Computer-implemented method for detecting and / or determining an anomaly of a centrifugal pump

Abstract

The invention relates to a computer-implemented method for detecting and / or determining an anomaly of a centrifugal pump (1), comprising the steps: in a normal state, accelerating and / or decelerating a rotor (4) of the centrifugal pump (1) to quantify at least one term of a dynamic rotor model of the centrifugal pump (1); in a fault state deviating from the normal state, accelerating and / or decelerating the rotor (4) of the centrifugal pump (1) to detect at least one disturbance parameter; and solving an inverse problem of the dynamic rotor model to identify the at least one disturbance parameter for detecting and / or determining the anomaly.

Description

Technical field

[0001] The invention relates to a computer-implemented method for detecting and / or determining an anomaly of a centrifugal pump, comprising the steps of: In a normal state, accelerating and / or decelerating a rotor of the centrifugal pump to quantify at least one term of a dynamic rotor model of the centrifugal pump, and in a fault state deviating from the normal state, accelerating and / or decelerating the rotor of the centrifugal pump to detect at least one disturbance parameter. Background of the invention

[0002] Centrifugal pumps are known from the prior art and are used to pump a liquid by means of the rotary motion of an impeller. The liquid to be pumped enters the pump chamber of the centrifugal pump through a suction port, is captured by the rotating impeller, and subsequently conveyed to a discharge port. Solid particles contained in the liquid can settle in the area of ​​the impeller and on the inside of the pump housing, thus negatively affecting the hydraulic and / or mechanical efficiency of the centrifugal pump or even causing it to become clogged and fail.

[0003] Although several methods for detecting and / or determining an anomaly and, in particular, for resolving blockages in centrifugal pumps are known from the prior art, current practice shows that the known methods are not ideal for protecting a centrifugal pump from damage due to such a blockage that may not be detected in time in a safe and reliable manner, and in particular for reliably detecting and / or determining a corresponding anomaly in the centrifugal pump. Description of the invention

[0004] Starting from this situation, it is an object of the present invention to provide a method for detecting and / or determining an anomaly of a centrifugal pump which, compared to solutions known from the prior art, can detect and classify the anomaly, and in particular a blockage, more reliably and quickly and / or initiate targeted measures to eliminate the anomaly, in particular to resolve the blockage.

[0005] The object of the invention is achieved by the features of the independent claim. Advantageous embodiments are specified in the dependent claims.

[0006] Accordingly, the task is solved by a computer-implemented method for detecting, determining and / or classifying an anomaly in a centrifugal pump, comprising the following steps: In a normal state, accelerating and / or decelerating a rotor of the centrifugal pump to quantify at least one term of a dynamic rotor model of the centrifugal pump; in a fault state deviating from the normal state, accelerating and / or decelerating the rotor of the centrifugal pump to detect at least one disturbance parameter, and solving an inverse problem of the dynamic rotor model to identify the at least one disturbance parameter for detecting, determining and / or classifying the anomaly.

[0007] A key aspect of the proposed solution is that the dynamic rotor model creates a digital twin of the centrifugal pump, with parameter estimation carried out by solving the inverse problem, for example by solving an optimization problem, in order to determine the anomaly, in particular a clogging situation of the centrifugal pump, based on the identified parameters.The anomaly could be, for example, bearing damage including wear and / or aging, seal damage including wear and / or aging, a particularly significant temperature change, a consequence such as expansion and / or viscosity change, misalignment of pump components, a consequence such as misalignment and / or gap dimension change, a blockage within the centrifugal pump, especially at different locations, a corrosion effect, a deposit effect, multi-component fluids in the impeller, multiphase or cavitating fluids in the impeller, an unknown increase in friction, etc. The dynamic rotor model determined in this way allows for significantly easier and more accurate detection and determination of anomalies.Put another way, the proposed method allows for a significantly better analysis of blockages or other possible mechanical malfunctions affecting the rotation of the centrifugal pump rotor. In the case of a blockage as an anomaly, a suitable unblocking routine can be selected to restore the centrifugal pump to its normal operating condition as quickly as possible.

[0008] In summary, the method provides a mathematical and / or physical analysis of a motor's start-up or deceleration phase, including the shaft and all rotating components of the centrifugal pump, compared to a previously defined digital twin of the centrifugal pump. This analysis aims to identify potential blockage situations and / or other resistance-related or resistance-induced torques and forces. Based on this classification of the blockage situation, for example, regarding the location of a blockage within the pump housing of the centrifugal pump, a suitable, problem-specific unblocking routine can be selected. The method thus enables a faster and more efficient unblocking sequence for wastewater or sewage pumps.

[0009] The proposed method is preferably used to identify blockages. In particular, the terms of the dynamic rotor model can be determined during a coordinated, preferably stepwise, ramp-up and / or coast-down sequence. To capture the at least one disturbance parameter, the method considers, in particular, a breakaway and / or static friction torque, a friction torque directly proportional to the angle of rotation (especially as stiffness), any number of friction torques directly proportional to angular velocities with different exponents (especially as damping of different orders), and / or allows the selection of a cleaning sequence optimally suited to the anomaly, depending on the classification of the blockage.The proposed method also allows for the detection of dry running, the detection of a particularly total blockage, differentiation with respect to both directions of rotation of the rotor, and / or preprocessing of raw time signals such as torque, angular velocity and / or rotation angle, such as smoothing and / or filtering of the signals.

