Control system for a fluid management system

Abstract

The invention is entitled "Control system for a fluid management system." The invention provides a control system comprising: a controller configured to: access an estimated torque and an estimated speed of a motor mechanically coupled to an impeller of a centrifuge; access at least one set of predetermined performance data values associated with a known speed of the impeller, wherein each set of predetermined performance data values comprises: a plurality of flow values and a plurality of performance metric values; determine an operating point of the centrifuge based on the estimated torque, the estimated speed, and the at least one set of predetermined performance data values; compare the determined operating point to a best efficiency point (BEP) associated with the centrifuge; and determine whether to change a speed of the motor based on the comparison.

Description

Technical Field

[0001] This disclosure relates to control systems for fluid management systems. Background Technology

[0002] An electric motor converts electrical energy into mechanical energy, which is then supplied to the impeller of a centrifuge. Centrifuges can be part of a fluid management system. Summary of the Invention

[0003] In one aspect, a control system includes: a controller configured to: access estimated torque and estimated speed of a motor mechanically coupled to an impeller of a centrifuge; access at least one set of predetermined performance data values ​​associated with a known speed of the impeller, wherein each set of predetermined performance data values ​​includes: a plurality of flow values ​​and a plurality of performance metrics; determine an operating point of the centrifuge based on the estimated torque, the estimated speed, and the at least one set of predetermined performance data values; compare the determined operating point with a best efficiency point (BEP) associated with the centrifuge; and determine, based on the comparison, whether to change the speed of the motor.

[0004] Implementations may include one or more of the following features. The controller may be configured to access multiple sets of predetermined data values ​​associated with the centrifuge, and in these implementations, each of these sets may be associated with a different known speed of the impeller, and performance metrics may include head values ​​and efficiency values. The controller may be further configured to compare an estimated speed of the motor with a known speed of the impeller; and if the similarity difference between the estimated speed of the motor and the known speed is within a speed threshold, the controller may determine machine power characteristics based on predetermined head values ​​and predetermined efficiency values; and if the similarity difference between the estimated speed of the motor and the known speed is not within a speed threshold, the controller may determine an updated set of head values ​​and an updated set of efficiency values; and the controller may determine machine power characteristics based on the updated set of head values ​​and the updated set of efficiency values. The controller may also be further configured to determine a power value corresponding to the estimated torque based on the machine power characteristics, and to determine a flow operating point, which is a flow value corresponding to the determined power value. To determine the centrifuge's operating point, the controller may be configured to determine an efficiency operating point and a head operating point based on the flow operating point. To compare the determined operating point with the Best Efficiency Point (BEP), the controller can be configured to compare the determined efficiency operating point with the BEP. If the controller changes the motor speed, then after the speed change, the controller can be further configured to: determine an updated set of head values ​​and an updated set of efficiency values ​​at the flow rate; and update the machine power characteristics based on the updated set of head values ​​and the updated set of efficiency values.

[0005] The controller can change the speed of the motor, thereby changing the flow rate of the fluid moved by the impeller, and the controller can also be further configured to re-determine the efficiency operating point after changing the speed of the motor.

[0006] On the other hand, the control system for the pump system includes a controller configured to: determine whether the current operating point of the pump system is within a bounded operating region, wherein the current operating point includes a current value of the flow rate of the fluid moved by the pump system and a current value of a performance metric; and the bounded operating region is defined by a minimum flow rate, a maximum flow rate, a minimum performance metric, and a maximum performance metric; and if the current operating point is not within the bounded operating region, the controller is configured to adjust parameters of a motor mechanically coupled to the pump system to change the current operating point until the current operating point is within the bounded operating region.

[0007] Implementations may include one or more of the following features. The controller may be configured to compare the current flow rate of the fluid moved by the pump system with the optimal efficiency point flow rate associated with the pump system before determining whether the current operating point is within a bounded operating region; if the current flow rate is less than the optimal efficiency point flow rate, the controller may increase the motor speed before determining whether the current operating point is within a bounded operating region; and if the current flow rate is greater than the optimal efficiency point flow rate, the controller may decrease the motor speed before determining whether the current operating point is within a bounded operating region. Motor parameters may include the motor speed; and if the current operating point is not within a bounded operating region and the current flow rate is less than the optimal efficiency point flow rate, the controller may decrease the motor speed until the current operating point is within a bounded operating region; and if the current operating point is not within a bounded operating region and the current flow rate is greater than the optimal efficiency point flow rate, the controller may increase the motor speed until the current operating point is within a bounded operating region.

[0008] The control system can also be configured to determine whether the current value of a performance metric is acceptable. Performance metrics may include operating efficiency, and to determine whether the current value of operating efficiency is acceptable, the controller can be configured to compare the current value of operating efficiency with an optimal efficiency point. If the difference between the current value of operating efficiency and the optimal efficiency point is less than an efficiency threshold, then the current value of operating efficiency is considered acceptable. Performance metrics may be flow rate or operating head.

[0009] In some implementations, one or more of the minimum flow rate, maximum flow rate, minimum value of the performance metric, and maximum value of the performance metric are set by the pump system operator.

[0010] On the other hand, the setpoint value of the flow rate of the fluid moved by the centrifuge is accessed; the duration of the first time period and the duration of the second time period are determined based on the setpoint value of the flow rate and the centrifuge's optimal efficiency point flow rate; the centrifuge is controlled to operate at the optimal efficiency point flow rate during the duration of the first time period; and the centrifuge is controlled to operate at zero flow rate during the duration of the second time period. The duration of the first time period and the duration of the second time period are such that the average flow rate of the fluid during the first time period and the second time period is equal to the setpoint value of the flow rate.

[0011] The implementation may include one or more of the following features: The first time period may immediately precede the second time period. A setpoint value for the flow rate can be received from the centrifuge operator. The centrifuge can be controlled by a motor control device that provides a motor power signal to a motor mechanically coupled to the centrifuge impeller.

[0012] Implementations of any of the techniques described herein may include apparatus, devices, controllers, control systems, and fluid management systems and / or methods. Details of one or more embodiments are set forth in the accompanying drawings and the following description. Other features will become apparent from the description, drawings, and claims. Attached Figure Description

[0013] Figure 1 This is a block diagram of an example fluid management system.

