A respiratory simulation system and its compensation method

Abstract

This invention provides a respiratory simulation system, comprising a mechanical system and a control system. The mechanical system includes a piston cylinder, a connecting device, and a driving device. The piston cylinder includes a piston cylinder and a piston, with the piston axially positioned within the piston cylinder. The driving device includes a servo motor, a ball screw, a slide, a limit switch, and a coupling. The servo motor is connected to the ball screw via the coupling, thereby driving the slide to perform a specified movement. The connecting device includes a piston connecting rod, a connecting panel, a driving connecting rod, and a driving panel. The control system includes a controller and a computer. The controller is bidirectionally connected to the servo motor, the computer, a temperature transmitter, a humidity transmitter, a pressure transmitter, an in-cylinder pressure transmitter, and a flow measurement device. The computer is suitable for writing control programs, establishing a standard respiratory model based on a standard respiratory curve, setting several calibration parameters, and calculating motion compensation. This invention also provides a compensation method to improve simulation accuracy.

Description

Technical Field

[0001] This invention belongs to the field of medical device technology, specifically relating to a high-precision respiratory simulation system that can calibrate a pulmonary function instrument and its compensation method. Background Technology

[0002] A respiratory simulation system uses the movement of a piston within a cylinder to simulate human breathing, outputting a standard airflow rate conforming to the corresponding calibration procedure to a pulmonary function analyzer, thereby calibrating the analyzer. Different pulmonary function analyzers may produce significantly different results when testing the same patient, posing challenges to clinical diagnosis. To address this issue of large discrepancies in measurements from different pulmonary function analyzers on the same subject, a high-performance respiratory simulation system is essential for calibrating the pulmonary function analyzer.

[0003] Existing respiratory simulation systems employ two types of piston pushers. One type simplifies the device structure and facilitates the calculation of airflow and uncertainty assessment by using a single pusher rod without internal guide rods or other components. However, this results in significant operational errors. The other type integrates several guide rods through the piston cylinder to reduce piston axial movement, but this increases the difficulty of flow rate calculation and uncertainty assessment. Furthermore, existing respiratory simulation systems require a large footprint, which is inconvenient for practical application.

[0004] Existing breathing simulation systems suffer from significant friction and poor fit between components due to factors such as device design, transmission method, and manufacturing process. Furthermore, the piston cylinder of the breathing simulation system also has manufacturing errors and wears down after a period of operation, resulting in a deviation between the output flow rate and the required flow rate. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention provides a respiratory simulation system and its compensation method.

[0006] This invention provides a respiratory simulation system, including a mechanical system and a control system;

[0007] The mechanical system includes a piston cylinder, a connecting device, and a driving device;

[0008] The piston cylinder includes a piston cylinder, a front end plate, a rear end plate, a bottom plate, a piston, and an outlet panel. The piston is axially movable within the piston cylinder. The front end plate and the rear end plate are assembled at both axial ends of the piston cylinder. The bottom plate is adapted to support the front end plate and the rear end plate. The outlet panel is mounted on the front end plate and has a flow output port. The front end plate has a circular hole adapted to connect the piston cylinder and the flow output port. The rear end plate has several rear vent holes adapted to connect the piston cylinder and the external environment. The bottom plate is adapted to be detachably mounted on a movable platform and a fixed platform.

[0009] The connecting device includes a piston connecting rod, a drive connecting rod, a linear bearing, a nut, a connecting panel, and a drive panel. The connecting panel is disposed on the outer side of the rear end plate, and the drive panel is fixedly disposed on the slide. The drive connecting rod is adapted to connect the drive panel and the connecting panel and is fixed by the nut. The piston connecting rod is adapted to connect the connecting panel and the piston and is fixed by the nut. The linear bearing is mounted on the rear end plate, and the piston connecting rod and the drive connecting rod pass through the linear bearing.

[0010] The driving device includes a servo motor, a ball screw, a slide table, a first limiter, and a second limiter. The servo motor is connected to the ball screw via a coupling and drives the slide table to perform reciprocating linear motion to simulate human breathing. The first limiter and the second limiter are respectively located near the axial ends of the ball screw. The first limiter and the second limiter are adapted to limit the movement range of the slide table, thereby limiting the movement range of the piston and preventing damage to the breathing simulation device.

[0011] Preferably, the piston cylinder includes a first axis extending along its axial direction, the first axis being perpendicular to the front end plate and the rear end plate, the first axis being parallel to the bottom plate, the first axis being adapted to pass through the center points of both ends of the piston cylinder, the center of the front end circular hole and the center of the piston, and the rear end vent hole being symmetrically arranged about the first axis.

[0012] Preferably, the outlet panel includes a second axis extending along its axial direction, the second axis being adapted to pass through the center of the flow outlet, the first axis coinciding with the second axis.

[0013] Preferably, the piston connecting rod is arranged symmetrically on the left and right, the piston connecting rod is arranged perpendicular to the piston and the connecting panel, and one end of the piston connecting rod is fixedly connected to the piston or integrally formed, and the other end of the piston connecting rod is fixed to the connecting panel.