[0010] The term "computer-implemented" means, in particular, that the proposed method can be executed by a computer, a computer-based controller, a microprocessor, is cloud-based, or similar. Preferably, all steps of the method are executed by the computer, i.e., in a computer-implemented manner. The normal state is understood to be, in particular, the state of the centrifugal pump in which the centrifugal pump, without increased friction or altered inertia, pumps a fluid of any origin, especially without problems. The acceleration and / or deceleration of the rotor can be performed under laboratory conditions, for example, using clear water. The term of the dynamic rotor model of the centrifugal pump, described below, is understood to be, for example, a friction term, a hydraulic torque term, and / or an inertia term.The acceleration and / or deceleration of the rotor of the centrifugal pump to detect the at least one disturbance parameter preferably takes place during regular operation of the centrifugal pump, for example when pumping wastewater.

[0011] A centrifugal pump is generally defined as a turbomachine that utilizes rotary motion and dynamic forces to pump predominantly liquids. Centrifugal pumps are preferably designed as wastewater pumps. In addition to tangential acceleration of the liquid, centrifugal force occurring in radial flow is used for pumping, so such pumps are also referred to as centrifugal pumps. Centrifugal pumps are preferably used for the hydraulic system of a building or other applications.

[0012] In normal operation of the centrifugal pump, the motor housing can be located above the pump housing. The impeller, driven by the motor via a shaft, is located within the motor housing and is used to pump the fluid. The motor housing can be fixedly connected to the pump housing and / or be a single unit. The centrifugal pump and the motor can each have their own shaft, which can be connected via a coupling. Preferably, the shaft projects from the motor housing into the pump housing on one drive side and / or is fixedly connected to the shaft on the drive side of the impeller. Accordingly, an inlet for the fluid to be pumped can preferably be located below or at the bottom of the pump housing.

[0013] The liquid preferably comprises water or another liquid medium such as wastewater. The liquid may also include solids such as impurities or waste of any kind, in particular feces, sediments, dirt, sand, or even small pieces of wood, brush, textiles, or rags, or the like. Preferably, the motor housing and / or the pump housing is made of metal, in particular cast iron or stainless steel, ceramic, and / or plastic. As already mentioned, within the scope of the invention, accelerating and / or decelerating the rotor in the normal state to quantify at least one term of the dynamic rotor model of the centrifugal pump means, in particular, during regular, trouble-free operation of the centrifugal pump, namely when the centrifugal pump is pumping a fluid, which may be fresh water or may contain one of the aforementioned solid components.The fault condition includes, in particular, a malfunction, bearing damage including wear and / or aging, seal damage including wear and / or aging, a particularly significant change in temperature, a consequence such as expansion and / or viscosity change, incorrect alignment of pump components, a consequence such as misalignment and / or gap dimension change, a blockage within the centrifugal pump, particularly at different locations, a corrosion effect, a deposit effect, multi-component fluids in the impeller, multiphase or cavitating fluids in the impeller, an unknown increase in friction, etc.

[0014] According to a preferred further development, the procedure includes the step: based on the specific anomaly, in particular automatically or manually transferring the centrifugal pump from the fault state to the normal state.

[0015] According to this advanced training, based on the specific anomaly—for example, in the case of a blockage—a suitable unblocking routine is selected to resolve the anomaly or blockage, enabling the centrifugal pump to return from the fault state to its normal state as quickly as possible. Preferably, the selection of the unblocking routine and / or the return of the centrifugal pump from the fault state to the normal state is automated, particularly by computer-based control. Such automated return can be achieved, for example, by the unblocking routine involving multiple changes in the direction and / or speed of rotation of the rotor. It can also be advantageous for the return of the centrifugal pump from the fault state to the normal state to be performed manually, for example, by user intervention. Such manual return could, for instance, be achieved by replacing a damaged impeller.

[0016] According to a further preferred embodiment, quantifying the dynamic rotor model, particularly force-based, comprises determining a braking torque of the normal state, in particular at least one friction term, a hydraulic torque term, and / or, in particular, a time-dependent torque as a function of an angular velocity of the rotor, and / or determining the total inertia of a rotating system of the centrifugal pump in the normal state, in particular including a portion of the fluid moved by the centrifugal pump. The quantification of the dynamic rotor model, particularly force-based, is carried out for the normal state, particularly under laboratory conditions, whereby, in particular, all braking torques of the rotor or the centrifugal pump are determined or measured beforehand.Preferably, the quantification of the dynamic rotor model, which is particularly force-based, includes capturing a braking torque of the normal state, consisting in particular of a total friction term and a hydraulic torque term, all in particular depending on the angular velocity of the rotor as a function of time, as well as capturing the total inertia of the rotating system in the normal state including the fluid moving along with it.

[0017] According to another preferred embodiment, quantification is carried out taking into account a pump characteristic curve, a system characteristic curve, in particular a geodetic height difference, and / or a gate valve, a bypass valve, and / or a check valve, and in particular the position of the valve, and / or the fill level of a pipeline and / or the length of the pipeline, a fluid temperature, a fluid viscosity, a fluid density, a pressure difference, a volume flow rate, a pump efficiency, and / or a valve opening degree. Data determined in this way can be stored in a database for a specific type of centrifugal pump in order to be used for comparison with the normal state, particularly in the event of a failure. The proposed method can be used in particular with the pressure-side valve closed.Apply with the check valve closed to generate a repeatable and comparable condition, virtually independent of the system. Furthermore, machine learning or artificial intelligence methods can be applied to further process the disturbance parameters, particularly for classification, after conducting numerous experiments and subsequently evaluating the results.

