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

Abstract

In certain embodiments, a vacuum generation system is provided that includes a cascade PID controller, a proportional valve, and a vacuum generator. The cascade PID controller enables 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 the vacuum generator entering a decreasing or non-monotonic region.

Description

[Technical Field]

[0001] Priority claim This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 077,753, filed September 14, 2020, and entitled "METHODS AND SYSTEMS FOR PROVIDING CONTROL STABILITY IN A VACUUM GENERATION SYSTEM USING CASCADE PROPORTIONAL-INTEGRAL-DERIVATIVE (PID) CONTROLLER," which has Brian T. Chiem as the inventor and is incorporated herein by reference in its entirety as if fully and completely set forth herein. Technical Field

[0002] The present disclosure generally relates to a method and system for providing control stability to a vacuum generation system using a cascade 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 such surgical procedures, bodily fluids and tissue may be aspirated from the surgical site.

[0004] Examples of ophthalmic procedures that involve the aspirating of fluids and tissues include vitreoretinal procedures. Vitreoretinal procedures may include a variety of surgical procedures performed to restore, maintain, or enhance vision. Vitreoretinal procedures may be suitable for treating many serious diseases of the back of the eye. Vitreoretinal procedures may be used to treat diseases 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 diseases of the back 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] A vitrectomy tool (also called a "cutter" or "vitreous cutter") may be used to remove the vitreous. In some instances, the vitrectomy tool may be powered by a pneumatic vitrectomy machine (e.g., a surgical console) that includes one or more pneumatic valves (also called drive valves). In such instances, the vitrectomy tool may function like a tiny guillotine with a vibrating microscopic cutter that removes the vitreous gel in a controlled manner. In some other instances, the vitrectomy tool may 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 via a tube that provides an aspiration channel.

[0006] Another example of an ophthalmic procedure in which bodily fluids and tissues are aspirated includes phacoemulsification. Phacoemulsification refers to cataract surgery in which the diseased lens is emulsified and aspirated from the lens capsule. In some instances, a phacoemulsification probe may break up the lens with ultrasound (or other techniques, such as laser light). To aspirate the broken-up lens, the phacoemulsification probe may be powered by a vacuum generator (e.g., a Venturi vacuum) 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 vacuum pressure. However, a common characteristic of such vacuum generators is that, above a certain amount of supply pressure, the vacuum generator's efficiency decreases, and as the supply pressure increases, the generated vacuum pressure decreases. For example, as the supply air pressure increases between 0 and 60 pounds per square inch gauge (psig), the vacuum pressure increases. However, as the supply air pressure increases between 60 and 87 psig, the vacuum pressure begins to decrease. More specifically, as the supply air pressure reaches approximately 60 psig or above, the vacuum pressure begins to decrease, thereby causing instability in standard PID controllers used to regulate the supply air pressure. In such an example, when the supply air pressure is in the 0 to 60 psig range, the vacuum generator may be considered to be operating in a monotonic region. On the other hand, when the supply air pressure exceeds 60 psig, the vacuum generator may be considered to be operating in a non-monotonic or decreasing region. Summary of the Invention

[0008] The present disclosure generally relates to a method and system for providing control stability to a vacuum generation system using a cascade proportional-integral-derivative (PID) controller.

[0009] In certain embodiments, a method for controlling vacuum pressure in a vacuum generation system is provided. 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 set point. The method further includes calculating a supply air pressure set point based on the first error. The method further includes receiving a supply air pressure sensor reading from the supply air pressure sensor. The method further includes calculating a second error between the supply air pressure sensor reading and the supply air pressure set point. The method further includes calculating a voltage level for controlling a proportional valve based on the second error. The method further includes providing the voltage level to the proportional valve. The method further includes providing the supply air pressure to a vacuum generator using the proportional valve based on the voltage level. The method further includes providing a vacuum pressure to a surgical instrument based on the supply air pressure using the vacuum generator.

