steering

Abstract

Control unit (1) with a detector for detecting a speed or position feedback value and with a function for detecting an irregularity on a motor, wherein the control unit (1) comprises: a motor control unit (100) which is set up to control the motor (50); an operating mode switching unit (110) which is configured to switch between operating modes of the motor (50); and an engine control system modification unit (120) configured to modify an engine control system which is used when the engine control unit (100) controls the engine (50) in the operating modes of the engine (50), wherein the operating modes include at least one normal operating mode as a regular operating mode and one diagnostic operating mode in which a malfunction of the motor (50) can be detected, and wherein The engine control system modification unit (120) is an engine control system which is used when the engine control unit (100) controls the engine (50) in diagnostic mode, to change the engine control system to increase the effect of a disturbance on the speed or position feedback value.

Description

BACKGROUND OF THE INVENTIONField of the invention

[0001] The invention relates to a controller and in particular to a controller configured to detect an abnormality of a motor based on a speed or position feedback value of the motor. State of the art

[0002] To detect or predict a failure of an industrial machine, such as a machine tool or a robot, it is common practice to install sensors near the monitored object, react to a malfunction, and evaluate the sensor detection values. However, given the cost and maintenance requirements, the number of such sensors should be kept to a minimum. Therefore, there is a need for a method that can detect an abnormality in an industrial machine without requiring the installation of additional sensors or the like.

[0003] Taking a motor in an industrial machine as an example, it is essential to detect the motor's speed or position for its control. Therefore, a motor is typically equipped with speed or position sensors so that control can be performed using position / speed feedback values ​​from these sensors. Therefore, it would be advantageous to use these sensor values ​​to detect abnormalities (faults). According to this description, fault detection includes the detection of an indication of an impending fault as well as the detection of the occurrence of a fault that would be problematic for the object under investigation.

[0004] For example, JP 2017-200710 A describes a conventional technique for detecting a malfunction (abnormality) in an industrial machine using such speed and position sensors, in which a malfunction of a robot is detected based on an error in the cycle time required for the tip of the robot to reach a target position. With this technique, the occurrence of a malfunction can be detected relatively easily (i.e., a high "required accuracy" is achieved), and this technique is used as a diagnostic method to facilitate the detection of a robot malfunction.

[0005] Generally, when controlling a motor, even if a fault occurs in a component of the motor or an industrial machine during motor operation, differences in speed and position due to the fault are not taken into account. Therefore, even when using the technique described in JP 2017 - 200 710 A, there is a problem in that the cycle time error in the event of a deviation from the normal state or an impending fault is unlikely to be large as long as the motor is controlled correctly, so in many cases the occurrence of a fault will go undetected.

[0006] US 2006 / 0 265 116 A1 describes a control system configured to diagnose an abnormality in an air-fuel ratio sensor when an engine has reached a predetermined operating state. In the corresponding diagnostic mode, a predetermined air-fuel ratio control is performed several times, accompanied by a measurement. JP 2 528 654 B2 describes, in this context, a self-diagnosis function, which is activated by a switch as soon as a display is connected to the corresponding control device. The self-diagnosis is performed by a microprocessor, and the result of this self-diagnosis is displayed on the display. BRIEF DESCRIPTION OF THE INVENTION

[0007] Accordingly, the object of the invention is to provide a control system which facilitates the monitoring of a precisely controlled motor.

[0008] According to the invention, in a controller for controlling a motor, the above problem is solved by improving the sensitivity of the disturbance detection by a speed or position feedback from the motor by changing the motor control parameters so that the change in the motor operation due to a disturbance is enhanced in a diagnostic operation so as to detect an abnormality related to the motor.