[0018] According to a further preferred embodiment, the dynamic rotor model includes a braking torque of the normal state that depends on a rotational speed and / or angular velocity according to the following equation M R φ ˙ t : = ∑ i = 1 N k i φ ˙ r i t + M T φ ˙ t + M I φ ˙ t , with ki Coefficients of the rotor's angular velocity, r i Exponents of the rotor's angular velocity, MT Moment function of a transition from static to sliding friction, especially of the rotor, and MI Torque of an impeller of a centrifugal pump.

[0019] The equation described above combines all braking moments of the centrifugal pump in normal conditions into a total braking moment.

[0020] According to another preferred embodiment, the dynamic rotor model, according to the following equation, comprises, in the normal state, an inertia term and a braking torque on the left side of the equation and a time-dependent motor torque on the right side of the equation. J φ ¨ t + M R φ ˙ t = M M t , with J moment of inertia, in particular as the sum of various inertial effects of rotating solid parts, fluid in the impeller and / or fluid in the pump housing and / or in parts of a piping system.

[0021] According to a further preferred embodiment, the acquisition of the dynamic rotor model in the normal state includes calculating and / or experimentally determining a moment of inertia. In particular, the acquisition of the dynamic rotor model in the normal state includes determining the moment of inertia of the entire rotating system of the centrifugal pump, especially including additive inertias due to fluid in the vicinity of the rotor, for example by experimental determination in the laboratory or based on a calculation.

[0022] According to another preferred embodiment, solving the inverse problem involves classifying the anomaly, the normal state, and / or the fault state. Based on the classification of the anomaly, a suitable measure can be selected, either manually or automatically, to correct the anomaly. According to a further preferred embodiment, the centrifugal pump is returned from the fault state to the normal state based on the classification of the anomaly and / or the fault state. Ideally, based on the classification, for example, in the case of a blockage, a suitable unblocking routine can be selected so that, after applying the unblocking routine, the centrifugal pump can be returned from the fault state to the normal state.

[0023] According to another preferred embodiment, the at least one disturbance parameter comprises a breakaway torque and / or a static friction torque of the fault condition and / or the acceleration of the rotor to detect the disturbance parameter comprises increasing a motor torque from zero up to an initial movement of the rotor, wherein a static friction torque of the anomaly results from a motor torque current at the initial movement minus a breakaway torque of the normal state.In a further preferred embodiment, the at least one fault parameter comprises a breakaway torque and / or a static friction torque of the fault condition, and / or the acceleration of the rotor to detect the fault parameter involves increasing the motor torque from zero until the rotor first starts moving. The static friction torque of the anomaly is calculated as the current motor torque at the time of initial movement minus the breakaway torque of the normal state. Preferably, a potential additional breakaway torque of the anomaly is first determined. For this purpose, the motor torque can be continuously and slowly increased from zero until the rotor first starts moving. The breakaway torque of the normal state is then subtracted from this current motor torque to obtain the static friction torque of the anomaly.

[0024] According to another preferred training method, the procedure includes the step: After the rotor has been moved for the first time, in particular after rapidly increasing the angular velocity of the rotor to a particularly constant but especially vanishingly small value by controlling and / or adjusting the motor torque, and after reaching the particularly constant but especially vanishingly small angular velocity, measuring and / or calculating a rotation angle of the rotor using an integration method, wherein the at least one disturbance parameter, which is particularly angle-related, is obtained as the derivative of the motor torque with respect to the rotation angle.

[0025] "Vanishingly small" means in particular ≥ 1 and ≤ 100 rotations of the rotor per minute, preferably ≥ 1 and ≤ 10 rotations of the rotor per minute.

[0026] The initial movement of the motor is, in particular, a breaking-in process. The rotor's angle of rotation can be measured directly or calculated using an integration method.

[0027] According to a further preferred embodiment, the procedure includes the following step: Determining K coefficients for angular velocities with different exponents and at least one disturbance parameter as velocity-independent Coulomb friction, corresponding to a coefficient of an angular velocity with exponent zero, by solving a system of linear equations with K + 1 linearly independent equations, whose equations can be associated with pairwise distinct constant angular velocities in a range between low and high rotational speeds of the rotor.

[0028] According to another preferred embodiment, the method comprises the step of calculating an additional moment of inertia, in particular with a positive or negative sign, during positive or negative acceleration within a predetermined angular velocity range. The acceleration can be constant, according to a predefined function, according to arbitrary functions, etc.

[0029] According to a further preferred embodiment, the method comprises the step of determining, based on a result of at least one of the four preceding refinements, the fault condition, including in particular no blockage, blockage between a rotating and a stationary part of the centrifugal pump, blockage leading to the stalling of an impeller of the centrifugal pump, or blockage within an impeller channel, and especially in impeller side spaces, in various gaps, at blade edges, on a tongue, and / or in a spiral of the centrifugal pump. Particularly preferably, the determination includes a mix of blockage locations, such as the pump housing, impeller channel, impeller edge, and / or gap between rotating and stationary parts, and / or consequences, such as no blockage, mild blockage, and / or severe blockage.

[0030] According to another preferred training method, the procedure includes the step: Storing the dynamic rotor model, in particular the normal state of the centrifugal pump, in a database, especially as a characteristic curve and / or a characteristic map, and / or recording the dynamic rotor model and / or the disturbance parameter as a function of temperature, liquid viscosity, liquid density, pressure difference, volume flow, pump efficiency and / or opening degree or position of valves or the check valve.

[0031] According to a further preferred embodiment, the method comprises the step of: stepwise, periodic and / or repetitive acceleration and / or deceleration.