[0014] Preferably, the drive linkages are arranged symmetrically on the left and right, the drive linkages are perpendicular to the drive panel and the connecting panel, and one end of the drive linkage is fixed to the connecting panel, while the other end of the drive linkage is fixed to the drive panel.

[0015] Preferably, the rear end plate includes a square opening at its lower end, and the servo motor is embedded in the square opening.

[0016] Preferably, the rear end plate includes several through holes disposed in its middle or upper part, and a linear bearing is installed in the through holes. The linear bearing includes a bearing sleeve and several balls fastened in the through holes. The balls are suitable for supporting the piston connecting rod or the drive connecting rod, and are also suitable for transmitting axial loads.

[0017] Preferably, the lower end of the front end plate and the lower end of the rear end plate are assembled to the axial ends of the base plate and enclose to form an installation space suitable for accommodating the drive device. After the drive device is assembled, it is encapsulated and fixed to the base plate.

[0018] The control system includes a controller and a computer;

[0019] The controller is bidirectionally connected to the servo motor, computer, temperature transmitter, humidity transmitter, pressure transmitter, cylinder pressure transmitter, and flow measurement device.

[0020] The computer uses software to write control programs, establishes a standard breathing model based on a standard breathing curve, sets several calibration parameters, and samples the actual output flow to establish a mathematical model of the piston cylinder. In subsequent use, it can perform motion compensation for the piston's displacement and speed.

[0021] A compensation method for a high-precision respiratory simulation system, suitable for calibrating and compensating the respiratory simulation system as described above, includes the following steps:

[0022] (1) Check the airtightness of the piston cylinder:

[0023] (1-1) Seal the flow output port of the piston cylinder, start the pressure transmitter inside the cylinder, and record the reading P0 of the pressure transmitter inside the cylinder at this time;

[0024] (1-2) Divide the total journey L into n equal segments, the length of which is... Let the position of each segment point be x. i x n It coincides with the destination of the journey;

[0025] (1-3) The servo motor drives the piston to move l iLet i∈[1,n], the horizontal load capacity of the servo motor be F, and observe the reading P of the pressure gauge inside the cylinder. i ;

[0026] (1-4) If P i If the piston rises first and then falls, it is considered that the sealing of this section of the piston cylinder is insufficient; if P i near The seal needs to be removed, the pressure reduced, and then resealed. P0 should be read again as the reference value for the next stage, and steps (1-1) to (1-3) should be repeated.

[0027] (1-5) Repeat steps (1-1) to (1-4) to test the sealing performance of the piston cylinder segment by segment.

[0028] (2) Model the piston cylinder and obtain the compensation coefficient:

[0029] (2-1) Connect the flow measurement device to the breathing simulation system. The computer issues a command to the breathing simulation system and starts the flow measurement device at the same time. The servo motor causes the piston to complete the uniform motion of the stroke L at a speed of v0. The flow measurement device measures the output flow rate Q(t) of the breathing simulation device during this process. These data are collected centrally. Liquid can be used instead of gas to obtain better data.

[0030] (2-2) The correspondence between x and Q(t) can be obtained through x = v0t, i.e. Q(x), where x is the actual stroke position of the piston and A is the cross section of the piston cylinder. Theoretically, Q(x) = v0A is a constant value, but because there is an error and it is considered that the main error is the machining error of the piston cylinder, Q(x) will fluctuate in reality.

[0031] A model is established for the piston cylinder, where x∈[x i-1 ,x i Within the range of ), the actual piston cylinder cross-sectional area is assumed to be A. i Actual piston cylinder cross-sectional area A i The difference between the theoretical piston cylinder cross-sectional area A0 and the actual cross-sectional area A0 is ΔA. i , i∈[1,n], and thus obtain A i The correspondence with x and ΔA i The correspondence with x, that is ΔA(x i )=A(x i )-A0, and A(x i Abbreviated as A i ΔA(x) i This is abbreviated as ΔA i ;

[0032] (2-3) The piston's operating speed that needs to be compensated for in each sub-stroke

[0033] (2-4) When the respiratory simulation system is performing other functions, input the set volume V, obtain the current piston position x, x∈[x], and obtain the current piston position x. n ,x n+1 When the piston is set to move from the first limiter to the second limiter, the movable volume margin V of the piston is calculated. 暂 =(x n+1 -x)A n+1 When the piston is set to move from the second limiter towards the first limiter, calculate the movable volume margin V of the piston. 暂 =(xx) n A n+1 ;

[0034] (2-5) When the piston is set to move from the first limiter to the second limiter, the parameter j is initialized to 0, and the volume margin V is temporarily compared with the input volume V:

[0035] If V 暂 If V > 0, then j = 0.

[0036] If V 暂 <V, then j+1, and V in terms of volume margin 暂 =(x n+1 -x)A n+1 Add the volume of the next interval

[0037] Then compare it with V. If it is less than V, continue adding until V is reached. 暂 If the value is greater than V, then determine the size of j;

[0038] If j = 1, then,

[0039] If j≥2, then j-1, we get:

[0040] (2-6) When the piston is set to move from the second limiter to the first limiter, initialize parameter j to 0 and set the volume margin V. 暂 Compare with the input volume V;

[0041] If V 暂 If V > 0, then j = 0.