[0014] Figure 2 is a block diagram of an example centrifuge.

[0015] Figure 3 is a block diagram of another example of a fluid management system.

[0016] Figure 4 , Figure 5 , Figure 9 , Figure 10 and Figure 15 These are flowcharts of various exemplary processes.

[0017] Figure 6 This is an example of a PQ curve.

[0018] Figure 7 This is an example of an efficiency curve.

[0019] Figure 8 and Figures 11 to 14 This is a diagram illustrating an example of the performance characteristic curves of a centrifuge.

[0020] Figure 16 This is an example of a graph showing how the impeller speed changes over time.

[0021] Figure 17 This is an example of a graph showing how the flow rate of a centrifuge changes over time. Detailed Implementation

[0022] refer to Figure 1 The diagram illustrates a block diagram of a fluid management system 100. The fluid management system 100 may be, for example, a pumping system. The fluid management system 100 includes a centrifuge 120 for moving fluids in process 170. Process 170 may be, for example, an industrial, commercial, or residential process. For example, process 170 may be: a cooling system; a heating, ventilation, and cooling (HVAC) system; a wastewater or waste liquid treatment system; a chemical treatment system; or a filtration system.

[0023] The fluid management system 100 includes a controller 150. As described below, the controller 150 determines the operating point of the centrifuge 120 without relying on sensors such as flow meters and pressure sensors. Furthermore, the controller 150 uses predetermined performance data 151 to determine the operating point, which is determined before the centrifuge 120 is deployed into the system, and characterization of the centrifuge 120 is not performed after it has been deployed into the system 100. The controller 150 also enables the centrifuge 120 to operate more efficiently.

[0024] Centrifuge 120 is driven by motor 140. Motor 140 can be a direct current (DC) motor or an alternating current (AC) motor. For example, motor 140 can be a brushless DC motor, a permanent magnet AC motor, or an AC induction motor. Motor 140 can be a single-phase motor or a multi-phase motor. Although Figure 1 A single motor is shown, but the fluid management system 100 may include more than one motor. The fluid management system 100 also includes a motor control unit 110 that provides a motor power signal 141 to the motor 140. The motor control unit 110 can be any type of device configured to drive the motor 140. For example, the motor control unit 110 may be a variable frequency drive (VDF) or an adjustable speed drive (ASD).

[0025] The motor power signal 141 is an AC electrical signal with a voltage (V) and current (i) sufficient to drive the motor 140. In embodiments where the motor 140 is a multiphase motor, the motor power signal 141 is a multiphase AC electrical signal. The motor 140 includes a stator 148 and a rotor 149. Each phase of the stator 148 includes one winding. The rotor 149 rotates relative to the stator 148 in response to receiving the motor power signal 141. The direction and speed of the rotor 149 are determined by the characteristics (amplitude, frequency, and / or phase) of the motor power signal 141.

[0026] Centrifuge 120 can be any type of centrifuge. For example, centrifuge 120 can be a pump, blower, or compressor. Referring also to FIG2, centrifuge 120 includes a body 121, an inlet 123 through which fluid flows into the body 121, an outlet 124 through which fluid flows out of the body 121, and an impeller 122. Impeller 122 is connected to rotor 149 via connecting rod 126. Connecting rod 126 is any type of connection capable of transmitting mechanical energy generated by motor 140 to impeller 122. For example, connecting rod 126 may include rod, gear, shaft, or combination of such devices. Rotation of impeller 122 applies rotational energy to the fluid in body 121 and transfers the fluid in body 121 between inlet 123 and outlet 124.

[0027] Centrifuge 120 is associated with performance metrics including head (H) and efficiency. The efficiency of centrifuge 120 is the relationship between input horsepower (which is input torque multiplied by the rotational speed of impeller 122) and flow rate (Q). The head (H) of machine 120 is the amount of pressure P required to achieve a given flow rate (Q) at outlet 124. Flow rate (Q) has a volumetric unit over time, such as cubic meters per second. Head (H) has a pressure unit, such as pounds per square inch or Pascal. The rotational speed or velocity of impeller 122 is expressed as the number of revolutions per unit time. The relationship between head (H) and flow rate (Q) is called the HQ curve. Centrifuge 120 is also associated with a system head (Hsys), which is the opposite of the flow produced by increasing head (H). System head (Hsys) takes into account the configurations and components used with centrifuge 120 (such as piping or other types of transfer systems that transport fluid between outlet 124 and process 170). The system head (Hsys) curve intersects the HQ curve at the operating point of centrifuge 120.

[0028] Centrifuge 120 is associated with predetermined performance data 151. The predetermined performance data 151 may be provided by the manufacturer of centrifuge 120 and may be collected before centrifuge 120 is put into use in fluid management system 100.

[0029] Figure 4 , Figure 5 , Figure 9 , Figure 10 and Figure 15 A flowchart is shown illustrating the process for determining the operating point of centrifuge 120 and / or controlling the operation of centrifuge 120 during use. Before discussing these techniques, an overview of exemplary embodiments of the motor control device 110 and controller 150 is discussed with reference to FIG3.

[0030] Figure 3 is a block diagram of a fluid management system 300 including a controller 350. The controller 350 is a derivative of the controller 150. Figure 1The fluid management system 300 includes a motor control unit 310 connected to the motor 140 via an electrical connection (such as a cable). The motor control unit 310 may be, for example, a variable speed drive (VSD), an adjustable speed drive (ASD), or a variable frequency drive (VFD). The motor control unit 310 provides a motor power signal 341 to the motor 140. The motor 140 drives the centrifuge 120.

[0031] Motor control unit 310 receives AC power from distribution network 301, which may be a multiphase power network supplying power to industrial, commercial, and / or residential customers, for example. AC distribution network 301 distributes AC power with a fundamental frequency (e.g., 50 Hz or 60 Hz). Distribution network 301 may have operating three-phase line-to-line voltages (e.g., up to 690 volts (RMS) for low voltages and above 690 V (e.g., 10 kV) for medium or high voltages). Network 301 may include, for example, one or more transmission lines, distribution lines, distribution or substation transformers, cables, and / or any other means for transmitting power.