[0032] According to another preferred further training, the procedure includes the step: comparison of the determined disturbance parameters with respective threshold values ​​in categories of disturbance parameters, in particular comprehensively: a) Disturbance parameters related to breakaway torque (static friction) b) Disturbance parameters related to constant torque (Coulomb sliding friction) c) Disturbance parameters related to angle of rotation (stiffness) d) Disturbance parameters related to angular velocity (damping) e) Disturbance parameters related to angular acceleration (inertia)

[0033] According to a further preferred embodiment, the method comprises the step of storing at least one term of the dynamic rotor model in the normal state of the centrifugal pump in the database in the form of a characteristic curve and / or a characteristic map for comparing the fault state with the normal state, in particular depending on liquid temperature, liquid viscosity, liquid density, pressure difference, volume flow rate, pump efficiency and / or depending on a system, in particular on the geodetic height difference, position of the valve and / or the check valve, the fill level of in particular all pipelines, lengths of in particular all pipelines and / or existence of a bypass.

[0034] According to another preferred embodiment, the method comprises the step of accelerating and / or decelerating over a particularly sufficiently large speed range, wherein the acceleration and / or deceleration can be carried out with a positive or negative acceleration that is always non-zero, in particular with a strictly monotonic speed profile, and / or in stages, in particular with a monotonic speed profile, with time intervals of, in particular, nearly constant angular velocity, in particular with intermediate periods of steady speed, and / or in particular with constant or true acceleration intervals, in particular with non-zero acceleration, between individual stages, a starting speed and a final speed and / or in any sequence.

[0035] According to a further preferred embodiment, the normal state can be taught and / or the rotor model applied to determine the fault parameters in various ways. The normal state of the centrifugal pump, particularly with regard to start-up and shutdown, can be determined for each individual application and stored in the form of a characteristic curve. Likewise, the normal state of the centrifugal pump, particularly with regard to start-up and shutdown, can be determined in advance for different applications and stored in the form of characteristic curves or maps for later selection. Finally, the normal state as well as the fault state of the centrifugal pump during start-up and / or shutdown can always be analyzed with the valve closed, particularly with the valve on a pressure side of the centrifugal pump closed, whereby the normal state is saved and stored in the database.

[0036] According to another preferred method, the procedure includes the following step: Determining, from the identified disturbance parameters (which can be viewed as coordinates of a multidimensional parameter space), what type of anomaly or disturbance is present, or to which class the respective anomaly or disturbance belongs. Such classification can also be supported by artificial intelligence methods, particularly machine learning methods, if a sufficient data basis is available.

[0037] According to a further preferred embodiment, the normal state can be defined as the fact that all disturbance parameters are smaller in magnitude than their respective threshold values, i.e., their magnitude is particularly close to zero. The normal state represents, in particular, the centrifugal pump upon delivery or commissioning in a given system or during operation without disturbance and / or without aging effects such as wear. According to another preferred embodiment, the fault state is defined as the fact that at least one disturbance parameter is greater than or equal to its respective threshold value in magnitude, i.e., its magnitude differs significantly from zero.

[0038] The fault condition can include, in particular, bearing damage including wear, seal damage including wear, and / or a particularly significant change in temperature and its consequences such as expansion and / or viscosity changes, incorrect alignment of pump components and the consequences such as misalignment and / or changes in clearance dimensions, and / or blockages within the centrifugal pump, especially at different locations, further wear effects, corrosion effects, deposit effects, and / or the presence of fluids with multiple components and / or phases within the pump. The threshold values ​​can be defined in advance experimentally or based on existing experience.

[0039] According to another preferred embodiment, time signals of torque, angle of rotation, and angular velocity can be acquired by hardware sensors and / or soft sensors. Hardware sensors are understood to be, in particular, sensors that directly measure quantities as a function of time; a sensor for the combined measurement of all relevant quantities is also conceivable. Soft sensors are understood to be, in particular, sensors that allow the measurement of basic signals from the motor and / or the frequency converter, adapted to a specific motor technology. A combination of hardware and soft sensors is also conceivable. Brief description of the drawings

[0040] The invention is explained in more detail below with reference to the accompanying drawings and by way of preferred embodiments.

[0041] The drawings show Fig. 1 a schematic view of a centrifugal pump for carrying out the proposed method according to a preferred embodiment of the invention, and Fig. 2 a flowchart for carrying out the proposed method according to the preferred embodiment of the invention. Detailed description of the implementation examples

[0042] Fig. 1 Figure 1 shows a schematic view of a centrifugal pump 1 for carrying out a method described below for detecting, determining and / or classifying an anomaly and, in particular in the case of a blockage, for subsequently resolving the blockage of the centrifugal pump 1 according to a preferred embodiment of the invention.

[0043] The centrifugal pump 1 has a conventional pump housing 2 with a suction opening 3, located at the bottom of the pump housing 2 in the figure, serving as the inlet. A rotor 4 is provided in the pump housing 2, extending vertically in the drawing. The rotor 4 is part of a motor 5, shown only partially, which is arranged opposite the suction opening 3. An impeller 6 is provided facing the suction opening 3 and is driven by the motor 5 via the rotor 4. Furthermore, the centrifugal pump 1 has a microprocessor-based control unit 7, in Fig. 1 only hinted at.

