A silent low-flow sampling pump based on magnetic force driving and a sampling method

Abstract

This invention discloses a silent, low-flow sampling pump and sampling method based on magnetic drive. A permanent magnet piston assembly is located in the center of the pump chamber, dividing the pump chamber into first and second air passage chambers. The permanent magnet is axially magnetized, and an electromagnetic coil is wound around each end of the pump chamber. A first inlet valve and a first outlet valve are located at the end of the pump chamber near the first air passage chamber, and a second inlet valve and a second outlet valve are located at the end near the second air passage chamber. Both the first and second inlet valves are connected to the sampling bottle, and both the first and second outlet valves are connected to the outside environment. An STM32 integrated H-bridge module is connected to the electromagnetic coils via control lines and to an ultrasonic position sensor via signal lines. The use of magnetic non-contact drive fundamentally reduces mechanical noise, precisely adjusts the current waveform of the electromagnetic coil, and directly controls the displacement and frequency of the permanent magnet piston assembly, avoiding backlash and hysteresis in sliding transmission. This method is particularly suitable for low-flow, precise sampling.

Description

Technical Field

[0001] This invention relates to the field of fluid sampling technology, and more specifically, to a low-flow, low-noise magnetically driven sampling pump suitable for precision analytical instruments, environmental monitoring, and medical diagnostics. Background Technology

[0002] In fields such as indoor air quality monitoring, environmental pollutant exposure assessment, and occupational health testing, low-flow active air sampling pumps are often required for long-term, stable sampling of target pollutants in the air. Existing sampling pumps mostly employ motor-driven diaphragm pumps or piston pumps, which have disadvantages including numerous mechanical transmission components, high noise levels, susceptibility to wear and tear during long-term operation leading to flow drift, and relatively complex structures with high maintenance costs. Furthermore, in noise-sensitive environments (such as bedrooms, offices, and hospital nighttime monitoring), the operating noise of traditional sampling pumps can negatively impact the usage scenario and user experience. For example, Chinese Patent Publication No. CN 219317133 U discloses a small-flow gas sampling pump that uses an electric drive unit (such as a drive motor) to convert rotary motion into linear reciprocating motion via a crank-slider mechanism (or an electric actuator), driving a piston unit to move within a cylinder. This, combined with a valve group consisting of one-way valves, enables directional gas intake and exhaust. Its structure is relatively simple and allows for automated sampling. However, this type of motor-driven solution has inherent drawbacks: mechanical transmission components such as the motor, reducer, and crank connecting rod inevitably generate mechanical vibration and noise during operation. Long-term wear of these components can lead to flow drift, affecting sampling accuracy. In noise-sensitive environments, this noise can also interfere with the environment. To address this issue, a magnetically driven pump is employed, utilizing the principle of magnetic coupling to achieve contactless transmission, theoretically enabling quiet operation and zero leakage. For example, Chinese Patent Publication No. CN 115289030 A discloses a novel shaftless, quiet, zero-leakage magnetically driven centrifugal pump that uses a magnetic field generated by a permanent magnet and an energized coil to drive the impeller for fluid transport. Chinese Patent Publication No. CN120487624 A discloses an electromagnetic pump with vibration detection and lubricant filtration functions. It employs a magnetic drive structure with internal and external magnetic rotors and integrates mechanical seals, vibration detection, and lubricant filtration functions, aiming to improve reliability and lifespan. However, these magnetically driven pumps are primarily used for liquid transport. Their structure (including impellers, volutes, complex magnetic circuits, and isolation sleeves) is relatively complex, resulting in higher size and cost. Furthermore, their driving principle and flow range are not directly applicable to ultra-low flow, intermittent gas sampling scenarios. In addition, while their quiet operation is significant among liquid pumps, their control accuracy is poor when modified for gas sampling.