[0009] The solution to the problem consists in a controller according to the features of patent claim 1 with a detector for detecting a speed or position feedback value and with a function for detecting an abnormality in the motor, the controller comprising: a motor control unit configured to control the motor, an operating mode switching unit configured to switch the operating modes of the motor, and a motor control system changing unit configured to change a motor control system that is used when the motor control unit controls the motor in each of the operating modes of the motor.The operation modes include at least a normal operation mode as the regular operation mode and a diagnostic operation mode in which an abnormality with respect to the motor is detected, wherein the motor control system changing unit changes a motor control system used when the motor control unit controls the motor in the diagnostic operation mode into a motor control system to increase an effect of a disturbance on the speed or position feedback value.

[0010] The engine control system changing unit may set at least one gain of the engine control system to a value different from the corresponding value in the normal mode in the diagnostic mode.

[0011] The engine control system modification unit can, in diagnostic mode, activate a filter configured to amplify only a specific frequency band in the engine control system.

[0012] The engine control system modification unit can stop a control signal for the engine at a predetermined time when the speed of the engine is fixed in the diagnostic mode.

[0013] The controller may further comprise an abnormality detection unit configured to detect the abnormality (malfunction) in the engine based on a feedback value detected by a detector in the diagnostic mode.

[0014] The solution to the problem also consists in an abnormality detection method according to the features of patent claim 6. This abnormality detection method is a method for detecting an abnormality in the operation of a motor equipped with a detector for detecting a speed or position feedback value, the method comprising the following steps: a step of changing a motor control system for controlling the motor to increase an effect of a disturbance on the speed or position feedback value, a step of causing the motor to perform a diagnostic operation, and a step of detecting the motor abnormality based on the feedback value obtained during the diagnostic operation.

[0015] With the invention, an abnormality arising in an engine can be accurately detected using sensors that are normally mounted on the engine, so that an abnormality in the operation of an industrial machine can be detected without additional, otherwise unnecessary sensors, thus reducing the generation and maintenance costs. BRIEF DESCRIPTION OF THE CHARACTERS Fig. 1 schematically shows the hardware configuration of a controller according to an embodiment; Fig. 2 schematically shows a functional block diagram of the controller according to the embodiment; Fig. 3 shows an example of an engine control system; Fig. 4 shows an example of the relationship between operating modes and engine control systems; and Fig. Figure 5 shows another example of the relationship between operating modes and engine control systems. DESCRIPTION OF PREFERRED EMBODIMENTS IN DETAIL

[0016] Fig. 1 schematically shows the hardware configuration with the main components of a controller according to an embodiment of the invention.

[0017] A controller 1 may be configured to control an industrial machine, such as a robot or a machine tool, or it may be mounted on a motor controller for controlling a motor, a servo amplifier, and the like. The controller 1 may also be mounted on a computer, such as a cell computer or a host computer, and may be connected directly or indirectly to a controller for controlling the industrial machine or motor, for example, via a wired or wireless network. The controller 1 according to this embodiment is used to control a machine tool.

[0018] A CPU 11 of the controller 1 according to this embodiment is a processor for general control of the controller 1 itself. The CPU 11 reads a system program from a ROM 12 via a bus 20 and controls the entire controller 1 according to this system program. A RAM 13 temporarily stores calculation data and display data, various data input by an operator via an input unit (not shown), and the like.

[0019] A non-volatile memory 14 is backed up, for example, by a battery (not shown), so that its storage state is maintained even when the controller 1 is turned off. The non-volatile memory 14 stores machining programs read from an external device 72 via an interface 15 or input via a display / MDI unit 70, as well as various data obtained from various components of the controller 1, the machine tool, sensors, and the like (e.g., signals indicating the execution states of the machining program commands and operating states of the machine tool, control parameters, positions, speeds, current and voltage values, and the like of a servo motor 50 and a spindle motor 62). The machining programs and the various data stored in the non-volatile memory 14 can be transferred to the RAM 13 upon execution and use.Various system programs, such as conventional analysis programs, are pre-written into ROM 12.