[0044] Finally, the centrifugal pump 1 has one or more sensors 8 for quantifying at least one term of a dynamic rotor model and / or for detecting at least one disturbance parameter of the centrifugal pump 1. The sensor 8 is configured accordingly as an acceleration and / or vibration sensor, in particular as a 3-axis acceleration and / or vibration sensor, as a pressure sensor and / or as a current sensor, and / or as a sensor for determining a motor torque, an angle of rotation and / or an angular velocity or a rotational speed. In the case of a configuration as an acceleration and / or vibration sensor, the sensor 8 is provided in particular in contact with, immediately adjacent to, and / or rigidly mounted, for example on a metal plate, in particular near a respective bearing point, on the motor 5, associated with the rotor 4, on the pump housing 2, on a motor housing of the motor 5, and / or associated with the impeller 6.In the case of a pressure sensor, the sensor 8 is provided on the pressure side and / or suction side, particularly at the suction opening 3. In the case of a current sensor, the sensor 8 measures a motor current drawn by the motor 5.

[0045] The computer-implemented method described below for detecting, determining, and / or classifying the anomaly of centrifugal pump 1 is performed by a processor and / or computer (not shown), in particular the controller 7. The method essentially uses a mathematical-physical approach to analyze pump behavior during the acceleration and / or deceleration of the rotor 4, especially during the start-up or shutdown phase of the motor 5. The approach consists of three main components: training a digital twin using a normal state, identifying anomaly parameters by solving an inverse problem, and classifying anomalies using the identified parameters.

[0046] Specifically, the procedure for detecting and / or determining the anomaly of centrifugal pump 1 comprises the following steps: In a normal state, accelerating and / or decelerating the rotor 4 of the centrifugal pump 1 to quantify at least one term of a dynamic rotor model of the centrifugal pump 1 100, in a fault state deviating from the normal state, accelerating and / or decelerating the rotor 4 of the centrifugal pump 1 to detect at least one disturbance parameter 200, and solving an inverse problem of the dynamic rotor model to identify the at least one disturbance parameter to detect and / or determine the anomaly 300.

[0047] Based on the identified anomaly, centrifugal pump 1 can be automatically or manually returned from the fault state to the normal state.

[0048] The dynamic rotor model of the centrifugal pump, which takes potential anomalies or malfunctions into account as variable terms, is described by the following physical equation of motion: J + λ φ ¨ = M M − ∑ i = 1 N k i φ ˙ r i − ∑ i = 1 K μ i φ ˙ s i − γφ − M T − M ψ − M I withk = ( k 1 , k 2 , ... , k N ) , r = ( r 1 , r 2 , ... , r N ) µ = ( µ 1 , µ 2 , ... , µ K ) , s = ( s 1 , s 2 , ... , s K ) MT = f 1 ( φ̇ ) , Mψ = f 2 ( φ̇ ) and MI = f 3 ( φ̇ ) Definition of the variables

[0049] t Time φ Angle of rotation φ˙ Angular velocity φ˙˙ Angular acceleration

[0050] Definition of known parameters (normal state) (determined especially during final acceptance testing of centrifugal pump 1, during commissioning of centrifugal pump 1 or at regular intervals) J moment of inertia (depending on the installation, valves, etc. of the centrifugal pump 1) as the sum of various inertial effects of rotating fixed parts of the centrifugal pump 1, liquid in the impeller 6, liquid in the pump housing 2 and piping system MM Engine torque k Vector of coefficients for angular velocity r Vector of exponents for angular velocity MT Resistance torque of a transition from static to sliding friction MI Impeller torque (depending on installation, valves, etc. of the centrifugal pump 1)

[0051] Definition of unknown (disturbance) parameters λ additional moment of inertia (negative values ​​are also possible) µ Vector of coefficients for angular velocity s Vector of exponents for the angular velocity (estimated especially through initial experiments) γ coefficient for the angle of rotation M ψAdditional resistance modulus of a transition from static to sliding friction with the following boundary conditions: M ψ = ε ... in the case of static friction at φ˙ = 0 M ψ = δ ... in the case of sliding friction after the transition for φ˙ » 0

[0052] The above equation essentially corresponds to Newton's second law, according to which force equals mass times acceleration. In the case of the rotation of centrifugal pump 1, the force becomes a torque, the mass a moment of inertia, and the acceleration an angular acceleration.

[0053] All moments acting on rotor 4, whether driving moments, braking frictional moments, etc., are summarized on the right-hand side of the equation. These moments can depend on time, the angle of rotation, and the angular velocity. The moments on the right-hand side of the equation can be divided into two groups. Firstly, there are moments that are always present, or in other words, always occur in the normal operating state of centrifugal pump 1. Secondly, there are additional frictional moments that only occur in the event of a fault or anomaly.

[0054] On the left side of the equation, the sum of all moments of inertia is multiplied by the angular acceleration. The sum of all moments of inertia includes, on the one hand, moments of inertia of the normal state and, on the other hand, moments of inertia of an anomaly, i.e., the fault state. An additional moment of inertia of an anomaly can be positive or negative, depending on the case.