[0010] In certain embodiments, a vacuum generation system is provided. 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 supply air pressure set point based on the first error. The vacuum generation system further includes a second PID controller configured to receive a second error between the supply air pressure sensor reading and the supply air pressure set point and calculate a voltage level based on the second error. The vacuum generation system further includes a proportional valve configured to receive the voltage level and provide a supply air pressure to the vacuum generator based on the voltage level. The vacuum generation system further includes a vacuum generator configured to provide a vacuum pressure to a surgical instrument based on the supply air pressure.

[0011] In certain embodiments, a vacuum generation system is provided comprising a memory containing executable instructions and a processor in data communication with the memory and configured to execute the instructions. The instructions are configured to cause the processor to receive a first error between a vacuum pressure sensor reading associated with a vacuum generator and a vacuum pressure set point, calculate a supply air pressure set point based on the first error, receive a second error between the supply air pressure sensor reading and the supply air pressure set point, calculate a voltage level based on the second error, and provide the voltage level to a proportional valve. The vacuum generation system further comprises a proportional valve configured to provide a supply air pressure to the vacuum generator based on the voltage level. The vacuum generation system further comprises a vacuum generator configured to provide a vacuum pressure to a surgical instrument based on the supply air pressure.

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

[0013] The accompanying drawings depict only examples of particular embodiments of the present disclosure and are not therefore to be considered as limiting the scope of the present disclosure. [Figure 1] FIG. 1 illustrates an example of a surgical console in accordance with certain embodiments. [Figure 2] FIG. 2 illustrates an exemplary vitrectomy probe, according to certain embodiments. [Figure 3] FIG. 3 illustrates 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, according to certain embodiments. [Figure 6] FIG. 6 illustrates a prior art vacuum generation system, according to certain embodiments. [Figure 7] FIG. 7 illustrates 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 illustrates an exemplary schematic vacuum generation system with a cascade PID controller, according to certain embodiments. [Figure 9] FIG. 9 illustrates an exemplary schematic vacuum generation system with a cascade PID controller, according to certain embodiments. [Figure 10] FIG. 10 illustrates an example of the operation of the vacuum generation system of FIG. 8, according to certain embodiments.

[0014] To facilitate understanding, the same reference numerals have been used, where possible, to designate identical elements common to the figures. Elements and features of one embodiment may be beneficially incorporated in other embodiments without further detail. DETAILED DESCRIPTION OF THE INVENTION

[0015] Although features of the present invention may be discussed below with respect to specific embodiments and figures, all embodiments of the present invention may include one or more of the advantageous features discussed herein. In other words, one or more embodiments may be discussed as having certain advantageous features, but one or more of such features may also be used in accordance with various other embodiments discussed herein. Similarly, while example embodiments may be discussed below as device, apparatus, or method embodiments, it should be understood that such example embodiments may be implemented in a variety of devices, apparatus, and methods.

[0016] FIG. 1 illustrates an example of a surgical console 101 according to certain embodiments. The surgical console 101 may be configured to drive one or more instruments 103, which may include instruments with suction capabilities, such as a vitrectomy tool, a phacoemulsification probe, and the like. 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 instrument 103 is a vitrectomy tool, the surgical console 101 includes one or more modules or components for providing power to the vitrectomy tool for cutting the vitreous body. For example, in certain embodiments, the surgical console 101 may include a pneumatic module that uses compressed gas, such as nitrogen, to power the vitrectomy tool. In certain other embodiments, the surgical console 101 may include a laser light source for generating laser light used by the vitrectomy tool to cut the vitreous body. In embodiments in which instrument 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.

[0017] 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. Instrument 103 is operably coupled to the vacuum generator via line 105, which connects to port 107. The vacuum generator creates a vacuum at the tip of instrument 103, causing surgically cut or emulsified material or tissue to be aspirated into instrument 103 and transported along line 105 to surgical console 101. It should be noted that line 105 may represent several tubes that may couple instrument 103 to surgical console 101. For example, line 105 may represent a pneumatic line or fiber optic cable for powering instrument 103 for cutting purposes, as well as a suction or vacuum line for returning aspirated material to surgical console 101.