[0042] If V 暂 <V, then j+1, and V in terms of volume margin 暂 =(xx) n A n+1Add the volume of the next interval

[0043] Then compare it with V. If it is less than V, continue adding until V is reached. 暂 If the value is greater than V, then determine the size of j;

[0044] If j = 1, then,

[0045] If j≥2, then j-1, we get:

[0046] In summary, the piston travel distance and speed after compensation and correction can be obtained.

[0047] (3) Model the piston cylinder and obtain the compression compensation coefficient, that is, the coefficient relating the piston movement speed to the gas flow output:

[0048] Based on a mathematical model of one-dimensional steady adiabatic isentropic flow, the relationships between the gas parameters inside the piston cylinder, the gas flow output port parameters, and the stagnation state parameters are listed:

[0049] According to the law of conservation of energy:

[0050] P r Stasis pressure

[0051] T r : Stagnation temperature ρ r Density of stagnant state

[0052] P1: Gas pressure inside the piston cylinder

[0053] T1: Gas temperature inside the piston cylinder; ρ1: Gas density inside the piston cylinder

[0054] A1': Piston cross-sectional area

[0055] v1: Piston speed

[0056] P2: Airflow output pressure

[0057] T2: Gas flow rate, outlet temperature; ρ2: Gas flow rate, outlet density.

[0058] A'2: Gas flow rate, outlet cross-sectional area; v2: Gas flow rate, outlet gas velocity. In the formula, k is the gas adiabatic coefficient; if the gas is air, k = 1.4. According to the ideal gas law, we get:

[0059] P r =ρ r RT r ...(2)

[0060] P1=ρ1RT1...(3)

[0061] P2=ρ2RT2...(4)R is the gas constant, with a value of R=287(J / kg*K).

[0062] According to the isentropic relationship:

[0063]

[0064] From equations (2) to (5), we can obtain:

[0065]

[0066]

[0067] According to the law of conservation of mass:

[0068] Q m =ρ1v1A1'=ρ2v2A'2...(9)

[0069] Substituting (7) and (8) into (9) yields:

[0070]

[0071] Among them, the stagnation temperature T r Since the gas constant R, piston cross-sectional area A'1, gas flow outlet cross-sectional area A'2, and gas adiabatic coefficient k are all constants, a compensation operation is performed based on the relationship between piston movement speed v1 and gas flow outlet velocity v2. The required piston movement speed v1 is obtained by setting the gas flow outlet velocity v2 according to the simulation needs.

[0072] The beneficial effects of this invention are:

[0073] (1) By setting up several drive connecting rods and piston connecting rods to drive the piston to move, without a guide rod that penetrates the piston cylinder, the principle of error averaging is used to reduce the piston's cylinder movement caused by a single rod, thereby improving the calibration accuracy.

[0074] (2) By arranging the piston cylinder and ball screw in parallel, the footprint is greatly reduced, and it can be installed on a smaller mobile platform, which facilitates the calibration work.

[0075] (3) By using ball screws and linear bearings with balls, the axial load is transmitted in a rolling manner, resulting in low frictional resistance, higher transmission efficiency, and faster start-up and shutdown, enabling the breathing simulation device to output data that better fits the standard breathing waveform. On the other hand, several balls directly bear the load, reducing the motion deviation caused by the weight of the device itself. At the same time, the application of error averaging effect can reduce the errors caused by inaccurate manufacturing and installation, deformation during operation, etc.

[0076] (4) By sampling the actual output flow rate, a mathematical model is established inside the piston cylinder, and the displacement and speed of the piston can be compensated in subsequent use. Furthermore, the pressure inside the piston cylinder under sealed condition is read and the sealing performance of the piston cylinder is automatically detected.

[0077] (5) By considering the compressibility of gas and the size of piston cylinder, a mathematical model is established. This mathematical model can be selectively applied to breathing simulation devices of various sizes. In the case of existing devices, the actual required running speed of the piston can be obtained by the required air flow output, which further improves the accuracy. Attached Figure Description

[0078] Figure 1 This is a schematic diagram of a respiratory simulation system for calibrating a pulmonary function instrument, provided by the present invention.

[0079] Figure 2 This is a cross-sectional schematic diagram of a respiratory simulation system for calibrating a pulmonary function instrument, provided by the present invention.

[0080] Figure 3 This is a schematic diagram of the framework of the present invention.

[0081] Figure 4 The mathematical model for this invention was established using MATLAB to solve the problem under the following conditions: piston peak speed of 0.5 m / s, period of 3 s, piston cross-sectional area of ​​0.038 square meters, and output port of 0.00018 square meters.

[0082] Figure 5 The mathematical model for this invention is established based on MATLAB simulation results with the piston set at a peak speed of 0.35 m / s, a period of 2.37 s, a piston cross-sectional area of ​​0.038 square meters, and an output port of 0.00018 square meters.