[0003] In summary, existing low-flow sampling pumps have shortcomings in terms of noise reduction, structural complexity, long-term operational stability, and specialized design for ultra-low flow gas sampling. Summary of the Invention

[0004] The purpose of this invention is to propose a magnetically driven, silent low-flow sampling pump specifically designed for low-flow active air sampling. This pump is simple in structure, operates quietly, provides stable flow, and is easy to maintain, thus solving the technical problems of existing sampling pumps, such as high noise, low control accuracy, and severe mechanical wear under low-flow conditions. To achieve the above objective, this invention provides a magnetically driven, silent low-flow sampling pump with the following technical solution: It has a hollow cylindrical pump chamber, with a permanent magnet piston assembly in the center. This assembly divides the pump chamber into a first air passage chamber and a second air passage chamber. The permanent magnet piston assembly consists of a permanent magnet and a rubber coating layer. The permanent magnet is surrounded by a rubber coating layer, and the permanent magnet is axially magnetized. The rubber coating layer is in a sealed sliding fit with the inner wall of the pump chamber. An electromagnetic coil is wound around each end of the pump chamber, designated as the first electromagnetic coil and the second electromagnetic coil, respectively. The pump chamber is located near the first air passage chamber... This end is equipped with a first inlet valve and a first outlet valve communicating with the first air passage chamber. The pump chamber at the end near the second air passage chamber is equipped with a second inlet valve and a second outlet valve communicating with the second air passage chamber. Both the first inlet valve and the second inlet valve are connected to the sampling bottle, and both the first outlet valve and the second outlet valve are connected to the outside. An ultrasonic position sensor for detecting the position of the permanent magnet piston assembly is provided outside the first air passage chamber. The ultrasonic position sensor is aligned with the center of the first air passage chamber. The STM32 integrated H-bridge module is connected to the first electromagnetic coil and the second electromagnetic coil via control lines, and connected to the ultrasonic position sensor via signal lines.

[0005] The sampling method of the present invention based on a magnetically driven silent low-flow sampling pump adopts the following technical solution:

[0006] Step 1): When the first electromagnetic coil is energized, the permanent magnet generates an axial electromagnetic attraction force, causing the permanent magnet piston assembly to slide to its limit position towards the end face of the first air passage chamber, and the second electromagnetic coil is de-energized.

[0007] Step 2): The STM32 integrated H-bridge module de-energizes the first electromagnetic coil and energizes the second electromagnetic coil. The permanent magnet piston assembly moves toward the side where the second electromagnetic coil is located. The gas in the sampling bottle is drawn into the first gas path chamber through the first inlet valve. The volume of the first gas path chamber increases, the second gas path chamber is compressed, and the second outlet valve is opened, thus executing the first gas path chamber intake and the second gas path chamber exhaust stroke.

[0008] Step 3): The STM32 integrated H-bridge module determines whether the permanent magnet piston assembly has reached the limit position in the second air passage chamber based on the feedback signal from the ultrasonic position sensor. If it has not reached the limit position, it continues to drive in the current direction; if it has reached the reversing position, it proceeds to Step 4).

[0009] Step 4): The STM32 integrated H-bridge module controls the second electromagnetic coil to be de-energized and the first electromagnetic coil to be energized, executing the exhaust stroke of the first air passage chamber and the intake stroke of the second air passage chamber.

[0010] Step 5): The STM32 integrated H-bridge module determines whether the piston has reached the limit position of the first air passage chamber based on the feedback signal from the ultrasonic position sensor. If it has not reached the limit position, it continues to drive in the current direction; if it has reached the reversing position, it returns to Step 2) and loops.

[0011] Step 6): The STM32 integrated H-bridge module determines whether the set running time or total sampling amount has been reached. If not, it returns to Step 2) to continue the detection. If it has been reached, the STM32 integrated H-bridge module cuts off the power supply to the first and second electromagnetic coils, the permanent magnet piston assembly stops moving, and the sampling ends.