[0032] The motor control unit 310 includes an electrical network 312 that receives AC power 305 from the distribution network 301 at an input node 314. The motor control unit 310 is enclosed in a housing or enclosure 311. The housing 311 is a three-dimensional body made of a solid and robust material that protects the electrical network 312. The motor control unit 310 also includes an output node 309. The motor 140 is connected to the motor control unit 310 at the output node 309.

[0033] Electrical network 312 generates an AC motor power signal 341 based on AC power 305 from distribution network 301. Electrical network 312 includes a converter 360 and an inverter 380. Converter 360 includes electrical network 362 configured to convert AC power 305 into direct current (DC) power 313. Converter 360 may be, for example, an active front end (AFE) or pulse width modulation (PWM) rectifier, or an 18-pulse rectifier. Electrical network 362 includes electronic components, such as diodes arranged to form a rectifier or in any other configuration that allows the conversion of AC power 305 into DC power 313.

[0034] Inverter 380 includes an electrical network 382 configured to convert DC power 313 into an AC motor power signal 341. Electrical network 382 may include power transistors or other controllable switching devices. For example, electrical network 382 may include three half-bridge circuits, each half-bridge circuit including two switching elements (such as power transistors) connected in series. Each pair of switching elements receives a direct current (DC) voltage from a DC power source (e.g., a battery, DC power supply, or other DC power source). In these embodiments, inverter 380 generates a three-phase pulse width modulation (PWM) signal by applying a command-based signal to each pair of switching elements. The characteristics (amplitude, frequency, and phase) of the three-phase PWM motor power signal 341 are determined by controlling the switching operation of the half-bridge circuits. PWM technology can be implemented based on any type of control algorithm, such as 6-step electronic commutation, various field-oriented controls, space vector PWM, or sinusoidal PWM.

[0035] The controller 350 is connected to the motor control device 310 via a control link 377. The control link 377 can be any type of path capable of carrying data, information, and / or commands. For example, the control link 377 can be a cable, a copper trace on a printed circuit board, or a wireless data connection. The controller 350 includes an electronic processing module 352, an electronic storage device 354, and an I / O interface 356. In some embodiments, the electronic processing module 352, the electronic storage device 354, and the I / O interface 356 are implemented as a microcontroller. Furthermore, although the controller 350 is shown external to the housing 311, the controller 350 may be encapsulated within the housing 311.

[0036] Electronic processing module 352 includes one or more electronic processors. The electronic processor of module 352 can be any type of electronic processor, can be of multiple types of processors, and may or may not include a general-purpose central processing unit (CPU), graphics processing unit (GPU), microcontroller, field-programmable gate array (FPGA), complex programmable logic device (CPLD), digital signal processor (DSP), microcontroller unit (MCU) and / or application-specific integrated circuit (ASIC).

[0037] Electronic storage device 354 is any type of electronic memory capable of storing data and instructions in the form of computer programs or software, and may include various types of memory. For example, electronic storage device 354 may include volatile and / or non-volatile components. Electronic storage device 354 is coupled to processing module 352, enabling processing module 352 to read data from electronic storage device 354 and write data to electronic storage device.

[0038] Processes 400, 500, 900, 1000, and 1500 can be implemented as a set of instructions stored on the electronic storage device 354 and executed by the electronic processing module 352. Additionally, PWM technology or other control technologies used in the electronic network 382 to drive the inverter 380 can be implemented as a set of executable instructions or computer software stored on the electronic storage device 354.

[0039] Furthermore, predetermined performance data 151 may be stored on electronic storage device 354. The predetermined performance data 151 includes N data values ​​for the head (H), where N is any integer greater than two, and each of the N data values ​​corresponds to the flow rate at outlet 124 for a specific rotational speed of impeller 122. For example, if N is 5, the predetermined performance data 151 includes five (5) values ​​for the head (H), where each of the five values ​​for the head (H) corresponds to a different flow rate at a specific rotational speed of impeller 122. The predetermined performance data 151 also includes an efficiency value for machine 120. The efficiency value provides the relationship between efficiency and flow rate. The efficiency value also includes the Optimal Efficiency Point (BEP), which is the maximum efficiency at which machine 120 can operate. BEP may be expressed as a percentage between 0% and 100% or as a value between 0 and 1.

[0040] The predetermined performance data 151 may include M sets of predetermined data, each of which is associated with a different speed of impeller 122, and where M is an integer value greater than 1. For example, the predetermined performance data 151 may include N pairs of head (H) and flow rate (Q) values ​​for each of the M different speeds of impeller 122. The M speeds that are part of the predetermined performance data 151 are referred to as the M predetermined impeller 122 speeds. Each of the M different speeds of impeller 122 is associated with a BEP flow rate (Q_BEP). The BEP flow rate at a particular impeller 122 speed is the most efficient flow rate for centrifuge 120. The BEP flow rate (Q_BEP) varies with the impeller 122 speed.

[0041] The predetermined performance data 151 may be stored as a set of discrete values. For example, the predetermined performance data 151 may be a set of M groups of N pairs of data values, where each pair of data values ​​includes a metric (e.g., head (H) or efficiency) value paired with an associated flow rate (Q) value. The predetermined performance data 151 may be stored in a lookup table or a database. In some embodiments, the predetermined performance data 151 may alternatively or additionally be stored in the form of a formula that associates one of the metrics (e.g., head (H) or efficiency) with the flow rate (Q).

[0042] I / O interface 356 is any interface that allows human operators, external devices, and / or autonomous processes to interact with controller 350. I / O interface 356 may include, for example, audio inputs and / or outputs (such as speakers and / or microphones), visual outputs (such as lights, light-emitting diodes (LEDs)), serial or parallel ports, Universal Serial Bus (USB) connections, and / or any type of network interface, such as Ethernet. I / O interface 356 may also allow contactless communication via, for example, IEEE 802.11, Bluetooth, mobile phone, or Near Field Communication (NFC) connections. Controller 350 may be operated, configured, modified, or updated, for example, through I / O interface 356.