[0055] To quantify at least one term of the dynamic rotor model of centrifugal pump 1 in the normal state, the aforementioned equation can be rearranged such that only anomaly terms remain on the left side, while only terms of the normal state, summarized as term M, remain on the right side: λ φ ¨ t + ∑ i = 1 K μ i φ ˙ s i t + γφ t + M ψ φ ˙ t = M φ ˙ φ ¨ t with M φ ˙ φ ¨ t = M M t − J φ ¨ t − ∑ i = 1 N k i φ ˙ r i t − M T φ ˙ t − M I φ ˙ t ∀ t ∈ I = 0 T ⊂ ℝ 0 + mit φ 0 = 0 und φ ˙ 0 = 0

[0056] Subsequently, the anomaly terms are set to zero, leaving only terms of the normal state, which will be examined in more detail below. λ = 0 , μ i = 0 ∀ i ∈ 1 , 2 , … , K , γ = 0 und M ψ = 0

[0057] The decelerating torque can be defined as follows: all braking torques of centrifugal pump 1 are combined into a total braking torque. The result is an equation with an inertia term and a braking torque on the left-hand side and the motor torque on the right-hand side. J φ ¨ t + ∑ i = 1 N k i φ ˙ r i t + M T φ ˙ t + M I φ ˙ t = M M t M R φ ˙ t : = ∑ i = 1 N k i φ ˙ r i t + M T φ ˙ t + M I φ ˙ t J φ ¨ t + M R φ ˙ t = M M t

[0058] The moment of inertia of the entire rotating system in the normal state, see above description of the symbols, can either be calculated in advance or determined experimentally by measuring quasi-stationary curves of torque and angular velocity. M R φ ˙ t = f 4 φ ˙ with φ̈ = 0

[0059] All braking moments, which have been combined into a total braking torque, can now be measured in advance under laboratory conditions as a function of the angular velocity. The following boundary conditions should be considered: Pump characteristic curve or pump characteristic map, system characteristic curve in particular geodetic height difference, gate valve or check valve and their position (%)

[0060] Other boundary conditions can include temperature, fluid viscosity, fluid density, pressure differential, flow rate, pump efficiency, valve opening state, etc. Such data, determined in the form of characteristic curves or maps, can be stored in a database for a specific pump type and / or a specific centrifugal pump 1. This data is subsequently required for comparison with the standard operating conditions and is retrieved again.

[0061] To identify at least one perturbation parameter, a stepwise procedure is applied during acceleration, allowing unknown perturbation parameters to be determined incrementally. Alternatively, other methods are possible, which can be used for both acceleration and deceleration phases, as well as for solving general or specific inversion, optimization, or parameter identification problems. In particular, there are other mathematical methods for parameter identification or for solving such an inverse problem. The method presented below is therefore only one of many possible procedures and thus merely an example.

[0062] Basic initial value problem for estimating the perturbation parameters: λ φ ¨ t + ∑ i = 1 K μ i φ ˙ s i t + γφ t + M ψ φ ˙ t = M M t − J φ ¨ t − M R φ ˙ t ∀ t ∈ I = 0 T ⊂ ℝ 0 + mit φ 0 = 0 und φ ˙ 0 = 0 Step 1 - Estimating the perturbation parameters for an initial perturbation (breaking out)

[0063] Continuous increase in motor torque until the rotor breaks free 4 φ ¨ t B = 0 , φ ˙ t B = 0 , φ t B = 0 M B : = M M t B M ψ 0 = M B − M R 0 = M B − M T 0 ε : = M ψ 0

[0064] First, a (potential) additional breakaway torque of the anomaly is determined (the breakaway torque of the normal state is already known). For this purpose, the motor torque is continuously and slowly increased from zero until rotor 4 first starts to move. The breakaway torque of the normal state is then subtracted from this current motor torque. The result represents a static friction torque of the anomaly. Step 2 - Estimating the constant disturbance parameter (see also notes and calculation method in step 4)

[0065] This disturbance parameter is implicitly calculated in step 4, since in step 4 a disturbance parameter of an occurring velocity-independent constant friction is considered as the coefficient of an angular velocity with an exponent of zero. The result is a sliding friction moment (Coulomb friction) of the anomaly. Step 3 - Estimating the angle-related disturbance parameter

[0066] After starting, the angular velocity of centrifugal pump 1 is rapidly increased to a very small but constant value. The motor torque is then adjusted to maintain this constant angular velocity. Once this angular velocity is reached, the angle of rotation is either measured directly or calculated using an integration method. The angle-related disturbance parameter is obtained as the derivative of the motor torque with respect to the angle of rotation. φ = ∫ t 1 t 2 φ ˙ t dt wobei φ ¨ t = 0 und φ ˙ t = const M M t = ∑ i = 1 K μ i φ ˙ s i t + γφ t + M ψ φ ˙ t + M R φ ˙ t = const + γφ t γ ≈ dM M dφ

[0067] At the end of this step, a comparison with a predefined threshold determines whether further identification will take place.

[0068] If the angle-related disturbance parameter is greater than or equal to a certain threshold value, a rapid or short-term standstill of the centrifugal pump 1 after a certain number of revolutions or a certain time period can be assumed (in particular, restricted rotation of the rotor 4). In this case, the identification procedure can be aborted.

[0069] If the angle-related disturbance parameter is below a certain threshold, the following steps should be taken (in particular, ensuring that infinite free rotation of rotor 4 is possible). In the following, it is assumed that γ is zero.

[0070] An alternative solution, applicable to various types of motors, initially assumes that γ is zero and proceeds to step 4. If rotor 4 can rotate freely, step 4 can be completed; the assumption was therefore correct. If rotor 4 cannot rotate freely (noticeable, in particular, upon reaching maximum motor torque or a certain threshold), step 4 is aborted; the assumption was therefore incorrect. In this alternative solution, γ is simply interpreted as a Boolean variable indicating an angle-related malfunction. Since such an anomaly ultimately leads to total stalling, the precise value of γ as a real-valued variable is not important, so representing it as a Boolean variable is sufficient. Step 4 - Estimating the velocity-related disturbance parameters

[0071] The coefficients for the angular velocities with different exponents, as well as the constant perturbation parameter, can be determined by defining a linear system of equations with K + 1 linearly independent equations. These equations are associated with pairwise distinct constant angular velocities within a specific range between low and high speeds.