[0083] Figure 6 The mathematical model for this invention is established based on Anasys Fluent simulation results with a piston peak speed of 0.35 m / s, a period of 2.37 s, a piston cross-sectional area of ​​0.038 square meters, and an output port of 0.00018 square meters.

[0084] In the figure, the components are: outlet panel 101, front end plate 102, piston cylinder 103, piston 104, rear end plate 105, vent 106, linear bearing 107, piston connecting rod 108, nut 109, connecting panel 110, nut 111, drive connecting rod 112, linear bearing 113, servo motor 114, coupling 115, first limiter 116, ball screw 117, slide table 118, drive panel 119, nut 120, second limiter 121, base plate 122, round hole 123, and output port 124. Detailed Implementation

[0085] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0086] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0087] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0088] Example 1

[0089] like Figure 1-3 As shown, a respiratory simulation system for calibrating a pulmonary function instrument includes a mechanical system comprising a piston cylinder, a connecting device, and a driving device. The piston cylinder includes an outlet panel 101, a front end plate 102, a piston cylinder 103, a piston 104, a rear end plate 105, and a bottom plate 122. The piston 104 is axially movable within the piston cylinder 103. The front end plate 102 and the rear end plate 105 are mounted at both axial ends of the piston cylinder 103. The bottom plate 122 is adapted to support the front end plate 102 and the rear end plate 105. The outlet panel 101 is mounted on the front end plate 102 and has an output port 124. The front end plate 102 has a circular hole 123 adapted to connect the piston cylinder 103 and the output port 124. The rear end plate 105 has two ventilation holes 106 adapted to connect the piston cylinder 103 and the external environment. The bottom plate 122 is adapted to be detachably mounted on a movable platform and a fixed platform. The drive device includes a servo motor 114, a ball screw 117, a slide 118, a first limiter 116, a second limiter 121, and a coupling 115. The connecting device includes two piston connecting rods 108, two drive connecting rods 112, a connecting panel 110, and a drive panel 119. The connecting panel 110 is located on the outside of the rear end plate 105, and the drive panel 119 is fixedly mounted on the slide 118. The drive connecting rods 112 are adapted to connect the drive panel 119 and the connecting panel 110, and the piston connecting rods 108 are adapted to connect the connecting panel 110 and the piston 104. The servo motor 114 is connected to the ball screw 117 through the coupling 115 and drives the slide 118 to reciprocate, thereby driving the piston 104 to reciprocate through the connecting device to simulate human breathing.

[0090] In this embodiment, the piston cylinder 103 includes a first axis extending axially thereafter, perpendicular to the front end plate 102 and the rear end plate 105, and parallel to the bottom plate 122. The first axis is adapted to pass through the center points of both ends of the piston cylinder 103, the center of the circular hole 123, and the center of the piston 104. The vent holes 106 are symmetrically arranged about the first axis. A 0°–180° line is defined, which is perpendicular to and coplanar with the first axis. The two vent holes 106 are located on the 90°–270° line. The outlet panel 101 includes a second axis extending axially thereafter, adapted to pass through the center of the outlet hole 124, and the first axis coincides with the second axis.

[0091] In this embodiment, the rear end plate 105 includes several through holes disposed in its middle or upper part. Linear bearings 107, suitable for supporting the piston connecting rod 108 or the drive connecting rod 112, are installed within the through holes. Each linear bearing 107 includes a bearing sleeve fastened within the through hole and several balls. The balls are suitable for supporting the piston connecting rod 108 or the drive connecting rod 112, and also for transmitting axial loads. The piston connecting rod 108 is symmetrically arranged about the first axial direction. The piston connecting rod 108 is perpendicular to the piston 104 and the connecting panel 110. One end of the piston connecting rod 108 is fixedly connected to the piston 104, and the other end is fixed to the connecting panel 110 by a first nut 109. Using a ball screw 117 and a linear bearing 107 as transmission components, the balls transmit axial load by rolling, resulting in lower frictional resistance, higher transmission efficiency, and faster start-stop compared to a sliding screw. This makes the axial movement of the piston 104 more precise, enabling the pulmonary function instrument calibration device to output data that more closely matches the standard respiratory waveform. Furthermore, the balls directly bear the load, reducing motion deviation caused by the weight of the device itself. Simultaneously, the application of error averaging reduces offsets caused by manufacturing inaccuracies, deformation during operation, or thermal expansion, mitigating impact and vibration, thereby reducing the off-center movement of the piston 104. The drive connecting rod 112 is symmetrically arranged on both sides, perpendicular to the drive panel 119 and the connecting panel 110. One end of the drive connecting rod 112 is fixed to the connecting panel 110 by a nut 109, and the other end is fixed to the drive panel 119 by a nut 120.