[0043] In some implementations, I / O interface 356 enables controller 350 to communicate with remote station 395. Remote station 395 can be any type of site through which an operator can communicate with controller 350 without physical contact with controller 350. For example, remote station 395 can be a computer-based workstation, smartphone, tablet, or laptop computer connected to controller 350 via a service protocol, or a remote control connected to controller 350 via radio frequency signals.

[0044] Figure 4 This is a flowchart of process 400. Process 400 is an example of a process for determining the operating point of centrifuge 120. Process 400 can be executed by controller 150 or controller 350. For example, machine-readable instructions for implementing process 400 can be stored on electronic storage device 374 and executed by electronic processing module 372. Process 400 has been discussed in relation to fluid management system 300; however, process 400 can be applied to other fluid management systems.

[0045] Access information related to motor 140 (410). The accessed information includes the speed of motor 140 (rotor 149 rotational speed) and the torque generated by motor 140 when motor 140 is operable and receives motor power signal 341. The speed of motor 140 and the torque generated by motor 140 can be obtained in any manner known in the art.

[0046] In some implementations, the speed of motor 140 and the torque generated by motor 140 are estimated relative to motor power signal 341 without using speed or torque sensors. For example, the speed and torque of motor 140 may be estimated based on the value or amplitude of the voltage of motor power signal 341, the frequency of the voltage and / or current of motor power signal 341, the load value of motor 140 (which may be directly sensed by a power sensor or approximately equal to the input power), and nameplate data associated with motor 140. Nameplate data includes the rated power, rated speed, rated frequency, and rated voltage of motor 140. An example of such a technique for estimating the speed and torque of motor 140 is provided in U.S. Patent 8,203,298. Nameplate information and instructions for estimating speed and torque may be stored on electronic storage device 354 and executed by electronic processing module 352.

[0047] In other examples, the estimated speed and torque are determined by a separate controller and provided to controller 350 via I / O interface 356. In other embodiments, the operator of the fluid management system 300 may provide estimated values ​​of the speed and torque of motor 140 to controller 350 via I / O interface 356. Furthermore, in some embodiments, the torque and / or speed of motor 140 are determined based on previous estimates, inputs, or known values ​​of torque and / or speed. For example, the speed of motor 140 may increase or decrease by a known constant compared to a previous speed. In these embodiments, the current speed of motor 140 is determined by adding or subtracting a known amount from a previous speed value.

[0048] Access predetermined performance data 151 (420). The predetermined performance data 151 may include, for example, five (5) values ​​of head (H) of machine 120 for five corresponding flow rates (Q), and five values ​​of efficiency of machine 120 for five corresponding flow rates (Q).

[0049] The operating point (430) of machine 120 is determined. The operating point is determined based on measured or estimated speed and torque from motor 140 at 410 and predetermined performance data 151 accessed from 420. The operating point determination does not rely on sensors associated with machine 120. For example, the operating point is determined without using flow meters or pressure gauges at inlet 123 or outlet 124. Furthermore, in embodiments where no sensors are used to estimate the speed and torque of motor 140, the operating point is determined or estimated solely based on motor power signal 341 and information about motor 140. Relative to Figure 5 A detailed example of determining the operating point of machine 120 is provided.

[0050] Figure 5This is a flowchart of process 500. Method 500 is another example of a process for determining the operating point of centrifuge 120. Process 500 can be executed by controller 150 or controller 350. For example, machine-readable instructions for implementing process 500 can be stored on electronic storage device 374 and executed by electronic processing module 372. Process 500 has been discussed in relation to fluid management system 300; however, process 500 can be applied to other fluid management systems.

[0051] The estimated speed (rpm_est) and torque (P_est) of motor 140 can be based on the above relative to Figure 4 The element under discussion (410) is obtained. The speed (rpm_est) of motor 140 is compared with the speeds of M predetermined impellers 122 (510). Specifically, controller 350 determines whether the estimated speed (rpm_est) of motor 140 corresponds to any of the M predetermined impeller speeds 122 (515). For example, in some embodiments, link 126 is configured such that the speed of rotor 149 is the same as the speed of impeller 122. In these embodiments, the estimated speed (rpm_est) is directly compared with the M predetermined impeller speeds 122. For example, the estimated speed (rpm_est) can be subtracted from each of the M predetermined impeller speeds 122 to determine whether the estimated speed (rpm_est) is the same as one of the M predetermined impeller speeds 122. In other embodiments, link 126 transmits the mechanical energy of rotor 149 to impeller 122 in a more complex manner (e.g., via a gear system), and the speed of rotor 149 is different from the speed of impeller 122. In these embodiments, the estimated speed (rpm_est) of the rotor 149 is first adjusted according to the influence of the connecting rod 126, and then the adjusted estimated speed is compared with M predetermined impeller 122 speeds to determine whether the estimated speed (rpm_est) corresponds to one of the M predetermined impeller 122 speeds.

[0052] First, we will discuss the case where the estimated speed (rpm_est) corresponds to one of M predetermined impeller speeds.

[0053] If the estimated speed (rpm_est) is the same as or differs from the speeds of M predetermined impellers 122 by a threshold difference, process 500 uses values ​​from predetermined performance data 151 associated with the predetermined impeller 122 speed to calculate the PQ curve (525). The PQ curve is the change in power (P) (e.g., in watts) used by machine 120 as a function of flow rate (Q). The PQ curve can be determined using Formula 1:

[0054]

[0055] Where k is an integer exponent value between 1 and N, P is the power used by centrifuge 120, Q is the flow rate, H is the head (H) at flow rate Q, ρ is the density of the fluid in body 121, g is the acceleration due to gravity, and η is the efficiency of machine 120. The N values ​​of Q and H in Equation 1 are derived from predetermined performance data 151 at a predetermined impeller speed 122, which corresponds to the estimated motor speed (rpm_est). The predetermined performance data 151 also includes the efficiency variation with flow rate, and the efficiency value corresponding to the flow rate Q used in Equation (1) is obtained from the predetermined performance data 151.

