Servo System

Abstract

To suitably perform data acquisition based on correlation between control axes for performing synchronous control in a servo system.SOLUTION: In a servo system including a control device and a plurality of servo drivers, a predetermined servo driver transmits a trigger signal for acquiring data related to a predetermined parameter to the remaining servo drivers via an inter-driver communication path, acquires data stored in a storage unit of the predetermined servo driver in a first period starting from a first timing in synchronous control, and sends the data to the control device via a control communication path. When each of the remaining servo drivers receives the trigger signal from the predetermined servo driver, each remaining servo driver acquires data in a second period starting from a second timing corresponding to the first timing, which is determined according to a communication delay in the inter-driver communication path, from among data stored in the storage unit of each remaining servo driver and sends the data to the control device via the control communication path.SELECTED DRAWING: Figure 3B

Description

[Technical Field]

[0001] The present invention relates to a servo system including a control device and a servo driver. [Background technology]

[0002] In a typical servo system, the servo driver that drives the motor performs control loop calculations related to position, speed, and current for servo control. A position command is issued to the servo driver from a higher-level control device (such as a PLC). The servo driver performs control loop calculations based on the received position command, generates a drive current to drive the motor, and supplies this drive current to the motor. The motor is driven by the drive current supplied, and the motor drive results detected by an encoder are provided as a feedback signal to the servo driver's control loop calculations. Furthermore, there are cases where multiple servo drivers are controlled simultaneously by a control device, resulting in more complex signal paths.

[0003] When multiple servo drivers are controlled by a control device, the signal paths become complicated, making it difficult to determine the cause of a communication error when one occurs. For example, Patent Document 1 discloses a configuration in which, in a combination of a host control device and multiple control devices, data communication lines and disconnection detection are installed in parallel between the control devices. In this configuration, when a communication error occurs, the presence or absence of a disconnection is determined using the disconnection detection line. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-167401 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-202001 Summary of the Invention [Problem to be solved by the invention]

[0005] In a servo system that includes a control device and multiple servo drivers, synchronous control may be performed among the multiple servo drivers. In synchronous control, servo control is performed synchronously on the control axes corresponding to each servo driver, so if an abnormality occurs in one control axis, it will affect the other control axes as well. Therefore, when an abnormality occurs during synchronous control, it is not sufficient to simply examine the control status of each control axis individually; it is necessary to accurately investigate the cause by taking into account the correlation between the control axes.

[0006] On the other hand, with conventional technology, even if data on each control axis is acquired to clarify the cause of an abnormality during synchronous control, it is difficult to acquire data that takes into account the correlation between the control axes. As a result, it is not possible to fully investigate the cause of an abnormality during synchronous control. Furthermore, by acquiring data that takes into account the correlation between the control axes, not only for abnormalities that occur during synchronous control but also in situations where an abnormality has not yet occurred, analysis to prevent abnormalities can be promoted, but conventional technology does not provide a suitable solution.

[0007] The present invention has been made in consideration of such problems, and aims to provide a technology for suitably acquiring data taking into account the correlation between control axes that perform synchronous control in a servo system including a control device and multiple servo drivers. [Means for solving the problem]

[0008] A servo system according to one aspect of the present disclosure includes a control device and a plurality of servo drivers, and transmits and receives control commands related to servo control between the control device and the plurality of servo drivers. a control communication path for transmitting data to the plurality of servo drivers, and an inter-driver communication path between the plurality of servo drivers that is different from the control communication path and enables the plurality of servo drivers to communicate with each other; each of the plurality of servo drivers has a storage unit that stores a transition of a predetermined parameter related to servo control in each servo driver when the plurality of servo drivers are performing synchronous control with each other; a predetermined servo driver among the plurality of servo drivers is configured to transmit a trigger signal for acquiring data related to the predetermined parameter to the remaining servo drivers among the plurality of servo drivers via the inter-driver communication path, acquire data stored in the storage unit of the predetermined servo driver for a first period starting from a first timing in the synchronous control, and send the data to the control device via the control communication path; and each of the remaining servo drivers, upon receiving the trigger signal from the predetermined servo driver, acquires data for a second period starting from a second timing corresponding to the first timing, which is determined according to a communication delay in the inter-driver communication path, from the data stored in its own storage unit, and send the data to the control device via the control communication path.