[0020] The interface 15 connects the controller 1 to the external device 72, e.g., an adapter. Programs, various parameters, and the like are read from the external device 72. The programs, parameters, and the like edited by the controller 1 can be stored in an external storage unit via the external device 72. A programmable machine controller (PMC) 16 controls the machine tool and its peripheral devices (e.g., an actuator such as a robot hand for tool change and sensors installed on the machine tool) by outputting signals to these devices via the input / output unit 17 according to a sequence program in the controller 1. Upon receiving signals from various switches on an operation panel on the main body of the machine tool and from the peripheral devices, the PMC 16 processes these signals and supplies corresponding signals to the CPU 11.

[0021] The display / MDI unit 70 is a manual data input device with a display, a keyboard, and the like. An interface 18 receives commands and data from the keyboard on the display / MDI unit 70 and forwards them to the CPU 11. An interface 19 is connected to the control panel 71, which is equipped with a manual pulse generator or the like for manual drive of the axes.

[0022] An axis control circuit 30 for controlling the axes of the machine tool receives a movement command for each axis from the CPU 11 and outputs a corresponding command for the axis to a servo amplifier 40. Upon receiving this command, the servo amplifier 40 drives a servo motor 50 to move the axis of the machine tool. The servo motor 50 for the axes has a built-in position / speed detector, and position / speed feedback signals are fed back from the position / speed detector to the axis control circuit 30 to perform position / speed control. The hardware diagram according to Fig. Figure 1 shows the axis control circuit 30, the servo amplifier 40, and the servo motor 50 as a single unit. However, these components are actually provided in multiples, depending on the number of axes of the machine tool to be controlled.

[0023] A spindle control circuit 60 receives a spindle rotation command and outputs a spindle speed signal to a spindle amplifier 61. Upon receiving this spindle speed signal, the spindle amplifier 61 rotates a spindle motor 62 of the machine tool according to the commanded rotation speed, thus driving a tool. A position encoder 63 is connected to the spindle motor 62. The position encoder 63 outputs feedback pulses synchronous with the rotation of the spindle, and the feedback pulses are read by the CPU 11. The feedback pulses are used to determine the rotation speed and position of the spindle.

[0024] Fig. 2 is a schematic functional block diagram of the controller 1 according to an embodiment.

[0025] The Fig. 2 are implemented when the CPU 11 of the controller 1 is Fig. 1 executes the respective system programs and controls the operation of the various parts of the controller 1.

[0026] The controller 1 of this embodiment includes a motor control unit 100, a mode switching unit 110, a motor control system changing unit 120, and an abnormality detection unit 130. The motor control unit 100 controls the servo motor 50 based on a machining operation command 200 or a diagnostic operation command 210. The mode switching unit 110 switches between normal machining control and diagnostic control. The motor control system changing unit 120 changes control parameters of the motor control system. The abnormality detection unit 130 detects a motor abnormality based on the speed or position feedback value fed back to the motor control unit 100.

[0027] The motor control unit 100 controls the servo motor 50 and the spindle motor 62 based on the machining operation command 200 according to the machining program stored in the non-volatile memory 14 (or according to the machining programs stored in the RAM 13, MDI programs input via the display / MDI unit 70, or the like). The motor control unit 100 switches the operation of the motor control from the normal mode to a diagnostic mode according to a command from the mode switching unit 110, and controls the servo motor 50 and the spindle motor 62 according to the diagnostic operation command 210 according to the machining programs stored in the non-volatile memory 14 (or according to the diagnostic programs stored in the RAM 13, MDI programs input via the display / MDI unit 70, or the like).

[0028] The mode switching unit 110 commands the motor control unit 100 to switch between the normal mode and the diagnostic mode at a predetermined time (described in more detail below). Upon a command to the motor control unit 100 to switch the mode, or according to a predetermined timing after the motor control unit 100 switches to the diagnostic mode, the mode switching unit 110 commands the motor control system changing unit 120 to individually change the settings of the motor control system, which is used when the motor control unit 100 controls the servo motor 50 or the spindle motor 62.

[0029] The time at which the mode switching unit 110 of the engine control unit 100 commands a mode switch may be determined, for example, as follows: a time at which a command is issued based on an operator input on the display / MDI unit 70 or on the operation panel 71; a point in time at which a point in time previously set in control 1 is reached; a point in time at which the execution of a machining program or a diagnostic program ends during a start-up process of the control system 1; or a time at which a command to switch the operating mode is issued by the machining program or the diagnostic program.

