Servo control device and servo system diagnostic method

Abstract

An aspect of a servo controller capable of accurately detecting an abnormality in a servo system is a servo controller for controlling a plurality of servo amplifiers that supply an electric current to each of a plurality of winding systems of an electric motor and adjusts a voltage such that an electric current feedback value equals an electric current command value, wherein the servo controller comprises: a normal operation control unit for inputting, as the electric current feedback value into the servo amplifiers, the value of the electric current flowing through the winding systems corresponding to the respective servo amplifiers; and a diagnostic operation control unit for inputting, as the electric current feedback value into two or more of the servo amplifiers to be checked, a representative value of the electric current flowing through the winding systems corresponding to the servo amplifiers to be checked, the electric current feedback value being equal between the servo amplifiers to be checked.

Description

Technical Field

[0006] , , , , ,

[0001] The present invention relates to a servo control device and a servo system diagnosis method.

Background Art

[0002] Generally, a servo amplifier is configured to be able to adjust an output voltage by means such as pulse width modulation (PWM), and feedback-controls the output voltage so that the value of the actual output current matches the current command value input from the servo control device.

[0003] There are cases where a motor having a plurality of winding systems is driven by a plurality of servo amplifiers (also referred to as drive circuits or drivers) for each winding system. In particular, when driving a high-output motor, driving by a plurality of servo amplifiers has the merit that the withstand voltage performance required for the servo amplifier is reduced and the equipment cost can be reduced.

[0004] In a system that drives a motor, it is desirable to detect abnormalities in a servo amplifier, a motor winding, etc. before causing a serious trouble. In a servo system in which a plurality of winding systems of a motor are respectively driven by individual servo amplifiers, it has been proposed to detect abnormalities for each system (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] [[ID=In the servo system described in Patent Document 1, abnormalities are detected based on deviations between systems of state variables such as voltage and current applied to the motor. However, simply comparing state variables between systems that are independently feedback-controlled can make it difficult to accurately detect abnormalities. For example, when comparing the current values ​​of winding systems, even if the impedance of one winding system changes due to an abnormality, the difference in current values ​​between systems is eliminated by feedback control that matches the output current value to the current command value. Therefore, a detectable deviation in the current values ​​between systems only occurs after the abnormality has become so severe that control by the servo amplifier is no longer possible. Furthermore, it is difficult to accurately detect the output voltage of the servo amplifier. For these reasons, a technology that can accurately detect abnormalities in a servo system is desired. [Means for solving the problem]

[0007] A motor control device according to one aspect of the present disclosure is a servo control device that controls a plurality of servo amplifiers that supply current to each winding system of an electric motor having a plurality of winding systems and adjust the voltage so that the current feedback value is equal to the current command value, comprising: a normal operation control unit that inputs the value of the current flowing through the winding system corresponding to each of the servo amplifiers as the current feedback value; and a diagnostic operation control unit that inputs a representative value of the current flowing through the winding system corresponding to the servo amplifier to be checked to two or more servo amplifiers to be checked as the current feedback value which is equal among the checked servo amplifiers.

[0008] A servo system diagnostic method according to another aspect of the present disclosure is a servo system comprising an electric motor having a plurality of winding systems and a plurality of servo amplifiers that supply current to each of the winding systems and adjust the voltage so that the current feedback value is equal to the current command value, comprising the steps of inputting a representative value of the current flowing through the winding system corresponding to the servo amplifier to be checked as the current feedback value which is equal among the servo amplifiers to be checked to two or more servo amplifiers to be checked, and determining that there is an abnormality in the servo system when the deviation of the current flowing through the winding system corresponding to the servo amplifier to be checked is greater than a predetermined value. [Effects of the Invention]

[0009] According to this disclosure, abnormalities in the servo system can be accurately detected. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows the configuration of a servo system equipped with a servo control device according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0011] Embodiments of this disclosure will be described below with reference to the drawings. Figure 1 is a diagram showing the configuration of a servo system S equipped with a servo control device 20 according to one embodiment of this disclosure. The servo system S also has a function to perform one embodiment of the servo system diagnostic method according to this disclosure.

[0012] The servo system S comprises a motor control device 100 having a servo control device 20 according to one embodiment of the present disclosure, and an electric motor 200 driven by the motor control device 100.

