Power conversion device, transport system, power conversion method, program, and diagnostic device

Abstract

The power conversion device (3) includes: a power conversion circuit (10) that converts primary-side electric power into secondary-side electric power and supplies the secondary-side electric power to a motor (6); and a control circuit (100) that controls the secondary-side electric power to follow a control command by the power conversion circuit (10), the control circuit (100) calculating a variation level that indicates a variation range of a driving force of the motor (6) in a sampling period of a prescribed length, and detecting an abnormality of a conveyance device (2) including the motor (6) and a conveyance section (5) driven by the motor (6) on the basis of the variation level.

Description

Technical Field

[0001] This disclosure relates to a power conversion device, a transmission system, a power conversion method, a procedure, and a diagnostic device. Background Technology

[0002] Patent document 1 discloses a transmission device that uses an inverter.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2007-70066 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] This disclosure provides a simplified and efficient power conversion device, transmission system, power conversion method, procedure, and diagnostic device for detecting anomalies in equipment.

[0008] Technical solution

[0009] One aspect of the power conversion device disclosed herein includes: a power conversion circuit that converts primary power into secondary power and supplies it to a motor; and a control circuit that, through the power conversion circuit, causes the secondary power to follow a control command, the control circuit calculating a variation level representing the variation amplitude of the driving force of the motor during a sampling period of a predetermined length, and detecting an abnormality of the device including the motor and a movable part driven by the motor based on the variation level.

[0010] Another aspect of the conveying system disclosed herein includes the aforementioned power conversion device and equipment, wherein the equipment has a conveying section as a movable part that supports and conveys objects, and a motor as a motor that drives the conveying section.

[0011] Another aspect of the power conversion method disclosed herein includes: a power conversion circuit that converts primary power into secondary power and supplies it to a motor, such that the secondary power follows a control command; calculating a variation level representing the magnitude of the variation in the driving force of the motor during a sampling period of a predetermined length; and detecting anomalies in the device including the motor and a movable part driven by the motor based on the variation level.

[0012] Another aspect of this disclosure is a procedure for causing a power conversion device to perform the following steps: by converting primary power into secondary power and supplying it to a motor, the secondary power follows a control command; calculating the variation level of the driving force of the motor during a sampling period of a specified length; and detecting anomalies in the device, including the motor and the movable part driven by the motor, based on the variation level.

[0013] Another aspect of the diagnostic device disclosed herein is based on the power supplied to the motor by the power conversion circuit to calculate the variation level of the driving force of the motor during a sampling period of a specified length, and based on the variation level, detects abnormalities in the device including the motor and movable parts.

[0014] Beneficial effects

[0015] According to this disclosure, a simplified and effective power conversion device, transmission system, power conversion method, procedure, and diagnostic device can be provided for detecting the abnormality of the equipment. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating the structure of a conveying system.

[0017] Figure 2 It is a block diagram representing the functional configuration of a power conversion device.

[0018] Figure 3 This is a block diagram illustrating the hardware configuration of a power conversion device.

[0019] Figure 4 This is a flowchart illustrating the control process of a power conversion circuit.

[0020] Figure 5 This is a flowchart illustrating the threshold setting process.

[0021] Figure 6 This is a flowchart illustrating the anomaly detection process.

[0022] Figure 7 This is a flowchart illustrating a variation of the threshold setting process.

[0023] Figure 8 This is a flowchart illustrating a variation of the anomaly detection process.

[0024] Figure 9 This is a block diagram representing a modified example of a diagnostic device. Detailed Implementation

[0025] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used to refer to the same elements or elements having the same function, and repeated descriptions are omitted.

[0026] [Conveying System]

[0027] Figure 1 The conveying system 1 shown is a system for conveying objects, and includes a conveying device 2, a power conversion device 3, and a host controller 4 (see reference). Figure 2). Specific examples of conveying devices 2 include belt conveyors, roller conveyors, etc.

[0028] Figure 1 The illustrated conveying device 2 is a roller conveyor, comprising a conveying section 5 and a motor 6. The conveying section 5 (movable part) includes multiple conveying rollers 7, a belt 8, multiple pulleys 9, and a load sensor 20. The multiple conveying rollers 7 are arranged along the conveying direction of the object and are configured perpendicular to the conveying direction. The multiple conveying rollers 7 rotate in the same direction while supporting the object, thereby conveying the object along the conveying direction. The belt 8 is mounted on the multiple pulleys 9 and is connected to the multiple conveying rollers 7.

[0029] Motor 6 drives conveyor unit 5. For example, motor 6 is a rotary electric motor that rotates at least one pulley 9. The torque of motor 6 that rotates pulley 9 is transmitted to multiple conveyor rollers 7 via belt 8. As a result, the multiple conveyor rollers 7 rotate in the same direction. Motor 6 can be either an induction motor or a synchronous motor.

[0030] The load sensor 20 senses the load on the conveying device 2 (e.g., the weight of the object being conveyed). The load sensor 20 may also be an inventory sensor that senses whether an object being conveyed is present or not.