[0018] 2 and 3 illustrate perspective and side views, respectively, of an exemplary vitrectomy tool 203, in accordance with certain embodiments described herein. For this reason, FIGS. 2 and 3 are described together for clarity. Vitrectomy tool 203 is an example of instrument 103. As shown in FIGS. 2-3 , vitrectomy tool 203 includes a probe 210 and a base unit 220. Probe 210 is disposed longitudinally partially through a distal end 221 of base unit 220 and may be attached to the base unit 220, directly or indirectly, within an internal chamber of the base unit 220. Probe 210 may be inserted into an eye to perform a vitrectomy. It should be noted that, as described herein, a distal end or distal portion of a component refers to an end or portion that is closer to a patient's body during use, whereas a proximal end or proximal portion of a component refers to an end or portion that is further from the patient's body.

[0019] Base unit 220 further provides port 223 at its proximal end 225 to allow one or more supply lines to be routed to the internal chamber of base unit 220. In certain embodiments, port 223 may represent two or more ports. In certain embodiments, port 223 may provide a connection between base unit 220 and a tube 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 coupled 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 body. In certain embodiments, port 223 may provide a connection to a pneumatic line coupled 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 body. It should be noted that, as one skilled in the art will appreciate, the vitrector 203 may be powered using other techniques. As will be further described with respect to Figure 4, the vitrector 203 includes a cutting port 216 at the distal portion of the probe 210. In certain embodiments, the vitrector 103 can cut and aspirate the vitreous through this port 216.

[0020] FIG. 4 illustrates an example cutting mechanism for use 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, where the distal probe 210 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 cutter port that is similar to and interacts with the cutter port 216 of the probe cutter 425 to enhance cutting efficiency and effectiveness. As the probe cutter 425 moves back and forth, the sharp tip of the probe cutter 425 alternately opens and closes the cutter port 216. Each cycle of the probe cutter 425 through the distal end of the probe 210 may cut through material, such as vitreous, within the cutter port 216 when the probe cutter 425 is closed. The surgically cut vitreous is then aspirated through probe 210. In certain embodiments, the surgically cut vitreous is aspirated from the circular area between the outer surface of probe cutter 425 and the inner surface of probe 210. Additionally or alternatively, in certain embodiments, the surgically cut vitreous is aspirated through probe cutter 425 (e.g., through a hollow section thereof).

[0021] It should be noted that Figures 2-3 show only one example of a vitrectomy tool. Additionally, Figure 4 shows only one example of a cutting mechanism that may be used as part of a vitrectomy tool. As noted above, a laser light or other mechanism may be used instead. Additionally, the tool 103 may be a phacoemulsification probe, as shown in Figure 5.

[0022] FIG. 5 illustrates an exemplary phacoemulsification probe 503 including a handpiece body 520 and a probe 510 that can be inserted into an 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 transmits ultrasound waves provided by an ultrasonic power line 524. The ultrasound emulsifies the crystalline lens. The cutting tip 516 also provides an aspiration port 518 through which the emulsified crystalline lens is aspirated as a result of vacuum pressure provided by an aspiration line 523. The probe 510 also has an irrigation port for cleaning the crystalline lens during the phacoemulsification process. It should be noted that FIG. 5 illustrates only one example of a phacoemulsification probe. Additionally, FIG. 5 illustrates only one example of an emulsification mechanism that may be used as part of a phacoemulsification probe.

[0023] As noted above, certain existing vacuum generators that may be used to enable an instrument 103 (e.g., vitrectomy tool 203, 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 such vacuum generators is that above a certain amount of supply air pressure, the efficiency of the vacuum generator decreases, and as the supply air pressure increases, the vacuum pressure generated decreases. An example of the operation of such a vacuum generator is shown in FIG. 6.

[0024] FIG. 6 shows 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 noted above, the vacuum generation system 600 may be positioned within a surgical console (e.g., surgical console 101) that is coupled to the instrument 103. In this manner, 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 input a supply of air, the pressure of which (i.e., supply air pressure 651) is set by the proportional valve 652, and creates a vacuum at a particular vacuum pressure 657. In a particular embodiment, the vacuum generator 650 is a Venturi vacuum generator that uses supply air flowing through a pump to create the vacuum. Those skilled in the art will understand the inner workings of a Venturi vacuum generator, and for the sake of brevity, details regarding such inner workings will not be described herein.

