Method and system for providing control stability in a vacuum generation system using an override proportional-integral-derivative (PID) controller

Abstract

Certain embodiments provide a vacuum generation system including an override PID controller, a proportional valve, and a vacuum generator. The override PID controller allows the vacuum generation system to control the operating range of the supply air pressure supplied to the vacuum generator. By controlling the operating range of the supply air pressure, the vacuum generation system can avoid entering a decreasing or non-monotonic region of the vacuum generator.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 077,757, entitled "METHODS AND SYSTEMS FOR PROVIDING CONTROL STABILITY IN A VACUUM GENERATION SYSTEM USING AN OVERRIDE PROPORTIONAL-INTEGRAL-DERIVATIVE (PID) CONTROLLER," filed September 14, 2020, inventor Brian T. Chiem, which is incorporated herein by reference in its entirety as if fully and completely set forth herein.

[0002] The present disclosure generally relates to methods and systems for providing control stability in vacuum generation systems using an override proportional-integral-derivative (PID) controller. [Background technology]

[0003] During small incision surgery, particularly ophthalmic surgery, small probes are inserted into the surgical site to cut, remove, or otherwise manipulate tissue. During these surgical procedures, fluids and tissue may be aspirated from the surgical site.

[0004] Examples of ophthalmic procedures in which fluids and tissues are aspirated include vitreoretinal procedures. Vitreoretinal procedures can include a variety of surgical procedures performed to restore, maintain, and improve vision. Vitreoretinal procedures can be appropriate for treating many serious conditions in the posterior segment of the eye. Vitreoretinal procedures can treat conditions such as age-related macular degeneration (AMD), diabetic retinopathy and diabetic vitreous hemorrhage, macular hole, retinal detachment, epiretinal membrane, CMV retinitis, and many other eye diseases. To treat certain conditions in the posterior segment of the eye, surgeons may first perform a vitrectomy as part of a vitreoretinal procedure. Vitreous removal refers to the surgical removal of the vitreous, a normally clear, gel-like substance that fills the center of the eye. The vitreous may make up approximately two-thirds of the eye's volume and is formed and shaped before birth.

[0005] Removal of the vitreous may involve a vitrector (also called a "cutter" or "vitreous cutter"). In some instances, the vitrector may be powered by a pneumatic vitrector (e.g., a surgical console) that includes one or more pneumatic valves (also called drive valves). In such instances, the vitrector operates like a small guillotine and can remove the vitreous gel in a controlled manner using a vibrating microcutter. In some other instances, the vitrector can cut the vitreous using some other technique, such as laser light or ultrasound. In addition to cutting the vitreous, the cutter may also be configured to aspirate the surgically cut vitreous. Suction may be provided by a vacuum generator (e.g., a Venturi vacuum) coupled to the cutter through a tube that provides an aspiration channel.

[0006] Other examples of ophthalmic procedures in which fluids and tissues are aspirated include phacoemulsification, which refers to cataract surgery in which a diseased lens is emulsified and aspirated out of the lens capsule. In some examples, a phacoemulsification probe can break up the lens with ultrasound (or other techniques such as laser light). To aspirate the broken down lens, the phacoemulsification probe can be powered by a vacuum generator (e.g., a Venturi vacuum) that is coupled to the phacoemulsification probe through a tube that provides an aspiration channel.

[0007] Certain existing vacuum generators, such as certain existing Venturi vacuum generators, operate using compressed air passing through an orifice to generate a vacuum. However, a common characteristic of these vacuum generators is that above a certain supply pressure, the vacuum generator becomes less efficient and generates less vacuum as the supply pressure increases. For example, in the range of 0 to 60 psig (pounds per square inch gauge), the vacuum pressure increases as the supply air pressure increases. However, the vacuum pressure begins to decrease as the supply air pressure increases within the range of 60 to 87 psig. More specifically, as the supply air pressure approaches, for example, 60 psig or above, the vacuum pressure begins to decrease, thereby causing instability in the drive of a standard PID controller used to regulate the supply air pressure. In such an example, when the supply air pressure is in the range of 0 to 60 psig, the vacuum generator may be said to be operating in a monotonic region. On the other hand, when the supply air pressure is above, for example, 60 psig, the vacuum generator may be said to be operating in a non-monotonic or decreasing region. Although 60 psig is used in the above example, it should be understood that other supply air pressure values ​​are also contemplated. Summary of the Invention [Means for solving the problem]

[0008] The present disclosure generally relates to methods and systems for providing control stability in vacuum generation systems using an override proportional-integral-derivative (PID) controller.

[0009] Certain embodiments provide a method for controlling vacuum pressure in a vacuum generation system. The method includes receiving a vacuum pressure sensor reading from a vacuum pressure sensor. The method further includes calculating a first error between the vacuum pressure sensor reading and a vacuum pressure setpoint. The method further includes calculating a first voltage level for controlling a proportional valve based on the first error. The method further includes receiving a supply air pressure sensor reading from a supply air pressure sensor. The method further includes calculating a second error between the supply air pressure sensor reading and the supply air pressure setpoint. The method further includes calculating a second voltage level for controlling the proportional valve based on the second error. The method further includes determining a lower voltage level of the first and second voltage levels. The method further includes providing the lower voltage level to the proportional valve. The method further includes causing a vacuum generator to provide supply air pressure based on the lower voltage level using the proportional valve. The method further includes providing vacuum pressure to a surgical tool based on the supply air pressure using the vacuum generator.

[0010] Certain embodiments provide a vacuum generation system. The vacuum generation system includes a first proportional-integral-derivative (PID) controller configured to receive a first error between a vacuum pressure sensor reading associated with a vacuum generator and a vacuum pressure set point and calculate a first voltage level for controlling a proportional valve based on the first error. The vacuum generation system further includes a second PID controller configured to receive a second error between a supply air pressure sensor reading and the supply air pressure set point and calculate a second voltage level based on the second error. The vacuum generation system further includes determining a lower voltage level of the first and second voltage levels. The vacuum generation system further includes a proportional valve configured to receive the lower voltage level and cause the vacuum generator to provide a supply air pressure based on the voltage level. The vacuum generation system further includes a vacuum generator configured to provide vacuum pressure to a surgical tool based on the supply air pressure.