[0031] like Figure 2 As shown, the power conversion device 3 converts the power from the power source 90 (primary-side power) into drive power (secondary-side power) and supplies it to the motor 6. The power source 90 can be alternating current (AC) or direct current (DC). The drive power is alternating current (AC). As an example, both the power source 90 and the drive power are three-phase AC. For example, the power conversion device 3 has a power conversion circuit 10 and a control circuit 100.

[0032] The power conversion circuit 10 converts primary-side power into secondary-side power and supplies it to the motor 6. For example, the power conversion circuit 10 includes a converter circuit 11, a smoothing capacitor 12, an inverter circuit 13, and a current sensor 14. The converter circuit 11, for example, is a diode bridge circuit or a PWM (pulse width modulation) converter circuit, which converts the power supply into direct current (DC). The smoothing capacitor 12 smooths the DC power. The inverter circuit 13 performs the power conversion between the DC power and the drive power.

[0033] For example, the inverter circuit 13 has multiple switching elements 15, and the aforementioned power conversion is performed by switching the multiple switching elements 15 on / off. The switching elements 15 are, for example, power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors), which are switched on / off according to a gate drive signal.

[0034] The current sensor 14 senses the current flowing between the inverter circuit 13 and the motor 6. For example, the current sensor 14 can be configured to sense the current of all three phases (U phase, V phase, and W phase) of a three-phase AC circuit, or it can be configured to sense the current of any two phases of the three-phase AC circuit. As long as zero-phase current is not generated, the sum of the currents of the U phase, V phase, and W phase is zero. Therefore, even when sensing the current of two phases, information about the current of all three phases can be obtained.

[0035] The configuration of the power conversion circuit 10 shown above is only one example. The configuration of the power conversion circuit 10 can be arbitrarily changed as long as it can generate drive power for the motor 6. The power conversion circuit 10 can also be a matrix converter circuit that performs bidirectional power conversion between power supply and drive power without DC conversion. When the power supply is DC, the power conversion circuit 10 may not have a converter circuit 11.

[0036] The control circuit 100 controls the power conversion circuit 10 in such a way that the secondary-side electrical quantity follows the control command. The secondary-side electrical quantity is a physical quantity related to the electrical state of the secondary side. Specific examples of secondary-side electrical quantities include power, voltage, and current. The control circuit 100 calculates the variation level of the driving force of the motor 6 within a sampling period of a specified length, and detects abnormalities in the conveying device 2 (equipment), which includes the motor 6 and the conveying unit 5 (a movable part driven by the motor 6), based on the variation level.

[0037] The malfunction of the conveying device 2 can be a malfunction of the motor 6 or a malfunction of the conveying section 5. Specific examples of malfunctions of the motor 6 include damage to the bearing. Specific examples of malfunctions of the conveying section 5 include damage to the bearing of the conveying roller 7, damage to the bearing of the pulley 9, damage to the belt 8, foreign objects entering between adjacent conveying rollers 7, foreign objects entering between the conveying roller 7 and the belt 8, and foreign objects entering between the belt 8 and the pulley 9.

[0038] Alternatively, the control circuit 100 sets a threshold based on the level of variation when the conveying device 2 is in an unloaded state (e.g., when there is no object being conveyed). After the threshold is set, the level of variation is calculated when the conveying device 2 is in an unloaded state, and an abnormality of the conveying device 2 is detected based on the level of variation and the threshold.

[0039] Alternatively, the control circuit 100 can detect abnormalities in the conveyor 2 based on the number of fluctuation levels that exceed a threshold among a plurality of fluctuation levels obtained by repeatedly calculating the fluctuation levels when the conveyor 2 is in an unloaded state.

[0040] Alternatively, the control circuit 100 acquires multiple sets of evaluation results (hereinafter referred to as "level groups") that respectively include the load level and the variation level representing the magnitude of the load (e.g., the weight of the object being transported) in the conveying device 2. Based on these multiple sets of evaluation results, a threshold distribution (profile) representing the relationship between the load level and a threshold is set. After the threshold distribution is set, a set of level groups including the load level and the variation level is acquired. Based on this set of level groups and the threshold distribution, anomalies in the conveying device 2 are detected.

[0041] Alternatively, the control circuit 100 can detect anomalies in the conveying device 2 based on the number of level groups exceeding a threshold distribution among multiple level groups, wherein the multiple level groups are obtained by repeatedly acquiring a set of level groups.

[0042] Alternatively, the control circuit 100 can calculate the voltage command corresponding to the frequency command based on the V / f method as the control command, and calculate the variation level based on the current flowing between the power conversion circuit 10 and the motor 6 and the frequency command.

[0043] For example, such as Figure 2 As shown, the control circuit 100, as a functional component (hereinafter referred to as "functional block"), includes an instruction calculation unit 111, a PWM control unit 112, a current acquisition unit 113, a current information storage unit 114, a load information acquisition unit 115, a change calculation unit 116, a threshold setting unit 117, a threshold storage unit 118, an abnormality detection unit 119, and an abnormality notification unit 121.