[0072] It is assumed that all these angular velocities are greater than a transition range from static to sliding friction (completely suppressed breakaway effect) with respect to the potential anomaly. Thus, the additional section modulus Mψ constant and corresponds in the following to the constant disturbance parameter δ from step 2. This still unknown disturbance parameter on the left side can also be interpreted as a coefficient for an angular velocity with an exponent of zero. φ ¨ t = 0 , φ ˙ t = schrittweise konstant , γ = 0 ∑ i = 1 K μ i φ ˙ s i t j + δ = ∑ i = 1 K μ i φ ˙ s i t j + δ φ ˙ 0 t j = M M t j − M R φ ˙ t j f ür j ∈ 1 , … , K + 1 und t 1 < ⋯ < t j < ⋯ < t K + 1 with l ≠ m ⇒ φ ˙ t l ≠ φ ˙ t m f ü r l , m ∈ 1 , … , K + 1

[0073] One possible method involves accelerating centrifugal pump 1 stepwise with K + 1 stages of constant angular velocities, where the angular velocity of a current stage is greater than the angular velocity of the previous stage. Thus, each individual time t j can be associated with a specific stage and a specific constant angular velocity. A standard solver can be used for the final solution of this system of linear equations.

[0074] Basically, a linear system of equations is formed with K + 1 linear independent equations to determine the K + 1 formulated unknown parameters. K + 1 Equations can be used with the K + 1The steps are associated with constant angular velocity. The angular velocities with exponents, on the other hand, represent the known or measured entries of the coefficient matrix. The right-hand side of the system of equations corresponds to the vector of the equally known differences between engine torque and braking torque at specific times.

[0075] Another way to solve this linear system of equations, or another way to calculate the parameters, could be to consider a larger number of stages in order to (intentionally) define an overdetermined system of equations that is ultimately solved approximately. Step 5 - Estimating the acceleration-related perturbation parameter

[0076] Estimating an additional moment of inertia using a strong acceleration (e.g., constant acceleration, predefined function, arbitrary function, etc.) within a specific angular velocity range. λ φ ¨ t ≈ M M t − J φ ¨ t − M R φ ˙ t − ∑ i = 1 K μ i φ ˙ s i t − δ where γ = 0

[0077] For the angular velocity range under consideration, it was again assumed that the breakaway effect had completely subsided.

[0078] For step 5, the following three methods can be used in particular: After step 4, the centrifugal pump 1 can be accelerated from a final speed stage to an operating speed or a maximum speed. After step 4, the motor torque can be briefly reduced or set to zero, thereby decreasing the angular velocity of rotor 4. After a short waiting period, the centrifugal pump can be accelerated to the operating speed or the maximum speed. An advantage over the first variant is that a larger speed range is available for acceleration. After step 4, the motor torque can be set to zero. Immediately afterward, the coasting behavior of the centrifugal pump 1 is analyzed. In this case, a negative, rather than a positive, acceleration is used to determine the inertia. This method would represent a certain time saving in determining all disturbance parameters. Classification of anomalies

[0079] By comparing theK + 4 Based on the estimated disturbance parameters and their corresponding thresholds, various anomalies can now be classified. This classification is explained below for each parameter individually. Classification Normal state Error condition Initial fault parameter criterion 0 ≤ ε < e 0 0 < ε 0 ≤ ε Result no additional initial effect Static friction (breaking free) Constant disturbance parameter criterion 0 ≤ δ < δ 0 0 < δ 0 ≤ δ Result no additional constant effect Sliding friction (speed-independent) Angle-related disturbance parameter criterion 0 ≤ γ < γ 0 0 < γ 0 ≤ γ Result no additional stiffness effect Required torque too high, no startup possible, classification stopped Speed-related disturbance parameter criterion ∀ i ∈ {1, ... , K} : 0 ≤ µ i < µ i ,0 ∃ i ∈ {1, ... , K} : 0 < µ i ,0 ≤ µ i Result no additional damping effect speed-dependent friction effects with different exponents Acceleration-related disturbance parameter criterion λ 0 - < λ < λ 0+ 0 < λ 0+ ≤ λ λ ≤ λ 0- < 0 Result no additional inertial effect Added or subtracted mass in the rotating system

[0080] The following two methods are particularly suitable for solving the inverse problem. Firstly, to identify all disturbance parameters, especially in steps 2 and 4, centrifugal pump 1 and its motor 5 can be accelerated in stages. In step 5, centrifugal pump 1 and its motor 5 can be accelerated finally over a sufficiently wide speed range to the actual operating speed of motor 5. In each stage of the acceleration sequence, the process waits until the speed reaches a steady state. These individual speed values ​​are then used to establish the system of equations for steps 2 and 4. Secondly, all speed values ​​for an acceleration sequence can be evaluated as a function of time. This allows for the analysis of dynamic profiles and accelerations between successive stages.Depending on the resolution of the rotational speed-time curves, a large number of equations result, leading to an overdetermined system of equations. This can then be solved, for example, using a least squares method. The advantage of this method lies in the simultaneous processing of steps 2, 4, and 5.