[0011] Certain embodiments provide a vacuum generation system comprising: a memory containing executable instructions; and a processor in data communication with the memory and configured to execute the instructions, the processor configured to: receive a first error between a vacuum pressure sensor reading associated with a vacuum generator and a vacuum pressure setpoint, calculate a first voltage level based on the first error, receive a second error between a supply air pressure sensor reading and the supply air pressure setpoint, calculate a second voltage level based on the second error, determine a lower voltage level of the first and second voltage levels, and supply the lower voltage level to a proportional valve. The vacuum generation system further comprises a proportional valve configured to cause the vacuum generator to provide a supply air pressure based on the lower voltage level. The vacuum generation system further comprises a vacuum generator configured to provide a vacuum pressure to a surgical tool based on the supply air pressure.

[0012] The following description and the associated drawings set forth in detail certain illustrative features of the one or more embodiments.

[0013] The accompanying drawings depict only examples of particular embodiments of the present disclosure and therefore should not be considered as limiting the scope of the present disclosure. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 illustrates an exemplary surgical console, in accordance with certain embodiments. [Figure 2] FIG. 2 illustrates an exemplary vitrectomy probe, according to certain embodiments. [Figure 3] FIG. 3 is a side view of the vitrectomy probe of FIG. 2, in accordance with certain embodiments. [Figure 4] FIG. 4 illustrates an exemplary cutting mechanism of the vitrectomy probe of FIG. 2, according to certain embodiments. [Figure 5] FIG. 5 illustrates an exemplary phacoemulsification probe, in accordance with certain embodiments. [Figure 6]FIG. 6 is a diagram illustrating a prior art vacuum generation system, according to certain embodiments. [Figure 7] FIG. 7 is a vacuum generation performance graph associated with the prior art vacuum generation system of FIG. 6, in accordance with certain embodiments. [Figure 8] FIG. 8 is a schematic diagram of an exemplary vacuum generation system having an override PID controller, in accordance with certain embodiments. [Figure 9] FIG. 9 is a schematic diagram of an exemplary vacuum generation system having an override PID controller, in accordance with certain embodiments. [Figure 10] FIG. 10 is a diagram illustrating an exemplary operation of the vacuum generation system of FIG. 8, in accordance with certain embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0015] To facilitate understanding, identical reference numerals have been used, whenever possible, to designate identical elements common to the figures, and it is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further description.

[0016] Although features of the present disclosure may be discussed with respect to certain embodiments and figures below, all embodiments of the present disclosure may include one or more of the advantageous features discussed herein. In other words, although one or more embodiments may be discussed as having certain advantageous features, one or more of such features may also be used in accordance with various other embodiments discussed herein. Similarly, although exemplary embodiments may be discussed below as device, apparatus, or method embodiments, it should be understood that such exemplary embodiments may be implemented in a variety of devices, apparatus, and methods.

[0017] FIG. 1 illustrates an exemplary surgical console 101, according to certain embodiments. The surgical console 101 may be configured to drive one or more tools 103, which may include a vitrectomy, a phacoemulsification probe, and other tools with suction capabilities. In operation, the surgical console 101 may function to assist a surgeon in performing various ophthalmic surgical procedures, such as vitrectomy, phacoemulsification, and similar procedures. In embodiments in which the tool 103 is a vitrectomy, the surgical console 101 includes one or more modules or components that power the vitrectomy for the purpose of cutting the vitreous. For example, in certain embodiments, the surgical console 101 may include a pneumatic module that uses compressed gas, such as nitrogen, to power the vitreous. In certain other embodiments, the surgical console 101 may include a laser light source for generating laser light used by the vitrectomy to cut the vitreous. In embodiments in which tool 103 is a phacoemulsification probe, surgical console 101 includes one or more modules or components that power the phacoemulsification probe to emulsify the lens during cataract surgery.

[0018] Surgical console 101 may include a display 109 for displaying information to a user (the display may also incorporate a touch screen for receiving user input). Surgical console 101 may also include a vacuum generator coupled to port 107. Tool 103 is operably coupled to the vacuum generator through line 105, which connects to port 107. The vacuum generator creates a vacuum at the tip of tool 103, which causes surgically cut or emulsified material or tissue to be vacuum-suctioned into tool 103 and transported along line 105 to surgical console 101. It should be noted that line 105 may be representative of multiple tubes that may couple tool 103 to surgical console 101. For example, line 105 may be representative of a pneumatic line or fiber optic cable for powering tool 103 for cutting purposes, as well as an aspiration or vacuum line for transporting aspirated material back to surgical console 101.

[0019] 2 and 3 illustrate perspective and side views, respectively, of an exemplary vitrector 203 according to certain embodiments described herein. Accordingly, FIGS. 2 and 3 are described together for clarity. The vitrector 203 is an example of a tool 103. As shown in FIGS. 2-3 , the vitrector 203 includes a probe 210 and a base unit 220. The probe 210 is disposed longitudinally partially through a distal end 221 of the base unit 220 and may be directly or indirectly attached within an internal chamber of the base unit 220. The probe 210 may be inserted into the eye to perform a vitrectomy. It should be noted that, as described herein, a distal end or portion of a component refers to an end or portion that is closer to the patient's body during use. Meanwhile, a proximal end or portion of a component refers to an end or portion that is further away from the patient's body.

