Dialysis system with reduced valve noise and valve position detection

Abstract

Systems and methods for reducing valve noise and detecting valve position in a medical fluid system are disclosed. A method includes transmitting, by a microcontroller, a control signal for closing a valve via a pulse width modulation (PWM) signal. The valve is configured to control fluid flow in a medical fluid system. The valve may open at least prior to transmission of the control signal. The valve includes a housing, an electromagnetic coil, and a plunger. The method further includes applying power to the valve to measure a voltage across the valve; and monitoring a voltage across the valve within a measurement interval based on a sense resistor. The measurement interval terminates when the voltage reaches a predetermined threshold voltage. The method further includes comparing the measured interval to a reference interval for a normally operating shut-off valve and generating an evaluation of the valve position based on the comparison.

Description

Technical Field

[0001] The present disclosure generally relates to medical fluid therapy and, more particularly, to dialysis fluid therapy using valves for medical fluid control. Background Art

[0002] For various reasons, a person's renal system may fail. Renal failure can produce a variety of physiological disorders. For example, the ability to balance water and minerals or excrete the daily metabolic load is no longer possible. Toxic end products of metabolism (such as urea, creatinine, uric acid, and other substances) may accumulate in the patient's blood and tissues.

[0003] Dialysis is used to treat declining renal function, particularly renal failure. Dialysis removes waste products, toxins, and excess water from the body that would normally be removed by a functioning kidney. Dialysis treatment for replacing renal function is critical for many people because this treatment is life-saving.

[0004] One type of renal failure therapy is hemodialysis ("HD"), which typically uses diffusion to remove waste products from the patient's blood. A diffusion gradient occurs across a semipermeable dialyzer between the blood and an electrolyte solution called dialysate or dialysis fluid to cause diffusion.

[0005] Hemofiltration ("HF") is an alternative renal replacement therapy that relies on the convective transport of toxins from the patient's blood. HF is achieved by adding replacement or substitution fluid to the extracorporeal circuit during treatment. During the course of an HF treatment, the replacement fluid and the fluid that accumulates between the patient and the treatment are ultrafiltered, thus providing a convective transport mechanism that is particularly beneficial for removing medium and large molecules.

[0006] Hemodiafiltration ("HDF") is a treatment modality that combines convective clearance and diffusive clearance. HDF uses dialysate (similar to standard hemodialysis) flowing through a dialyzer to provide diffusive clearance. In addition, a substitution solution is provided directly to the extracorporeal circuit to provide convective clearance.

[0007] Most HD, HF, and HDF treatments are performed in a center. There is a current trend towards home hemodialysis (“HHD”), in part because HHD can be performed daily, which provides therapeutic benefits compared to in-center hemodialysis treatments, which are typically performed every two or three weeks. Studies have shown that more frequent treatments remove more toxins and waste and reduce interdialytic fluid overload compared to patients receiving less frequent but potentially longer treatments. Patients receiving more frequent treatments do not experience as many down cycles (fluctuations in fluid and toxins) as in-center patients, who have built up toxins over two or three days prior to treatment. In some areas, the nearest dialysis center may be many miles from the patient's home, resulting in home treatment times taking up much of the day. Treatments at a center near the patient's home may also take up much of the patient's day. By comparison, HHD can be performed at night or during the day while the patient is relaxed, working, or otherwise productive.

[0008] Another type of renal failure therapy is peritoneal dialysis (“PD”), which injects a dialysis solution (also known as dialysis fluid) into the peritoneal cavity of a patient via a catheter. The dialysis fluid contacts the peritoneum within the peritoneal cavity of the patient. Waste, toxins, and excess water pass from the patient's bloodstream through capillaries in the peritoneum and enter the dialysis fluid due to diffusion and osmosis, i.e., an osmotic gradient appears across the peritoneum. Osmotic agents in the PD dialysis fluid provide the osmotic gradient. The used or spent dialysis fluid is drained from the patient's body, thereby removing waste, toxins, and excess water from the patient's body. This cycle is repeated, e.g., multiple times.

[0009] There are multiple types of peritoneal dialysis therapies, including continuous ambulatory peritoneal dialysis (“CAPD”), automated peritoneal dialysis (“APD”), tidal flow dialysis, and continuous flow peritoneal dialysis (“CFPD”). CAPD is a manual dialysis treatment. Here, the patient manually connects the implanted catheter to the drain tube to allow the used or spent dialysis fluid to drain from the peritoneal cavity. The patient then switches the fluid connection so that the patient catheter is connected to a fresh dialysis fluid bag to inject and introduce fresh dialysis fluid into the patient's body through the catheter. The patient disconnects the catheter from the fresh dialysis fluid bag and allows the dialysis fluid to dwell within the peritoneal cavity, where transfer of waste, toxins, and excess water occurs. After the dwell period, the patient repeats the manual dialysis procedure, e.g., four times a day. Manual peritoneal dialysis requires a significant amount of time and effort from the patient, leaving much room for improvement.

[0010] Automated peritoneal dialysis (“APD”) is similar to CAPD in that the dialysis treatment includes drain, fill, and dwell cycles. However, the APD machine typically performs these cycles automatically while the patient is sleeping. The APD machine enables the patient to avoid manually performing the treatment cycles and also avoids delivering supplies during the day. The APD machine is fluidly connected to an implanted catheter, a source or bag of fresh dialysis fluid, and a fluid drain tube. The APD machine pumps fresh dialysis fluid from the dialysis fluid source through the catheter and into the patient's peritoneal cavity. The APD machine also allows the dialysis fluid to dwell in the peritoneal cavity and allows for the transfer of waste, toxins, and excess water. The source can include multiple liters of dialysis fluid, including multiple solution bags.

[0011] The APD machine pumps used or spent dialysis fluid from the patient's peritoneal cavity through the catheter for drainage. As with the manual process, several drain, fill, and dwell cycles occur in the dialysis device. A “last fill” may occur at the end of the APD treatment. The fluid from the last fill can be retained in the patient's peritoneal cavity until the next treatment begins, or it can be manually drained at some point during the day.

[0012] Except for CAPD, which typically does not involve a machine, each of the above dialysis modalities uses automated valves to control whether dialysis fluid, blood, or other fluids can flow. The valves also control the direction of fluid flow, such as the location from which the fluid comes or the destination of the fluid flow. Different types of valves are used in dialysis systems. One type of valve is typically used with a disposable cartridge that has a rigid plastic portion and a valve seat that define a fluid flow path and one or more flexible membranes that cover one or more sides of the rigid plastic portion. The disposable cartridge is typically loaded into a dialysis machine or cycler that is capable of closing a designated portion of one or more plastic sheets against the valve seat to block fluid flow and forcing or allowing the plastic to move away from the valve seat to allow fluid flow.

[0013] Another type of automatic valve is the electromagnetic pinch valve, which alternatively clamps shut a tube carrying dialysis fluid, blood, or other fluids to block fluid flow. Here, a rigid plastic disposable cartridge is not needed, thus saving costs. There are generally two types of pinch valves, electromagnetic pinch valves and electric pinch valves. Another type of automatic valve is the electromagnetic plunger valve. The electromagnetic plunger valve uses a plunger (e.g., a metal block that moves through an electromagnetic coil via electromagnetic induction) to move a rod that is pressed against a seat to stop fluid flow (or move the rod to press against the seat to cause fluid flow). One problem with electromagnetic pinch valves and electromagnetic plunger valves (collectively referred to herein as "solenoid valves") is noise. For example, an electromagnetic plunger valve typically energizes a coil that moves the plunger within a housing. The plunger can move when the coil is energized to allow the tube to open for fluid flow. When energy is removed from the coil, a compression spring is allowed to push the plunger in the opposite direction against a stop or wall located at the opposite end of the tube to block the tube. The plunger moving in either direction encounters a stroke end, which involves the plunger directly contacting a fixed surface or, in the case where there is a tube therebetween, making contact. Noise is generated when the plunger contacts the stroke end. Noise from solenoid valves can interfere with the patient and is problematic. This is especially true for APD treatments, which are typically performed at night while the patient is sleeping.

[0014] Another problem with solenoid valves is that it is difficult to know that the valve has opened when energized (or closed when de-energized). That is, it is difficult to know that the energization of the coil has actually moved the plunger (e.g., in an electromagnetic plunger valve), or has actually removed the clamping of the tube (e.g., in an electromagnetic pinch valve) such that it no longer blocks the tube or fluid flow. Assuming the valve is open when it may not actually be open can result in undesirable situations.