[0092] In this embodiment, the drive device further includes limiters disposed at both axial ends adjacent to the ball screw 117. The limiters include a first limiter 116 disposed adjacent to the rear end plate 105 and a second limiter 121 disposed adjacent to the front end plate 102. The limiters are adapted to limit the movement range of the slide 118, thereby limiting the movement range of the piston 104. The lower ends of the front end plate 102 and the lower ends of the rear end plate 105 are assembled to the axial ends of the base plate 122 and enclose an installation space suitable for accommodating the drive device. After the drive device is assembled, it is encapsulated and fixed to the base plate 122. The rear end plate 105 includes a square opening disposed at its lower end, and the servo motor 114 is embedded in the square opening.

[0093] In this embodiment, the respiratory simulation system further includes a control system, which comprises a controller and a computer. The computer is adapted to program control procedures, establish a standard respiratory model based on a standard respiratory curve, set several calibration parameters, and calculate motion compensation. The controller includes a driver adapted for bidirectional connection to the servo motor 114 and a PLC. The PLC includes a command conversion module adapted for bidirectional connection to the computer, a drive module adapted for bidirectional connection to the driver, and modules corresponding to temperature transmitters, humidity transmitters, pressure transmitters, cylinder pressure transmitters, and flow measurement devices.

[0094] The process of the computer issuing motion commands to the servo motor 114 is as follows: the command conversion module converts the motion commands output by the computer into drive commands and transmits them to the driver through the drive module. The driver then converts the drive commands into electrical signals to drive the servo motor 114 to work.

[0095] The process by which the servo motor 114 feeds back its own status to the computer is as follows: The servo motor 114 can simultaneously feed back electrical signals reflecting its own motion status to the driver. The driver converts the electrical signals into status feedback signals and provides them to the command conversion module through the drive module. The command conversion module converts the status feedback signals and feeds them back to the computer. The computer then compares the feedback signals with the standard breathing model and calibration parameters to calculate motion compensation.

[0096] The computer activates the temperature, pressure, and humidity transmitters according to calibration requirements. These transmitters transmit industrial standard electrical signals to the controller, which converts them and feeds them back to the computer. This allows the computer to obtain temperature, pressure, and humidity parameters, enabling it to convert the output gas of the respiratory simulation system between ambient temperature (ATP) and human body temperature (BTPS) conditions. Specifically: BTPS uses a temperature of 37°C, ambient pressure, and 100% humidity; ATP uses ambient temperature, ambient pressure, and ambient humidity. The temperature, humidity, and pressure transmitters are activated to acquire ambient temperature, humidity, and pressure, and then... The volume conversion factor is obtained, thus yielding the corrected gas volume.

[0097] Example 2

[0098] A compensation method for a respiratory simulation system, suitable for calibrating and compensating a respiratory simulation system as shown on the figure, includes the following steps:

[0099] (1) Check the airtightness of the piston cylinder, as follows:

[0100] (1-1) Let the position of piston 104 when slide table 118 abuts against the first limiter 116 be the starting point, and the position of piston 104 when slide table 118 abuts against the second limiter 121 be the ending point. Take the direction from the starting point to the ending point as the positive x-axis, and the total stroke as L. Divide the total stroke L evenly into n sub-strokes, with each sub-stroke having a length of l = L Record each score

[0101]

[0102] The segment position is x i x n It coincides with the destination of the journey;

[0103] (1-2) Seal the front outlet 124 of the piston cylinder, turn on the pressure transmitter inside the cylinder and record the reading P0 at this time;

[0104] (1-3) The servo motor drives the piston 104 to a displacement il, i∈[1,n]. The horizontal load capacity of the servo motor is F. Observe the reading P of the pressure gauge inside the cylinder. i ;

[0105] (1-4) If P i If the piston rises first and then falls, it is considered that the sealing of this section of piston cylinder 103 is insufficient; if P i near The seal needs to be removed, the pressure reduced, and then resealed. The P value needs to be read again. i Use this as a baseline for the next stage, and repeat steps (1-1) to (1-3).

[0106] (1-5) Repeat steps (1-1) to (1-4) to test the sealing performance of piston cylinder 103 segment by segment.

[0107] (2) Model the piston cylinder 103 and obtain the compensation coefficient:

[0108] (2-1) Connect the flow measurement device to the breathing simulation system. The computer issues a command to the breathing simulation system and simultaneously starts the flow measurement device. The servo motor 114 is adapted to drive the piston 104 to move to the first limiter 116 and then to the second limiter 121 at a speed v0, for a stroke L. The flow measurement device measures the output flow rate Q(t) of the breathing simulation device during this process.

[0109] (2-2) The correspondence between x and Q(t) can be obtained through x = v0t, i.e. Q(x), where x is the actual stroke position of the piston and A is the cross section of the piston cylinder. Theoretically, Q(x) = v0A is a constant value, but because there is an error and it is considered that the main error is the machining error of the piston cylinder, Q(x) will fluctuate in reality.