[0056] Figure 6 An example of determining the PQ curve 604 is shown. The PQ curve 604 is found by determining N values ​​of P using Formula 1, and then determining the relationship between the N values ​​of P and the N values ​​of Q. This relationship can be found using any type of curve fitting or data fitting technique. Figure 6 In the example, the power (P) required by centrifuge 120 increases linearly with the flow rate (Q).

[0057] The motor power used in centrifuge 120 lies on a defined PQ curve (530). According to Equation 2, the power provided by motor 140 is related to the motor's torque and speed:

[0058] P_motor = Torque * Speed ​​Formula (2).

[0059] The estimated torque (P_est) and estimated speed (rpm_est) of motor 140 are obtained from (410). Therefore, the power (P_motor) supplied to centrifuge 120 can be determined according to Equation 2. After determining (P_motor), the corresponding operating flow rate (Q_op) is determined according to the P_Q curve. See again Figure 6 Q_op is shown on the horizontal axis.

[0060] The operating point of centrifuge 120 is determined (535). Since the estimated motor speed (rpm_est) is determined to correspond to one of M predetermined impeller 122 speeds, the predetermined performance data 151 includes the values ​​of head (H) and efficiency of centrifuge 120 as a function of flow rate (Q) for the value of head (H) and efficiency of centrifuge 120 at the current flow rate (Q_op). Therefore, the head (H) and efficiency of centrifuge 120 at the current flow rate (Q_op) can be determined. The operating point can be the head (H) and the corresponding flow rate (Q_op) and / or the efficiency value (η_op) and the corresponding flow rate (Q_op). Figure 7 The diagram illustrates the use of efficiency curves derived from efficiency data included in predetermined performance data 151 to determine operating efficiency (η_op).

[0061] Controller 350 determines whether the operating efficiency (η_op) is acceptable (545). To determine whether the operating efficiency (η_op) is acceptable, controller 350 compares the operating efficiency (η_op) with the optimal efficiency point (BEP) of centrifuge 120. For example, the operating efficiency (η_op) can be compared with the BEP by subtracting the operating efficiency (η_op) from the BEP, determining the ratio between the operating efficiency (η_op) and the BEP, or by determining the percentage difference between the operating efficiency (η_op) and the BEP and comparing the result with an efficiency threshold. The efficiency threshold can be, for example, a percentage (such as 1%, 2%, or 5%) or a value (such as 0.01, 0.02, or 0.05). The efficiency threshold can be stored on electronic storage device 374. The efficiency threshold can be provided by the operator of fluid management system 300, for example via I / O interface 376, so that the threshold can be adjusted according to the application.

[0062] If the result compared with BEP is less than the efficiency threshold, then the operating efficiency (η_op) is close enough to BEP, and the operating efficiency (η_op) of centrifuge 120 is acceptable. If the operating efficiency (η_op) is acceptable, centrifuge 120 is operating effectively, and process 500 ends or returns to (510) to continue monitoring centrifuge 120.

[0063] If the operating efficiency (η_op) is unacceptable, controller 350 changes the speed (550) of motor 140 so that the operating efficiency of centrifuge 120 is closer to the BEP. Changing the speed of motor 140 changes the speed of impeller 122 and the operating point of centrifuge 120. In other words, changing the speed of motor 140 changes the operating efficiency (η_op). Controller 350 changes the speed of motor 140 by controlling inverter 380 to change the characteristics (amplitude, frequency, and / or phase) of motor power signal 341.

[0064] After the controller 350 adjusts the motor 140, a new speed (rpm_new) and torque (torque_new) of the motor 140 are determined at (410). The data (520) in the predetermined performance data 151 are adjusted according to the new speed (rpm_new) using the similarity law. The similarity law is the relationship between the pressure head (H), efficiency, and impeller 122 speed. The similarity law is:

[0065]

[0066]

[0067]

[0068] Where the subscript 0 indicates the initial value, Q is the flow rate, H is the head, r is the rotational speed of the impeller 122, and P is the mechanical power supplied to the centrifuge 120. In this example, r0 is (rpm_est), which is the speed of the motor 140 before adjustment, and r is the updated estimated speed (rpm_new) determined after controlling the inverter 380 to change the speed of the motor 140. Equations 3 and 4 are used to determine the updated HQ curve. The similarity law assumes that the efficiency of the centrifuge 120 remains the same even if the speed of the impeller 122 changes. Therefore, the relationship between efficiency and flow rate (Q) included in the predetermined performance data 151 is not updated.

[0069] The updated PQ curve (525) is determined. The PQ curve can be determined using Equation 1, the updated HQ curve is determined at (520) using the similarity law, and the efficiency data is determined from the predetermined performance data 151. Alternatively, Equation 5 can be used to update the PQ curve determined in the previous performance at (525).

[0070] Process 500 then proceeds to (530) to position the power used by centrifuge 120 at the updated estimated speed (rpm_new). The power (P_new) supplied by motor 140 at the updated estimated speed (rpm_new) is determined based on Equation 2. After determining the power supplied to centrifuge 120 at the updated speed (P_new), the updated flow rate (Q_updated) achieved by supplying power (P_new) at the updated estimated speed (rpm_new) is determined according to the updated P_Q curve.

[0071] The operating point is determined again (535). To determine the operating point (based on the speed variation of impeller 122), the head (H) value associated with the updated flow rate (Q_updated) is determined based on the updated HQ curve derived using formulas (3) and (4). The efficiency at Q_updated is determined based on the efficiency curve included in the pre-determined performance data 151 (540). The efficiency at Q_updated is estimated to determine whether it is acceptable (545). Controller 350 continues to perform in this manner (520)-(545) until the current operating efficiency (η_op) determined at (540) is acceptable, or until process 500 stops (e.g., by the operator).

[0072] The above discussion pertains to an example where the initial motor speed estimate (rpm_est) corresponds to one of M predetermined speeds. Returning to the discussion at (515), if the initial motor speed estimate (rpm_est) does not correspond to any of the M predetermined impeller 122 speeds, then process 500 proceeds from (515) to (520) before proceeding to (525). At (520), the similarity law is applied to the H and Q values ​​in the predetermined performance data 151, and at (525), the corrected data obtained by applying the similarity law is used to determine the PQ curve. Controller 350 continues to execute (520)-(545) until the operating efficiency (η_op) determined at (540) is acceptable, or until process 500 stops.