[0020] Base unit 220 further provides a port 223 at its proximal end 225 for one or more supply lines routed into the internal chamber of base unit 220. In certain embodiments, port 223 may be representative of two or more ports. In certain embodiments, port 223 may provide a connection between base unit 220 and a tubing or vacuum line (e.g., line 105 in FIG. 1 ) of a vacuum generator (e.g., a vacuum generator in surgical console 101) for suction. In certain embodiments, port 223 may provide a connection to a fiber optic cable that couples to one or more laser light sources (e.g., in surgical console 101) to provide laser light used by vitrector 203 to cut the vitreous. In certain embodiments, port 223 may provide a connection to a pneumatic line that couples to a pneumatic module (e.g., in surgical console 101) that uses compressed gas, such as nitrogen, to power vitrector 203 to cut the vitreous. It should be noted that, as one skilled in the art would understand, the vitrector 203 may be powered using other technologies. As further described in connection with FIG. 4, the vitrector 203 includes a cutting port 216 at the distal portion of the probe 210. In certain embodiments, the vitrector 203 can cut and aspirate the vitreous through this port 216.

[0021] FIG. 4 illustrates an example of a cutting mechanism used in combination with the vitrector 203 of FIGS. 2 and 3. More specifically, FIG. 4 illustrates the distal end of the probe 210 of the vitrector 203, which houses a probe cutter 425 that functions as a cutting device. The probe cutter 425 reciprocates within the probe 210. In certain embodiments, the probe cutter 425 is a hollow tube with a sharp tip. In certain embodiments, the probe cutter 425 includes a cutting port that is similar to and interacts with the cutting port 216 of the probe cutter 425 to enhance cutting efficiency and effectiveness. As the probe cutter 425 moves back and forth, the probe cutter 425 alternately opens and closes the cutting port 216 with the sharp tip of the probe cutter 425. Each cycle of the probe cutter 425 through the distal end of the probe 210 can cut material, such as vitreous, within the cutting port 216 when the probe cutter 425 is closed. The surgically cut vitreous is then aspirated through the probe 210. In certain embodiments, the surgically cut vitreous is aspirated from the circular region between the outer surface of the probe cutter 425 and the inner surface of the probe 210. In certain embodiments, the surgically cut vitreous is additionally or alternatively aspirated through the probe cutter 425 (e.g., through a hollow section thereof).

[0022] It should be noted that Figures 2-3 show only one example of a vitrectomy. Also, Figure 4 shows only one example of a cutting mechanism that may be used as part of a vitrectomy. As mentioned above, a laser light or other mechanism may be used instead. Additionally, tool 103 may be a phacoemulsification probe, as shown in Figure 5.

[0023] FIG. 5 illustrates an exemplary phacoemulsification probe 503 including a handpiece body 520 and a probe 510 that can be inserted into the eye to perform phacoemulsification. A cutting tip 516 extends beyond the distal end of the probe 510. The cutting tip 516 is a hollow, cylindrical tube or shaft that propagates ultrasound waves provided by an ultrasound power line 524. The ultrasound waves emulsify the crystalline lens. The cutting tip 516 also provides an aspiration port 518 through which the emulsified lens is aspirated as a result of vacuum pressure provided by an aspiration line 523. The probe 510 also has an irrigation port for irrigating the lens during the phacoemulsification process. Note that FIG. 5 illustrates only one example of a phacoemulsification probe. Also, FIG. 5 illustrates only one example of an emulsification mechanism that may be used as part of a phacoemulsification probe.

[0024] As discussed above, certain existing vacuum generators that may be used to enable a tool 103 (e.g., a vitrector 203, a phacoemulsification probe 503, etc.) to aspirate material from a surgical site (e.g., a patient's eye) operate using compressed air flowing through an orifice to generate vacuum pressure. However, a common characteristic of these vacuum generators is that above a certain amount of supply air pressure, the vacuum generator becomes less efficient, generating less vacuum pressure as the supply air pressure increases. Figure 6 illustrates an exemplary operation of these vacuum generators.

[0025] FIG. 6 is a high-level diagram illustrating the operation of an exemplary prior art vacuum generation system 600. As shown, the vacuum generation system 600 includes a vacuum generator 650, such as a Venturi vacuum, that generates a vacuum pressure. As described above, the vacuum generation system 600 may be located within a surgical console (e.g., surgical console 101) that couples to a tool 103. Thus, the vacuum pressure provided by the vacuum generation system 600 may be used for the aspiration procedures described above. The vacuum generation system 600 also includes a proportional valve 652. The vacuum generator 650 takes as an input a supply of air, the pressure of which (i.e., the supply air pressure 651) is set by the proportional valve 652, and creates a vacuum having a specific vacuum pressure 657. In a specific embodiment, the vacuum generator 650 is a Venturi vacuum generator that creates a vacuum via a pump with the supply of air passing through the pump. Because those skilled in the art will understand the internal structure of a Venturi vacuum generator, details related to such internal structure will not be described herein for the sake of brevity.

[0026] As described above, proportional valve 652 sets the supply air pressure 651 for the supply air provided to vacuum generator 650. A proportional valve provides a change in output pressure or flow rate in the same proportion as a change in input. For example, doubling the input will double the output. In FIG. 6 , proportional valve 625 is operably coupled to an air compressor or air source reservoir 658. Proportional valve 625 takes compressed air as an input and adjusts the pressure (by providing less or more air) based on an input voltage 653 provided to proportional valve 652. The higher the voltage 653, the higher the supply air pressure 651. Vacuum generation system 600 also includes a PID controller 654 used to control vacuum pressure 657. Generally, a PID controller provides a calculated value for driving an actuator (e.g., proportional valve 652) based on the amount of error (calculated as the difference between the desired set point and the last sensor reading), an integral, and a derivative of the error trend.

