pre-calibrated relationship between the output power and the flow rate curve, and then multiplied by the correction factor.

5. The flow control device for a DC water pump as described in claim 4, characterized in that, Based on the estimated flow rate, the PWM signal is adjusted via PID control, including: If the working state is no-load state, normal pumping state or water circuit blockage state, the difference between the estimated flow rate and the preset target flow rate is calculated to obtain the flow deviation, and the corresponding PWM signal is output according to the flow deviation. If the operating state is a pump stall state, then the PWM signal output is cut off.

6. The flow control device for a DC water pump as described in claim 1, characterized in that, The current sampling unit includes a sampling resistor to convert the operating current of the DC water pump into a first voltage signal through the sampling resistor.

7. The flow control device for a DC water pump as described in claim 1, characterized in that, The voltage amplification unit includes two operational amplifier stages to amplify the first voltage signal.

8. A flow control method for a DC water pump, characterized in that, The flow control device applied to the DC water pump as described in any one of claims 1-7, the control method comprising the following steps: Obtain the operating current of the DC water pump and convert it into a first voltage signal; The first voltage signal is amplified to obtain the second voltage signal; The operating state of the DC water pump is obtained based on the second voltage signal, and the estimated flow rate is obtained based on the operating state. The estimated flow rate is used to adjust the PWM signal via PID control to control the flow rate of the DC water pump.

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