[0044] The instruction calculation unit 111 calculates a control instruction. For example, the instruction calculation unit 111 calculates a voltage instruction corresponding to a frequency instruction as a control instruction based on a V / f ratio. The voltage instruction includes the magnitude of the voltage instruction (hereinafter referred to as the "voltage instruction value") and the phase angle of the voltage instruction (hereinafter referred to as the "voltage phase angle"). For example, the instruction calculation unit 111 calculates the voltage instruction value corresponding to the frequency instruction according to a predetermined instruction distribution, and calculates the voltage phase angle based on the frequency instruction. The instruction calculation unit 111 may also calculate a voltage instruction vector with one axis component of an orthogonal coordinate axis (with the voltage instruction value) and the other axis component being zero, along with the voltage phase angle, as a control instruction. The voltage instruction vector thus calculated may also be further subjected to resistor voltage drop compensation and non-interference compensation to become a voltage instruction vector.

[0045] It should be noted that the instruction calculation unit 111 can obtain frequency instructions from the host controller 4, or it can store preset frequency instructions internally. The instruction calculation unit 111 can also obtain frequency instructions from the input device 102 (described later). A specific example of the host controller 4 could be a programmable logic controller (PLC). The instruction calculation unit 111 repeatedly performs voltage instruction calculations within a predetermined control cycle.

[0046] The PWM control unit 112 controls the power conversion circuit 10 in such a way that the secondary side power supply follows the control command calculated by the command calculation unit 111. For example, the PWM control unit 112 makes the voltage in the drive power supply follow the voltage command. For example, the PWM control unit 112 switches the on / off state of multiple switching elements 15 of the inverter circuit 13 in such a way that it outputs a voltage consistent with the voltage command to the motor 6.

[0047] The current acquisition unit 113 acquires current information from the current sensor 14. For example, the current acquisition unit 113 performs a three-phase to two-phase transformation and a coordinate transformation on the current information acquired from the current sensor 14 to calculate the current vector in the rotating coordinate system. As an example, the current acquisition unit 113 calculates the current component in the direction of the coordinate axis (δ-axis) parallel to the voltage command vector or the induced voltage vector of the motor 6, i.e., the δ-axis current, and the current component in the direction of the coordinate axis (γ-axis) perpendicular to the δ-axis, i.e., the γ-axis current. It should be noted that when the voltage command vector is determined by performing the above-mentioned resistor voltage drop compensation and non-interference compensation, the induced voltage vector is equal to the voltage command vector before these compensations are performed.

[0048] This coordinate transformation requires adjusting the phase of the rotating coordinate system relative to the fixed coordinate system. For example, the current acquisition unit 113 uses the voltage phase angle calculated by the instruction calculation unit 111 as the phase of the rotating coordinate system. For example, the current acquisition unit 113 calculates the delta-axis current and the gamma-axis current based on the current information acquired from the current sensor 14 and the voltage phase angle. The current acquisition unit 113 repeatedly performs the acquisition of current information and the calculation of the delta-axis current and the gamma-axis current in the aforementioned control cycle.

[0049] The load information acquisition unit 115 acquires load-related information (hereinafter referred to as "load information") from the load sensor 20. For example, the load information acquisition unit 115 acquires information from the load sensor 20 indicating whether the conveying device 2 is in an unloaded state. The load information acquisition unit 115 may also acquire the aforementioned load level from the load sensor 20. The load information acquisition unit 115 may also acquire load information from the host controller 4. The current information storage unit 114 stores the delta-axis current and γ-axis current calculated by the current acquisition unit 113 in a corresponding manner with the load information acquired by the load information acquisition unit 115 according to a timing sequence.

[0050] The variation calculation unit 116 calculates the variation level of the driving force of the motor 6 within a sampling period of a specified length. The length of the sampling period is longer than the length of the control cycle. For example, the length of the sampling period is 5 to 300,000 times the length of the control cycle.

[0051] As an example, the variation calculation unit 116 calculates the variation level representing the amplitude of the δ-axis current variation during the sampling period. As described above, the δ-axis current is calculated based on the current information obtained from the current sensor 14 and the voltage phase angle calculated according to the frequency command. Therefore, calculating the variation level representing the amplitude of the δ-axis current variation is an example of calculating the variation level based on the current flowing between the power conversion circuit 10 and the motor 6 and the frequency command.

[0052] The aforementioned variation level can be the difference between the maximum and minimum values ​​of the delta-axis current during the sampling period, or it can be the standard deviation of the delta-axis current during the sampling period. The variation calculation unit 116 can also repeatedly calculate the variation level with a period equal to or longer than the sampling period.

[0053] The threshold setting unit 117 sets a threshold based on the level of variation when the conveyor 2 is in an unloaded state. For example, the threshold setting unit 117 calculates the threshold by adding a predetermined margin to the level of variation when the conveyor 2 is in an unloaded state. The threshold setting unit 117 may also calculate the threshold by adding a predetermined margin to the average of multiple levels of variation calculated when the conveyor 2 is in an unloaded state. The threshold setting unit 117 may also calculate the threshold based on the average of multiple levels of variation calculated when the conveyor 2 is in an unloaded state and the standard deviation of those multiple levels of variation. As an example, the threshold setting unit 117 may also calculate the threshold by adding the value obtained by multiplying the average by a predetermined factor to the average. The threshold setting unit 117 may also set the maximum value of the MD (Mahathano distance) values ​​of the multiple levels of variation calculated when the conveyor 2 is in an unloaded state as the threshold. The MD value is the value obtained by multiplying a matrix of values ​​obtained by subtracting the average of multiple levels of variation from each of the multiple levels of variation, a covariance matrix of the multiple levels of variation, and the inverse matrix of values ​​obtained by subtracting the average of multiple levels of variation from each of the multiple levels of variation. The threshold storage unit 118 stores the threshold set by the threshold setting unit 117.