[0027] To explain the operation of the PID controller 654 with a simple example, the PID controller 654 takes as input an error value corresponding to the difference between the current vacuum pressure and the vacuum pressure set point 656. The PID controller 654 then calculates both the derivative and the integral of this error value with respect to time. Based on such calculations, the PID controller 654 then provides an output (e.g., in the form of a voltage value). The output can be calculated in different ways, as will be understood by those skilled in the art. In one example, the output is calculated by multiplying the magnitude of the error by a proportional gain (K P ) multiplied by the integral gain (K i ) multiplied by the differential gain (K d )

[0028] The vacuum pressure set point 656 refers to a particular vacuum pressure that may be desired by a user of the corresponding tool 103 (e.g., vitrector 203, phacoemulsification probe 503, etc.). A user may change the vacuum pressure set point 656 by providing input to the surgical console 101 through a graphical user interface displayed on the display 109 of the surgical console 101, a foot pedal of the surgical console 101, or some other mechanism. The current vacuum pressure refers to the last sensor reading of the vacuum pressure provided to the PID controller 654 by the vacuum pressure sensor 659. For example, the vacuum pressure sensor 659 may sense the current vacuum pressure periodically or continuously.

[0029] Thus, the PID controller 654 periodically or continuously calculates (e.g., using a driver circuit) the amount of voltage 653 to provide to the proportional valve 652 to help the vacuum generation system 600 ultimately reach the vacuum pressure set point 656. As discussed above, the higher the voltage 653, the higher the supply air pressure 651 and therefore the higher the vacuum pressure 657. Thus, by controlling the voltage 653 based on the error calculated by the PID controller 654, the vacuum generation system 600 can control the vacuum pressure 657.

[0030] However, in vacuum generation system 600, once supply air pressure 651 exceeds a certain amount, vacuum generator 650 becomes less efficient and generates less vacuum pressure 657 as supply air pressure 651 increases.

[0031] FIG. 7 illustrates a vacuum generation performance graph 700 of a prior art vacuum generation system, such as vacuum generation system 600. As shown in graph 700, the vacuum pressure (measured in mmHg, which refers to millimeters of mercury) increases as the supply air pressure increases within a range from 0 to a certain threshold (e.g., 60 psig (pounds per square inch gauge)). However, the vacuum pressure begins to decrease as the supply air pressure increases above the threshold. For example, as the supply air pressure increases to approximately 60 psig, the vacuum pressure begins to decrease, thereby causing instability in the operation of a standard PID controller (e.g., PID controller 654). Note that 60 psig is an example, and different vacuum generators may have different thresholds. For example, the supply air pressure set point may be in the range of approximately 40 to 60 psig.

[0032] Therefore, using a single PID controller, such as the method described in connection with vacuum generation system 600, can cause the operation of vacuum generation system 600 to become unstable when the system reaches a decreasing or non-monotonic region (e.g., 60-87 psig). For example, in such a situation, PID controller 654 senses that vacuum pressure 657 is lower than vacuum pressure set point 656, causing PID controller 654 to increase voltage 653. The increased voltage further opens proportional valve 652, allowing more supply air (i.e., higher supply air pressure 651), thereby causing vacuum generator 650 to further decrease vacuum pressure 657. The further decrease in vacuum pressure 657 causes PID controller 654 to again increase voltage 653, repeating the cycle. In such a situation, vacuum generation system 600 is driven to its limit and becomes unstable. To recover from this instability, the vacuum pressure set point 656 must be decreased below the current vacuum pressure 657, which causes the PID controller 654 to decrease the voltage 653 until the vacuum generation system 600 returns to a monotonic region (e.g., 0-60 psig supply air pressure). Thus, the vacuum generation system 600 may experience an initial increase and subsequent decrease in vacuum pressure until it reaches the vacuum pressure set point 656. As a result, the vacuum generation system 600 may experience sluggish or sluggish performance in reaching the desired vacuum pressure set point in the above-described circumstances.

[0033] Accordingly, certain embodiments described herein relate to a vacuum generation system including a first feedback loop and a first and second override PID controller corresponding to the first and parallel second feedback loops, respectively. The first PID controller is configured to perform a calculation based on an error between a current vacuum pressure and a vacuum pressure set point, and the second override PID controller is configured to perform a calculation based on an error between a current supply air pressure and a supply air pressure set point. The calculations performed by the first and second feedback loops are then compared to determine a lower or minimum voltage to be used to power the vacuum generation system.

[0034] 8 depicts a high-level diagram illustrating an exemplary operation of a vacuum generation system 800, according to certain embodiments. As shown, the vacuum generation system 800 includes a first feedback loop 810 having a first PID controller 868 configured to take as an input a first loop vacuum pressure error (“first loop error”) 880 corresponding to the difference between the current vacuum pressure 857 (corresponding to the most recent sensor reading provided by the vacuum pressure sensor 659) and the vacuum pressure set point 656. Using the first loop error 880, the first PID controller 868 is then configured to calculate both the derivative and integral of the first loop error 880 with respect to time. The first PID controller 868 further calculates a proportional term using the first loop error. Based on such calculations, the PID controller 868 is configured to provide as an output a first voltage 886 corresponding to a control value for minimizing the difference between the current vacuum pressure 857 and the vacuum pressure set point 656.

[0035] Vacuum generation system 800 further includes a second feedback loop 820 having a second override PID controller 866 that takes as an input an override loop error 884, where the override loop error 884 corresponds to the difference between a supply air pressure setpoint 882 (determined or provided by a user) and a current supply air pressure 851. The current supply air pressure 851 corresponds to the most recent sensor reading provided by a supply air pressure sensor 860. In certain embodiments, the supply air pressure setpoint 882 may be provided within a range of 0 to 60 psig (e.g., corresponding to the monotonic region of vacuum generator 650). For example, the supply air pressure setpoint 882 may be set to a maximum supply air pressure (e.g., 60 psig, which may be unchanging (e.g., constant) or static during use) corresponding to the maximum vacuum pressure of the monotonic region of vacuum generator 650. As explained further below, limiting the range of the supply air pressure helps ensure the stability of vacuum generation system 800.