[0012] The beneficial effects of adopting the above technical solution in this invention are:

[0013] 1. Quiet Operation: This invention employs a magnetic non-contact drive, eliminating the physical friction and impact of mechanical transmission components such as gears, bearings, and connecting rods present in traditional motor drives, fundamentally reducing mechanical noise. Combined with the sound-insulating composite material design of the pump body, residual electromagnetic vibration noise is further absorbed, achieving ultra-quiet operation.

[0014] 2. High-precision low-flow control: By precisely adjusting the current waveform of the electromagnetic coil through STM32, the displacement and frequency of the permanent magnet piston assembly can be directly controlled, avoiding backlash and hysteresis in sliding transmission, which is especially suitable for low-flow precision sampling.

[0015] 3. Compact structure and long service life: By eliminating the complex mechanical transmission mechanism, the structure is more compact and easier to miniaturize and integrate. Due to the absence of mechanically worn parts, the pump's reliability and service life are significantly improved.

[0016] 4. Low pulsation output: By generating optimized PWM current drive waveforms (such as sine waves) through STM32, the movement of the permanent magnet piston assembly can be smoother. Combined with the fast response of the one-way valve, the flow pulsation phenomenon commonly found in traditional reciprocating pumps is effectively reduced. Attached Figure Description

[0017] Figure 1 This is a partial cross-sectional view of the structure of a magnetically driven silent low-flow sampling pump according to the present invention.

[0018] Figure 2 for Figure 1 Sectional front view;

[0019] Figure 3 for Figure 1 AA section enlarged view;

[0020] Figure 4 for Figure 1 Control circuit block diagram;

[0021] Figure 5 for Figure 1 A schematic diagram of the actual application structure layout;

[0022] Figure 6 for Figure 1 A schematic diagram illustrating the principle of air intake in the first air passage chamber.

[0023] Figure 7 for Figure 1 A schematic diagram illustrating the principle of air intake in the second air passage chamber.

[0024] Figure 8 for Figure 1 The flowchart of the sampling pump is shown.

[0025] Figure 9 for Figure 1 Schematic diagram of the motion principle of the permanent magnet piston assembly under axial electromagnetic force when the first electromagnetic coil is energized;

[0026] Figure 10 for Figure 1 Schematic diagram of the motion principle of the permanent magnet piston assembly under axial electromagnetic force when the second electromagnetic coil is energized.

[0027] Explanation of reference numerals in the attached drawings: 1-Pump body; 101-First air passage chamber; 102-Second air passage chamber; 103-First air inlet valve; 104-First air outlet valve; 105-Second air inlet valve; 106-Second air outlet valve; 107-Pump body anti-corrosion layer; 108-Pump body sound insulation layer; 109-Pump body outer shell base layer; 2-Permanent magnet piston assembly; 201-Permanent magnet; 202-Rubber coating layer; 301-First electromagnetic coil; 302-Second electromagnetic coil; 4-Ultrasonic position sensor; 5-STM32 integrated H-bridge module; 6-Power / data cable connector; 7-Sampling bottle bracket; 8-First sampling bottle; 801-First sampling air inlet; 802-Second air outlet; 9-Second sampling bottle; 10-Air passage three-way valve. Detailed Implementation

[0028] like Figure 1 and Figure 2As shown, the present invention includes a pump body 1, which has a hollow cylindrical structure, and a pump chamber extending axially is formed inside the hollow cylindrical structure. A permanent magnet piston assembly 2 is provided in the middle of the pump chamber of the pump body 1. The permanent magnet piston assembly 2 is in sealed contact with the pump body 1 and can slide back and forth along the central axis of the pump body 1, dividing the pump chamber into a first air passage chamber 101 and a second air passage chamber 102.

[0029] The permanent magnet piston assembly 2 consists of a permanent magnet 201 and a rubber coating layer 202. The permanent magnet 201 is magnetized along the axial direction, preferably a neodymium iron boron permanent magnet. A rubber coating layer 202 is wrapped around the permanent magnet 201. The flexible rubber coating layer 202 and the permanent magnet 201 are integrally formed by molding or bonding. The rubber coating layer 202 is in a sealing sliding fit with the inner wall of the pump body 1, which not only plays a role in gas sealing, but also plays a role in buffering, vibration reduction and noise reduction.