[0054] The anomaly detection unit 119 detects anomalies in the conveying device 2 based on the level of variation. For example, after setting a threshold by the threshold setting unit 117, the anomaly detection unit 119 obtains the level of variation calculated by the variation calculation unit 116 when the conveying device 2 is in an unloaded state, and detects anomalies in the conveying device 2 based on this level of variation and the threshold. For example, the anomaly detection unit 119 detects an anomaly in the conveying device 2 if the level of variation exceeds the threshold.

[0055] The anomaly detection unit 119 can also detect anomalies in the conveying device 2 based on the number of variation levels that exceed a threshold among a plurality of variation levels, wherein the plurality of variation levels are obtained by the variation calculation unit 116 repeatedly calculating the variation levels when the conveying device 2 is in an unloaded state. For example, the anomaly detection unit 119 can also detect anomalies in the conveying device 2 when the number of variation levels that exceed a threshold exceeds a predetermined number of times.

[0056] The anomaly notification unit 121 outputs information about the anomaly detected by the anomaly detection unit 119 in the form of visual or auditory information. For example, the anomaly notification unit 121 displays the situation where the anomaly detected by the anomaly detection unit 119 is displayed on the display device 101 (described later).

[0057] Figure 3 This is a block diagram illustrating the hardware configuration of the power conversion device 3. For example... Figure 3As shown, the power conversion device 3 includes a control circuit 100, a display device 101, and an input device 102. The control circuit 100 includes one or more processors 191, a memory 192, a storage device 193, a switch control circuit 194, and an input / output port 195. The memory 193 is, for example, a storage medium that can be read by a computer, such as a non-volatile semiconductor memory. The memory 193 stores a program for causing the power conversion device to perform the following steps: making the secondary power supply follow control commands by converting primary power into secondary power and supplying it to the motor 6 through the power conversion circuit 10; calculating the variation level of the driving force of the motor during a sampling period of a specified length; and detecting abnormalities in the conveying device 2, which includes the motor and the conveying unit 5 driven by the motor, based on the variation level.

[0058] Memory 192 temporarily stores the program loaded from the storage medium of memory 193 and the calculation results obtained by processor 191. Processor 191 and memory 192 cooperate to execute the program, thereby forming the functional blocks of control circuit 100. Switch control circuit 194 switches the multiple switching elements 15 in inverter circuit 13 on / off according to instructions from processor 191, thereby outputting the drive power to motor 6. Input / output port 195 inputs and outputs electrical signals between inverter circuit 13, current sensor 14, display device 101 and input device 102 according to instructions from processor 191.

[0059] Display device 101 includes, for example, an LCD monitor for displaying information to the user. Input device 102 is, for example, a keypad for acquiring input information entered by the user. Display device 101 and input device 102 can also be integrated, such as a so-called touch panel. Display device 101 and input device 102 can be embedded in power conversion device 3 or located in an external device connected to power conversion device 3.

[0060] [Electricity conversion process]

[0061] Next, as an example of a power conversion method, a control process executed by the control circuit 100 is illustrated. This process includes: a power conversion circuit 10 that converts primary-side power into secondary-side power and supplies it to the motor 6, causing the secondary-side power to follow a control command; calculating the variation level of the driving force of the motor 6 within a sampling period of a predetermined length; and detecting anomalies in the conveying device 2, which includes the motor 6 and the conveying unit 5 driven by the motor 6, based on the variation level. For example, this process includes a control process for the power conversion circuit 10, a threshold setting process, and an anomaly detection process.

[0062] The control circuit 100 executes the control process and threshold setting process of the power conversion circuit 10 in parallel, and then executes the control process and anomaly detection process of the power conversion circuit 10 in parallel. For example, the control circuit 100 executes the threshold setting process if no threshold is set after the power conversion circuit 10 is started. The control circuit 100 may also execute the threshold setting process according to user input indicating the setting of the threshold (e.g., input to input device 102). The control circuit 100 may always execute the anomaly detection process after the threshold is set, or it may execute the anomaly detection process according to user input indicating anomaly confirmation (e.g., input to input device 102). The control process, threshold setting process, and anomaly detection process of the power conversion circuit 10 are illustrated in detail below.

[0063] (Control process of power conversion circuit)

[0064] like Figure 4 As shown, the control circuit 100 sequentially executes steps S01, S02, S03, S04, S05, S06, and S07. In step S01, the instruction calculation unit 111 calculates a control instruction. For example, the instruction calculation unit 111 calculates the voltage instruction based on a frequency instruction. For example, the instruction calculation unit 111 calculates the voltage instruction value and the voltage phase angle based on the frequency instruction. In step S02, the instruction calculation unit 111 outputs a control instruction to the PWM control unit 112. Correspondingly, the PWM control unit 112 controls the power conversion circuit 10 in a manner that makes the secondary-side electrical quantity follow the control instruction.