[0030] The operating mode switching unit 110 may be configured to either switch only the engine control system of the engine for engine diagnosis or also switch the control systems of other engines controlled by the controller 1.

[0031] The engine control system switching unit 120 changes the control parameters of the engine control system for the engine control unit 100 to control the engine. The engine control system changing unit 120 changes the engine control system to the normal engine control system (the engine control system originally set by the operator for processing) when the engine control unit 100 is switched to the normal mode, while the system is switched to the diagnostic control system when the engine control unit 100 is switched to the diagnostic mode. By changing the engine control system, the engine control system changing unit 120 performs, for example, a change in the control parameters of the engine control system, the addition or removal of a filter to or from the engine control system, a change in the connection of the engine control system, or the like.

[0032] Fig. 3 shows an example of the motor control system of the servo motor 50 under control of the motor control unit 100.

[0033] In normal operating mode, the engine control system is Fig. 3 a speed control of the servo motor 50 carried out on the basis of control parameters K p , K i , K d and C, which are set so that the motor operation is stable or the speed of the servomotor 50 strives for a target speed following a disturbance, even if the disturbance tends to change. Even if, for example, a bearing of the servomotor 50 is disturbed due to friction or the like, the target speed can be maintained through the intervention of the motor control system. After that, if the motor control unit 100 is switched to the diagnostic mode, the motor control system modification unit 120 changes the control parameters K p , K i , K daccording to the command from the mode switching unit 110 and changes the control by the engine control system so that the response action to the engine control is reduced (in particular, the proportional, integral and derivative gains K p , K i , K d reduced). In this way, when an abnormality occurs due to friction or the like in the bearing of the servo motor 50 in the diagnostic mode, the degree of deviation from the target speed increases, so that the degree of the abnormality is clearly reflected in the speed feedback.

[0034] According to another example of the modification of the motor control system by the motor control system modification unit 120, the motor control system modification unit 120 may be configured to amplify a vibration at a specific frequency by adding a filter to amplify the specific frequency to the motor control system (or removing a filter that attenuates the specific frequency, or inserting a filter that preferentially passes the specific frequency) when the motor control unit 100 is switched to the diagnostic mode. With this modification, the vibration generated by the servo motor 50 according to the specific frequency is clearly reflected in the speed feedback, so that an abnormality related to the specific frequency can be easily detected.

[0035] As another example of the modification of the motor control system by the motor control system modification unit 120, the motor control system modification unit 120 may also be configured to cause the servo motor 50 to perform an inertial operation by setting the gains of the motor control system to zero (or stopping the control output of the servo motor 50) by the motor control unit 100 according to a predetermined timing in the diagnostic mode. By modifying the motor control system in the manner described above after setting the speed of the servo motor 50 to a predetermined value, the servo motor 50 can be caused to perform an inertial operation, thereby enabling the detection of an abnormality that is likely to be reflected in the speed feedback during the resulting deceleration.

[0036] The modification of the motor control system by the motor control system modification unit 120 can be carried out in any manner, as long as it enables the detection of an indication of a violation of the servo motor 50 by influencing the speed or position feedback signal. For example, the modification can be carried out with respect to an element in the control loop of the motor control system or outside of it. The motor control system can be different from that described in Fig. 3, depending on the purpose and use of the industrial machine in which the engine control system is installed. The modification of the engine control system by the engine control system modification unit 120 can be used for any of these systems. While the engine control system according to Fig. 3 is based on a speed control loop, the change can also be applied to a motor control system based on a position control loop, a current control loop, or a combination of such loops. Each motor control system exhibits specific responses to a disturbance (abnormality). Only an experiment or the like needs to be conducted in advance to determine the type of change in the motor control system and the respective magnitude of the change following a disturbance in the diagnostic mode, so that the change in the motor control system in the diagnostic mode can be determined according to the result of the experiment.