[0015] For each of the above problems, an improved way to operate solenoid valves is needed. Summary of the Invention

[0016] The present disclosure describes methods for operating solenoid valves used in medical fluid systems such as automated peritoneal dialysis ("PD") systems, which improve the usability of the valves. While the system is described primarily in the context of PD, the improved solenoid valve operation of the present disclosure is applicable to machines for any dialysis mode described herein, such as online HD, HF, HDF, acute HD, HF, and HDF. The improved solenoid valve operation of the present disclosure is also applicable to any medical fluid system in which treatment fluid flow or patient fluid flow is controlled via one or more valves.

[0017] In a PD example, the system includes a PD machine or cycler. The PD machine is mainly described herein as a durable system that attempts to limit disposable waste as much as possible, for example, via the use of an electromechanical piston pump that pumps medical fluid or PD fluid through the body of the pump. The PD fluid pump can also be an electromechanically driven gear pump, peristaltic pump, or centrifugal pump. In another alternative embodiment, a pneumatically driven PD fluid pump can be employed. Any of the above pumping scenarios can be used in combination with the electromechanical actuated solenoid valves of the present disclosure. In one embodiment, the PD machine or cycler is capable of delivering fresh heated PD fluid to the patient at a pressure of, for example, 14 kPa (2.0 psig) or higher. The PD machine is capable of removing used PD fluid or effluent from the patient at a negative pressure of, for example, -9 kPa (-1.3 psig) or even greater. The fresh PD fluid to be delivered to the patient can be first heated to body fluid temperature, such as 37 °C.

[0018] The PD machine or cycler also includes a plurality of valves, any one or more or all of which can be solenoid valves. The solenoid valves discussed herein can be of any kind or type. For example, one type of solenoid valve uses an internal fluid path that opens or closes depending on whether the coil is energized. This type of solenoid valve is well suited for durable or reusable versions of the PD machine or cycler. Another type of solenoid valve operates by releasing or closing a flexible tube depending on whether the coil is energized. This type of solenoid valve is well suited for versions of the PD machine or cycler that operate with a disposable kit, but can also be used with durable versions of the PD machine or cycler that have internal flexible tubing for operating with the solenoid valve.

[0019] The systems and associated methods of the present disclosure automatically determine the position or status of the solenoid valve, which can be used to detect stuck valves and other valve failures. In addition to detecting faults, the automatic detection of valve position also allows for the automatic self-calibration of the solenoid valve hardware. Self-calibration also helps to implement the noise reduction methods discussed herein. The system includes electrical hardware and software and is configured to control electromechanical devices, such as solenoid valves.

[0020] Noise reduction

[0021] The PD machine or cycler of the present system operates together with the solenoid valve under the control of the control unit. In various embodiments, the control unit controls the movement of the solenoid valve to minimize the amount of sound emitted during impact during valve activation and deactivation. The control includes using a PWM drive waveform delivered via a microcontroller that is programmed such that the PWM duty cycle increases from zero percent to one hundred percent (closing the valve) and decreases from one hundred percent to zero percent on a curved curve rather than instantaneously jumping or dropping. The curved curve becomes more horizontal towards the end of the plunger stroke, thereby reducing the impact force generated by the valve stem and reducing the sound or noise generated in relation to the end of opening or closing the solenoid valve. In one embodiment, the curved curve is electrically implemented at the valve coil via a metal oxide semiconductor field effect transistor ("MOSFET") and a diode.

[0022] Determine the position of the solenoid valve

[0023] As discussed herein, a solenoid valve is typically opened by energizing a coil that moves a plunger within the housing of the solenoid valve (e.g., as in an electromagnetic plunger valve) and / or releases the clamping state of a tube (e.g., as in an electromagnetic pinch valve). It is desirable and necessary to evaluate the position of the solenoid valve of a medical fluid machine or cycler (e.g., PD, HD, HF, HDF, and / or CRRT machines or cyclers) to ensure that the valve is not stuck or otherwise damaged. Additionally, for the noise reduction system and associated methods disclosed herein, valve stem position detection is useful such that the noise reduction PWM drive waveform is ensured to start when the valve stem is in the fully open position or fully closed position as needed.

[0024] In an embodiment, an analog signal is delivered along a position detection line that extends from a point electrically upstream of the MOSFET to a multiplexer that allows sequential analysis of multiple solenoid valves. The output from the multiplexer is delivered to a comparator that compares the analog signal of each valve with a threshold. When the analog signal of a valve reaches the threshold, the comparator outputs a signal. The comparator outputs the signal to a microcontroller that is programmed to determine the valve stem position of a particular valve based on the moment the signal is received.

[0025] According to the disclosure set forth herein and without limiting the disclosure in any way, in a first aspect of the disclosure that can be combined with any other aspect or a part thereof, a medical fluid system is disclosed. The medical fluid system includes a drive circuit, a valve, and a microcontroller. The drive circuit is configured to control the valve via a pulse width modulation (PWM) signal in response to a control signal received from the microcontroller. The valve is configured to control the fluid flow in the medical fluid system. The valve includes a housing, an electromagnetic coil, and a plunger. The valve is configured to enable fluid flow through a tube by applying a voltage to the electromagnetic coil via the drive circuit to move the plunger within the housing.

[0026] In a second aspect of the disclosure that can be combined with any other aspect or a part thereof, the instructions, when executed by the processor, further cause the processor to: apply power to the valve via the drive circuit to measure the voltage across the valve; monitor the voltage across the valve via the drive circuit based on a sense resistor associated with the valve during a measurement interval, wherein the measurement interval terminates when the voltage reaches a predetermined threshold voltage; compare the measurement interval with a reference interval of a normally operating closed valve; and generate an assessment of the valve position based on the comparison of the measurement interval with the reference interval.

[0027] In a third aspect of the disclosure that can be combined with any other aspect or a part thereof, the valve is further configured to: close the flow of the medical fluid through the tube by removing the application of the voltage to the electromagnetic coil via the drive circuit to move the plunger in a direction opposite to the housing to block the tube. Additionally, the instructions, when executed by the processor, further cause the processor to: transmit a second control signal to the drive circuit, the second control signal causing the drive circuit to ramp down the PWM signal to the electromagnetic coil to a duty cycle of 0%. The ramp down of the PWM signal causes the plunger to move in the opposite direction, and the movement results in a reduced sound generated by the corresponding plunger compared to an operation without the PWM signal.

[0028] In a fourth aspect of the present disclosure, which can be combined with any other aspect or a part thereof, the instructions, when executed by the processor, further cause the processor to perform: applying a second electrical power to the valve via the drive circuit to measure a second voltage across the valve; monitoring the second voltage across the valve via the drive circuit based on a sense resistor associated with the valve and within a second measurement interval, wherein the second measurement interval terminates when the second voltage reaches the predetermined threshold voltage; comparing the second measurement interval with a second reference interval of a normally operating open valve; and generating a second assessment of the valve position based on the comparison of the second measurement interval with the second reference interval.

[0029] In a fifth aspect of the present disclosure, which can be combined with any other aspect or a part thereof, a method for determining a valve position in a medical fluid system is disclosed. The method includes: transmitting, by a microcontroller having a processor, a control signal for closing a valve, wherein the valve is configured to control fluid flow in the medical fluid system, wherein the valve is at least open prior to transmitting the control signal, and wherein the valve includes a housing, an electromagnetic coil, and a plunger; applying electrical power to the valve via a drive circuit to measure a voltage across the valve; monitoring the voltage across the valve via the drive circuit based on a sense resistor associated with the valve and within a measurement interval, wherein the measurement interval terminates when the voltage reaches a predetermined threshold voltage; comparing the measurement interval with a reference interval of a normally operating closed valve; and generating an assessment of the valve position based on the comparison.

[0030] In a sixth aspect of the present disclosure, which can be combined with any other aspect or a part thereof, the method further includes setting the power level to zero and for a predetermined time period before applying power to the valve to desaturate the electromagnetic coil during the predetermined time period.

[0031] In a seventh aspect of the present disclosure, which can be combined with any other aspect or a part thereof, the predetermined time period is 5 milliseconds.

[0032] In an eighth aspect of the present disclosure, which can be combined with any other aspect or a part thereof, monitoring the voltage across the valve includes receiving an indication from a comparator connected to the drive circuit of when the voltage reaches the predetermined threshold voltage.

[0033] In a ninth aspect of the present disclosure, which can be combined with any other aspect or a part thereof, the method further includes: transmitting, by the microcontroller, a second control signal for opening the valve; applying a second electric power to the valve via the drive circuit to measure a second voltage across the valve; monitoring, based on the sense resistor and via the drive circuit, the second voltage across the valve within a second measurement interval, wherein the second measurement interval terminates when the second voltage reaches a second predetermined threshold voltage; comparing the second measurement interval with a second reference interval for a normally operating open valve; and generating a second evaluation of the valve position based on a comparison between the second measurement interval and the second reference interval.