[0065] In step S03, the current acquisition unit 113 acquires current information from the current sensor 14, and calculates the delta-axis current and the γ-axis current based on the current information and the voltage phase angle. In step S04, the current acquisition unit 113 writes the delta-axis current and the γ-axis current into the current information storage unit 114.

[0066] In step S05, the load information acquisition unit 115 acquires the aforementioned load information. In step S06, the load information acquisition unit 115 writes the load information into the current information storage unit 114 in a manner that establishes a correspondence with the delta-axis current and γ-axis current written by the current acquisition unit 113 in step S04. In step S07, the instruction calculation unit 111 waits for the aforementioned control cycle to elapse. The control circuit 100 repeats the above process.

[0067] (Threshold setting process)

[0068] like Figure 5As shown, the control circuit 100 first executes steps S11 and S12. In step S11, the variation calculation unit 116 waits for the sampling period to pass. In step S12, the variation calculation unit 116 determines whether the conveying device 2 was in an unloaded state during the sampling period based on the load information stored in the current information storage unit 114. If it is determined in step S12 that the conveying device 2 is not in an unloaded state, the control circuit 100 returns the processing to step S11.

[0069] If it is determined in step S12 that the conveying device 2 is in an unloaded state, the control circuit 100 executes steps S13, S14, and S15. In step S13, the variation calculation unit 116 calculates the aforementioned variation level. For example, the variation calculation unit 116 calculates the variation level representing the amplitude of the variation in the delta-axis current during the sampling period. In step S14, the threshold setting unit 117 counts the number of samples. In step S15, the threshold setting unit 117 confirms whether the number of samples has reached a preset number (hereinafter referred to as "threshold setting number").

[0070] If, in step S15, it is determined that the number of samples has not reached the threshold set number, the control circuit 100 returns the processing to step S11. Then, the calculation of the variation level when the conveying device 2 is in an unloaded state is repeated until the number of samples reaches the threshold set number.

[0071] If, in step S15, it is determined that the number of samplings has reached the threshold set number, the control circuit 100 executes steps S16 and S17. In step S16, the threshold setting unit 117 sets a threshold based on multiple levels of variation obtained by repeatedly calculating the level of variation. For example, the threshold setting unit 117 calculates the threshold based on the average and standard deviation of the multiple levels of variation. For example, the threshold setting unit 117 calculates the threshold by adding the average value to the standard deviation multiplied by a predetermined factor. In step S17, the threshold setting unit 117 writes the threshold to the threshold storage unit 118. The threshold setting process is then complete.

[0072] (Anomaly detection process)

[0073] like Figure 6 As shown, the control circuit 100 first executes steps S21 and S22. In step S21, the variation calculation unit 116 waits for the sampling period to pass. In step S22, the variation calculation unit 116 determines whether the conveying device 2 was in an unloaded state during the sampling period based on the load information stored in the current information storage unit 114. If it is determined in step S22 that the conveying device 2 is not in an unloaded state, the control circuit 100 returns the processing to step S21.

[0074] If it is determined in step S22 that the conveying device 2 is in an unloaded state, the control circuit 100 executes steps S23, S24, and S25. In step S23, the variation calculation unit 116 calculates the aforementioned variation level. For example, the variation calculation unit 116 calculates the variation level representing the amplitude of the variation in the delta-axis current during the sampling period. In step S24, the anomaly detection unit 119 counts the number of samplings. In step S25, the anomaly detection unit 119 confirms whether the variation level calculated by the variation calculation unit 116 in step S23 exceeds the threshold of the threshold storage unit 118.

[0075] If, in step S25, it is determined that the change level exceeds the threshold, the control circuit 100 executes step S26. In step S26, the anomaly detection unit 119 counts the number of errors.

[0076] Next, the control circuit 100 executes step S27. If it is determined in step S25 that the change level does not exceed the threshold, the control circuit 100 executes step S27 instead of step S26. In step S27, the anomaly detection unit 119 confirms whether the number of samplings has reached a preset number (hereinafter referred to as "anomaly determination number").

[0077] If, in step S27, it is determined that the number of samples has not reached the number of abnormal determinations, the control circuit 100 returns the processing to step S21. Afterward, it repeatedly checks whether the change level exceeds the threshold until the number of samples reaches the number of abnormal determinations.

[0078] If, in step S27, it is determined that the number of sampling attempts has reached the abnormality determination threshold, the control circuit 100 executes step S28. In step S28, the abnormality detection unit 119 confirms whether the number of errors exceeds a preset threshold (the aforementioned threshold number).

[0079] If, in step S28, the number of errors is determined to exceed the threshold, the control circuit 100 executes steps S29 and S31. In step S29, the anomaly detection unit 119 detects an anomaly. In step S31, the anomaly notification unit 121 displays the situation detected by the anomaly detection unit 119 on the display device 101.