[0110] A model is established for the piston cylinder, where x∈[x i-1 ,x i Within the range of ), the actual piston cylinder cross-sectional area is assumed to be A. i Actual piston cylinder cross-sectional area A i The difference between the theoretical piston cylinder cross-sectional area A0 and the actual cross-sectional area A0 is ΔA. i , i∈[1,n], and thus obtain A i The correspondence with x and ΔA i The correspondence with x, that is ΔA(x i )=A(x i )-A0, and A(x i Abbreviated as A i ΔA(x) i This is abbreviated as ΔA i ;

[0111] (2-3) The piston's operating speed that needs to be compensated for in each sub-stroke

[0112] (2-4) When the respiratory simulation system is performing other functions, input the set volume V, obtain the current piston position x, x∈[x], and obtain the current piston position x. n ,x n+1 When piston 104 is set to move from the first limiter 116 to the second limiter 121, calculate the movable volume margin V of piston 104. 暂 =(x n+1 -x)A n+1 When piston 104 is set to move from the second limiter 121 to the first limiter 116, calculate the movable volume margin V of piston 104. 暂 =(xx) n A n+1 ;

[0113] (2-5) When the piston 104 is set to move from the first limiter 116 to the second limiter 121, the parameter j is initialized to 0, and the volume margin V is temporarily compared with the input volume V:

[0114] If V 暂 If V > 0, then j = 0.

[0115] If V 暂 <V, then j+1, and V in terms of volume margin 暂 =(x n+1 -x)A n+1 Add the volume of the next interval

[0116] Then compare it with V. If it is less than V, continue adding until V is reached. 暂 If the value is greater than V, then determine the size of j;

[0117] If j = 1, then,

[0118] If j≥2, then j-1, we get:

[0119] (2-6) When piston 104 is set to move from the second limiter 121 to the first limiter 116, first calculate the volume margin V of the current piston 104 interval. 暂 =(xx) n A n+1 Initialize parameter j to 0, and set the volume margin V. 暂 Compare with the input volume V;

[0120] If V 暂 If V > 0, then j = 0.

[0121] If V 暂 <V, then j+1, and V in terms of volume margin 暂 =(xx) n A n+1 Add the volume of the next interval

[0122] Then compare it with V. If it is less than V, continue adding until V is reached. 暂 If the value is greater than V, then determine the size of j;

[0123] If j = 1, then,

[0124] If j≥2, then j-1, we get:

[0125] In summary, the piston travel distance and speed after compensation and correction can be obtained.

[0126] (3) Model the piston cylinder and obtain the relationship between the piston 104 moving speed and the gas flow output.

[0127] Based on a mathematical model of one-dimensional steady adiabatic isentropic flow, the relationships between gas parameters, gas flow output port parameters, and stagnation state parameters inside piston cylinder 103 are listed:

[0128] According to the law of conservation of energy:

[0129]

[0130] P r Stasis pressure

[0131] T r : Stagnation temperature

[0132] ρ r Density of stagnant state

[0133] P1: Gas pressure inside the piston cylinder

[0134] T1: Piston cylinder gas temperature

[0135] ρ1: Gas density inside the piston cylinder

[0136] A1': Piston cross-sectional area

[0137] v1: Piston speed

[0138] P2: Airflow output pressure

[0139] T2: Airflow output temperature

[0140] ρ2: Gas flow rate at the outlet density

[0141] A'2: Cross-sectional area of ​​the airflow outlet

[0142] v2: Gas flow rate at the output port

[0143] In the formula, k is the adiabatic coefficient of the gas; if the gas is air, k = 1.4.

[0144] According to the ideal gas law:

[0145] P r =ρ r RT r ...(2)

[0146] P1=ρ1RT1...(3)

[0147] P2=ρ2RT2...(4)R is the gas constant, with a value of R=287(J / kg*K).

[0148] According to the isentropic relationship:

[0149]

[0150] From equations (2) to (5), we can obtain:

[0151]

[0152] According to the law of conservation of mass:

[0153] Q m =ρ1v1A1'=ρ2v2A'2...(9)

[0154] Substituting (7) and (8) into (9) yields:

[0155]

[0156] Among them, the stagnation temperature T r If the gas constant R, piston cross-sectional area A1', gas flow outlet cross-sectional area A'2, and gas adiabatic coefficient k are all constants, then the relationship between the piston 104 movement speed v1 and the gas flow outlet 124 gas velocity v2 can be obtained.

[0157] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A respiratory simulation system, characterized in that, Including mechanical systems and control systems, The mechanical system includes a piston cylinder, a connecting device, and a driving device. The piston cylinder includes a piston cylinder, a front end plate, a rear end plate, a bottom plate, a piston, and an outlet panel. The piston is axially movable within the piston cylinder. The front end plate and the rear end plate are assembled at both axial ends of the piston cylinder. The bottom plate is adapted to support the front end plate and the rear end plate. The outlet panel is mounted on the front end plate and has a circular vent hole. The front end plate has a front vent hole adapted to connect the piston cylinder with the circular vent hole. The rear end plate has several rear vent holes adapted to connect the piston cylinder with the external environment. The bottom plate is adapted to be detachably mounted on a movable platform and a fixed platform. The driving device includes a servo motor, a ball screw, a slide table, a first limiter, and a second limiter. The servo motor is connected to the ball screw via a coupling, thereby driving the slide table to perform reciprocating linear motion. The first limiter and the second limiter are respectively arranged adjacent to the two axial ends of the ball screw. The first limiter and the second limiter are adapted to limit the movement range of the slide table, thereby limiting the movement range of the piston. The connecting device includes several piston connecting rods, several drive connecting rods, a connecting panel, and a drive panel. The connecting panel is disposed on the outside of the rear end plate, and the drive panel is fixedly disposed on the slide. The drive connecting rods are adapted to connect the drive panel and the connecting panel, and the piston connecting rods are adapted to connect the connecting panel and the piston. The servo motor drives the slide to reciprocate through a ball screw, and then drives the piston to reciprocate through the connecting device to simulate human breathing. The control system includes a controller, a computer, a temperature transmitter, and pressure transmitters respectively installed inside and outside the piston cylinder. The computer is adapted to write control programs through software, establish a standard breathing model based on a standard breathing curve, set several calibration parameters, and calculate motion compensation. The controller is bidirectionally connected to the servo motor, the computer, the temperature transmitter, and the pressure transmitter to form a closed loop.