[0073] Figure 8 This is a graph illustrating the performance characteristics of centrifuge 120. Figure 8 This includes three HQ curves 801a, 801b, and 801c (shown as short dashed lines). Each of curves 801a, 801b, and 801c represents the HQ curve of the impeller 122 at different speeds. Curve 801a is used for speeds greater than curve 801b, and curve 801b is used for speeds greater than curve 801c. Figure 8 It also includes three efficiency curves 802a, 802b, and 802c (shown as long dashed lines). Each curve 802a, 802b, and 802c represents the variation of a specific efficiency with flow rate (Q). Efficiency curves 802a, 802b, and 802c are part of predetermined performance data 151. Figure 8 In the example, curve 802b is used for BEP, and curves 802a and 802c are used for lower efficiencies. For example, curve 802b may represent 70% efficiency as a function of flow rate (Q), and curves 802a and 802c may each represent 60% efficiency as a function of flow rate (Q).

[0074] Figure 8 This also includes a system head (Hsys) curve 803 (shown as a solid line). The system head (Hsys) curve 803 is the variation of system head (Hsys) with flow rate (Q). The system head (Hsys) curve is determined by agitating the speed of motor 140 (e.g., at 550 in process 500) and then recalculating the operating point at (535). Figure 8In the example shown, (520)-(550) were executed three times, and three operating points 804a, 804b, and 804c were determined. Operating points 804a, 804b, and 804c are the locations where the system head curve 803 intersects with the HQ curves 802a, 802b, and 802c. The Hsys curve was determined by performing curve fitting on the determined operating points 804a, 804b, and 804c. The optimal efficiency point flow rate (Q_BEP) for a specific impeller speed 122 is the flow rate at the point where the highest efficiency curve (802b in this example) intersects with the HQ curve. The optimal efficiency point flow rate (Q_BEP) is labeled as 805a, 805b, and 805c.

[0075] Compared to Figure 9 Further discussion of examples related to Q_BEP. Figure 9 This is a flowchart of process 900. Process 900 is used to regulate the speed of motor 140 to achieve more efficient operation of centrifuge 120. Process 900 can be executed by controller 150 or controller 350. For example, machine-readable instructions for implementing process 900 can be stored on electronic storage device 374 and executed by electronic processing module 372. Process 900 has been discussed in relation to fluid management system 300; however, process 900 can be applied to other fluid management systems.

[0076] Process 900 includes (545), which has been discussed above. If the efficiency determined at (540) is acceptable, process 900 ends. If the efficiency determined at (540) is unacceptable, controller 350 compares Q_op with Q_BEP. Q_op is the flow rate (Q) associated with the operating point determined in (535). Q_BEP is the flow rate at the intersection of the highest efficiency curve corresponding to the speed of impeller 122 and the HQ curve. For example, and referring to Figure 8 If H_Q curve 801b is the HQ curve of the impeller 122's speed, then the operating point is 804b (corresponding to...). Figure 8 The Qop_b) and the BEP operation point is 805b (corresponding to Figure 8 QBEP_b).

[0077] When centrifuge 120 operates at its highest efficiency, Q_op equals Q_BEP. If Q_op does not equal Q_BEP, the speed of motor 140 is adjusted to move Q_op closer to or equal to Q_BEP, as described below.

[0078] At (947), Q_op is estimated to determine if Q_op is less than Q_BEP. If Q_op is less than Q_BEP, controller 350 increases the speed of motor 140 (950_2). If Q_op is less than Q_BEP, centrifuge 120 is too large, and increasing the flow rate (Q) will move the operating point closer to Q_BEP. Therefore, the flow rate is increased by increasing the speed of motor 140.

[0079] If Q_op is greater than Q_BEP (such as in relative to Q_BEP) Figure 8 In the example discussed, the controller reduces the speed of motor 140 (950_1). If Q_op is greater than Q_BEP, the centrifuge 120 is too small, and reducing the flow rate (Q) will move the operating point closer to Q_BEP. Therefore, the flow rate is reduced by decreasing the speed of motor 140.

[0080] The speed of motor 140 can be decreased at (950_1) or increased at (950_2) by a predetermined constant amount stored in electronic storage device 354. The increase and decrease amounts can be the same. For example, the speed of motor 140 can decrease at (950_1) or increase by 5 revolutions per minute at (950_2). In other embodiments, the amount by which the speed of motor 140 increases or decreases depends on operating conditions. For example, the amount by which the speed of motor 140 increases or decreases can be a fixed percentage of the current estimated speed of motor 140.

[0081] After the speed of motor 140 decreases at (950_1) or increases at (950_2), the speed and torque of motor 140 are estimated using (410). If the speed of motor 140 decreases at (950_1), the operating point is determined again at (960_1). If the speed of motor 140 increases at (950_2), the operating point is determined at (960_2). Elements (960_1) and (960_2) are identical and both implement process 500. Figure 5 Elements (520)-(540) of ). Elements (960_1) and (960_2) in Figure 9 The motor 140 is shown as a separate element, but can be implemented as a single module, function, or set of machine-executable instructions that take input commands specifying an increase or decrease in speed and generate output commands that act on inverter 380 to adjust motor 140 accordingly. Process 900 continues until the efficiency determined at (545) is considered acceptable.

[0082] Figure 10This is a flowchart of process 1000. Process 1000 is used to enable centrifuge 120 to achieve peak efficiency within a bounded operating region. The bounded operating region may be user-defined and does not necessarily include the flow rate associated with BEP (Q_BEP). Process 1000 may be executed by controller 150 or controller 350. For example, machine-readable instructions for implementing process 1000 may be stored on electronic storage device 374 and executed by electronic processing module 372. Process 1000 has been discussed in relation to fluid management system 300; however, process 1000 may be applied to other fluid management systems.