[0037] The change of the engine control system for each operation mode by the engine control system change unit 120 can also be set in advance in the non-volatile memory 14. Then, according to Fig. 4 the engine control system can also be set in advance in conjunction with the operating modes so that the change of the corresponding engine control system can be carried out by recourse to the non-volatile memory 14 when switching the operating mode.

[0038] The abnormality detection unit 130 obtains the speed or position feedback value of the motor (servo motor 50 or spindle motor 62) that is the subject of abnormality detection from the motor control unit 100 and performs the abnormality detection based on the obtained speed or position feedback values. The abnormality detection unit 130 detects the abnormality in a motor using a conventional abnormality detection method. In a simple embodiment of the abnormality detection, the abnormality detection unit 130 can be configured to determine an abnormality in the motor, for example, when a difference between a feedback value obtained in the diagnostic mode and a feedback value of the motor in the normal mode, which was obtained in advance, exceeds a predetermined threshold.

[0039] If the motor abnormality is expected to be detectable with a higher probability, unsupervised learning is provided for the abnormality detection unit 130, and the transition of the motor's feedback value during normal operation is learned in the diagnostic mode to generate a cluster in advance. To detect regular or abnormal motor operation, the motor's feedback value in the diagnostic mode is input to the unsupervised learning unit, so that it can be determined that the motor is abnormal if the input feedback value deviates from the cluster of the motor's feedback values ​​during normal operation. For the diagnostic mode, clusters during normal motor operation and clusters for individual abnormalities (bearing malfunction, winding malfunction, axle malfunction, etc.) are generated in advance.Then, in the diagnostic mode for detecting the regularity or abnormality of the engine operation, the feedback value of the engine can be input into the learning unit for unsupervised learning, so that it can be determined whether the engine is operating normally or a fault has occurred, that is, the occurrence of an abnormality can be detected by means of the cluster into which the input feedback value fits.

[0040] A learning unit for supervised learning can also be introduced into the abnormality detection unit 130, wherein learning data for the case of normal operation of the engine and learning data for the case of abnormal operation of the engine are generated based on feedback values ​​detected in the diagnostic mode, and machine learning is then performed based on such learning data. To detect normal operation or abnormal operation of the engine, the feedback value of the engine in the diagnostic mode can then be input to the learning unit, so that a determination regarding normal operation or abnormal operation can be output.

[0041] Even when using supervised learning, the anomaly determination can be carried out by generating learning data for individual anomalies (anomaly concerning a bearing, anomaly concerning a winding, anomaly concerning an axis fault, etc.).

[0042] The controller 1 according to this embodiment is configured so that the abnormality detection unit 130 can detect an engine abnormality by modifying the engine control system so that the engine operation is significantly susceptible to a disturbance (abnormality) in the diagnostic mode. In the controller 1 according to this embodiment, a significant difference is generated between the feedback value detected during normal engine operation and the feedback value detected during abnormal engine operation in the diagnostic mode, so that the engine abnormality can be detected with good sensitivity even if only a simple structure is employed for the abnormality detection unit 130.When a machine learning device is used in the abnormality detection unit 130, machine learning can be performed with a relatively small amount of learning data because the difference between regular and abnormal operation becomes clear, so that the cost of the learning process can also be reduced.

[0043] In a modification of the controller 1 according to the above embodiment, several diagnostic operating modes can be provided for the engine control unit 100, which can be switched by means of the operating mode switching unit 110. Irregularities in the operation of engines can depend on the causes or the locations of the occurrence of an irregularity, and the settings of the engine control system with which the individual irregularities can be easily determined from the feedback value can depend on the causes or the location of the irregularity. For this purpose, Fig.Five engine control systems are set for the individual diagnostic modes, with the diagnostic modes being individually assigned to the possible causes of abnormalities and the abnormality locations from which detection is likely to be expected, and a diagnostic mode command 210 is provided for each of the diagnostic modes. The mode switching unit 110 commands the engine control unit 100 to switch the normal mode to diagnostic modes 1, 2, 3, etc. according to a predetermined time sequence. In these individual diagnostic modes, the engine control system changing unit 120 changes the engine control system of the engine control unit 100 to the respective engine control systems corresponding to the different diagnostic modes, with the engine control unit 100 executing the diagnostic mode commands 210 for the respective diagnostic modes.In this way, irregularities occurring in the engine can be detected with high accuracy, and the causes of the irregularities and their locations can also be easily determined.