[0034] In a tenth aspect of the present disclosure, which can be combined with any other aspect or a part thereof, any feature, function, and alternative described in conjunction with Figures 1 to 16 any one or more of the figures can be combined with any feature, function, and alternative described in conjunction with Figures 1 to 16 any other figure.

[0035] According to the above aspects and the present disclosure set forth herein, an advantage of the present disclosure is to provide a medical fluid system having improved solenoid valve operation.

[0036] Another advantage of the present disclosure is to provide a medical fluid system having a solenoid valve method that reduces noise generated by valve operation.

[0037] Another advantage of the present disclosure is to provide a medical fluid system having a solenoid valve method that enables determination of the position or state of the solenoid valve, and this determination of the position or state of the solenoid valve can be used to detect when the solenoid valve is stuck or has other faults.

[0038] Yet another advantage of the present disclosure is to provide a medical fluid system having a solenoid valve method that enables determination of the position or state of the solenoid valve using information from the solenoid valve itself, thereby reducing the required hardware.

[0039] Yet another advantage of the present disclosure is to provide a medical fluid system having a solenoid valve method that enables the solenoid valve to self-calibrate.

[0040] Yet another advantage of the present disclosure is to provide a medical fluid system having a solenoid valve method that enables determination of the position or state of the solenoid valve with high precision and high resolution (e.g., better than 0.01 mm).

[0041] Still yet another advantage of the present disclosure is to provide a medical fluid system having a solenoid valve method that uses common low-cost electrical components.

[0042] Additional features and advantages are described in, and will be apparent from, the following detailed description and the accompanying drawings. The features and advantages described herein are not all-inclusive, and in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings and description. Moreover, any particular embodiment need not have all of the advantages listed herein, and it is contemplated that the various advantageous embodiments may be claimed separately. Additionally, it should be noted that the language used in this specification has been principally selected for readability and guidance purposes, and not to limit the scope of the inventive subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 FIG. is a schematic view of an embodiment of an automated PD system with a solenoid valve, according to a non-limiting embodiment of the present disclosure.

[0044] Figure 2 FIG. is a cross-sectional front view of an embodiment of a two-way valve that can be used with the system and associated method of the present disclosure, according to a non-limiting embodiment of the present disclosure.

[0045] Figure 3 FIG. is a cross-sectional front view of an embodiment of a three-way valve that can be used with the system and associated method of the present disclosure, according to a non-limiting embodiment of the present disclosure.

[0046] Figure 4 FIG. is an example solenoid valve drive circuit for the system and associated method of the present disclosure, according to a non-limiting embodiment of the present disclosure, which can be used to reduce the operating noise associated with the solenoid valve.

[0047] Figure 5 FIG. is a pulse width modulation ("PWM") graph of a noisy valve that does not use the PWM drive waveform of the present disclosure, according to a non-limiting embodiment of the present disclosure.

[0048] Figure 6 FIG. is a PWM graph of a quiet valve that uses the PWM drive waveform of the present disclosure for both energization and de-energization, according to a non-limiting embodiment of the present disclosure.

[0049] Figure 7 FIG. is an example extended solenoid valve drive circuit for multiple valves, according to a non-limiting embodiment of the present disclosure, which can be used to reduce the operating noise associated with the solenoid valve and which multiplexes the outputs from multiple valve circuits.

[0050] Figure 8 FIG. is an electrical schematic of a drive circuit for determining the position of a valve stem in a given solenoid valve, according to an example embodiment of the present disclosure.

[0051] Figure 9is a graphical output from a valve stem position test configuration according to a non - limiting embodiment of the present disclosure, which shows the position of an inductor - based valve.

[0052] Figure 10 is a data output from a valve stem position test configuration according to a non - limiting embodiment of the present disclosure, which shows the position of a plunger in a valve over time.

[0053] Figure 11 shows various waveforms from a valve stem position test according to a non - limiting embodiment of the present disclosure, which shows the measured voltage over time to determine the position of the valve when it is open and when it is closed.

[0054] Figure 12 shows an average waveform from multiple valve stem position tests according to a non - limiting embodiment of the present disclosure, which shows characteristic transition points of the valve.

[0055] Figure 13 and Figure 14 shows valve stem 170, 210 position test data obtained after the gate drive has desaturated according to a non - limiting embodiment of the present disclosure.

[0056] Figure 15 shows recorded valve stem position test data according to a non - limiting embodiment of the present disclosure, which shows that when the valve is commanded to transition from an open state to a closed state, the valve stem is stuck closed, the valve stem functions normally, and the valve stem is stuck open.

[0057] Figure 16 shows recorded valve stem position test data according to a non - limiting embodiment of the present disclosure, which shows that when the valve is commanded to transition from a closed state to an open state, the valve stem is stuck closed, the valve stem functions normally, and the valve stem is stuck open. Detailed Description

[0058] System overview

[0059] Now referring to the drawings and particularly to Figure 1 , there is shown an example system 10 including solenoid valve operation of the present disclosure. System 10 includes a dialysis machine 20, such as an automated peritoneal dialysis (“PD”) machine, and a control unit 100 having one or more processors 102, one or more memories 104, a video controller 106, and a user interface 108. Control unit 100 controls all electrical fluid flow and heating components of system 10 and receives outputs from all sensors of system 10. System 10 in the illustrated embodiment includes durable and reusable components that come into contact with medical fluids, such as PD fluid, which require the PD machine or cycler 20 to be disinfected between treatments, for example, by heat disinfection.

[0060] Figure 1 System 10 therein includes an inline resistance heater 56, reusable supply lines or tubes 52a1 to 52a4 and 52b, an air trap 60 operating together with corresponding upper level sensor 62a and lower level sensor 62b, an air trap valve 54d, an exhaust valve 54e positioned along an exhaust line 52e, a reusable line or pipe 52c, a dialysis fluid pump 70, temperature sensors 58a and 58b, pressure sensors 78a, 78b1, 78b2 and 78c, reusable patient lines or tubes 52f and 52g which have corresponding valves 54f and 54g, a double lumen reusable patient line 28, a hose reel 80 for retracting the patient line 28, a reusable drain line or pipe 52i extending to a drain line connector 34 and having a drain line valve 54i, and first and second reusable recirculation and disinfection lines or pipes 52r1 and 52r2 operating together with corresponding disinfection valves 54r1 and 54r2. A third recirculation or disinfection line or pipe 52r3 extends between disinfection connectors 30a and 30b for use during disinfection. A fourth recirculation or disinfection line or pipe 52r4 extends between disinfection connectors 30c and 30d for use during disinfection.

[0061] System 10 further includes PD fluid containers or bags 38a to 38c (e.g., holding the same or different PD fluid formulations), which are respectively connected to the distal ends 24d of reusable PD fluid lines 24a to 24c. System 10d further includes a fourth PD fluid container or bag 38d, which is connected to the distal end 24d of a reusable PD fluid line 24e. The fourth PD fluid container or bag 38d may hold the same or different (e.g., icodextrin) type of PD fluid as provided in the PD fluid containers or bags 38a to 38c. The reusable PD fluid lines 24a to 24c and 24e extend out through an orifice (not shown) defined or provided by the housing 22 of the cycler 20 in one embodiment.

[0062] The system 10 in the illustrated embodiment includes four disinfection connectors 30a - 30d for connecting respectively to the distal ends 24d of reusable PD fluid lines 24a - 24c and 24e during disinfection. The system 10 also provides a patient line connector 32 including a lumen (e.g., a U - shaped lumen) that directs fresh or used dialysis fluid from one PD fluid chamber of the double - lumen reusable patient line 28 to the other PD fluid chamber. Reusable supply lines or tubes 52a1 - 52a4 are in communication with reusable supply lines 24a - 24c and 24e respectively. Reusable supply lines or tubes 52a1 - 52a3 operate with valves 54a - 54c respectively to allow PD fluid from a desired PD fluid container or bag 38a - 38c to be drawn into the cycler 20. In the illustrated example, the three - way valve 94a allows the control unit 100 to select between (i) 2.27% (or other percentage) glucose dialysis fluid from container or bag 38b or 38c and (ii) icodextrin from container or bag 38d. In the illustrated embodiment, the icodextrin from container or bag 38d is connected to the normally - closed port of the three - way valve 94a.

[0063] Figure 1 Also shown, the system 10 includes and uses a disposable filter kit 40 that is in fluid communication with the fresh and used PD fluid chambers of the double - lumen reusable patient line 28. The disposable filter kit 40 includes a disposable connector 42 connected to the distal end 28d of the reusable patient line 28. The disposable filter kit 40 includes a connector 48 connected to the patient delivery kit. The disposable filter kit 40 also includes a sterilizing - grade filter membrane 46 that further filters the fresh PD fluid.