[0083] Process 1000 includes some elements of processes 500 and 900 discussed above. At (545), the acceptability of the current operating efficiency (η_op) of centrifuge 120 is estimated. If the current operating efficiency (η_op) is unacceptable, the current operating flow rate (Q_op) is compared with the flow rate associated with BEP (Q_BEP) at (947). The speed of motor 140 is decreased at (950_1) or increased at (950_2), and the new operating point of centrifuge 120 at the new speed of motor 140 is determined at (960_1) or (960_2), respectively, as relative to... Figure 9 The subject of discussion.

[0084] First, we discuss an example where the current operating flow (Q_op) is less than Q_BEP. The updated operating point determined at (960_2) includes the head (H) value and the corresponding flow (Q_op). Figure 11 An example of an operating point with a head (H) value and a flow rate (Q_op) is shown. Figure 11 The bounded operating region 1190, the system head (Hsys) curve 1103, the HQ curve 1101b, and the maximum efficiency curve 1102b are also shown. Q_BEP is the point where the efficiency curve 1102b intersects the Hsys curve 1103.

[0085] The bounded operating region 1190 is the area within the HQ space defined by the maximum head (H2), minimum head (H1), minimum flow rate (Q1), and maximum flow rate (Q2). The bounded operating region 1190 includes H1, H2, Q1, and Q2, as well as all values ​​of the head (H) between H1 and H2, and all values ​​of the flow rate (Q) between Q1 and Q2. The bounded operating region 1190 can be defined based on predetermined values ​​of H1, H2, Q1, and Q2 loaded by the manufacturer onto the electronic storage device 374. In some embodiments, the operator of the controller 350 can input user-defined values ​​of H1, H2, Q1, and Q2 via the I / O interface 376. Therefore, the bounded operating region 1190 can be user-defined and thus customized according to the end-user's application.

[0086] In process 1000, the speed of motor 140 is adjusted until centrifuge 120 reaches the most efficient operating point within the bounded operating region 1190. The value of (Q_op) and the head (H) found in (960_2) are compared with H1, H2, Q1, and Q2 to determine if the current operating point is within the bounded operating region 1190 (1065_2). If the head (H) is between H1 and H2 and Q_op is between Q1 and Q2, then the current operating point (Q_op) is within the bounded operating region 1190. Figure 11 In the example, the current operation point (Q_op) is within the bounded operation region 1190. Procedure 1000 returns to (545) to determine if the current efficiency (η_op) is acceptable. Procedure 1000 continues until an acceptable efficiency is found within the operation region 1190.

[0087] In relative to Figure 11 In the example discussed, Q_BEP is within the bounded operation region 1190. However, the bounded operation region does not necessarily include Q_BEP. Figure 12 An example of another bounded operating region 1290 excluding Q_BEP is shown. In this example, the current operating point (Q_op) is initially less than Q_BEP, and the speed of motor 140 increases (950_2). After the speed of motor 140 increases, the speed and torque of motor 140 are estimated using (410). The current operating point (Q_op and pressure head (H)) is estimated at 960_2. The current operating point Q_op is compared with Q1 and Q2, and the pressure head (H) is compared with H1 and H2 to determine whether the current operating point is within the bounded operating region 1290. Figure 12 In the example shown, the current operating point is within the bounded operating region 1290. Process 1000 returns to (545) to compare the current flow (Q_op) with Q_BEP and continues to increase the speed of motor 140 until the current operating point determined at (960_2) is determined to be outside the bounded operating region 1290 at (1065_2). Then the speed of motor 140 is decreased (1068) and the current operating point (960_2) is determined until the current operating point is within the region of operation 1290.

[0088] In this example, Q_BEP is not within the area of ​​operation 1290, so the speed of motor 140 is adjusted until Q_op equals the flow rate associated with point 1206. Point 1206 is on the boundary of the bounded operating area 1290 and on the side closest to BEP. Point 1206 is considered to be within the bounded operating area 1290, and process 1000 returns to (545) and ends because Q_op is now closest to Q_BEP and is also within the operating area 1290.

[0089] Next relative to Figure 13 and Figure 14 Discuss examples where the current operation flow (Q_op) is greater than Q_BEP. Figure 13 In the example, the speed of motor 140 is reduced (950_1) to bring the current operating point (Q_op) closer to Q_BEP. The speed and torque of motor 140 are estimated (410), and the new operating point (960_1) is estimated. If the new operating point is within the bounded operating region 1390 (such as in...), Figure 13 In the example shown), process 1000 returns to (545). Process 1000 continues in this manner until the current flow (Q_op) is acceptable.

[0090] Figure 14 An example is shown where Q_BEP is outside the bounded operating region 1490. The speed of motor 140 is decreased (950_1), and a new operating point (960_1) is determined. The operating point is not within the bounded operating region 1490 (1065_1), and the speed of motor 140 is increased (1067). Whenever the speed of motor 140 increases at (1067), the operating point (960_1) is estimated. The speed of motor 140 is increased until the operating point flow (Q_op) is located at point 1406 on the boundary of the bounded operating region 1490. Point 1406 is the flow closest to Q_BEP within the bounded operating region 1490. Process 1000 ends because the most effective flow within the bounded operating region 1490 has been determined.

[0091] Other implementations of processes 500, 900, and 1000 are also possible. For example, element (545) is discussed above as an evaluation of the efficiency of centrifuge 120 at the current operating point. For example, in the example above, the difference between BEP and the current operating efficiency (η_op) is compared with a threshold. If the absolute value of the difference is less than the threshold, the current operating efficiency (η_op) is considered acceptable.

[0092] However, other implementations of (545) can be used in any of processes 500, 900, and 1000. For example, in some implementations, (545) determines the absolute value of the difference between the current operating point flow rate (Qop) determined at (540) and a predefined flow rate (Qset), and compares this difference with a threshold (th_Q). If the absolute value of the difference is less than the threshold (th_Q), the current operating point flow rate is considered acceptable. Implementing (545) in this way allows centrifuge 120 to be adjusted to any set flow rate point (Qset) using processes 500, 900, and / or 1000. Furthermore, in some implementations, electronic storage device 374 includes instructions for comparing a user-provided Qset value with information about centrifuge 120 to ensure that the value of Qset is a flow rate value achievable with centrifuge 120.