[0036] Using override loop error 884, override PID controller 866 is then configured to calculate both the derivative and integral of override loop error 884 with respect to time. Override PID controller 866 further calculates a proportional term using override loop error 884. Based on such calculations, PID controller 866 is configured to provide as an output a second voltage 890 corresponding to a control value to minimize the difference between current supply air pressure 851 and supply air pressure setpoint 882.

[0037] The first voltage 886 calculated by the first PID controller 868 and the second voltage 890 calculated by the override PID controller 866 are compared by a minimum control effort analyzer 894 to determine a lower voltage 898 corresponding to the lower voltage level of the first voltage 886 and the second voltage 890. The lower voltage 898 is then provided to the proportional valve 652, which then sets the supply air pressure 851 based on the provided lower voltage 898. As previously described, the vacuum generator 650 takes as input supply air, the pressure of which (i.e., supply air pressure 851) is set by the proportional valve 652, and generates a vacuum having a particular vacuum pressure 857. In some embodiments, the integral value calculated by the loop having the lower voltage level (i.e., the integral value determined by the first PID controller 868 when the first voltage 886 is less than the second voltage 890, or the integral value determined by the override PID controller 866 when the second voltage 890 is less than the first voltage 886) is provided to both the first PID controller 868 and the override PID controller 866 for use as the integral value in the next voltage calculation.

[0038] The use of both the first PID controller 868 and the override PID controller 866 enables the vacuum generation system 800 to control the vacuum pressure 857 by limiting the range of the supply air pressure 851 provided to the vacuum generator 650, thereby eliminating or reducing the possibility of the vacuum generator 650 operating in its decreasing and non-monotonic range. More specifically, the first PID loop with the first PID controller 868 uses vacuum pressure feedback including the current vacuum pressure 857 (e.g., a primary parameter) and the desired vacuum pressure set point 656 to output a first voltage 886. Meanwhile, the override PID loop with the override PID controller 866 takes supply air pressure feedback including the supply air pressure set point 882 and the current supply air pressure 851 (e.g., a secondary parameter) and outputs a second voltage 890.

[0039] During operation, in certain embodiments, the first feedback loop 810 generally controls the vacuum-generation system 800 when the supply air pressure 851 falls below the supply air pressure set point 882 (e.g., 60 psig). In such an example, the first voltage 886 generated by the first PID controller 868 is lower than the second voltage 890 generated by the override PID controller 866 and is provided to the proportional valve 652 to control the supply air pressure 851. However, when the supply air pressure 851 approaches, equals, or exceeds the supply air pressure set point 882, the second feedback loop 820 controls the vacuum-generation system 800 by providing the second voltage 890 to the proportional valve 652, which is then lower than the first voltage 886. Thus, second feedback loop 820 acts to monitor supply air pressure 851 and takes over control of system 800 from first feedback loop 810 when supply air pressure 851 approaches, equals, or exceeds supply air pressure setpoint 882, thereby preventing vacuum generation system 800 from entering a non-monotonic region or minimizing the amount of time vacuum generation system 800 operates in a non-monotonic region. Furthermore, by utilizing minimum control effort analyzer 984, there is a seamless transition between control by first feedback loop 810 and control by second feedback loop 820.

[0040] Thus, in certain embodiments, transient effects may cause vacuum generation system 800 to enter a non-monotonic region as a result of supply air pressure 851 exceeding supply air pressure set point 882. In such a situation, second feedback loop 820 becomes the active controller that drives vacuum generation system 800 back toward supply air pressure set point 882, thereby making vacuum generation system 800's presence in the non-monotonic region temporary, as opposed to permanent. In other words, second voltage 890 may be greater than first voltage 886 for a short period of time in the non-monotonic region, but override PID controller 866 will quickly reduce second voltage 890 such that second feedback loop 820 takes control and proportional valve 652 decreases supply air pressure 851 until supply air pressure set point 882 is reached.

[0041] In other words, as described herein, the use of both the first PID controller 868 and the override PID controller 866 allows the vacuum generation system 800 to control an operating range of a secondary parameter (e.g., supply air pressure) that can prevent the vacuum generation system 800 from entering a decreasing or non-monotonic region of the vacuum generator 650. Preventing the vacuum generation system 800 from experiencing accidental suction and entering a decreasing and non-monotonic region of the vacuum generator 650 improves the performance responsiveness (e.g., performance speed) of the vacuum generation system 800 because the system does not have to recover from instability.

[0042] It is further noted that the override PID controller designs described herein may be implemented in a variety of other systems that operate using a primary parameter (e.g., vacuum pressure) and a secondary parameter (e.g., supply air pressure), such that the primary parameter is calculated based on the secondary parameter, similar to vacuum generation system 800. By implementing the override PID controller designs described herein in such systems, the secondary parameter may be controlled based on a minimum output (e.g., voltage value) corresponding to a lower voltage level among a first output (e.g., first voltage 886) and a second output (e.g., second voltage 890), where the first output is calculated based on a current primary parameter (e.g., vacuum pressure 857) and a primary parameter set point (e.g., vacuum pressure set point 656), and the second output (e.g., second voltage 890) is calculated based on a current secondary parameter (e.g., supply air pressure 851) and a secondary parameter set point (e.g., supply air pressure set point 882).

[0043] In other words, any system operating with linear and quadratic parameters as described above can benefit from the override PID controller design described herein.

[0044] It should also be noted that the ranges provided herein for input, output, or set points are exemplary. In other words, these ranges may be fine-tuned based on manufacturing and / or user preferences, as well as the type and characteristics of the system's components. For example, a vacuum generation system may use a vacuum generator that does not enter its non-monotonic operating range until the supply air pressure reaches 90 psig. In such a case, the supply air pressure set point range may be defined as 0 to 90 psig. In another example, a different type of vacuum generator may enter its non-monotonic operating range when the supply air pressure reaches 40 psig. In such a case, the supply air pressure set point range may be defined as 0 to 40 psig. As one skilled in the art will appreciate, other ranges for input, output, or set points may similarly be varied depending on the above factors as well as other factors.