[0030] The pump chamber sidewall consists of three layers, from the inside out: a corrosion-resistant layer 107, a sound-insulating layer 108, and a shell substrate layer 109, all tightly bonded together and made of sound-insulating composite material. Steps are provided around the outer periphery of the sound-insulating layer 108 at both ends of the pump chamber. An electromagnetic coil, a first electromagnetic coil 301, and a second electromagnetic coil 302 are wound on each step. The first electromagnetic coil 301 and the second electromagnetic coil 302 are multi-turn enameled wire windings arranged in a densely packed circular shape. The outer diameter of the first electromagnetic coil 301 and the second electromagnetic coil 302 is the same as the inner diameter of the shell substrate layer 109, and they are enclosed and protected by the shell substrate layer 109.

[0031] At the end of the pump chamber near the first air passage chamber 101, there is a first air inlet and a first air outlet. A first air inlet valve 103 is installed at the first air inlet, and a first air outlet valve 104 is installed at the first air outlet. Both the first air inlet and the first air outlet communicate with the first air passage chamber 101, and the first air outlet valve 104 connects the first air passage chamber 101 to the outside. At the end of the pump chamber near the second air passage chamber 102, there is a second air inlet and a second air outlet. A second air inlet valve 105 and a second air outlet valve 106 are installed there, respectively. Both the second air inlet valve 105 and the second air outlet valve 106 communicate with the second air passage chamber 102, and the second air outlet valve 106 connects the second air passage chamber 102 to the outside. Each air inlet and air outlet valve is a one-way valve, and can adopt a reed valve, umbrella valve, or ball valve structure to ensure unidirectional gas flow and prevent backflow.

[0032] An ultrasonic position sensor 4 is installed outside the first air passage chamber 101. The ultrasonic position sensor 4 is fixedly mounted on the pump body 1, aligned with the center of the first air passage chamber 101, with a pre-set initial effective sensing distance. The ultrasonic position sensor 4 is 5cm away from the inner wall of the first air passage chamber 101 to detect the position of the permanent magnet piston assembly 2. It outputs a position signal representing the axial position of the permanent magnet piston assembly 2 in real time, forming a closed-loop control to ensure the stability of the flow output. The first inlet valve 103 and the first outlet valve 104 are located on either side of the ultrasonic position sensor 4, symmetrically arranged with respect to the center of the ultrasonic position sensor 4 and the center of the first air passage chamber 101. Figure 3 As shown.

[0033] An STM32 integrated H-bridge module 5 is mounted on the pump body 1. The STM32 integrated H-bridge module 5 is located outside the first air passage chamber 101, and is combined with, for example... Figure 4 As shown, the STM32 integrated H-bridge module 5 is powered by an external power supply and is connected to the first electromagnetic coil 301 and the second electromagnetic coil 302 via control lines. The STM32 integrated H-bridge module 5 generates a sinusoidal or square wave current. By adjusting the frequency and amplitude of the drive current, it controls the reciprocating frequency and stroke of the permanent magnet piston assembly 2, thereby achieving precise flow regulation. By controlling the working current of the first electromagnetic coil 301 and the second electromagnetic coil 302 through the drive current, the coils generate electromagnetic forces of different magnitudes, attracting the permanent magnet piston assembly 2 to slide back and forth. The STM32 integrated H-bridge module 5 is also connected to an ultrasonic position sensor 4 via a signal line. The ultrasonic position sensor 4 feeds back the axial position signal of the permanent magnet piston assembly 2 it collects to the STM32 integrated H-bridge module 5. The STM32 integrated H-bridge module 5 internally includes a power drive circuit, namely the H-bridge drive circuit, used to output adjustable current to the corresponding first electromagnetic coil 301 and second electromagnetic coil 302 according to programmed instructions.