[0093] To provide another example, in some implementations, (545) determines the absolute value of the difference between the current operating head (H) determined at (540) and a predefined or user-supplied head (Hset) value, and compares this difference with a threshold (th_H). If the absolute value of the difference is less than the threshold (th_H), the current operating head (H) is considered acceptable. Implementing (545) in this way allows the centrifuge 120 to be adjusted to any head (H) value using processes 500, 900, and / or 1000. Furthermore, in some implementations, the electronic storage device 374 includes instructions for comparing the user-supplied Hset value with information about the centrifuge 120 to ensure that the value of Hset is a head (H) value that can be achieved with the centrifuge 120.

[0094] Figure 15 This is a flowchart of process 1500. Process 1500 is used to operate centrifuge 120 at a varying rate and therefore with varying performance metrics. The average of the performance metrics is equal to the user-requested value of that metric. Figure 16 It is a graph showing the speed of impeller 122 or motor 140 changing over time. Figure 17 It is a graph showing the flow rate (performance metric) of centrifuge 120 over time. Figure 16 and Figure 17 They have the same time scale. For example... Figure 16 and Figure 17 As shown, the speed and flow rate of impeller 122 change over time.

[0095] Process 1500 can be executed by controller 150 or controller 350. For example, machine-readable instructions for implementing process 1500 can be stored on electronic storage device 374 and executed by electronic processing module 372. Process 1500 has been discussed in relation to fluid management system 300; however, process 1500 can be applied to other fluid management systems.

[0096] The setpoint value (1510) of the access metric. The setpoint value may be, for example, the flow rate (Qset) input by the end user into the controller 350 using the I / O interface 376. The centrifuge 120 is controlled to operate in an on-off mode, such that the machine 120 repeatedly alternates between an on state and an off state, and the average value of the metric over time is the setpoint value (Qset). The metric has a first value during a first time period and a second value during a second time period. When the machine 120 operates in an on-off mode, the second value of the metric is 0, and the machine 120 is off during the second time period. Continuing with the example where the end user wants to control the machine 120 with an average flow rate having Qset and also wants to control the machine 120 in an on-off mode, Equation (6) shows the relationship between Q1, t2, t1 and Qset:

[0097]

[0098] Where t1 is a first finite time period, t2 is a second finite time period, and Q1 is the flow rate during the on state in the first time period t1. For example, the value of Q1 can be Q_BEP. By using Q_BEP as the value of Q1, the centrifuge 120 operates effectively when in the on state. The end user can specify the value of t1 or t2. In some embodiments, the end user specifies a value of Q1 other than Q_BEP.

[0099] Centrifuge 120 is controlled to operate at a first value measured during the first time period (1520). Continuing with the example above and referring to... Figure 16 and Figure 17 Centrifuge 120 is controlled such that the flow rate is Q1 during a first time period t1. Centrifuge 120 can be controlled using process 900, wherein (545) is configured to estimate whether the flow rate at the current estimated operating point is equal to Q1, and process 900 adjusts the speed of motor 140 until the flow rate at the operating point is Q1.

[0100] Centrifuge 120 is controlled to operate at a second value of the metric during the second time period (1530). Continuing with the example above, the second value of the flow rate is 0 because machine 120 is turned off during the second time period. In this example, centrifuge 120 is controlled by turning off machine 120. In other examples, the second value of the metric is non-zero, and machine 120 is controlled using, for example, process 900 to operate machine 120 at the second value of the metric in the manner discussed in (520).

[0101] These and other embodiments are within the scope of the claims.

Claims

1. A control system comprising: a controller configured to: access an estimated torque and an estimated speed of a motor mechanically coupled to an impeller of a centrifuge; access at least one set of predetermined performance data values associated with a known speed of the impeller, wherein each set of predetermined performance data values includes a plurality of flow values and a plurality of performance metric values; determine an operating point of the centrifuge based on the estimated torque, the estimated speed, and the at least one set of predetermined performance data values, wherein the operating point is a head and corresponding flow and / or efficiency values and corresponding flow; compare the determined operating point to a best efficiency point, BEP, associated with the centrifuge; and determine whether to change a speed of the motor based on the comparison.

2. The control system of claim 1, wherein the controller is configured to access a plurality of sets of predetermined data values associated with the centrifuge, and wherein each of the plurality of sets is associated with a different known speed of the impeller, and the performance metric values include predetermined head values and predetermined efficiency values.

3. The control system of claim 2, wherein the controller is further configured to compare the estimated speed of the motor to the different known speeds of the impeller; and if a difference in similarity of the estimated speed of the motor and one of the different known speeds is within a speed threshold, the controller is configured to determine a machine power characteristic based on the predetermined head value and the predetermined efficiency value; and if the similarity difference value of the estimated speed of the motor and one of the different known speeds is not within the speed threshold, the controller is configured to determine an updated set of head values and an updated set of efficiency values; and the controller is configured to determine the machine power characteristic based on the updated set of head values and the updated set of efficiency values.

4. The control system of claim 3, wherein the controller is further configured to determine a power value corresponding to the estimated torque from the machine power characteristic, and wherein the controller is further configured to determine a flow operating point that is the flow value corresponding to the determined power value.

5. The control system of claim 4, wherein to determine the operating point of the centrifuge, the controller is configured to determine an efficiency operating point and a head operating point based on the flow operating point.

6. The control system of claim 5, wherein to compare the determined operating point to the best efficiency point, BEP, the controller is configured to compare the determined efficiency operating point to the best efficiency point, BEP.

7. The control system of claim 6, wherein if the controller changes the speed of the motor, after changing the speed of the motor, the controller is further configured to: determine an updated set of head values at the flow value and an updated set of efficiency values at the flow value; and the controller is configured to update the machine power characteristic based on the updated set of head values and the updated set of efficiency values.

8. The control system of claim 1, wherein the controller changes the speed of the motor, thereby changing a flow rate of fluid moved by the impeller, and the controller is further configured to determine the operating point again after changing the speed of the motor.

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