[0045] Also, while two feedback loops have been described above, it should be noted that three or more feedback loops can be used in combination. For example, the vacuum generation system 800 can further include a third feedback loop having a second override PID controller configured to take as an input a third loop error corresponding to the difference between the current supply air pressure and a second supply air pressure set point (determined or provided by a user). In certain embodiments, the second supply air pressure set point can be set to a minimum supply air pressure (e.g., that may be constant during use) corresponding to the minimum vacuum pressure in the monotonic region of the vacuum generator 650. Using the third loop error, the second override PID controller can be configured to determine a third voltage as an output, which can then be compared to the first voltage 886 before the minimum control effort analyzer 894 or to a lower voltage 898 after the minimum control effort analyzer 894. Upon comparison, the higher of the compared voltage levels (e.g., the maximum value) can be provided as an output by the maximum control effort analyzer. Thus, a minimum operating range for vacuum generation system 800 can be established using the same system architecture, but with an additional feedback loop. In some embodiments, using a second override loop may not require using a minimum output. For example, a minimum comparator can be used between the vacuum pressure and the first override loop, and a maximum comparator can be used between the result of the minimum comparator and the output of the second override loop. In some embodiments, the same sensor can be used. For example, if supply pressure is used, a second override loop can be used to prevent the supply air pressure from becoming too low or too high.

[0046] As one skilled in the art will appreciate, there are various ways in which vacuum generation system 800 may be implemented. For example, in certain embodiments, all components of the system may be configured to communicate digitally. In such embodiments, the use of digital-to-analog converters (DACs) or analog-to-digital converters (ADCs) may not be necessary. In certain other embodiments, all components of the system may be analog. Similarly, in such embodiments, the use of digital-to-analog converters (DACs) or analog-to-digital converters (ADCs) may not be necessary. In certain other embodiments, some components of the system may be analog and some may be digital. For example, in certain other embodiments, first PID controller 868, override PID controller 866, and minimum control effort analyzer 894 may correspond to software instructions that may be retrieved from memory and then executed by a processor. In such embodiments, because any output provided by the processor is digital, digital-to-analog converters (DACs) may be used to enable the processor to communicate with some of the analog components of the system (e.g., driver circuit, proportional valve 652, etc.). Similarly, ADCs may be used by certain components, such as supply air pressure sensor 860 and vacuum pressure sensor 659, to communicate with the processor.

[0047] FIG. 9 illustrates a vacuum generation system 900 corresponding to an exemplary implementation of vacuum generation system 800. Vacuum generation system 900 includes a processor and memory (collectively “processor and memory 980”) for performing calculations of first loop error 880 and override loop error 884, as well as PID calculations for first PID controller 868 and override PID controller 866. Processor and memory 980 can also calculate a lower voltage 898 corresponding to the lower voltage level of first voltage 886 and second voltage 890. The processor is configured to retrieve and execute programming instructions stored in memory. The processor may include a single central processing unit (CPU), multiple CPUs, a single CPU with multiple processing cores, etc. The memory may be one or more of readily available memory, such as random access memory (RAM), read-only memory (ROM), floppy disk, hard disk, solid-state, flash memory, magnetic memory, or any other form of digital storage, local or remote. In certain embodiments, the memory includes instructions that, when executed by the processor, perform calculations of first loop error 880 and override loop error 884, first PID controller 868 and override PID controller 866, and PID calculations for lower voltage 898. In certain embodiments, the processor and memory 980 may be the main processor and memory of a surgical console 101 that may implement or include the vacuum generation system 900.

[0048] As mentioned above, one or more DACs and ADCs may be used to communicate between the processor and other components in the system. For example, the processor may indicate a calculated minimum voltage value to interface 862, which may include a DAC as well as a driver circuit. When the driver circuit receives an analog signal from the DAC indicating the calculated minimum voltage value, the driver circuit provides a corresponding amount of voltage to proportional valve 652. The use of a DAC and a driver circuit is merely exemplary. As one skilled in the art would understand, other types of interfaces may be used instead. Furthermore, in certain embodiments, supply air pressure sensor 860 and vacuum pressure sensor 659 are analog components. Thus, supply air pressure sensor 860 may use interface 870, which may be an ADC, to communicate with the processor. Similarly, vacuum pressure sensor 659 may use interface 864, which may also be an ADC, to communicate with the processor.

[0049] Figure 10 illustrates an example operation 1000 of a vacuum generation system, according to some embodiments. In certain embodiments, operation 1000 is performed by vacuum generation system 800 of Figure 8. Process 1000 is described herein with reference to Figure 8 and its components.

[0050] At 1002, a vacuum generation system (eg, vacuum generation system 800) receives a vacuum pressure sensor reading from a vacuum pressure sensor (eg, vacuum pressure sensor 659).

[0051] At 1004, the vacuum generation system calculates a first loop error (e.g., first loop error 880) between the vacuum pressure sensor (e.g., vacuum pressure sensor 659) reading and the vacuum pressure set point (e.g., vacuum pressure set point 656).

[0052] At 1006, the vacuum generation system calculates (e.g., using the first PID controller 868) a first voltage level for controlling a proportional valve (e.g., the proportional valve 652) based on the first loop error.

[0053] At 1008, the vacuum generation system receives a supply air pressure sensor reading from a supply air pressure sensor (eg, supply air pressure sensor 860).

[0054] At 1010, the vacuum generation system calculates the override loop error (eg, override error 884) between the supply air pressure sensor reading and the supply air pressure set point 882.

[0055] At 1012, the vacuum generation system calculates (e.g., using a second PID controller (e.g., override PID controller 866)) a second voltage level or value for controlling a proportional valve (e.g., proportional valve 652), where the second voltage value is based on the override loop error.