[0025] As described above, proportional valve 652 sets the supply air pressure 651 of the supply air provided to vacuum generator 650. A proportional valve is used to vary the 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 increasing or decreasing the 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 further includes a PID controller 654 used to control vacuum pressure 657. Generally, a PID controller provides calculations for driving an actuator (e.g., proportional valve 652) based on an error amount (calculated as the difference between a desired set point and the last sensor reading), an integral, and a derivative of the error trend.

[0026] To illustrate the operation of PID controller 654 with a simple example, PID controller 654 takes as an input an error value corresponding to the difference between the current vacuum pressure and vacuum pressure set point 656. PID controller 654 then calculates both the derivative and integral of this error value with respect to time. Based on such calculations, PID controller 654 then provides an output (e.g., in the form of a voltage value). As one skilled in the art will appreciate, the output may be calculated in different ways. In one example, the output may be equal to the proportional gain (Kp) × magnitude of the error + integral gain (Ki) × integral of the error + derivative gain (Ka) × derivative of the error.

[0027] Vacuum pressure set point 656 refers to a particular vacuum pressure that may be desired by a user of the corresponding instrument 103 (e.g., vitrectomy tool 203, phacoemulsification probe 503, etc.). A user may change vacuum pressure set point 656 by providing input to surgical console 101 through a graphical user interface displayed on display 109 of surgical console 101, a foot pedal of surgical console 101, or some other mechanism. Current vacuum pressure refers to the last sensor reading of the vacuum pressure provided by vacuum pressure sensor 659 to PID controller 654. For example, vacuum pressure sensor 659 may sense the current vacuum pressure periodically or continuously.

[0028] To this end, the PID controller 654 periodically or continuously calculates the amount of voltage 653 that should be provided to the proportional valve 652 (e.g., using a driver circuit) to help the vacuum generation system 600 ultimately achieve a vacuum pressure set point 656. As noted 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.

[0029] However, in vacuum generation system 600, above a certain amount of supply air pressure 651, vacuum generator 650 becomes less efficient and generates less vacuum pressure 657 as supply air pressure 651 increases.

[0030] FIG. 7 illustrates a vacuum generation performance graph 700 for a prior art vacuum generation system, such as vacuum generation system 600. As shown in graph 700, as the supply air pressure increases from 0 to a certain threshold (e.g., 60 psig (pounds per square inch gauge)), the vacuum pressure (measured in mmHg, which refers to millimeters of mercury) increases. However, as the supply air pressure rises above the threshold, the vacuum pressure begins to decrease. For example, as the supply air pressure reaches and increases to approximately 60 psig, the vacuum pressure begins to decrease, thereby causing a standard PID controller (e.g., PID controller 654) to become unstable. It should be noted that 60 psig is an example, and different vacuum generators may have different thresholds.

[0031] Thus, as described in connection with vacuum generation system 600, using a single PID controller can cause vacuum generation system 600 to become unstable when it reaches a decreasing or non-monotonic region (e.g., between 60 and 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 opens proportional valve 652 even further, allowing for increased supply air (i.e., higher supply air pressure 651), 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, and the cycle repeats. In such a situation, vacuum generation system 600 is driven to its limits and becomes unstable. To recover from this instability, the vacuum pressure set point 656 must be lowered below the current vacuum pressure 657, which causes the PID controller 654 to reduce the voltage 653 until the vacuum generation system 600 returns to a monotonic region (e.g., a supply air pressure of 0 to 60 psig). Thus, the vacuum generation system 600 may experience an initial rise and subsequent fall in vacuum pressure until it reaches the vacuum pressure set point 656. As a result, the vacuum generation system 600 may be sluggish or slow in reaching the desired vacuum pressure set point in the above situation.

[0032] To this end, certain embodiments described herein relate to a vacuum generation system with a cascade PID controller including an outer-loop PID controller and an inner-loop PID controller, where the outer-loop PID controller is configured to perform calculations based on an error between a current vacuum pressure and a vacuum pressure set point, while the inner-loop PID controller is configured to perform calculations based on an error between a current supply air pressure and a supply air pressure set point.