[0034] A power / data cable socket 6 is provided at the end of the pump chamber for connecting the power supply and data cable.

[0035] like Figure 5 , Figure 6 and Figure 7As shown, a first sampling bottle 8 and a second sampling bottle 9 are provided outside the pump chamber and are fixed together on the sampling bottle support 7. The second sampling bottle 9 is a blank bottle and serves as a blank control. The first sampling bottle 8 is filled with the target gas absorption solution required for quantitative sampling. Both the first sampling bottle 8 and the second sampling bottle 9 are provided with a first sampling air inlet 801 and a second air outlet 802. The first air inlet valve 103 and the second air inlet valve 105 are respectively connected to the gas path three-way valve 10 in an airtight manner through Teflon air sampling tubes. The gas path three-way valve 10 is connected to the second air outlet 802 of the first sampling bottle 8 in an airtight manner through a Teflon air sampling tube. The first air outlet valve 104 is unidirectionally connected to the atmosphere for unidirectional exhaust, and similarly, the second air outlet valve 106 is also unidirectionally connected to the atmosphere for unidirectional exhaust. At the start of sampling, ambient air enters through the first sampling inlet 801. The target gas is absorbed by the absorbent liquid, and the remaining air is discharged through the absorbent liquid and enters the second air outlet 802, where it is drawn into the gas path chamber during the inhalation stroke. For example, if the first gas path chamber 101 is in the inhalation stroke, the first inlet valve 103 and the second outlet valve 106 are open. Ambient air enters through the first sampling inlet 801, the target gas is absorbed by the absorbent liquid, and the remaining air is discharged through the absorbent liquid. After passing through the second air outlet 802, it is drawn into the first gas path chamber 101 through the first inlet valve 103. At this time, the first gas path chamber 101 is the gas path chamber during the inhalation stroke, and the volume of the first gas path chamber 101 increases. When the volume of the second air passage chamber 102 decreases, the air in the second air passage chamber 102 is discharged to the outside through the second outlet valve 106. When the second air passage chamber 102 performs the inhalation stroke, the second inlet valve 105 and the first outlet valve 104 are in the open state. Ambient air enters through the first sampling inlet 801, the target gas is absorbed by the absorbent liquid, the remaining air is discharged through the absorbent liquid, and then drawn into the second air passage chamber 102 through the second inlet valve 105 after passing through the second air outlet 802. At this time, the second air passage chamber 102 is the air passage chamber of the inhalation stroke. The volume of the second air passage chamber 102 increases, the volume of the first air passage chamber 101 decreases, and the air in the first air passage chamber 102 is discharged to the outside through the first outlet valve 104.

[0036] like Figure 1-7 and Figure 8 As shown, the working process of the sampling pump is as follows:

[0037] Step 1: Power on the STM32 integrated H-bridge module 5 and complete the self-test of each module. Read the initial position signal of the ultrasonic position sensor 4, energize the first electromagnetic coil 301, and return the permanent magnet piston assembly 2 to its starting position, that is, slide it to the limit position in the direction close to the end face of the first air passage chamber 101. At this time, the second electromagnetic coil 302 is de-energized, and the preset target flow rate / speed is read.

[0038] like Figure 9As shown, when the first electromagnetic coil 301 is energized, an axial magnetic field is generated inside the pump body 1, which exerts an axial electromagnetic attraction on the permanent magnet 201, attracting the permanent magnet piston assembly 2 to move towards the side where the first electromagnetic coil 301 is located. The direction of the permanent magnet magnetic field lines starts from the N pole outside the magnet and returns to the S pole.