[0056] At 1014, the vacuum generation system determines a minimum voltage level corresponding to the lower of the first and second voltage levels, the minimum voltage level being associated with an input to the proportional valve.

[0057] At 1016, the vacuum generation system provides a minimum voltage level to the proportional valve.

[0058] At 1018, the vacuum generation system uses a proportional valve to provide a supply air pressure to a vacuum generator (eg, vacuum generator 650) based on a minimum voltage level.

[0059] At 1020, the vacuum generation system uses a vacuum generator to provide vacuum pressure to a surgical tool (e.g., tool 103 in FIG. 1 ) based on the supply air pressure. In some embodiments, the integral value calculated by the loop having the lower voltage level (i.e., the integral value determined by first PID controller 868 when first voltage 886 is less than second voltage 890, or the integral value determined by override PID controller 866 when second voltage 890 is less than first voltage 886) is provided to both first PID controller 868 and override PID controller 866 for use as the integral value in the next voltage calculation.

[0060] The foregoing description is provided to enable those skilled in the art to practice the various embodiments described herein. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments. Accordingly, the claims are not intended to be limited to the embodiments shown herein, but are to be accorded the full scope consistent with the language of the claims.

[0061] Illustrative Embodiments Embodiment 1: A method of controlling vacuum pressure in a vacuum generation system, the method including: receiving a first parameter sensor reading from a first parameter sensor; calculating a first error between the first parameter sensor reading and a first parameter set point; determining a first voltage value based on the calculated first error; receiving a second parameter sensor reading from a second parameter sensor; calculating a second error between the second parameter sensor reading and a second parameter set point; determining a second voltage value based on the calculated second error; determining a lower value of the first and second voltage values; providing an input having the lower value to an actuator; and using the actuator to provide a second parameter to a device based on the input.

[0062] Embodiment 2: A method of controlling vacuum pressure in a vacuum generation system, the method including: receiving a first parameter sensor reading from a first parameter sensor; calculating a first error between the first parameter sensor reading and a first parameter setpoint; calculating, using a first proportional-integral-derivative (PID) controller, a first value associated with a first input to an actuator based on the first error; receiving a second parameter sensor reading from a second parameter sensor; calculating a second error between the second parameter sensor reading and a second parameter setpoint; calculating, using a second PID controller, a second value associated with the second input to the actuator based on the second error; determining a lower value of the first and second values; providing the first or second input having the lower value to the actuator; using the actuator to provide a second parameter to a device based on the provided input; and using the device to provide a first parameter to a tool based on the second parameter.

[0063] Embodiment 3: The method of embodiment 2 described above, further comprising: receiving a third parameter sensor reading from a third parameter sensor; calculating a third error between the third parameter sensor reading and a third parameter setpoint; calculating, using a third PID controller, a third value associated with a third input to the actuator based on the third error; determining a lowest value among the first, second, and third values; and providing the first, second, or third input having the lowest value to the actuator.

[0064] Embodiment 4: The method of embodiment 3 described above, wherein the third parameter is a temperature limit that prevents overheating of the proportional valve by limiting the voltage provided to the proportional valve. According to aspect (1), there is provided a method for controlling vacuum pressure in a vacuum generation system, comprising: receiving a vacuum pressure sensor reading from the vacuum pressure sensor; calculating a first error between the vacuum pressure sensor reading and a vacuum pressure set point; calculating a first voltage level for controlling a proportional valve based on the first error; receiving a supply air pressure sensor reading from a supply air pressure sensor; calculating a second error between the supply air pressure sensor reading and a supply air pressure set point; calculating a second voltage level for controlling the proportional valve based on the second error; determining a lower voltage level of the first and second voltage levels; providing an input voltage level to the proportional valve corresponding to the lower voltage level; using the proportional valve to provide a supply air pressure to a vacuum generator based on the low voltage level; using the vacuum generator to provide vacuum pressure to a surgical tool based on the supply air pressure; The method includes: According to aspect (2), calculating the first voltage level is performed by a first proportional-integral-derivative (PID) controller, and calculating the second voltage level is performed by a second PID controller. According to aspect (3), the first PID controller determines a first integral value, the second PID controller determines a second integral value, and the integral value determined by the PID controller having the lower voltage level of the first or second voltage level is provided to both the first PID controller and the second PID controller for use as the integral value in subsequent voltage determinations. According to aspect (4), calculating the second voltage level based on the second error includes limiting the supply air pressure set point to a range corresponding to a monotonic operating range of the vacuum generator. According to aspect (5), the supply air pressure set point is constant and is set equal to the maximum supply air pressure within the range. According to aspect (6), the first PID controller is a primary driver of the vacuum generation system and drives the vacuum generation system when the first voltage level is lower than the second voltage level. According to aspect (7), the second PID controller drives the vacuum generation system when the second voltage level is lower than the first voltage level. According to an eighth aspect, there is provided a vacuum generation system, comprising: receiving a first error between a vacuum pressure sensor reading associated with the vacuum generator and a vacuum pressure set point; Calculating a first voltage level based on the first error a first proportional-integral-derivative (PID) controller configured as follows: receiving a second error between the supply air pressure sensor reading and the supply air pressure setpoint; Calculating a second voltage level based on the second error. a second PID controller configured as follows: determining a lower voltage level between the first voltage level and the second voltage level; Relaying the low voltage level to a proportional valve a minimum control effort analyzer configured to: causing a vacuum generator to provide supply air pressure based on the low voltage level; The proportional valve configured as above; providing a vacuum pressure to a surgical tool based on the supplied air pressure; The vacuum generator configured as described above. A vacuum generation system comprising: According to aspect (9), a vacuum pressure sensor configured to provide the vacuum pressure sensor reading; a supply air pressure sensor configured to provide said supply air pressure sensor reading; Further provided with: According to aspect (10), the second PID controller controls the proportional valve when the supply air pressure is equal to or exceeds a supply air pressure set value of the second PID controller. According to aspect (11), the supply air pressure setting value can be between approximately 40 and 60 psig. According to aspect (12), there is provided a vacuum generation system, comprising: a memory containing executable instructions; a processor in data communication with the memory and configured to execute the instructions, the processor comprising: receiving a first error between a vacuum pressure sensor reading associated with the vacuum generator and a vacuum pressure set point; calculating a first voltage level based on the first error; receiving a second error between the supply air pressure sensor reading and the supply air pressure set point; calculating a second voltage level based on the second error; causing a proportional valve to provide a lower voltage level between the first voltage level and the second voltage level; a processor configured to a proportional valve configured to cause a vacuum generator to provide a supply air pressure based on the low voltage level; a vacuum generator configured to provide a vacuum pressure to the surgical tool based on the supply air pressure; A vacuum generation system comprising: According to aspect (13), a vacuum pressure sensor configured to provide the vacuum pressure sensor reading; a supply air pressure sensor configured to provide said supply air pressure sensor reading; Further provided with: According to aspect (14), calculating the second voltage level based on the second error includes limiting the supply air pressure set point to a range corresponding to a monotonic operating range of the vacuum generator. According to aspect (15), calculating the second voltage level based on the second error includes limiting the supply air pressure set point to a range of 0 to 60 psig (pounds per square inch gauge).