[0033] FIG. 8 depicts a high-level diagram illustrating an exemplary operation of vacuum generation system 800, according to certain embodiments. As shown, vacuum generation system 800 includes an outer PID controller 868 configured to take as an input an outer loop error 880 corresponding to the difference between a current vacuum pressure 857 (corresponding to the most recent sensor reading provided by vacuum pressure sensor 659) and a vacuum pressure set point 656. External PID controller 868 is then configured to use outer loop error 880 to calculate both the derivative and integral of outer loop error 880 with respect to time. Based on such calculations, external PID controller 868 is configured to provide a supply air pressure set point 882 as an output. In certain embodiments, external PID controller 868 may be configured to limit the output (supply air pressure set point 882) to a range of 0 to 60 psig (corresponding to the monotonic region of vacuum generator 650). For example, external PID controller 868 may be configured to ensure that supply air pressure set point 882 does not exceed a defined range. As explained further below, limiting the range of supply air pressure helps ensure the stability of the vacuum generation system 800.

[0034] Vacuum generation system 800 further includes an inner PID controller 866 that takes as an input an inner loop error 884, where inner loop error 884 corresponds to the difference between a supply air pressure set point 882 (provided by outer PID controller 868) and a current supply air pressure 851. Current supply air pressure 851 corresponds to the most recent sensor reading provided by supply air pressure sensor 860.

[0035] Next, the internal PID controller 866 is configured to use the inner loop error 884 to calculate both the derivative and integral of the inner loop error 884 with respect to time. Based on such calculations, the internal PID controller 866 is configured to determine a voltage value as an output. A constant amount of voltage 886 corresponding to the voltage value calculated by the internal PID controller 866 is then provided to the proportional valve 652. The proportional valve 652 then sets the supply air pressure 851 based on the provided voltage 886. As previously described, the vacuum generator 650 takes as an input supply air, whose pressure (i.e., supply air pressure 651) is set by the proportional valve 652, and creates a vacuum at a particular vacuum pressure 857. In certain embodiments, the internal PID controller 866 is configured to limit its output to the operating range of the proportional valve 652. For example, if the proportional valve 652 is a 5V (volt) actuator, the internal PID controller 866 is configured to limit its output to a range of 0 to 5V.

[0036] By using both the external PID controller 868 and the internal PID controller 866, the vacuum generation system 800 can 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 region. More specifically, the outer PID loop, including the external PID controller 868, uses vacuum pressure feedback, including the current vacuum pressure (primary parameter), and the desired vacuum pressure set point 656 to output a supply air pressure set point 882 (an intermediate parameter set point). The inner PID loop, including the internal PID controller 866, then takes the supply air pressure set point 882 and the supply air pressure feedback, including the current supply air pressure (an intermediate parameter), to calculate a desired output, indicated by a voltage value. A voltage 886 is then provided to the proportional valve 652 based on the calculated voltage value. In this manner, the output (vacuum pressure) of the outer loop can be controlled by limiting the output (supply air pressure) to a certain range.

[0037] In other words, as described herein, by using a cascade PID controller (e.g., including an external PID controller and an internal PID controller), the vacuum generation system 800 can control the operating range of the intermediate parameter (supply air pressure). Based on this, the vacuum generation system 800 can prevent the vacuum generator 650 from entering a decreasing or non-monotonic region. Preventing the vacuum generation system 800 from accidentally being suctioned and entering a decreasing or non-monotonic region of the vacuum generator 650 improves the performance responsiveness (performance speed) of the vacuum generation system 800 because the system does not need to recover from instability.

[0038] It should be noted that the cascade PID controller design described herein can be implemented in a variety of other systems that operate with a primary parameter (vacuum pressure) and an intermediate parameter (supply air pressure) similar to vacuum generation system 800, such that the primary parameter (vacuum pressure) is based on an output (voltage value) calculated based on the current intermediate parameter (supply air pressure) and the intermediate parameter set point (supply air pressure set point), which is itself calculated based on the current primary parameter (vacuum pressure) and the primary parameter set point (vacuum pressure set point). In other words, any system that operates with such primary and intermediate parameters can benefit from the cascade PID controller design described herein.