[0080] Next, the control circuit 100 executes step S32. If it is determined in step S28 that the number of errors has not exceeded the threshold, the control circuit 100 executes step S32 instead of steps S29 and S31. In step S32, the anomaly detection unit 119 resets the sampling count and the number of errors to zero. The control circuit 100 repeats the above process. It should be noted that the above process shows an example of confirming the number of errors according to each anomaly determination, but the anomaly detection unit 119 may also detect anomalies based solely on whether the total number of errors exceeds the threshold. In this case, steps S27 and S32 are not required.

[0081] [Variation Example]

[0082] The above example illustrates a mechanism for detecting anomalies based on a threshold set under no-load conditions and a fluctuation level calculated under no-load conditions. However, threshold setting and anomaly detection can also be performed under conditions that are not no-load conditions. For example, the control circuit 100 can also acquire load levels and fluctuation levels in groups, and detect anomalies in the conveying device 2 based on thresholds and fluctuation levels corresponding to the load levels.

[0083] The threshold setting unit 117 acquires multiple sets of level groups, each including load level and variation level, and sets a threshold distribution representing the relationship between load level and threshold based on these multiple sets of level groups. For example, the threshold setting unit 117 sets a threshold based on the variation level for each of the multiple different load levels, thereby setting multiple threshold datasets, each including load level and threshold, as a threshold distribution. The threshold setting unit 117 may also set a function expressing the relationship between load level and threshold as a threshold distribution based on multiple threshold datasets. The threshold storage unit 118 stores the threshold distribution set by the threshold setting unit 117.

[0084] The threshold setting unit 117 sets a threshold corresponding to the load level based on the load level and the threshold distribution. When the threshold distribution consists of multiple threshold datasets, the threshold setting unit 117 can also calculate the threshold corresponding to the load level by interpolating the multiple threshold datasets. When the threshold distribution is a function, the threshold setting unit 117 calculates the threshold corresponding to the load evaluation value by inputting the load evaluation value into the function.

[0085] After setting the threshold distribution by the threshold setting unit 117, the anomaly detection unit 119 acquires a set of levels including load level and fluctuation level, and detects anomalies in the conveyor device 2 based on this set of levels (hereinafter referred to as the "inspection object") and the threshold distribution. For example, the anomaly detection unit 119 causes the threshold setting unit 117 to set a threshold corresponding to the load level of the inspection object. Hereinafter, this threshold is referred to as a temporary threshold. The threshold setting unit 117 sets a temporary threshold corresponding to the load level of the inspection object based on the threshold distribution. The anomaly detection unit 119 detects an anomaly in the conveyor device 2 when the fluctuation level of the inspection object exceeds the temporary threshold. For example, the control circuit 100 can always perform the anomaly detection process after the temporary threshold is set, or it can perform the anomaly detection process according to user input indicating anomaly confirmation (e.g., input to the input device 102).

[0086] The anomaly detection unit 119 repeatedly acquires a set of level groups according to the prescribed repetition conditions, thereby acquiring multiple sets of inspection objects. Anomalies in the conveying device 2 are detected based on the number of inspection objects exceeding a threshold distribution among these multiple sets of inspection objects. The threshold setting process and anomaly detection process in this modified example are illustrated below.

[0087] (Threshold setting process)

[0088] like Figure 7 As shown, the control circuit 100 first executes steps S41, S42, S43, and S44. In step S41, the variation calculation unit 116 waits for the sampling period to elapse. In step S42, the variation calculation unit 116 calculates the variation level. In step S43, the threshold setting unit 117 counts the number of samples. In step S44, the threshold setting unit 117 confirms whether the number of samples has reached the threshold set number.

[0089] If, in step S44, it is determined that the number of samples has not reached the threshold set number, the control circuit 100 returns the processing to step S41. Then, the calculation of the variation level is repeated until the number of samples reaches the threshold set number.

[0090] If, in step S44, it is determined that the number of samplings has reached the threshold set number, the control circuit 100 executes steps S45, S46, and S47. In step S45, similar to step S16, the threshold setting unit 117 sets a threshold based on multiple variation levels. In step S46, the threshold setting unit 117 writes a threshold dataset corresponding to the load level during the sampling period and the threshold calculated in step S45 into the threshold storage unit 118. In step S47, the threshold setting unit 117 confirms whether the number of threshold datasets stored in the threshold storage unit 118 has reached the necessary number for threshold distribution.

[0091] If, in step S47, it is determined that the number of threshold datasets has not reached the necessary amount, the control circuit 100 executes step S48. In step S48, the threshold setting unit 117 waits for a change in the load level. For example, the threshold setting unit 117 waits for the current load level to become a value different from the load level of the threshold dataset written in step S46. Then, the control circuit 100 returns to step S41. Thereafter, until the number of threshold datasets reaches the necessary amount, the threshold calculation and the writing of threshold datasets are repeatedly performed while changing the load level.

[0092] If, in step S47, it is determined that the number of threshold datasets has reached the necessary quantity, multiple threshold datasets are set as a threshold distribution. The threshold setting unit 117 may also set a function expressing the relationship between the load level and the threshold as the threshold distribution based on multiple threshold datasets. The threshold setting process is now complete.