Claims

1. 1. A method for controlling vacuum pressure in a vacuum generation system, comprising: a processor of the vacuum generation system receiving a vacuum pressure sensor reading from a vacuum pressure sensor; the processor calculating a first error between the vacuum pressure sensor reading and a vacuum pressure set point; the processor calculating a first voltage level for controlling a proportional valve based on the first error; the processor receiving a supply air pressure sensor reading from a supply air pressure sensor; the processor calculating a second error between the supply air pressure sensor reading and a supply air pressure set point; the processor calculating a second voltage level for controlling a proportional valve based on the second error; the processor determining a lower voltage level of the first and second voltage levels; the vacuum generation system providing an input voltage level to the proportional valve corresponding to the lower voltage level; causing the proportional valve of the vacuum generation system to provide a supply air pressure to a vacuum generator based on the low voltage level; the vacuum generator of the vacuum generation system providing vacuum pressure to a surgical tool based on the supply air pressure; A method comprising:

2. 2. The method of claim 1, wherein calculating the first voltage level is performed by a first proportional-integral-derivative (PID) controller and calculating the second voltage level is performed by a second PID controller.

3. 3. The method of claim 2, wherein the first PID controller determines a first integral value and the second PID controller determines a second integral value, and wherein the integral value determined by the PID controller having the lower of the first voltage level or the second voltage level is provided by the processor to both the first PID controller and the second PID controller for use as the integral value in subsequent voltage determinations.

4. 2. The method of claim 1, wherein calculating the second voltage level based on the second error comprises limiting the supply air pressure set point to a range corresponding to a monotonic operating range of the vacuum generator.

5. 5. The method of claim 4, wherein the supply air pressure set point is constant, and the supply air pressure set point is set equal to a maximum supply air pressure within the range.

6. 4. The method of claim 3, wherein the first PID controller is a primary driver of the vacuum generation system and drives the vacuum generation system when the first voltage level is lower than the second voltage level.

7. The method of claim 6 , wherein the second PID controller activates the vacuum generation system when the second voltage level is lower than the first voltage level.

8. 1. A vacuum generation system comprising: receiving a first error between a vacuum pressure sensor reading associated with the vacuum generator and a vacuum pressure set point; Calculating a first voltage level based on the first error a first proportional-integral-derivative (PID) controller configured as follows: receiving a second error between the supply air pressure sensor reading and the supply air pressure setpoint; Calculating a second voltage level based on the second error a second PID controller configured as follows: determining a lower voltage level between the first voltage level and the second voltage level; Relaying the low voltage level to a proportional valve a minimum control effort analyzer configured to: causing a vacuum generator to provide supply air pressure based on the low voltage level; The proportional valve configured as above; providing a vacuum pressure to a surgical tool based on the supplied air pressure; The vacuum generator configured as described above. A vacuum generation system comprising:

9. a vacuum pressure sensor configured to provide said vacuum pressure sensor reading; a supply air pressure sensor configured to provide said supply air pressure sensor reading; The vacuum generation system of claim 8 further comprising:

10. 9. The vacuum generation system of claim 8, wherein the second PID controller controls the proportional valve when the supply air pressure equals or exceeds a supply air pressure setpoint of the second PID controller.

11. The vacuum generation system of claim 10, wherein the supply air pressure setpoint can be between approximately 40 and 60 psig.

12. 1. A vacuum generation system comprising: a memory containing executable instructions; a processor in data communication with the memory and configured to execute the instructions, the processor comprising: receiving a first error between a vacuum pressure sensor reading associated with the vacuum generator and a vacuum pressure set point; calculating a first voltage level based on the first error; receiving a second error between the supply air pressure sensor reading and the supply air pressure set point; calculating a second voltage level based on the second error; causing a proportional valve to provide a lower voltage level between the first voltage level and the second voltage level; the processor configured to a proportional valve configured to cause a vacuum generator to provide a supply air pressure based on the low voltage level; a vacuum generator configured to provide a vacuum pressure to the surgical tool based on the supply air pressure; A vacuum generation system comprising:

13. a vacuum pressure sensor configured to provide said vacuum pressure sensor reading; a supply air pressure sensor configured to provide said supply air pressure sensor reading; The vacuum generation system of claim 12 further comprising:

14. 13. The vacuum generation system of claim 12, wherein calculating the second voltage level based on the second error includes limiting the supply air pressure set point to a range corresponding to a monotonic operating range of the vacuum generator.

15. 15. The vacuum generation system of claim 14, wherein calculating the second voltage level based on the second error includes limiting the supply air pressure set point to a range of 0 to 60 psig (pounds per square inch gauge).

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