[0064] In one embodiment, the system 10 is configured such that the drain line 52i during filling is fluidly connected downstream of the dialysis fluid pump 70. In this way, if the drain valve 54i fails or leaks in some way during patient fill of patient P, the fresh PD fluid is pushed along the disposable drain line 36 rather than used PD fluid potentially being drawn into the pump 70. In one embodiment, the disposable drain line 36 is removed for disinfection while the drain line connector 34 is capped via a cap 34c.

[0065] System 10 also includes a leak detection pan 82 located at the bottom of the housing 22 of the cycler 20 and a corresponding leak detection sensor 84 output to the control unit 100. In the illustrated example, system 10 is provided with an additional pressure sensor 78c upstream of the dialysate fluid pump 70, which allows the measurement of the suction pressure of the pump 70 to assist the control unit 100 in more accurately determining the pump volume. The additional pressure sensor 78c in the illustrated embodiment is positioned along the discharge line 52e, which may be filled with air or a mixture of air and PD fluid, but should still be at the same negative pressure as the PD fluid within the PD fluid line 52c.

[0066] Figure 1 System 10 in the example of includes redundant pressure sensors 78b1 and 78b2, and the output of one of the redundant pressure sensors 78b1 and 78b2 is used for pump control as discussed herein, while the output of the other pressure sensor is a safety or watchdog output to ensure that the control pressure sensor reads accurately. The pressure sensors 78b1 and 78b2 are positioned along a line including the third recirculation valve 54r3. In yet another example, system 10 may employ one or more four-ways marked with an X via Figure 1 which can (i) reduce the total amount and volume of tubing that can be reused internally, (ii) reduce the number of valves required, and (iii) minimize the portion of the fluid circuit shared by fresh and used PD fluid.

[0067] In Figure 1 System 10 in the example of also includes a source of acid, such as a citric acid container or bag 66. The citric acid container or bag 66 is selectively fluidly connected to the second three-way valve 94b via a citric acid valve 54m positioned along the citric acid line 52m. The citric acid line 52m is connected to the normally closed port of the second three-way valve 94b in one embodiment to provide a redundant valve between the citric acid container or bag 66 and the PD fluid circuit during processing. The redundant valve ensures that no citric acid (or other) acid reaches the treatment fluid line during processing. Alternatively, citric acid (or other) acid is used during disinfection.

[0068] It should be understood that system 10 does not need to (i) be a dialysis system, or (ii) use redundant or durable components that are disinfected between uses in order to employ the sensor thermoelectric heating of the present disclosure. System 10 may alternatively be any type of medical fluid system and may employ a disposable kit having a disposable pumping portion in contact with the corresponding medical fluid. In the main example described herein, the solenoid valve is described as operating with a PD machine or cycler 20.

[0069] Any one or more or all of the valves 54a to 54h, 54m and 54r1 to 54r4, 94a and 94b can be solenoid valves, which can be of a valve type using the following internal fluid path that opens or closes depending on whether the coil is energized. This type of solenoid valve is well-suited for durable or reusable versions of PD machines or cyclers. Another type of solenoid valve for the valves 54a to 54h, 54m and 54r1 to 54r4 operates by releasing or closing a flexible tube depending on whether the coil is energized. This type of solenoid valve is well-suited for versions of PD machines or cyclers that operate with a disposable kit, but can also be used with durable versions of PD machines or cyclers that have an internal flexible tubing for operating with the solenoid valve.

[0070] Now referring to Figure 2 , a suitable two-way solenoid valve 154 for the two-way valves 54a to 54h, 54m and 54r1 to 54r4 is shown. Figure 2 The valve 154 is of a valve type using the following internal fluid path that opens or closes depending on whether the coil is energized. The valve 154 includes two main sections, namely a solenoid section 160 and a valve section 180. The solenoid section 160 includes a solenoid housing 162. The solenoid housing 162 supports a coil 164 that extends around the inner wall 162i of the housing 162 and is energized to move or translate an electromagnet core plunger 166. A compression spring 168 is provided and positioned to bias the plunger 166 to a closed position when energy is removed from the coil 164.

[0071] Figure 2 It is shown that the plunger 166 has a contact end 166e. In addition, a stop 162s is provided on the core 162c of the solenoid housing 162. When the coil 164 is energized, a magnetic field is induced, causing the electromagnet core plunger 166 to translate from right to left within the inner wall 162i of the housing 162 such that the contact end 166e of the plunger 166 abuts against the stop 162s to provide a travel end for the plunger 166 in the valve open position. The abutting contact of the end 166e with the stop 162s causes noise, which can become problematic for PD patients, especially when the patient is trying to sleep. Structures and related methods for helping to reduce the noise caused by the abutting contact of the end 166e with the stop 162s are described herein.

[0072] Figure 2Shows a two-way solenoid valve 154 in a closed or no-fluid-flow state. Here, the coil 164 is de-energized, causing the compression spring 168 to push the contact end 166e of the plunger 166 away from the stopper 162s provided at the core 162c of the solenoid housing 162. The rod end 166l of the plunger 166 translates, causing the rod 170 rotatably held at the rod end 166l of the plunger 166 to tilt, so as to close the fluid path within the valve section 180 of the valve 154.

[0073] The valve section 180 of the valve 154 includes a valve housing 182. The valve housing 182 defines a fluid inlet 184 and a fluid outlet 186. The portion of the rod 170 extending into the valve housing 182 is fitted with a membrane or a plug 188, which can be made of a medically safe compressible (sealable) rubber such as silicone. In Figure 2 the closed position, with the coil 164 de-energized and the compression spring 168 extended, the rod 170 pivots the membrane or the plug 188 so as to contact and seal the interior of the outlet 186 (e.g., the inclined port 186p), thereby preventing fluid flow. When the coil 164 is energized, the plunger 166 moves leftward, thus compressing the spring 168 and pivoting the rod 170 such that the membrane or the plug 188 moves away from the inclined port 186p of the outlet 186 and stops in a substantially vertical position. Here, a fluid such as water or PD fluid can flow from the fluid inlet 184, around the membrane or the plug 188, and through the fluid outlet 186.

[0074] When the valve 154 is closed and the membrane or the plug 188 seals against the inclined port 186p of the fluid outlet 186, the fluid pressure downstream of the outlet 186 is less than the fluid pressure upstream of the fluid inlet 184. The pressure increment helps to seal the membrane or the plug 188 against the inclined port 186p, such that the compression spring 168 does not need to provide the force (or all of the required force) required to hold the membrane or the plug against the inclined port in a sealed state. The main function of the compression spring 168 is to translate the plunger 166 when the coil 164 is de-energized. However, it should be understood that when the valve 154 is to be closed, the pressure increment that helps to seal the membrane or the plug 188 against the inclined port 186p also resists the magnetic force induced when the coil 164 is energized. Structures and associated functions for ensuring that the valve 154 is correctly opened when commanded to open are described herein.

[0075] Now referring to Figure 3 , shows a suitable three-way solenoid valve 194 for three-way valves 94a, 94b. Figure 3Valve 194 is of a valve type that uses the following internal fluid path, which opens or closes depending on whether the coil is energized. Similar to valve 154, valve 194 includes two main sections, namely a solenoid section 200 and a valve section 220. Solenoid section 200 is substantially the same as solenoid section 160 of valve 154. The solenoid section includes a solenoid housing 202 that supports a coil 204, and the coil 204 is energized to move or translate an electromagnet core plunger 206. A compression spring 208 is provided and positioned to bias the plunger 206 to a closed position when energy is removed from the coil 164. The plunger 206 has a contact end 206e that abuts a stop 202s provided at the core 202c of the solenoid housing 202 when the coil 204 is energized. The abutting contact between the end 206e and the stop 202s causes noise, which can become problematic for PD patients, especially when the patient is trying to sleep. Structures and related methods that help reduce the noise caused by the abutting contact between the end 206e and the stop 202s are described herein.

[0076] Figure 3 A three-way solenoid valve 194 in a normally closed state is shown. Here, the coil 204 is not energized, such that the compression spring 208 pushes the contact end 206e of the plunger 206 away from the stop 202s provided at the core 202c of the solenoid housing 202. The rod end 206l of the plunger 206 translates such that a rod 210 rotatably held at the rod end 206l of the plunger 206 is tilted to close the fluid path located within the valve section 220 of valve 194.