[0039] Step 2: Switch the energizing state of the electromagnetic coils. The STM32 integrated H-bridge module 5 de-energizes the first electromagnetic coil 301 and simultaneously energizes the second electromagnetic coil 302. For example... Figure 10 As shown, an axial magnetic field is generated inside the pump body 1, which exerts an axial electromagnetic attraction on the permanent magnet 201, attracting the permanent magnet piston assembly 2 to move towards the side where the second electromagnetic coil 302 is located, that is, towards the end of the second air passage chamber 102. Figure 6 As shown, at this time, the gas in the first sampling bottle 8 is drawn into the first gas path chamber 101 through the second gas path chamber 102, the gas path three-way valve 10 and the first inlet valve 103. The volume of the first gas path chamber 101 increases, the second gas path chamber 102 is compressed, and the gas in the chamber pushes open the second outlet valve 106 to be discharged, thus executing the first gas path chamber 101 intake and the second gas path chamber 102 exhaust stroke.

[0040] Step 3: The STM32 integrated H-bridge module 5 adjusts the current (duty cycle) applied to the currently energized second electromagnetic coil 302 via PWM. If the actual speed is too slow (e.g., back pressure increases), the current is increased to enhance the electromagnetic attraction; if the actual speed is too fast (e.g., back pressure decreases), the current is decreased to weaken the electromagnetic attraction, ensuring the stable movement speed of the permanent magnet piston assembly 2, thereby maintaining a constant gas flow.

[0041] Step 4: PID closed-loop speed regulation of STM32 integrated H-bridge module 5. STM32 integrated H-bridge module 5 acquires the position signal fed back by ultrasonic position sensor 4 in real time, calculates the actual movement speed of permanent magnet piston assembly 2 by taking the time derivative of the position signal, compares the actual speed with the set target speed, and uses PID algorithm to calculate the current correction of second electromagnetic coil 302.

[0042] Step 5: The STM32 integrated H-bridge module 5 determines whether the permanent magnet piston assembly 2 has reached the limit position in the second air passage chamber 102 based on the feedback signal from the ultrasonic position sensor 4. If the reversing position has not been reached, the current direction drive continues; if the reversing position has been reached, proceed to step 6.

[0043] Step 6: Switch the energizing state of the electromagnetic coils. The STM32 integrated H-bridge module 5 controls the second electromagnetic coil 302 to be de-energized, while simultaneously controlling the first electromagnetic coil 301 to be energized, executing the exhaust stroke of the first air passage chamber 101 and the intake stroke of the second air passage chamber 102. For example... Figure 9As shown, an axial magnetic field is generated inside the pump body 1, which exerts an axial electromagnetic attraction on the permanent magnet 201, attracting the permanent magnet piston assembly 2 to move towards the side where the first electromagnetic coil 301 is located, that is, towards the end of the first air passage chamber 101. Figure 7 As shown, at this time, the gas in the first sampling bottle 8 is drawn into the second gas path chamber 102 through the second gas path chamber 102, the gas path three-way valve 10 and the second air inlet valve 105. The volume of the second gas path chamber 102 increases, the first gas path chamber 101 is compressed, and the gas in the chamber pushes open the first air outlet valve 104 to be discharged.

[0044] Step 7: Similar to step 3, the STM32 integrated H-bridge module 5 adjusts the current applied to the first electromagnetic coil 301 via PWM, increasing or decreasing the current to enhance or weaken the electromagnetic attraction, ensuring the stable movement speed of the permanent magnet piston assembly 2.

[0045] Step 8: Repeat step 4 to calculate the current correction of the first electromagnetic coil 301.

[0046] Step 9: The STM32 integrated H-bridge module 5 determines whether the piston has reached the limit position of the first air passage chamber 101 based on the feedback signal of the ultrasonic position sensor 4. If the reversing position has not been reached, the current direction drive continues; if the reversing position has been reached, the cycle returns to step 2.

[0047] Step 10: The STM32 integrated H-bridge module 5 determines whether the set running time or total sampling amount has been reached. If not, it returns to step 2 to continue detecting position, commutation, and adjusting current, repeating the above reciprocating motion process. If the set time or total sampling amount has been reached, the STM32 integrated H-bridge module 5 cuts off the power supply to the first electromagnetic coil 301 and the second electromagnetic coil 302, the permanent magnet piston assembly 2 stops moving, and sampling ends.