[0039] Additionally, it should be noted that the ranges provided herein for inputs, outputs, or set points are exemplary. In other words, such 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. The vacuum generator does not enter its non-monotonic operating region 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 region 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 will be appreciated by those skilled in the art, other ranges for inputs, outputs, or set points may similarly be modified depending on factors such as those listed above.

[0040] 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 of the system's components 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 of the system's components 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 of the system's components may be analog and some may be digital. For example, in certain other embodiments, external PID controller 868 and internal PID controller 866 may correspond to software instructions that can be read from memory and 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 allow the processor to communicate with some of the system's analog components (e.g., drive circuitry, 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.

[0041] 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 referred to as “processor and memory 980”) for performing the PID calculations for outer PID controller 868 and inner PID controller 866, as well as the calculation of outer loop error 880 and inner loop error 884. The processor is configured to read and execute programming instructions stored in the memory. The processor may include a single 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 the PID calculations for outer PID controller 868 and inner PID controller 866, as well as the calculation of outer loop error 880 and inner loop error 884. In certain embodiments, processor and memory 980 may be the main processor and memory of surgical console 101 that may implement or include vacuum generation system 900 .

[0042] As described above, one or more DACs and ADCs may be used for communication between the processor and other components in the system. For example, the processor may display a calculated voltage value on interface 862. Interface 862 may include a driver circuit as well as a DAC. When the driver circuit receives an analog signal from the DAC representing the calculated voltage value, the driver circuit provides a corresponding amount of voltage to proportional valve 652. The use of a DAC and 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. As such, 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 be an ADC, to communicate with the processor.

[0043] 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. Operation 1000 is described herein with reference to Figure 8 and its components.

[0044] 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).

[0045] At 1004, the vacuum generation system calculates the outer loop error (eg, outer loop error 880) between the vacuum pressure sensor reading and the vacuum pressure set point (eg, vacuum pressure set point 656).

[0046] At 1006, the vacuum generation system calculates (eg, using an external PID controller (eg, external PID controller 868)) a supply air pressure set point (eg, supply air pressure set point 656) based on the outer loop error.

[0047] 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).

[0048] At 1010, the vacuum generation system calculates the inner loop error (eg, inner loop error 884) between the supply air pressure sensor reading and the supply air pressure set point 882.

[0049] At 1012, the vacuum generation system calculates (e.g., using an internal PID controller (e.g., internal PID controller 866)) a voltage level or value for controlling a proportional valve (e.g., proportional valve 652). The voltage value is based on the inner loop error. The voltage level is related to the input to the proportional valve.

[0050] At 1014, the vacuum generation system provides a voltage level (eg, a voltage having a calculated voltage value) to the proportional valve.

[0051] At 1016, the vacuum generation system uses a proportional valve to provide a supply air pressure to a vacuum generator (e.g., vacuum generator 650) based on the voltage level.

[0052] At 1018, the vacuum generation system uses a vacuum generator to provide vacuum pressure based on the supply air pressure to a surgical instrument (eg, instrument 103 of FIG. 1).

[0053] The foregoing description is provided to enable those skilled in the art to practice the various embodiments described herein. Various modifications to such embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments. Thus, 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. Illustrative Embodiments

[0054] Embodiment 1 A method for controlling vacuum pressure in a vacuum generation system includes 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 an intermediate parameter setpoint based on the first error, receiving an intermediate parameter sensor reading from the intermediate parameter sensor, calculating a second error between the intermediate parameter sensor reading and the intermediate parameter setpoint, calculating a value associated with an input to an actuator based on the second error, providing an input having the calculated value to the actuator, providing a second parameter to an apparatus using the actuator based on the input, and providing a first parameter to an instrument using the apparatus based on the second parameter.

[0055] Embodiment 2 A method for controlling vacuum pressure in a vacuum generation system, the method including the steps of 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 an intermediate parameter setpoint based on the first error using a first proportional-integral-derivative (PID) controller, receiving an intermediate parameter sensor reading from the intermediate parameter sensor, calculating a second error between the intermediate parameter sensor reading and the intermediate parameter setpoint, calculating a value related to an input to an actuator based on the second error using a second PID controller, providing an input having the calculated value to the actuator, providing a second parameter to an apparatus based on the input using the actuator, and providing a first parameter to an instrument based on the second parameter using the apparatus.