2. The respiratory simulation system according to claim 1, characterized in that, The piston cylinder includes a first axis extending along its axial direction, the first axis being perpendicular to the front end plate and the rear end plate, the first axis being parallel to the bottom plate, the first axis being adapted to pass through the center points of both ends of the piston cylinder, the center of the front vent hole and the center of the piston, and the rear vent hole being symmetrically arranged about the first axis. The outlet panel includes a second axis extending along its axial direction, the second axis being adapted to pass through the center of the circular vent hole, the first axis coinciding with the second axis.

3. A respiratory simulation system according to claim 2, characterized in that, The piston connecting rod is symmetrically arranged on the left and right sides, and is perpendicular to the piston and the connecting panel. One end of the piston connecting rod is fixedly connected to the piston or integrally formed, and the other end of the piston connecting rod is fixed to the connecting panel by a first nut. The drive linkages are symmetrically arranged on the left and right sides, and are perpendicular to the drive panel and the connecting panel. One end of the drive linkage is fixed to the connecting panel by a first nut, and the other end of the drive linkage is fixed to the drive panel by a second nut.

4. A respiratory simulation system according to claim 3, characterized in that, The rear end plate includes several through holes disposed in its middle or upper part. A linear bearing is installed in the through hole. The linear bearing includes a bearing sleeve and several balls fastened in the through hole. The balls are suitable for supporting the piston connecting rod or the drive connecting rod, and are also suitable for transmitting axial loads.

5. A respiratory simulation system according to claim 4, characterized in that, The lower end of the front end plate and the lower end of the rear end plate are assembled to the axial ends of the base plate and enclose to form an installation space suitable for accommodating the drive device. After the drive device is assembled, it is encapsulated and fixed to the base plate.

6. A respiratory simulation system according to claim 5, characterized in that, The ball screw includes a screw, a screw nut, and balls. The screw is a threaded shaft with a semi-circular helical groove. The inner circumferential wall of the screw nut is also machined with a semi-circular helical groove. The screw and the semi-circular helical groove on the screw nut combine to form a helical raceway with a circular cross-section. The balls roll along the helical raceway. The slide is fixedly mounted on the screw nut. The output shaft of the servo motor drives the screw to rotate through the coupling. The balls roll forward in the helical raceway, thereby driving the screw nut and the slide to perform linear motion.

7. A respiratory simulation system according to claim 1, characterized in that, The controller includes a driver and a PLC adapted for bidirectional connection to the servo motor. The PLC includes a command conversion module adapted for bidirectional connection to the computer and a drive module adapted for bidirectional connection to the driver, and the command conversion module and the drive module are bidirectionally connected. The process by which the computer issues motion commands to the servo motor is as follows: the command conversion module is adapted to convert the motion commands output by the computer into drive commands and transmits them to the driver through the drive module; the driver then converts the drive commands into electrical signals to drive the servo motor to work. The process by which the servo motor feeds back its own state to the computer is as follows: The servo motor can simultaneously feed back an electrical signal reflecting its own motion state to the driver. The driver converts the electrical signal into a state feedback signal and provides it to the command conversion module through the drive module. The command conversion module converts the state feedback signal and feeds it back to the computer. The computer then compares the feedback signal with the standard breathing model and calibration parameters to calculate motion compensation.

8. A respiratory simulation system according to claim 7, characterized in that, The control system includes a temperature transmitter and a pressure transmitter installed on the outlet panel. The PLC includes a pressure module and a temperature module. The pressure module is bidirectionally connected to the pressure transmitter and the command conversion module, respectively. The temperature module is bidirectionally connected to the temperature transmitter and the command conversion module, respectively. The process by which the computer issues switching commands to the temperature transmitter and the pressure transmitter according to calibration requirements is as follows: the command conversion module is adapted to convert the switching commands output by the computer into switching instructions and transmit them to the temperature module and the pressure module, thereby controlling the temperature transmitter and the pressure transmitter to turn on or off through the temperature module and the pressure module. The process by which the computer obtains temperature and pressure parameters from the temperature transmitter and the pressure transmitter according to calibration requirements is as follows: The temperature transmitter and the pressure transmitter transmit industrial standard electrical signals to the temperature module and the pressure module, and the command conversion module converts the industrial standard electrical signals and feeds them back to the computer, thereby enabling the computer to obtain temperature and pressure parameters, and thus perform gas volume conversion between room temperature conditions (ATP) and human body conditions (BTPS) for the input and output gases of the respiratory simulation system.