[0048] The present invention achieves stepless flow rate regulation by using an STM32 integrated H-bridge module 5 to adjust the current applied to the electromagnetic coil (duty cycle) via PWM and other methods. A larger current results in a stronger electromagnetic attraction, leading to faster reciprocating motion of the permanent magnet piston assembly 2 and a larger intake / exhaust volume per unit time; consequently, a larger sampling flow rate. Conversely, a smaller current reduces the sampling flow rate. This allows for continuous and smooth adjustment of the output flow rate without hardware replacement, achieving stepless speed regulation. The air sampling pump of this invention is designed to operate at a flow rate 0.1 L / min lower than the minimum flow rate limit of standard atmospheric samplers.

[0049] The implementation of speed closed-loop stable control in this invention involves: An STM32 integrated H-bridge module 5 acquiring the position signal fed back by the acoustic position sensor 4 in real time; obtaining the actual piston speed and arrival time by calculating the time derivative of the position signal; comparing the actual speed with the set target speed; and using a PID closed-loop algorithm to correct the electromagnetic coil current in real time; when the back pressure increases, causing the piston movement to slow down, the STM32 integrated H-bridge module 5 automatically increases the current to compensate, and vice versa, thereby ensuring the stability of the piston speed and reciprocating frequency, and keeping the output flow constant under load fluctuations. Furthermore, the position signal is also used to determine the commutation time of coil energization and de-energization, achieving precise commutation, avoiding piston impact at both ends, and further reducing noise and energy consumption.

Claims

1. A magnetically driven, silent, low-flow sampling pump, comprising a hollow cylindrical pump chamber, characterized in that: A permanent magnet piston assembly (2) is provided in the middle of the pump chamber, which divides the pump chamber into a first air passage chamber (101) and a second air passage chamber (102). The permanent magnet piston assembly (2) consists of a permanent magnet (201) and a rubber coating layer (202). The permanent magnet (201) is surrounded by a rubber coating layer (202). The permanent magnet (201) is magnetized along the axial direction. The rubber coating layer (202) is in a sealing sliding fit with the inner wall of the pump cavity. An electromagnetic coil is wound around each end of the pump chamber, namely the first electromagnetic coil (301) and the second electromagnetic coil (302). The pump chamber is provided with a first inlet valve (103) and a first outlet valve (104) at the end near the first gas path chamber (101), and a second inlet valve (105) and a second outlet valve (106) at the end near the second gas path chamber (102). The first inlet valve (103) and the second inlet valve (105) are both connected to the sampling bottle, and the first outlet valve (104) and the second outlet valve (106) are both connected to the outside. An ultrasonic position sensor (4) for detecting the position of the permanent magnet piston assembly (2) is provided outside the first air passage chamber (101). The STM32 integrated H-bridge module (5) is connected to the first electromagnetic coil (301) and the second electromagnetic coil (302) via control lines, and to the ultrasonic position sensor (4) via signal lines.

2. The silent, low-flow sampling pump based on magnetic drive according to claim 1, characterized in that: The pump chamber sidewall consists of a tightly fitted anti-corrosion layer (107), a sound insulation layer (108), and a shell substrate layer (109) from the inside out.

3. The silent, low-flow sampling pump based on magnetic drive according to claim 2, characterized in that: Steps are provided on the outer periphery of the sound insulation layer (108) at both ends of the pump cavity. An electromagnetic coil is wound on each of the two steps, namely the first electromagnetic coil (301) and the second electromagnetic coil (302). The outer diameter of the first electromagnetic coil (301) and the second electromagnetic coil (302) is the same as the inner diameter of the outer shell base layer (109) and is wrapped by the outer shell base layer (109).