[0077] The valve section 220 is where the three-way valve 194 differs from the two-way valve 154. The valve section 220 includes a valve housing 222 that defines a fluid inlet 224, a normally closed fluid outlet 226, and a normally open fluid outlet 228. The portion of the rod 210 that extends into the valve housing 222 is fitted with a membrane or plug 230, which can also be made of a medically safe compressible (sealable) rubber such as silicone. Figure 3In the normally closed position, with the coil 204 de-energized and the compression spring 208 extended, the rod 210 pivots the diaphragm or plug 230 to contact and seal the internal (e.g., beveled) port 226p of the normally closed fluid outlet 226, thereby preventing fluid from flowing through the normally closed outlet. When the coil 204 is energized, the plunger 206 moves to the left to compress the spring 208 and pivot the rod 210 such that the diaphragm or plug 230 moves away from the beveled port 226p of the normally closed fluid outlet 226 and instead contacts and seals the internal (e.g., beveled) port 228p of the normally open fluid outlet 228, thereby preventing fluid from flowing through the normally open outlet. In the normally closed state, the three-way valve 194 allows fluid such as water or PD fluid to flow from the fluid inlet 224 through the normally open fluid outlet 228. In the normally open state, the three-way valve 194 allows fluid such as water or PD fluid to flow from the fluid inlet 224 through the normally closed fluid outlet 228.

[0078] The higher fluid pressure through the fluid inlet 224 helps to seal the diaphragm or plug 230 against both the normally closed port 226p and the normally open port 228p, where the pressure in the normally closed fluid outlet 226 and the normally open fluid outlet 228 is less. However, it should be understood that the pressure increment that helps to seal the diaphragm or plug 230 against the beveled ports 226p, 228p also resists (i) the magnetic force induced when the coil 164 is energized to open the normally closed fluid outlet 226, and (ii) the force of the compression spring 208 when the coil 164 is de-energized to open the normally open fluid outlet 226. Structures and associated functions for ensuring that the normally closed fluid outlet 226 is properly opened when commanded to open are described herein.

[0079] Method of solenoid valve for reducing noise

[0080] As previously discussed, a reliable method for reducing the noise caused by solenoid valves in medical fluid delivery operations is desired and needed. Noise reduction is particularly relevant for peritoneal dialysis systems, which operate close to the patient, and the operation of peritoneal dialysis systems may occur at night when the patient is sleeping, and reducing noise is critical. A desired PD system can be a PD system with a noise level maintained below 33 decibels. Figure 4 An example solenoid valve drive circuit 110 for the systems and associated methods of the present disclosure is shown, which can be used to reduce the operating noise associated with solenoid valves.

[0081] The drive circuit 110 includes a programmable microcontroller 112, which is provided as the control unit 100 ( Figure 1part of (). The microcontroller 112 includes a Pulse Width Modulation ("PWM") channel output 114, which is greater than 20 kHz in one embodiment. The PWM drive waveform is delivered along line 116 to a Metal Oxide Semiconductor Field Effect Transistor ("MOSFET") 120. Although the MOSFET 120 in the illustrated example may be an IRF640 MOSFET, the MOSFET 120 may alternatively be any N-channel logic level gate MOSFET capable of handling greater than 323 mA. The MOSFET 120 operates in conjunction with a diode 130 to power the coil 164 of the two-way valve 154 or the coil 204 of the three-way solenoid valve 194. Although the diode 130 in the illustrated example may be a 1N400X diode, a similar diode may alternatively be used. It is noted that the MOSFET 120 and the diode 130 may be standard and relatively inexpensive components.

[0082] Figure 5 The operation of the solenoid valves 154, 194 without using the drive circuit 110 is shown, where the PWM signal instantaneously transitions from zero percent to one hundred percent to energize the coils 164, 204, and instantaneously transitions from one hundred percent to zero percent to de-energize the coils 164, 204. In both cases, a large clicking sound or noise occurs. Here, in one test, the PWM frequency is greater than 20 kHz, for example 78.1 kHz.

[0083] Figure 6 The operation of the solenoid valves 154, 194 using the drive circuit 110 is shown. The drive circuit 110 is programmed via software to follow a first curved PWM curve 132 from zero percent to one hundred percent and a second curved PWM curve 134 from one hundred percent to zero percent. In both cases, the large clicking sound or noise is eliminated. In the illustrated embodiment, the first curved PWM curve 132 executes 256 steps at 5 milliseconds / step, for a total of 1.28 seconds to fully energize the coils 164, 204. Additionally, in the illustrated embodiment, the second curved PWM curve 134 executes 120 steps at 40 milliseconds / step, for a total of 4.8 seconds to fully de-energize the coils 164, 204. Here, again, the PWM frequency is greater than 20 kHz, for example 78.1 kHz in one test. From Figure 6 It should be understood that the drive circuit 110 does not require position feedback, and both actuation and de-actuation are quiet. Additionally, the solenoid valves 154, 194 open and close as Figure 5 decisively as in without using the drive circuit 110.

[0084] Figure 7 The drive circuit 110 is shown expanded to drive multiple coils 164, 204 of multiple solenoid valves 154, 194.Figure 7 The drive circuit 110 of Figure 7 also includes a programmable microcontroller 112, which is provided as part of the control unit 100 ( Figure 1 ). Figure 7 The drive circuit 110 of Figure 7 includes a plurality (e.g., two) of PWM channel outputs 114. The PWM drive waveforms are delivered from the PWM channel outputs 114 to the shift register 118 along line 116. The shift register 118 includes cascaded flip-flops sharing a single clock signal, which causes the PWM drive waveforms to shift from one MOSFET 120, diode 130, and solenoid valves 154, 194 to the next, e.g., the nth MOSFET 120, diode 130, and solenoid valves 154, 194. Figure 7 It is shown that the drive circuit 110 can include a limited number of PWM channel outputs 114 to drive a plurality of solenoid valves 154, 194, thereby greatly reducing the noise output.

[0085] Determine the position of the solenoid valve

[0086] As previously discussed, a reliable method for verifying the position of the rods 170, 210 within the solenoid valves 154, 194 is desired and needed to ensure that the valves are not stuck or otherwise damaged. Knowing the position of the rods 170, 210 also allows for self-calibration of the above-described noise-reducing PWM drive waveforms, where (i) the fully closed or zero percent PWM position of the rods 170, 210 can be verified by the microcontroller 110 before sending the noise-reducing PWM drive waveform 132 to the solenoid valve, and (ii) the fully open or one hundred percent PWM position of the rods 170, 210 can be verified by the microcontroller 110 before sending the noise-reducing PWM drive waveform 134 to the solenoid valve. To obtain the position of the rods 170, 210 within the solenoid valves 154, 194 respectively, a resistor 136 (e.g., a 0.1 ohm resistor) is placed between the MOSFET 120 and ground 138. Additionally, for each valve 154, 194, a position detection line 142 extends from a point between the MOSFET 120 and the resistor 136 to the analog multiplexer 140. The multiplexer 140 selects between a plurality of analog signals traveling along the position detection line 142 for output to a single output line 144 extending from the multiplexer 140. The multiplexer 140 enables a plurality of valves 154, 194 to share a single comparator 150.

[0087] Comparator 150 is configured to compare an analog position detection signal from one of solenoid valves 154, 194 and traveling along position detection line 142 with threshold signal 152. The comparison performed by comparator 150 results in an output indicating the position of rods 170, 210 within solenoid valves 154, 194, which is delivered along comparator output line 146 to a general purpose input / output (GPIO) port 148 of programmable microcontroller 110. The programmable microcontroller 110 uses programmed software to analyze the comparator output so as to know / verify the positions of rods 170, 210 within solenoid valves 154, 194 by sampling each valve via multiplexer 140.

[0088] Figure 8 is an electrical schematic diagram of a drive circuit 110 for determining the position of a valve stem in a given solenoid valve according to an exemplary embodiment of the present disclosure. As Figure 8 shown, drive circuit 110 includes an electromagnetic inductor coil 802 for driving the valve. Current for driving electromagnetic inductor coil 802 can be provided via a voltage source 804 (e.g., 24 V (volts)). Sense resistor 806 can be used to measure current 820 driving electromagnetic inductor coil 802 (e.g., by dividing the voltage by the resistance of sense resistor 806). For example, current 820 through sense resistor 806 can be substantially the same as the current through electromagnetic coil inductor 802 (e.g., to trigger the solenoid valve). Thus, if the voltage across sense resistor 806 is to be measured, the voltage will be proportional to current 820. In Figure 8 the example drive circuit 110 shown, sense resistor 806 exhibits a resistance of 0.1 ohm.