[0093] (Anomaly detection process)

[0094] like Figure 8 As shown, the control circuit 100 first executes steps S51, S52, S53, S54, and S55. In step S51, the variation calculation unit 116 waits for the sampling period to elapse. In step S52, the variation calculation unit 116 calculates the variation level. In step S53, the anomaly detection unit 119 causes the threshold setting unit 117 to set a threshold (the temporary threshold) corresponding to the load level. The threshold setting unit 117 sets the temporary threshold corresponding to the load level based on the threshold distribution in the threshold storage unit 118.

[0095] In step S54, the anomaly detection unit 119 counts the number of samples. In step S55, the anomaly detection unit 119 confirms whether the variation level calculated by the variation calculation unit 116 in step S52 exceeds the temporary threshold set by the threshold setting unit 117 in step S53.

[0096] If, in step S55, it is determined that the change level exceeds a temporary threshold, the control circuit 100 executes step S56. In step S56, the anomaly detection unit 119 counts the number of errors.

[0097] Next, the control circuit 100 executes step S57. If it is determined in step S55 that the change level has not exceeded the temporary threshold, the control circuit 100 does not execute step S56 but executes step S57. In step S57, the anomaly detection unit 119 confirms whether the number of samplings has reached the above-mentioned anomaly determination number.

[0098] If, in step S57, it is determined that the number of samples has not reached the number of abnormal determinations, the control circuit 100 returns the processing to step S51. Afterward, it repeatedly checks whether the change level exceeds a temporary threshold until the number of samples reaches the number of abnormal determinations.

[0099] If, in step S57, it is determined that the number of sampling attempts has reached the abnormality determination threshold, the control circuit 100 executes step S58. In step S58, the abnormality detection unit 119 confirms whether the number of errors exceeds the aforementioned threshold.

[0100] If, in step S58, the number of errors is determined to exceed the threshold, the control circuit 100 executes steps S59 and S61. In step S59, the anomaly detection unit 119 detects an anomaly. In step S61, the anomaly notification unit 121 displays the situation detected by the anomaly detection unit 119 on the display device 101.

[0101] Next, the control circuit 100 executes step S62. If it is determined in step S58 that the number of errors has not exceeded the threshold, the control circuit 100 executes step S62 instead of steps S59 and S61. In step S62, the anomaly detection unit 119 resets the sampling count and the number of errors to zero. The control circuit 100 repeats the above process. It should be noted that the above process shows an example of confirming the number of errors according to each anomaly determination, but the anomaly detection unit 119 may also detect anomalies based solely on whether the total number of errors exceeds the threshold. In this case, steps S57 and S62 are not required.

[0102] [Effects of this implementation method]

[0103] As described above, the power conversion device 3 includes: a power conversion circuit 10 that converts primary power into secondary power and supplies it to the motor 6; and a control circuit 100 that, through the power conversion circuit 10, makes the secondary power follow the control command, and the control circuit 100 calculates the variation level of the driving force of the motor 6 within a sampling period of a specified length, and detects abnormalities in the conveying device 2, which includes the motor 6 and the conveying unit 5 driven by the motor 6, based on the variation level.

[0104] According to this power conversion device 3, malfunctions of the conveying device 2 can be detected with high reliability based on information about the driving force that can be obtained from the power conversion device 3. Therefore, the configuration for detecting malfunctions of the conveying device 2 is simplified and effective.

[0105] Alternatively, the control circuit 100 sets a threshold based on the level of variation when the conveyor 2 is in an unloaded state. After setting the threshold, the control circuit calculates the level of variation when the conveyor 2 is in an unloaded state, and detects abnormalities in the conveyor 2 based on this level of variation and the threshold. In this case, the measurement reference for the variation amplitude used to set the threshold is consistent with the measurement reference for the variation amplitude in abnormality detection, thus enabling the detection of abnormalities in the conveyor 2 with higher reliability.

[0106] Alternatively, the control circuit 100 can detect abnormalities in the conveyor 2 based on the number of fluctuation levels exceeding a threshold among a plurality of fluctuation levels, wherein the plurality of fluctuation levels are obtained by repeatedly calculating the fluctuation levels when the conveyor 2 is in an unloaded state. In this case, abnormalities in the conveyor 2 can be detected with higher reliability.

[0107] Alternatively, the control circuit 100 acquires multiple sets of levels, including load levels and fluctuation levels representing the magnitude of the load in the conveying device 2. Based on these multiple sets of levels, it sets a threshold distribution representing the relationship between the load level and a threshold. After setting the threshold distribution, it acquires a set of levels including the load level and fluctuation level, and detects abnormalities in the conveying device 2 based on this set of levels and the threshold distribution. In this case, the threshold changes according to the weight of the conveyed load, thus enabling the detection of abnormalities in the conveying device 2 with higher reliability.

[0108] Alternatively, the control circuit 100 can detect anomalies in the conveying device 2 based on the number of level groups exceeding a threshold distribution among multiple evaluation results, wherein these multiple evaluation results are obtained by repeatedly acquiring a set of evaluation results. In this case, anomalies in the conveying device 2 can be detected with higher reliability.