[0013] The electric motor 200 has multiple winding systems. In Figure 1, the electric motor 200 has two winding systems, but the number of winding systems is not particularly limited. The electric motor 200 is typically a three-phase AC motor, and may be an induction motor or a synchronous motor. In this embodiment, the wiring that supplies power from the motor control device 100 to the electric motor 200 is provided with current detectors 201 and 202 that detect the value of the current supplied to each winding. The current detectors 201 and 202 may each consist of multiple ammeters that detect the current value of each phase supplied to the winding system of the electric motor 200.

[0014] The motor control device 100 includes a plurality of servo amplifiers 11, 12 corresponding to the winding system of the electric motor 200, and a servo control device 20 that controls the servo amplifiers 11, 12.

[0015] The servo amplifiers 11 and 12 are provided in a one-to-one correspondence with the winding systems of the electric motor 200 and supply current to the corresponding winding systems. The servo amplifiers 11 and 12 also adjust the voltage so that the current feedback value is equal to the current command value specified by the servo control device 20. Typically, the servo amplifiers 11 and 12 are configured to perform vector control, adjusting the voltage so that the component of the output current that forms the magnetic flux (d-axis current) and the component that generates torque (q-axis current) match the command values. Normally, all servo amplifiers 11 and 12 supplying power to the same electric motor 200 receive the same current command value.

[0016] The servo control device 20 may be configured to include a normal operation control unit 21, a diagnostic operation control unit 22, an abnormality determination unit 23, a program control unit 24, an operation management unit 25, a start control unit 26, and a manual selection unit 27. The servo control device 20 can be realized, for example, by having a computer device having a processor, memory, input / output interface, etc., execute an appropriate control program. Each component of the servo control device 20 is a classification of the functions of the servo control device 20 and does not necessarily have to be clearly distinguishable in terms of physical configuration and program configuration. Furthermore, the servo control device 20 may be part of the functions of a control device of equipment including a servo system S. For example, if multiple drive axes of a machine tool are each electric motors 200, multiple motor control devices 100 may be realized as part of a numerical control device that controls the operation of the machine tool.

[0017] The normal operation control unit 21 inputs the current values ​​flowing through the corresponding winding systems to the servo amplifiers 11 and 12 as current feedback values. By individually feeding back the current of the winding systems corresponding to the servo amplifiers 11 and 12 in this way, variations between winding systems can be suppressed, enabling highly accurate and responsive control of the motor 200. For this reason, the motor control device 100 normally inputs current feedback values ​​individually to the servo amplifiers 11 and 12 via the normal operation control unit 21.

[0018] The diagnostic operation control unit 22 inputs a representative value of the current flowing through the winding system corresponding to the servo amplifiers 11 and 12 to be checked to two or more servo amplifiers 11 and 12 as a common current feedback value that is equal among the checked servo amplifiers. If there are no abnormalities in the servo amplifiers 11 and 12 and their corresponding winding systems, their circuit characteristics will be the same, and therefore the output voltage and output current of the servo amplifiers 11 and 12 will be approximately the same. However, if an abnormality occurs in the servo amplifiers 11 and 12 and their corresponding winding systems, a difference will occur in the current values ​​of the winding systems.

[0019] As the representative value input by the diagnostic operation control unit 22 to the servo amplifiers 11 and 12 as the current feedback value, the current value of any winding system may be used, but it is preferable to use the average value of the current flowing through the winding system to be confirmed. By using the average value as the representative value, when the current value of the winding system in which an abnormality has occurred is used as the representative value, it is possible to prevent the servo amplifiers 11 and 12 of other winding systems from outputting abnormal voltages and making the output of the motor 200 inappropriate.

[0020] When the motor 200 has three or more winding systems, the diagnostic operation control unit 22 may input the representative value to all the servo amplifiers as the current feedback value. Thereby, it is possible to easily and quickly detect a system in which an abnormality is suspected.