Claims

1. 1. A method for controlling vacuum pressure in a vacuum generation system, comprising: the vacuum generation system includes a first proportional-integral-derivative (PID) controller and a second proportional-integral-derivative (PID) controller; The method comprises: the vacuum generation system receiving a vacuum pressure sensor reading from a vacuum pressure sensor; the vacuum generation system calculating a first error between the vacuum pressure sensor reading and a vacuum pressure set point; the vacuum generation system calculating a supply air pressure set point based on the first error; receiving a supply air pressure sensor reading from a supply air pressure sensor by the vacuum generation system; the vacuum generation system calculating a second error between the supply air pressure sensor reading and the supply air pressure set point; the vacuum generating system calculating a voltage level for controlling a proportional valve based on the second error; and providing the voltage level to the proportional valve; the vacuum generation system using the proportional valve to provide a supply air pressure to a vacuum generator based on the voltage level; the vacuum generation system using the vacuum generator to provide a vacuum pressure based on the supply air pressure to a surgical instrument.

2. The method of claim 1, wherein the first proportional-integral-derivative (PID) controller calculates the supply air pressure set point.

3. The method of claim 2, wherein the second proportional-integral-derivative (PID) controller calculates the voltage level.

4. 2. The method of claim 1, wherein calculating the supply air pressure set point based on the first error includes the first proportional-integral-derivative (PID) controller limiting the supply air pressure set point to a range corresponding to a monotonic operating range of the vacuum generator.

5. 2. The method of claim 1, wherein calculating the supply air pressure set point based on the first error includes the first proportional-integral-derivative (PID) controller limiting the supply air pressure set point to a range of 0 to 60 pounds per square inch gauge (psig).

6. 2. The method of claim 1, wherein calculating the voltage level for controlling the proportional valve includes the second proportional-integral-derivative (PID) controller limiting the voltage level to an operating voltage range of the proportional valve.

7. receiving a first error between a vacuum pressure sensor reading associated with the vacuum generator and a vacuum pressure set point; a first proportional-integral-derivative (PID) controller configured to calculate a supply air pressure setpoint based on the first error; receiving a second error between the supply air pressure sensor reading and the supply air pressure set point; a second proportional-integral-derivative (PID) controller configured to calculate a voltage level based on the second error; receiving the voltage level; a proportional valve configured to provide a supply air pressure to a vacuum generator based on the voltage level, A vacuum generation system, wherein the vacuum generator is configured to provide a vacuum pressure based on the supply air pressure to a surgical instrument.

8. 8. The vacuum generation system of claim 7, further comprising: a vacuum pressure sensor configured to provide the vacuum pressure sensor reading; and a supply air pressure sensor configured to provide the supply air pressure sensor reading.

9. 8. The vacuum generation system of claim 7, wherein the first proportional-integral-derivative (PID) controller configured to calculate the supply air pressure set point based on the first error comprises the first proportional-integral-derivative (PID) controller configured to limit the supply air pressure set point to a range corresponding to a monotonic operating range of the vacuum generator.

10. 8. The vacuum generation system of claim 7, wherein the first proportional-integral-derivative (PID) controller configured to calculate the supply air pressure set point based on the first error comprises the first proportional-integral-derivative (PID) controller configured to limit the supply air pressure set point to a range of 0 to 60 pounds per square inch gauge (psig).

11. 8. The vacuum generation system of claim 7, wherein the second proportional-integral-derivative (PID) controller configured to calculate the voltage level for controlling the proportional valve comprises the second proportional-integral-derivative (PID) controller configured to limit the voltage level to an operating voltage range of the proportional valve.

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

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

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

15. 13. The vacuum generation system of claim 12, wherein calculating the supply air pressure set point based on the first error includes limiting the supply air pressure set point to a range of 0 to 60 pounds per square inch gauge (psig).

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