4. A silent, low-flow sampling pump based on magnetic drive according to claim 1, characterized in that: The ultrasonic position sensor (4) is aligned with the center of the first air passage chamber (101), and the ultrasonic position sensor (4) is 5 cm away from the inner wall of the first air passage chamber (101).

5. A magnetically driven silent low-flow sampling pump according to claim 4, characterized in that: The first intake valve (103) and the first exhaust valve (104) are located on both sides of the ultrasonic position sensor (4) and are arranged symmetrically with respect to the center of the ultrasonic position sensor (4).

6. A silent, low-flow sampling pump based on magnetic drive according to claim 1, characterized in that: The STM32 integrated H-bridge module (5) has a power drive circuit inside, which outputs adjustable current to the first electromagnetic coil (301) and the second electromagnetic coil (302) according to the programming instructions.

7. A magnetically driven silent low-flow sampling pump according to claim 1, characterized in that: The flexible rubber coating (202) and the permanent magnet (201) are integrally formed by molding or bonding.

8. A sampling method based on a magnetically driven silent low-flow sampling pump as described in claim 1, characterized in that... It includes the following steps: Step 1): The first electromagnetic coil (301) is energized and the second electromagnetic coil (302) is de-energized. The permanent magnet (201) generates an axial electromagnetic attraction force, causing the permanent magnet piston assembly (2) to slide to its limit position in the direction close to the end face of the first air passage chamber (101). Step 2): The STM32 integrated H-bridge module (5) de-energizes the first electromagnetic coil (301) and energizes the second electromagnetic coil (302). The permanent magnet piston assembly (2) moves toward the side where the second electromagnetic coil (302) is located. The gas in the sampling bottle (8) is drawn into the first gas path chamber (101) through the first inlet valve (103). The volume of the first gas path chamber (101) increases, the second gas path chamber (102) is compressed, and the second outlet valve (106) is opened. The first gas path chamber (101) is drawn in and the second gas path chamber (102) is exhausted. Step 3): The STM32 integrated H-bridge module (5) determines whether the permanent magnet piston assembly (2) has reached the limit position in the second air passage chamber (102) based on the feedback signal from the ultrasonic position sensor (4). If it has not reached the limit position, it continues to drive in the current direction; if it has reached the reversing position, it proceeds to step 4). Step 4): The STM32 integrated H-bridge module (5) controls the second electromagnetic coil (302) to be de-energized and the first electromagnetic coil (301) to be energized, executing the first air passage chamber (101) to exhaust and the second air passage chamber (102) to inhale. Step 5): The STM32 integrated H-bridge module (5) determines whether the piston has reached the limit position of the first air passage chamber (101) based on the feedback signal of the ultrasonic position sensor (4). If it has not reached the limit position, it continues to execute the current direction drive; if it reaches the reversing position, it returns to step 2) and loops. Step 6): The STM32 integrated H-bridge module (5) determines whether the set running time or total sampling amount has been reached. If not, it returns to step 2) to continue the detection. If it has been reached, the STM32 integrated H-bridge module (5) cuts off the power supply to the first electromagnetic coil (301) and the second electromagnetic coil (302), the permanent magnet piston assembly (2) stops moving, and the sampling ends.

9. The sampling method according to claim 8, characterized in that: The STM32 integrated H-bridge module (5) adjusts the current applied to the first electromagnetic coil (301) and the second electromagnetic coil (302) through PWM, thereby enhancing or weakening the electromagnetic attraction and stabilizing the movement speed of the permanent magnet piston assembly (2).

10. The sampling method according to claim 8, characterized in that: The STM32 integrated H-bridge module 5 collects the position signal fed back by the ultrasonic position sensor (4) in real time, calculates the time derivative of the position signal, calculates the actual movement speed of the permanent magnet piston assembly (2), compares the actual speed with the set target speed, and uses the PID algorithm to calculate the current correction amount of the first electromagnetic coil 301 and the second electromagnetic coil (302).

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