[0089] Current 820 for driving the electromagnetic coil can pass through transistor 808 (e.g., MOSFET (IRF640)) under the command of a microcontroller (e.g., microcontroller 112). For example, a pulse width modulation (PWM) waveform can be generated by associated PWM hardware in the microcontroller. The PWM waveform can drive the gate 810 of transistor 808. Sense resistor 806 can be used to measure current 820 entering electromagnetic coil valve 802. In some embodiments, current 820 can be filtered using an RC filter 816 (e.g., a low pass filter) including, for example, a capacitor and a resistor. Current 820 can enter comparator 812. Comparator 812 is configured to compare the voltage associated with current 820 described above with a threshold voltage supplied by threshold voltage source 814. For example, as Figure 8As shown, the threshold voltage can be 0.7 volts. When the current 820 associated with the voltage through the electromagnetic coil transistor 802 is higher than the threshold voltage 814, the comparator 812 is configured to generate a digital output (e.g., a "high" or "1" signal), which is sent to a microcontroller (e.g., microcontroller 112) via the GPIO line 818. The voltage associated with the current 820 can be used to generate waveforms discussed herein, for example, with respect to subsequent figures. In some embodiments, the threshold voltage can be configured to suit the voltage range of the expected current 820, which can depend on the resistance value of the sense resistor 806 placed in the drive circuit 110.

[0090] Figure 9 is a graphical output from the valve stem 170, 210 position test configuration according to an exemplary embodiment of the present disclosure, which shows the position of the inductor-based valve. Specifically, Figure 9 shows two curves: the top curve 900a, which shows the variation of the voltage 902 with respect to the time 904 shown on the x-axis, based on the current 820 sensed in the drive circuit 110 (e.g., based on the resistance of the sensor resistor 806); and the bottom curve 900b, which shows the digital output of the comparator 812 over the same time range. It is contemplated that the position of the plunger (e.g., a metal block) within the electromagnetic coil, which indicates the position of the valve, reflects the inductance of the electromagnetic coil. Thus, by measuring the inductance of the electromagnetic coil, the extent of the plunger within the electromagnetic coil can be determined (e.g., whether the plunger is fully inside, fully outside, or somewhere in between). For example, a plunger that is fully inside the electromagnetic coil can produce a higher inductance than when the plunger is outside or not fully inside. When the valve is open (e.g., and not actuated), there may be less plunger within the magnetic field induced by the electromagnetic coil (since the plunger may be partially outside the electromagnetic coil), resulting in a lower inductance. However, due to the lower inductance, the magnetic field can accumulate faster, causing the current flowing through the electromagnetic coil to change faster over time. Since the current is related to the voltage (e.g., based on the sense resistor 806), the voltage changes faster over time, causing the voltage to reach a given threshold voltage (e.g., 30 millivolts) relatively faster in time. Conversely, when the solenoid valve is closed, there can be more plunger within the electromagnetic coil and thus more plunger within the magnetic field induced by the electromagnetic coil. This presence may increase the inductance, causing the current to change more slowly. Since the current is related to the voltage (e.g., based on the sense resistor 806), the voltage changes more slowly over time, causing the voltage to reach a given threshold voltage (e.g., 30 millivolts) relatively more slowly in time.

[0091] As shown in graph 900a, curve 910 represents the voltage over time in the scenario where the valve is open (e.g., and not actuated), while curve 912 represents the voltage over time in the scenario where the valve is closed. As described above, curve 910 shows that when the valve is open, the associated voltage reaches a given threshold voltage of 30 millivolts much faster at time 906 than curve 912 reaches the same threshold voltage at time 908. Thus, this difference is the result of a difference in the position of the plunger within the electromagnetic coil, which results in different inductance levels, and these different inductance levels result in a difference in the time it takes for the electromagnetic coil to reach the threshold voltage. Therefore, the difference between times 906 and 908 can reflect the change in inductance. For the Figure 9 specific valve associated with the graphical results shown, when the valve is open (e.g., when the plunger is not fully within the magnetic field of the electromagnetic coil), the inductance of the valve is 113 mH (millihenries). However, when the valve is closed (e.g., the plunger is further pulled into the electromagnetic coil), the inductance of the valve is 128 millihenries. Thus, the difference between times 906 and 908 can correspond to the difference between these inductances (113 millihenries and 128 millihenries). By precisely measuring the time, it is possible to distinguish between an open valve and a closed valve.

[0092] As shown in graph 900b, the digital output of the comparator of the drive circuit 110 associated with the valve described above shows curves 914 and 916 corresponding to curves 910 and 912 respectively. Curve 914, which represents the digital output of the comparator for the open valve in graph 900b, shows that when the voltage associated with the open electromagnetic coil exceeds the voltage threshold, the comparator generates a high signal (e.g., a true or "1" signal). When the voltage associated with the open electromagnetic coil exceeds the voltage threshold, curve 916, which represents the digital output of the comparator for the closed valve in graph 900b, generates a low signal (e.g., a false or "0" signal). However, due to the difference in inductance associated with the open valve and the closed valve (e.g., 113 millihenries vs. 128 millihenries respectively), which conversely results in a difference in the time it takes for the applied voltage to reach the voltage threshold, there is a difference in the time at which the digital output of the comparator shifts its signal for the corresponding curves (e.g., as shown in graph 900b).

[0093] Figure 10 is data output from a valve stem 170, 210 position test configuration according to a non - limiting embodiment of the present disclosure, which shows the position of the plunger within the valve over time. For example, Figure 10 graph 1002 shows a data output indicating the position of the plunger after the valve is conventionally opened or conventionally closed, and Figure 10Graph 1004 shows the data output indicating the position of the plunger after the valve has been opened or closed using the previously discussed system and method to reduce noise. In these graphs 1002 and 1004, the vertical axis represents time and the horizontal axis represents the position of the plunger (e.g., from 0 mm (millimeters) to 1.8 millimeters). The graphs show at high resolution that the plunger can move a distance of 1.8 millimeters to actuate the valve. Each row is a sampling point at a given time and the displacement is represented by a digital number. As Figure 10 shown in the graph, the systems and methods presented herein can allow for determining the position of the valve (e.g., via the position of the plunger in the valve) at high resolution (e.g., better than one-hundredth of a millimeter).

[0094] Figure 11 shows various waveforms from the valve stem 170, 210 position tests according to non-limiting embodiments of the present disclosure, which show the measured voltage over time to determine the position of the valve when the valve is open and when the valve is closed. For example, graphs 1102 and 1104 present the voltage measured at the intersection of the drive circuit 110 (e.g., Figure 8 the current 820), which is coupled to the voltage 810 provided to the gate of the transistor 808 (e.g., gate drive). Graph 1102 shows the measured voltage over time to determine the actual position of the valve when the valve is reported to be in the open state, and graph 1104 shows the measured voltage over time to determine the actual position of the valve when the valve is reported to be in the closed state. Additionally, graph 1106 superimposes graph 1104 with a reference waveform 1108, where graph 1104 depicts the actual measured voltage over time of the valve reported to be in the closed state and the reference waveform 1108 is the reference voltage over time of the valve actually in the closed state. Graph 1110 superimposes the reference waveform of the reference voltage over time of the valve actually in the open state with the reference waveform 1108 of the reference voltage over time of the valve actually in the closed state. For each of these graphs, the measured voltage can be based on the sense resistor 806 used in the drive circuit 110. In some aspects, the waveforms can be measured or output by a processor or microprocessor (e.g., at the microcontroller 112).

[0095] The time difference between edge 1112 and edge 1114 (e.g., the time difference to reach a threshold voltage) respectively indicates valve opening or valve closing. As previously described, when the valve is open (e.g., when the plunger is partially outside the magnetic field of the electromagnetic coil associated with the valve), the inductance of the electromagnetic coil can be at its lowest point, thus causing the current level of the current entering the valve to rise more quickly until it reaches the threshold voltage. Since the current is proportional to the measured voltage (e.g., based on the sense resistor 806), the waveform of the open valve shows a faster rise of the measured voltage to the threshold voltage. This faster rise is shown, for example, in graph 1102 and edge 1112. When the valve is closed, the plunger can be further within the magnetic field of the electromagnetic coil, causing the current to rise more slowly. Thus, as shown in graphs 1104 and 1106, the measured voltage (e.g., across the sense resistor 806) may take longer to reach the same threshold voltage.

[0096] For the valve for which the actual state (e.g., open or closed) or the position of the plunger has not been determined or confirmed, the voltage can be measured similarly (e.g., using the sense resistor 806 as used in the drive circuit 110). The microcontroller 112 can search for transitions of the measured voltage in the waveform of the measured voltage (e.g., as in edges 1112 and 1114). Such a transition can be the point at which the measured voltage reaches the threshold voltage. The microcontroller 112 can determine the time it takes for the valve to reach this transition (e.g., the threshold voltage). The position of the plunger within the valve and thus the state of the valve can be determined by identifying whether the time to reach the transition is closer to the time it takes to reach edge 1114 (e.g., in this case, the valve can be closer to the closed state) or closer to the time it takes to reach edge 1112 (e.g., in this case, the valve can be closer to the open state). Thus, based on the time it takes for the valve to reach the threshold voltage and comparing this time with the known times to reach the threshold voltage in the closed and open states, the exact point of the plunger can be determined. For example, if the time it takes for the measured voltage in the valve to reach the threshold voltage is midway between the times to reach edges 1112 and 1114, the position of the plunger within the valve is midway between fully inside and fully outside, causing the valve to be neither open nor closed (i.e., the valve is stuck). In some embodiments, the microcontroller 112 can perform image processing on the measured voltage of the valve to obtain a clearer waveform for better identification of the transition point (e.g., the time it takes for the measured voltage to reach the threshold voltage).