[0044] According to a further modification of the controller 1 according to the above embodiment, a plurality of gradually differentiated diagnostic modes are provided for the engine control unit 100, which are switched through by the mode switching unit 110. In this modification, a diagnostic mode in which a wider range of abnormalities can be detected and a diagnostic mode in which more specific abnormalities can be detected are predetermined in advance. These diagnostic modes can be used to gradually narrow down the causes and locations of engine abnormalities, so that the diagnostic operations are executed in each diagnostic mode while switching the modes sequentially, starting with the diagnostic mode in which the widest range of abnormalities can be detected.

[0045] Embodiments of the invention have been described in more detail above, but the invention is not limited thereto and can be modified and implemented in a suitable manner.

[0046] For example, in the above embodiments, the controller 1 is implemented in the controller for controlling the machine tool. On the other hand, the controller 1 may also be implemented as a motor control system or may be installed in a computer such as a host computer. Functional devices may be provided and installed for each of these devices. For example, the motor control unit 100, the operation mode switching unit 110, and the motor control system changing unit 120 described above may be functionally arranged according to the respective characteristics of the application. In particular, the abnormality detection unit 130 may be installed in a host computer connected via a bus or a network after the units 100, 110, and 120 are installed in the motor control system.In the present invention, the mode switching unit 110 and the engine control system changing unit 120 are tools for effective abnormality detection, so no serious problems arise when they are installed in any of the devices. By using a machine learning device in the abnormality detection unit 130, the cost of the entire system can be kept low by locating the abnormality detection unit 130 in the host computer, allowing it to be used in conjunction with multiple industrial machines.

Claims

[1] A controller (1) having a detector for detecting a speed or position feedback value and having a function for detecting an abnormality in a motor, the controller (1) comprising: an engine control unit (100) configured to control the engine (50); an operating mode switching unit (110) configured to switch between operating modes of the motor (50); and an engine control system changing unit (120) configured to change an engine control system used when the engine control unit (100) controls the engine (50) in the operating modes of the engine (50), wherein the operating modes include at least one normal operating mode as a control-compliant operating mode and a diagnostic operating mode in which an abnormality of the engine (50) can be detected, and wherein the motor control system changing unit (120) changes a motor control system, which is used when the motor control unit (100) controls the motor (50) in the diagnostic mode, into a motor control system to increase an effect of a disturbance on the speed or position feedback value. [2] The controller (1) according to claim 1, wherein the engine control system changing unit (120) sets at least one gain of the engine control system in the diagnostic mode to a value different from the corresponding value in the normal mode. [3] The controller (1) according to claim 1, wherein the engine control system changing unit (120) activates a filter configured to amplify only a specific frequency band in the engine control system in the diagnostic mode. [4] The controller (1) according to claim 1, wherein the engine control system changing unit (120) interrupts a control signal to the engine (50) in the diagnostic mode at a predetermined time at which the speed of the engine (50) is fixed. [5] The controller (1) according to any one of claims 1 to 4, further comprising an abnormality detection unit (130) configured to detect an abnormality of the engine (50) based on a feedback value detected by a detector in the diagnostic mode. [6] An abnormality detection method for detecting an abnormality in a motor (50) provided with a detector for detecting a speed or position feedback value, the abnormality detection method comprising the steps of: a step of changing a motor control system for controlling the motor (50) to increase an effect of a disturbance on the speed or position feedback value; a step of causing the engine (50) to perform a diagnostic operation; and a step of detecting an engine abnormality based on the feedback value obtained in diagnostic mode.

Images