[0021] Further, when the motor has three or more winding systems, the diagnostic operation control unit 22 designates at least two or more of the servo amplifiers as the confirmation targets, and inputs only to the servo amplifiers to be confirmed the representative value of the current flowing through the winding system corresponding to those servo amplifiers as the feedback value, and the current values of the currents flowing through the winding systems corresponding to the remaining servo amplifiers may be individually input as the current feedback values. Thereby, while maintaining the operation of the machine tool or the like including the servo system S, it is possible to switch the servo amplifier that feeds back the representative value and confirm the presence or absence of an abnormality in the servo amplifier or the corresponding winding system in order.

[0022] For example, when controlling a motor having eight winding systems, it is conceivable to designate only two servo amplifiers as the confirmation targets. Specifically, by individually feeding back the current values of the corresponding winding systems to the servo amplifiers that supply power to six winding systems, and feeding back the representative values of the currents of the corresponding two winding systems to the remaining two servo amplifiers, it is possible to minimize the decrease in the accuracy and responsiveness of the motor control as a whole. Therefore, while continuing the operation of the machine tool or the like, it is possible to detect an abnormality in the servo amplifier that feeds back the representative value or the corresponding winding system. By sequentially changing the confirmation targets, it is possible to detect an abnormality in the entire servo system.

[0023] When the deviation between the current flowing through the winding system corresponding to the servo amplifier 11 to be confirmed and the current flowing through the winding system corresponding to the servo amplifier 12 to be confirmed is greater than a predetermined value, the abnormality determination unit 23 determines that there is an abnormality in the servo amplifier 11, 12 to be confirmed or the corresponding winding system. Further, the abnormality determination unit 23 may be configured to perform notifications such as alarm reporting and output of an abnormality signal when it is determined that there is an abnormality in the winding system.

[0024] Specifically, the abnormality determination unit 23 may be configured to determine that there is an abnormality in the winding system when the deviation of the average value of the actual current flowing through the winding system with the representative value of the current of the corresponding winding system as the current feedback value is greater than or equal to a predetermined abnormality threshold. Further, the abnormality determination unit 23 may determine that there is an abnormality in the winding system when the standard deviation or the like of the actual current values of the winding systems of the servo amplifiers with equal representative values as the current feedback values is greater than or equal to a predetermined abnormality threshold. The abnormality threshold may be a fixed value set as, for example, a ratio to the maximum current in the specifications of the electric motor 200, or may be a value dynamically calculated as a value obtained by multiplying a ratio preset in the current command value.

[0025] The program control unit 24 sets a current command value according to an operation program. As described above, when the servo system S forms a part of a machine tool, it is a well-known technique to use a numerical control device that sets a current command value from a machining program described in a language such as G code as an operation program.

[0026] The operation management unit 25 causes the diagnostic operation control unit 22 to execute control when the output of the current command value by the program control unit 24 is paused. The pause of the output of the current command value means that the current command value is set to zero not transiently, and it may be not only when the operation program is not executed but also when waiting for the operation of the electric motor 200 to stop during the operation program. In this way, by using the idle time to check for abnormalities in the servo amplifiers 11, 12 and the electric motor 200, proper operation of a machine tool or the like can be ensured.

[0027] The startup control unit 26 performs control by the diagnostic operation control unit when the servo control device 20 is started. The control by the diagnostic operation control unit 22 may be configured to be performed at the first startup after a predetermined period has elapsed since the previous control by the diagnostic operation control unit 22. The startup control unit 26 can also ensure the proper operation of machine tools, etc., by confirming that there are no abnormalities in the servo system S as part of the initialization operation of the servo system S, such as confirming the origin of the electric motor 200.

[0028] The manual selection unit 27 selects, according to the operator's input, whether to control the system using the normal operation control unit 21 or the diagnostic operation control unit 22. The manual selection unit 27 may also be configured to allow the operator to select the item to be checked when using the diagnostic operation control unit 22. By being able to check for abnormalities in the servo system S according to the operator's request, more appropriate operation of machine tools and the like becomes possible.

[0029] As is clear from the above explanation, the servo system diagnostic method performed in the servo system S includes the steps of: inputting a representative value of the current flowing through the winding systems corresponding to the servo amplifiers 11 and 12 to be checked as an equal current feedback value between the checked servo amplifiers, to two or more servo amplifiers 11 and 12 to be checked by the diagnostic operation control unit 22; and determining that there is an abnormality in the servo system S if the deviation of the current flowing through the winding systems corresponding to the servo amplifiers 11 and 12 to be checked is greater than a predetermined value by the abnormality determination unit 23.