[0097] The microcontroller 112 is configured to provide information indicating whether the valve is in the commanded position. In some embodiments, the microcontroller 112 may generate an alert (e.g., via the user interface 108) after detecting that the valve is not in the commanded position. Additionally or alternatively, the microcontroller 112 may pause the dialysis treatment. In some cases, the microcontroller 112 may attempt to re-actuate the valve multiple times to move the valve to the commanded position. When the valve position is still incorrect, the microcontroller 112 may then generate an alert.

[0098] Figure 12 Shown is an average waveform from multiple valve stem 170, 210 position tests performed on the valve, which shows a characteristic transition point 1202 of the valve. The transition point 1202 may indicate the average time at which the average measured voltage from the valve reaches a threshold voltage. As Figure 12 shown, averaging the multiple waveforms results in a very noisy average waveform. For example, the individual pulses of the various duty cycles in the average waveform may not be distinguishable. Even so, the transition point 1202 can be readily identified and can be used to determine the valve position with high resolution (e.g., at least better than 0.01 mm resolution). Additionally, the various duty cycles can determine how much total power goes to the valve to generate the waveform of the measured voltage.

[0099] As will be discussed herein with respect to subsequent figures, measuring the position of the valve when the valve is not actuated (e.g., when the valve is not powered) may involve different preprocessing steps than when the valve is actuated, because the electromagnetic coil associated with the valve may saturate and this saturation may affect the waveform of the measured voltage.

[0100] Figure 13 and Figure 14 Shown is valve stem 170, 210 position test data recorded after the gate drive has been desaturated, according to a non-limiting embodiment of the present disclosure. In some embodiments, in order to effectively evaluate the waveform output of the measured voltage of the valve, the microcontroller 112 may need to temporarily turn off the pulse width modulation (PWM), such that the power supplied to the drive circuit 110 drops to zero and remains at zero for a predetermined period of time (e.g., 5 milliseconds). Movement of the plunger associated with the valve to anywhere during this predetermined period can be prevented (e.g., due to the mass of the plunger) or the plunger associated with the valve can be prevented from moving to anywhere during this predetermined period. Additionally, the microcontroller 112 may turn off the power during this predetermined period in order to desaturate the electromagnetic coil associated with the valve. The predetermined period can be long enough for the electromagnetic coil to make a useful measurement during the measurement interval by minimizing the noise caused by saturation, but not long enough to release the valve or cause the valve to flutter. After the predetermined period has elapsed, the microcontroller 112 may re-power the valve (e.g., by causing current to flow to the gate of the transistor 808).

[0101] Therefore, as Figure 13 shown, when measuring the state of a given valve and the position of a plunger associated with the valve, the microcontroller 112 can cause the power applied by the gate drive 1302 to change from its previous phase 1304 to zero, where power may have been applied to drive the valve via pulse width modulation. The exact power previously applied to the valve can vary, resulting in different waveforms in phase 1304, as will be discussed with respect to Figure 14 . Subsequently, the gate drive can reduce the power to the valve and / or apply zero power to the valve during a desaturation phase 1306 that lasts for a predetermined period of time (e.g., 5 milliseconds). After the predetermined period of time has elapsed, the valve can be ready (e.g., desaturated) for its voltage to be measured (e.g., over a measurement interval 1308). A corresponding waveform 1310 of the measured voltage including a transition point 1312 is also shown. Thus, the measurement interval 1308 can be the time it takes for the measured voltage of the valve to reach the transition point 1312 (i.e., the threshold voltage).

[0102] Figure 14 Test data of the positions of valve stems 170, 210 are shown after the gate drive has desaturated, where the valve was previously applied with different levels of power. For example, graph 1402 shows the waveform generated when the microcontroller 112 applies PWM at 1%, graph 1404 shows the waveform generated when the microcontroller 112 applies PWM at 50%, and graph 1406 shows the waveform generated when the microcontroller 112 applies PWM at 99%. The yellow traces in graphs 1402 - 1406 and Figure 13 are the measured voltages across the valve (e.g., based on the measured voltage across the sense resistor 806) and can thus indicate the current flowing through the valve. For each previously existing PWM level (e.g., graphs 1402 - 1406), during the corresponding desaturation phase (e.g., desaturation phase 1306), the applied current goes to 0 amperes and then rises during the corresponding measurement interval (e.g., measurement interval 1308).

[0103] When the rising current causes the voltage applied across the valve to reach the threshold voltage, comparator 812 can provide a signal to indicate the transition point (i.e., the point at which the measured voltage reaches the threshold voltage). The microcontroller 112 can thus measure the time it takes for the voltage to reach the voltage threshold by determining when comparator 812 sends the signal after the start of measurement interval 1308. For example, once the valve reaches the transition point, comparator 812 can send a low-to-high digital signal to microcontroller 112 via IO line 818, and microcontroller 112 can detect the low-to-high signal and can end the timer in response to the detection to mark the time that occurred during the measurement interval. Microcontroller 112 can thereafter resume driving the valve at whatever PWM duty cycle it was set to prior (e.g., in previous phase 1304).

[0104] Figure 15 and Figure 16 illustrates recorded valve stem 170, 210 position test data, showing valve stem 170, 120 in a jammed closed position, valve stem 170, 120 functioning normally, and the valve stem in a jammed open position. Specifically, Figure 15 illustrates the three above-described position test data for a valve commanded to change from an open state to a closed state, but only one of the three position test data (i.e., position test data 1504) shows the valve actually actuating normally in response to the command. Similarly, Figure 16 illustrates the three above-described position test data for a valve commanded to change from a closed state to an open state, but only one of the three position test data (i.e., position test data 1604) shows the valve actually actuating normally in response to the command. This position test data is based on inductance measurements of the valve when it is commanded to actuate.

[0105] As Figure 15 and Figure 16 shown, due to saturation in the electromagnetic coils associated with the valve, each of the position test data 1502 - 1506, 1602 - 1606 slopes downward. It should be understood that if the valve is not actuated at all, this position test data 1502 - 1506, 1602 - 1606 could be largely horizontal (e.g., having little to no slope). However, since when the valve is commanded to actuate (e.g., from an open state to a closed state in Figure 15 and from a closed state to an open state in Figure 16receives position test data as it transitions from the closed state to the open state), the electromagnetic coil associated with the valve begins to saturate, causing the downward slopes in position test data 1502 - 1506, 1602 - 1606. As previously discussed, the microcontroller 112 can mitigate the noise caused by saturation during measurement interval 1308 by going through a desaturation phase 1306, during which the power applied to the valve is set to zero for a predetermined period of time. However, even with the downward slopes caused by saturation, Figure 15 and Figure 16 it is also very clear when the valve is operating normally (e.g., position test data 1504 and 1604), as opposed to being stuck open (e.g., position test data 1502 and 1602) or stuck closed (e.g., position test data 1506 and 1606). Additionally, when the valve is operating normally in both scenarios, Figure 15 shows the actual transition 1508 of the valve from the open state to the closed state, and Figure 16 shows the actual transition 1508 of the valve from the closed state to the open state. However, in Figure 15 tracking the position test data from left to right as the valve is commanded to close, and in Figure 16 tracking the position test data from right to left as the valve is commanded to open. Thus, depending on whether the valve is commanded to open (e.g., Figure 15 ), or commanded to close (e.g., Figure 16 ), the corresponding transition points 1508 and 1608 can occur at different locations and / or times. Additionally, the corresponding transition points 1508 and 1608 can vary based on specific characteristics of the valve (e.g., manufacturing batch), or can change over time as the valve wears.

[0106] Thus, in some embodiments, a generic waveform can be used to compare the measured voltage of the valve (e.g., based on sense resistor 806) to a generic threshold voltage. The generic waveform can be customized such that the transition points of the measured voltage from the valve asymptotically align with the threshold voltage.

[0107] It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Accordingly, these changes and modifications are intended to be covered by the appended claims. For example, while MOSFETs and NPN transistors are described as the transistors used to assist in noise reduction during solenoid valve actuation and de-actuation, other transistors can similarly be used to slow down the plunger in the solenoid valve and thus similarly reduce noise. In another example, while different valve embodiments have been discussed primarily in connection with peritoneal dialysis (“PD”), the valve embodiments can be used with other medical fluid systems and associated machines, such as machines for hemodialysis (“HD”), hemofiltration (“HF”), hemodiafiltration (“HDF”), and continuous renal replacement therapy (“CRRT”).