[0081] The described embodiments are merely examples that can be modified and / or supplemented in various ways within the scope of the claims. Each feature described for a specific embodiment can be used independently or in combination with other features in any other embodiment. Each feature described for an embodiment of a particular category can also be used accordingly in an embodiment of another category. Reference symbol list

[0082] centrifugal pump 1 Pump housing 2 Suction opening 3 rotor 4 Motor 5 balance bike 6 steering 7 sensor 8 In a normal state, accelerating and / or decelerating a rotor of the centrifugal pump to quantify at least one term of a dynamic rotor model of the centrifugal pump; 100 in a fault condition deviating from the normal state, accelerating and / or decelerating the rotor of the centrifugal pump to detect at least one disturbance parameter; 200 solving an inverse problem of the dynamic rotor model to identify the at least one disturbance parameter for detecting and / or determining the anomaly.

Claims

1. Computer-implemented method for detecting and / or determining an anomaly of a centrifugal pump (1), comprising the steps: in a normal state, accelerating and / or decelerating a rotor (4) of the centrifugal pump (1) to quantify at least one term of a dynamic rotor model of the centrifugal pump (1) (100), in a fault state deviating from the normal state, accelerating and / or decelerating the rotor (4) of the centrifugal pump (1) to detect at least one disturbance parameter (200), and solving an inverse problem of the dynamic rotor model to identify the at least one disturbance parameter for detecting and / or determining the anomaly (300).

2. Method according to the preceding claim, comprising the step: based on the determined anomaly, in particular automatically or manually transferring the centrifugal pump (1) from the fault state to the normal state.

3. Method according to one of the preceding claims, wherein the quantification of the dynamic rotor model, in particular force-based and / or moment-based, comprises capturing a braking torque of the normal state, in particular a friction term, a hydraulic torque term, and / or in particular time-dependent, as a function of an angular velocity of the rotor (4), and / or the quantification of the dynamic rotor model, in particular force-based, comprises capturing a total inertia of a rotating system of the centrifugal pump (1) in the normal state, in particular including a fluid partially moved by the centrifugal pump (1).

4. Method according to the preceding claim, wherein the quantification is carried out taking into account a characteristic curve and / or a characteristic map, taking into account a system characteristic curve, in particular taking into account a geodetic height difference, and / or taking into account a gate valve, a valve, a bypass and / or a check valve, and in particular a position of the valve and / or taking into account a fill level of a pipeline and / or length of the pipeline.

5. Method according to one of the preceding claims, wherein the dynamic rotor model is a braking torque of the normal state that depends on a rotational speed and / or angular velocity. M R φ ˙ t : = ∑ i = 1 N k i φ ˙ r i t + M T φ ˙ t + M I φ ˙ t includes, with k i Coefficients of the angular velocity of the rotor (4), r i Exponents of the angular velocity of the rotor (4), M T Moment function of a transition from static to sliding friction, especially of the rotor, and M I Torque of an impeller (6) of the centrifugal pump (1).

6. Method according to the preceding claim, wherein the dynamic rotor model, according to the following equation, has in the normal state an inertia term and a braking torque on a left side of the equation and a time-dependent motor torque on a right side of the equation, J φ ¨ t + M R φ ˙ t = M M t includes, with J moment of inertia, in particular as the sum of various inertial effects of rotating solid parts, fluid in the impeller (6) and / or fluid in the pump housing (2) and / or in parts of a piping system of the centrifugal pump (1).

7. Method according to one of the preceding claims, wherein the acquisition of the dynamic rotor model in the normal state comprises calculating and / or experimentally determining a moment of inertia.

8. Method according to any of the preceding claims, wherein solving the inverse problem comprises classifying the anomaly and / or the fault condition.

9. Method according to claim 2 and the preceding claim, wherein the centrifugal pump (1) is transferred from the fault state to the normal state based on the classification of the anomaly and / or the fault state.

10. Method according to one of the preceding claims, wherein the at least one disturbance parameter comprises a breakaway torque, in particular a static friction, a constant torque, in particular a Coulomb sliding friction, and / or a coefficient of a rotation angle, in particular a stiffness, and / or a coefficient of an angular velocity, in particular a damping, and / or a coefficient of an angular acceleration, in particular an inertia.

11. Method according to one of the preceding claims, wherein the at least one disturbance parameter comprises a breakaway torque and / or a static friction torque of the fault condition and / or the acceleration of the rotor (4) to detect the disturbance parameter comprises increasing a motor torque from zero up to an initial movement of the rotor (4), wherein a static friction torque of the anomaly results from a motor torque current at the initial movement minus a breakaway torque of the normal state.

12. Method according to the preceding claim, comprising the step: after the initial movement of the rotor (4), in particular rapidly increasing an angular velocity of the rotor (4) to a particularly constant value by controlling and / or adjusting the motor torque and after reaching the particularly constant angular velocity, measuring and / or calculating a rotation angle of the rotor (4) by means of an integration method, wherein the particularly angle-related at least one disturbance parameter results as the derivative of the motor torque with respect to the rotation angle.

13. Method according to one of the two preceding claims, comprising the step of: determining KCoefficients for angular velocities with different exponents and of at least one disturbance parameter, as velocity-independent Coulomb friction, corresponding to a coefficient of an angular velocity with exponent zero, by solving a system of linear equations with K + 1 linearly independent equations, whose equations can be associated with pairwise distinct constant angular velocities in a range between low and high rotational speeds of the rotor (4).

14. Method according to any of the preceding claims, comprising the step: calculating an additional moment of inertia during positive or negative acceleration in a predetermined angular velocity range.

15. Method according to at least one of the four preceding claims, comprising the step: Determining, based on a result of at least one of the four preceding claims, the fault condition comprising in particular no blockage, blockage between a rotating and a stationary part of the centrifugal pump (1), blockage leading to the standstill of an impeller (6) of the centrifugal pump (1) or blockage within an impeller channel of the centrifugal pump (1).

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