[0030] In the servo system S, the diagnostic operation control unit 22 inputs a representative value of the current flowing through the winding system corresponding to the servo amplifiers 11 and 12 to be checked as a common current feedback value. As a result, if there are no abnormalities in the servo amplifiers 11 and 12 and the winding system to be checked, the current flowing through the winding system becomes approximately equal, preventing large variations in current values ​​caused by, for example, the rotational position of the motor 200, disturbances, control delays, etc. Therefore, signs of failure, such as changes in winding impedance, can be detected early.

[0031] Although embodiments of this disclosure have been described above, the present invention is not limited to the embodiments described above. Furthermore, the effects described in the embodiments described above are merely a list of preferred effects arising from the present invention, and the effects of the present invention are not limited to those described in the embodiments described above.

[0032] For example, the motor control device according to this disclosure may be configured to display the current value to be checked on a screen and leave the final determination of whether or not there is an abnormality to the operator. In addition, in a servo system, the current detector may be provided inside the servo amplifier or the electric motor. Furthermore, the motor control device according to this disclosure has a configuration in which the operation management unit, the start control unit and the manual selection unit can be omitted. [Explanation of Symbols]

[0033] 11,12 Servo amplifier 20 Servo control devices 21 Normal Operation Control Unit 22 Diagnostic Operation Control Unit 23 Abnormality determination section 24 Program Control Unit 25. Operations Management Department 26 Startup Control Unit 27 Manual Selection Section 100 Motor control device 200 Electric motor 201,202 Current detectors S Servo System

Claims

1. A servo control device that supplies current to each of the winding systems of an electric motor having multiple winding systems and controls multiple servo amplifiers that adjust the voltage so that the current feedback value is equal to the current command value, Each of the plurality of servo amplifiers is provided with a normal operation control unit that individually inputs the value of the current flowing through the corresponding winding system as the current feedback value, A diagnostic operation control unit that, in an alternative manner to the normal operation control unit, performs control and inputs to two or more servo amplifiers designated as targets for verification a representative value of the current flowing through two or more winding systems corresponding to the servo amplifiers designated as targets for verification, as the current feedback value which is equal among the targets for verification. An abnormality determination unit, which, when controlled by the diagnostic operation control unit, determines whether there is an abnormality in the servo amplifier or the corresponding winding system to be checked, and provides notification if an abnormality is determined, A servo control device equipped with the following features.

2. The servo control device according to claim 1, wherein the abnormality determination unit determines that there is an abnormality in the servo amplifier or the corresponding winding system when the deviation of the representative value of the current flowing through the winding system to which the input is received is greater than a predetermined value.

3. A program control unit sets the current command value according to the operating program, When the program control unit pauses outputting the current command value, the operation management unit causes the diagnostic operation control unit to execute control, A servo control device according to claim 1 or 2, further comprising:

4. A servo control device according to any one of claims 1 to 3, further comprising a startup control unit that performs control by the diagnostic operation control unit when the servo control device is started.

5. The servo control device according to any one of claims 1 to 4, wherein the diagnostic operation control unit uses the average value of the current flowing through the winding systems corresponding to the two or more servo amplifiers as the representative value.

6. A servo system that performs normal operation comprising an electric motor having multiple winding systems, and multiple servo amplifiers that supply current to each of the winding systems and adjust the voltage so that the current feedback value is equal to the current command value, wherein the value of the current flowing through the corresponding winding system is individually input to each of the servo amplifiers as the current feedback value, Alternatively, in addition to the normal operation, a diagnostic operation is performed in which a representative value of the current flowing through the two or more winding systems corresponding to the servo amplifiers to be checked is input as an equal current feedback value among the checked servo amplifiers to two or more servo amplifiers to be checked. During the execution of the diagnostic operation, if the deviation of the representative value of the current flowing through the winding system corresponding to the servo amplifier to be checked from the average value of the current flowing through the input winding system is greater than a predetermined value, it is determined that there is an abnormality in the servo system. A diagnostic method for a servo system, comprising the following features.

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