Claims

1. A medical fluid system, comprising: a valve configured to control fluid flow in the medical fluid system, wherein the valve includes a housing, an electromagnetic coil, and a plunger, and wherein the valve is configured to enable fluid flow through a tube by applying a voltage to the electromagnetic coil to move the plunger within the housing; a drive circuit configured to control the valve of the medical fluid system via a pulse width modulation (PWM) signal in response to a control signal; and a microcontroller including a processor and a memory, wherein the memory stores instructions that, when executed by the processor, cause the processor to: transmit a control signal to the drive circuit, the control signal causing the drive circuit to apply a PWM signal to the electromagnetic coil of the valve and cause the PWM signal to ramp up, wherein the ramping up of the PWM signal causes the plunger to move slowly until the plunger reaches an end position within the housing, and wherein the slow movement of the plunger reduces the sound generated by the plunger.

2. The medical fluid system according to claim 1, wherein, The instructions, when executed by the processor, further cause the processor to: apply power to the valve via the drive circuit to measure the voltage across the valve; monitor the voltage across the valve via the drive circuit based on a sense resistor associated with the valve during a measurement interval, wherein the measurement interval terminates when the voltage reaches a predetermined threshold voltage; compare the measurement interval with a reference interval of a normally operating closed valve; and generate an assessment of the valve position based on the comparison of the measurement interval with the reference interval.

3. The medical fluid system according to claim 1 or 2, wherein, The valve is further configured to close the flow of medical fluid through the tube by removing the applied voltage to the electromagnetic coil via the drive circuit to move the plunger in a direction opposite the housing to block the tube, wherein the instructions, when executed by the processor, further cause the processor to: transmit a second control signal to the drive circuit, the second control signal causing the drive circuit to ramp down the PWM signal to the valve to a duty cycle of 0%, wherein the ramping down of the PWM signal causes the plunger to move in the opposite direction and in a manner that reduces the sound generated by the corresponding plunger compared to an operation without the PWM signal.

4. The medical fluid system according to claim 3, wherein, The instructions, when executed by the processor, further cause the processor to: apply a second power to the valve via the drive circuit to measure a second voltage across the valve; monitor the second voltage across the valve via the drive circuit based on the sense resistor associated with the valve during a second measurement interval, wherein the second measurement interval terminates when the second voltage reaches the predetermined threshold voltage; compare the second measurement interval with a second reference interval of a normally operating open valve; and generate a second assessment of the valve position based on the comparison of the second measurement interval with the second reference interval.

5. The medical fluid system according to claim 1, wherein, The valve, the drive circuit, and the microcontroller are included in a peritoneal dialysis machine or a hemodialysis machine.

6. A method for determining a valve position in a medical fluid system, the method comprising: Transmitting, by a microcontroller having a processor, a control signal for closing a valve, wherein the valve is configured to control a fluid flow in the medical fluid system, wherein the valve is open at least before transmitting the control signal, and wherein the valve includes a housing, an electromagnetic coil, and a plunger; Applying power to the valve via a drive circuit to measure a voltage across the valve; Monitoring, via the drive circuit, the voltage across the valve based on a sense resistor associated with the valve during a measurement interval, wherein the measurement interval terminates when the voltage reaches a predetermined threshold voltage; Comparing the measurement interval with a reference interval of a normally operating closed valve; and Generating, based on the comparison, information indicating whether the valve is closed.

7. The method according to claim 6, further comprising, before applying power to the valve, Setting a power level to zero and maintaining it for a predetermined period of time to desaturate the electromagnetic coil during the predetermined period of time.

8. The method according to claim 7, wherein The predetermined period of time is 5 milliseconds (ms).

9. The method according to claim 6, wherein Monitoring the voltage across the valve includes: Receiving, from a comparator connected to the drive circuit, an indication of when the voltage reaches the predetermined threshold voltage.

10. The method according to claim 6, further comprising: Transmitting, by the microcontroller, a second control signal for opening the valve; Applying a second power to the valve via the drive circuit to measure a second voltage across the valve; Monitoring, via the drive circuit, the second voltage across the valve based on the sense resistor during a second measurement interval, wherein the second measurement interval terminates when the second voltage reaches a second predetermined threshold voltage; Comparing the second measurement interval with a second reference interval of a normally operating open valve; And Generating, based on a comparison between the second measurement interval and the second reference interval, second information indicating whether the valve is open.

11. A medical fluid system, comprising: A valve configured to control a fluid flow in the medical fluid system, wherein the valve includes a housing, an electromagnetic coil, and a plunger, and wherein the valve is configured to enable fluid flow by applying a voltage to the electromagnetic coil to move the plunger within the housing; A drive circuit configured to control the valve of the medical fluid system via a pulse width modulation (PWM) signal in response to a control signal; and A microcontroller including a processor and a memory, wherein the memory stores instructions that, when executed by the processor, cause the processor to: Transmit a control signal for closing the valve, wherein the valve is open at least before transmitting the control signal, Apply power to the valve via the drive circuit to measure a voltage across the valve, Monitor, via the drive circuit, the voltage across the valve based on a sense resistor associated with the valve during a measurement interval, wherein the measurement interval terminates when the voltage reaches a predetermined threshold voltage, Compare the measurement interval with a reference interval of a normally operating closed valve, and Generate information indicating whether the valve is closed based on the comparison.

12. The medical fluid system according to claim 11, wherein, When executed by the processor, the instruction further causes the processor to: Before applying power to the valve, set the power level to zero and continue for a predetermined period of time to desaturate the electromagnetic coil within the predetermined period of time.

13. The medical fluid system according to claim 12, wherein, The predetermined period of time is 5 milliseconds (ms).

14. The medical fluid system according to claim 11, wherein, Monitoring the voltage across the valve includes receiving an indication from a comparator connected to the drive circuit of when the voltage reaches the predetermined threshold voltage.

15. The medical fluid system according to claim 11, wherein, When executed by the processor, the instruction further causes the processor to: Transmit a second control signal for opening the valve; Apply a second power to the valve via the drive circuit to measure a second voltage across the valve; Monitor the second voltage across the valve via the drive circuit based on the sense resistor within a second measurement interval, wherein the second measurement interval terminates when the second voltage reaches a second predetermined threshold voltage; Compare the second measurement interval with a second reference interval of a normally operating open valve; and And Generate second information indicating whether the valve is open based on the comparison between the second measurement interval and the second reference interval.

16. The medical fluid system according to claim 11, wherein, The valve, the drive circuit, and the microcontroller are included in a peritoneal dialysis machine or a hemodialysis machine.

17. A method for controlling a valve, the method comprising: Transmit, by a microcontroller having a processor, a control signal for causing a drive circuit to apply a PWM signal to an electromagnetic coil of a valve and cause the PWM signal to ramp up, wherein the valve is configured to enable fluid flow by applying a voltage to the electromagnetic coil to move a plunger within a housing, wherein the ramp up of the PWM signal causes the plunger to move slowly until the plunger reaches an end position within the housing, and wherein the slow movement of the plunger reduces the sound generated by the plunger.

18. The method according to claim 17, further comprising: Apply power to the valve via the drive circuit to measure the voltage across the valve; Monitor the voltage across the valve via the drive circuit based on a sense resistor associated with the valve within a measurement interval, wherein the measurement interval terminates when the voltage reaches a predetermined threshold voltage; Compare the measurement interval with a reference interval of a normally operating closed valve; and Generate an assessment of the valve position based on the comparison between the measurement interval and the reference interval.

19. The method according to claim 17 or 18, wherein, The valve is further configured to block the flow of medical fluid by removing the application of the voltage to the electromagnetic coil via the drive circuit to move the plunger in a direction opposite to the housing, and the method further comprises: Transmit, by the microcontroller, a second control signal to the drive circuit, the second control signal causing the drive circuit to ramp down the PWM signal to the electromagnetic coil to a duty cycle of 0%, wherein the ramp down of the PWM signal causes the plunger to move in the opposite direction and in a manner that reduces the sound generated by the corresponding plunger compared to the operation without the PWM signal.

20. The method according to claim 19, further comprising: applying a second electric power to the valve via the drive circuit to measure a second voltage across the valve; monitoring, via the drive circuit, the second voltage across the valve within a second measurement interval based on a sense resistor associated with the valve, wherein the second measurement interval terminates when the second voltage reaches the predetermined threshold voltage; comparing the second measurement interval with a second reference interval of a normally operating open valve; and generating a second evaluation of the valve position based on the comparison between the second measurement interval and the second reference interval.

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