9. A compensation method for a respiratory simulation system, characterized in that, It is suitable for calibrating and compensating the respiratory simulation system as described in any one of claims 1-8, comprising the following steps: (1) Check the airtightness of the piston cylinder; (2) Model the piston cylinder and obtain the compensation coefficient: (2-1) Connect the flow measurement device to the breathing simulation system. The computer issues a command to the breathing simulation system and starts the flow measurement device at the same time. The servo motor is adapted to drive the piston to complete the uniform motion of the stroke L at a speed of v0. The flow measurement device measures the output flow rate Q(t) of the breathing simulation system during this process. (2-2) The correspondence between x and Q(t) can be obtained through x = v0t, that is, Q(t) = xA = v0At, Q(x) = v0A, where x is the actual stroke position of the piston and A is the cross-sectional area of ​​the piston cylinder; A model is established for the piston cylinder, where x∈[x i-1 ,x i Within the range of ), the actual piston cylinder cross-sectional area is assumed to be A. i Actual piston cylinder cross-sectional area A i The difference between the theoretical piston cylinder cross-sectional area A0 and the actual cross-sectional area A0 is ΔA. i , i∈[1,n], and thus obtain A i The correspondence with x and ΔA i The correspondence with x, that is, ΔA(x i )=A(x i )-A0, and A(x i Abbreviated as A i ΔA(x) i This is abbreviated as ΔA i ; (2-3) The piston's operating speed that needs to be compensated for in each sub-stroke i∈[1,n]; (2-4) When a volume V of gas needs to be input, obtain the current piston position x, x∈[x... n ,x n+1 When the piston is set to move from the first limiter to the second limiter, the movable volume margin V of the piston is calculated. 暂 =(x n+1 -x)A n+1 When the piston is set to move from the second limiter towards the first limiter, calculate the movable volume margin V of the piston. 暂 =(xx) n A n+1 ; (2-5) When the piston is set to move from the first limiter to the second limiter, the parameter j is initialized to 0, and the volume margin V is set to 0. 暂 Compare with the input volume V: If V 暂 If > V, then j = 0. If V 暂 <V and in terms of volume margin V 暂 =(x n+1 -x)A n+1 Add the volume of the next interval Then j = 1, If V 暂 <V and in terms of volume margin V 暂 =(x n+1 -x)A n+1 In addition to the volume of at least two intervals Then j≥2, (2-6) When the piston is set to move from the second limiter to the first limiter, the parameter j is initialized to 0, and the volume margin V is set to 0. 暂 Compare with the input volume V: If V 暂 If > V, then j = 0. If V 暂 <V, then j+1, and V in terms of volume margin 暂 =(xx) n A n+1 Add the volume of the next interval Then compare it with V. If it is less than V, continue adding until V is reached. 暂 If the value is greater than V, then determine the size of j; If j = 1, then, If j≥2, then j-1, we get:

10. The compensation method for the respiratory simulation system according to claim 9, characterized in that, It also includes step (3): The piston cylinder is modeled to obtain the compression compensation coefficient, which is the coefficient relating the piston movement speed to the gas flow output: Based on a mathematical model of one-dimensional steady adiabatic isentropic flow, the relationships between the gas parameters inside the piston cylinder, the gas flow output port parameters, and the stagnation state parameters are listed: According to the law of conservation of energy: P r Stasis pressure T r : Stagnation temperature ρ r Density of stagnant state P1: Gas pressure inside the piston cylinder T1: Piston cylinder gas temperature ρ1: Gas density inside the piston cylinder A'1: Piston cross-sectional area v1: Piston speed P2: Airflow output pressure T2: Airflow output temperature ρ2: Gas flow rate at the outlet density A'2: Cross-sectional area of ​​the airflow outlet v2: Gas flow rate at the output port In the formula, k is the adiabatic coefficient of the gas. If the gas is air, k = 1.

4. According to the ideal gas law, we get: P r =ρ r RT r ...(2) P1=ρ1RT1...(3) P2=ρ2RT2...(4) R is the gas constant, with a value of R = 287 (J / kg*K). According to the isentropic relationship: From equations (2) to (5), we can obtain: According to the law of conservation of mass: Q m =ρ1v1A1'=ρ2v2A'2...(9) Substituting (7) and (8) into (9) yields: Among them, the stagnation temperature T r Since the gas constant R, piston cross-sectional area A'1, gas flow outlet cross-sectional area A'2, and gas adiabatic coefficient k are all constants, a compensation operation is performed based on the relationship between piston movement speed v1 and gas flow outlet velocity v2. The required piston movement speed v1 is obtained by setting the gas flow outlet velocity v2 according to the simulation needs.

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