[0109] Alternatively, the control circuit 100 can calculate the voltage command corresponding to the frequency command based on the V / f method, and calculate the fluctuation level based on the current flowing between the power conversion circuit 10 and the motor 6 and the frequency command. In this case, even in the drive of the conveyor 2 based on V / f control, abnormalities of the conveyor 2 can be detected with high reliability.

[0110] The embodiments have been described above, but this disclosure is not necessarily limited to the above embodiments, and various modifications can be made without departing from its spirit. In the above embodiments, the diagnostic device calculates the variation level of the driving force of the motor 6 during a sampling period of a predetermined length based on the power supplied to the motor 6 by the power conversion circuit 10, and detects abnormalities in the conveying device 2 based on the variation level. The diagnostic device is embedded in the control circuit 100 of the power conversion device 3, but is not necessarily limited thereto. Figure 9As shown, the diagnostic device 200 can also be configured as a separate unit from the power conversion device 3. The diagnostic device 200 can also be embedded in the host controller 4.

[0111] The equipment to be detected for anomalies is not limited to conveyor device 2. The diagnostic device only needs to have a motor and a movable part driven by the motor, and can be used for anomaly detection in all equipment. The motor is not limited to a rotary electric motor. For example, the motor can also be a linear motor.

[0112] Explanation of reference numerals in the attached figures

[0113] 1: Conveying system;

[0114] 2: Conveying device (equipment);

[0115] 3: Power conversion device;

[0116] 5: Conveying section (movable part);

[0117] 6: Motor;

[0118] 10: Power conversion circuit;

[0119] 100: Control circuit;

[0120] 200: Diagnostic device.

Claims

1. A power conversion device comprising: The power conversion circuit converts primary power into secondary power and supplies it to the motor. The control circuit, through the power conversion circuit, ensures that the secondary-side electrical quantity follows the control command. The control circuit performs a threshold setting process and an anomaly detection process. The threshold setting process includes: If it is determined that the conveying device, including the motor and the movable part driven by the motor, is in an unloaded state during a sampling period of a specified length, the variation level of the driving force of the motor is calculated and the number of samplings is counted. If the number of samplings reaches a threshold value, then the threshold is set based on the calculated level of change. The anomaly detection process, following the threshold setting process, includes: The level of variation when the conveying device is in an unloaded state is calculated, and anomalies of the conveying device are detected based on the level of variation and the threshold.

2. The power conversion device according to claim 1, wherein, The control circuit detects abnormalities in the conveying device based on the number of fluctuation levels exceeding the threshold among a plurality of fluctuation levels obtained by repeatedly calculating the fluctuation levels when the conveying device is in an unloaded state.

3. The power conversion device according to claim 1, wherein, The control circuit acquires multiple sets of levels, including load levels representing the magnitude of the load in the conveying device and the variation levels, and sets a threshold distribution representing the relationship between the load level and a threshold based on the multiple sets of levels. After the threshold distribution is set, the control circuit acquires a set of levels including the load level and the fluctuation level, and detects abnormalities of the conveying device based on the set of levels and the threshold distribution.

4. The power conversion device according to claim 3, wherein, The control circuit detects anomalies in the conveying device based on the number of level groups exceeding the threshold distribution among multiple level groups, wherein the multiple level groups are obtained by repeatedly acquiring the set of level groups.

5. The power conversion device according to any one of claims 1 to 4, wherein, The control circuit calculates the voltage command vector corresponding to the frequency command according to the V / f method as the control command, and calculates the fluctuation level based on the current flowing between the power conversion circuit and the motor and the frequency command.

6. A conveying system comprising: The power conversion device as claimed in any one of claims 1 to 5; and The conveying device The conveying device has a conveying section that supports and conveys objects as the movable part. The conveying device has a motor that drives the conveying section as the motor.

7. A power conversion method, comprising: By converting primary power into secondary power and supplying it to the motor, the secondary power can follow the control command. The threshold setting process and the anomaly detection process are performed. The threshold setting process includes: if it is determined that the conveying device including the motor and the movable part driven by the motor is in an unloaded state during a sampling period of a specified length, then the variation level of the driving force of the motor is calculated and the number of samplings is counted; if the number of samplings reaches the threshold setting number, then the threshold is set according to the calculated variation level. The anomaly detection process, following the threshold setting process, includes: calculating the level of variation when the conveying device is in an unloaded state; and detecting anomalies in the conveying device based on the level of variation and the threshold.

8. A diagnostic device that calculates, based on power supplied to a motor by a power conversion circuit, a level of variation representing the magnitude of the variation in the driving force of the motor over a sampling period of a predetermined length. The threshold setting process and the anomaly detection process are executed, wherein the threshold setting process includes: If it is determined that the conveying device, including the motor and the movable part driven by the motor, is in an unloaded state during a sampling period of a specified length, the variation level of the driving force of the motor is calculated and the number of samplings is counted. If the number of samplings reaches a threshold value, then the threshold is set based on the calculated level of change. The anomaly detection process, following the threshold setting process, includes: calculating the level of variation when the conveying device is in an unloaded state; And to detect abnormalities in the conveying device based on the level of change and the threshold.

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