[0009] In a servo system configured in this manner, control commands related to servo control of a motor or the like to which a drive current is supplied by the servo driver are transmitted and received via a control communication path. This transmission and reception is performed under the control of a control device, and is therefore affected by the processing by the control device. On the other hand, the inter-driver communication path for mutual communication between servo drivers does not involve the control device directly in the transmission and reception of signals, so signals can be sent and received quickly between servo drivers regardless of the processing by the control device.

[0010] Here, when each servo driver performs synchronous control, the memory unit is configured to store the transitions of predetermined parameters related to the servo control performed by each servo driver. The predetermined parameters may be any parameters related to servo control, such as the results of calculations by the position control unit and the speed control unit, or detected position information and detected speed information fed back to these control units. In addition, since there is generally an upper limit to the storage capacity of the memory unit, the sampling period for storing the predetermined parameters can be adjusted taking that storage capacity into consideration. To store the transitions, it is preferable to associate the values ​​of the predetermined parameters with the timing (time) of sampling in each servo driver. Regarding the time information in each servo driver, it is preferable that common time information be provided to each servo driver from the control device via a control communication path, and this common time information is preferably used when storing the transitions of the predetermined parameters.

[0011] Then, a predetermined servo driver transmits a trigger signal to the remaining servo drivers via the inter-driver communication path. The trigger signal is a signal for consolidating data related to predetermined parameters stored in the memory units of each servo driver on the control device side. By transmitting the trigger signal via the inter-driver communication path, the remaining servo drivers can quickly receive the trigger signal regardless of the processing of the control device, and can start processing the data related to the predetermined parameters stored in their respective memory units.

[0012] Here, the predetermined servo driver is in a position to issue a trigger signal, so it can arbitrarily determine the first timing, which is the start timing of the first period for acquiring data from the storage unit. On the other hand, each of the remaining servo drivers is in a position to start acquiring data from the storage unit after receiving the trigger signal. Therefore, each of the remaining servo drivers determines the second timing, which is the start timing of the second period for acquiring data from the storage unit, taking into account the communication delay in the inter-driver communication path, i.e., the time required for the trigger signal to be delivered from the predetermined servo driver to the remaining servo drivers. Since the inter-driver communication path is a communication path that does not go through a control device, This allows for stable and fast communication between the servo drivers, making it possible to clearly determine the correlation between the data acquired from a specific servo driver and the data acquired from the remaining servo drivers, and to effectively utilize the data collected in the control device.

[0013] Preferably, the first timing and the second timing are the same timing. Also, preferably, the length of the second period is the same as the length of the first period. Under these conditions, by having each servo driver acquire data from the storage unit, data that can be used to appropriately compare the servo control status during synchronous control on the control axes corresponding to each servo driver is collected in the control device.

[0014] Here, two examples of the trigger signal are shown below. In the first form, the trigger signal may be a signal for stopping all control axes related to the synchronous control when an abnormality occurs in the control axis corresponding to the predetermined servo driver. In this case, the predetermined servo driver may stop the control axis corresponding to the predetermined servo driver upon transmitting the trigger signal, and each of the remaining servo drivers may stop the control axis corresponding to itself upon receiving the trigger signal. In the first form, when an abnormality occurs in a predetermined servo driver during synchronous control, data related to the servo control at the time of the abnormality is acquired and collected in the control device. This makes it possible to appropriately grasp the status of servo control in each servo driver related to the abnormality, thereby facilitating smooth investigation of the cause of the abnormality.

[0015] In a second embodiment of the trigger signal, the trigger signal may be a signal for periodically collecting data on the predetermined parameters for all control axes related to the synchronous control. In this case, the predetermined servo driver may transmit the trigger signal at a predetermined cycle determined based on the capacity of the memory unit of each of the plurality of servo drivers. In the second embodiment, the trigger signal is output from the predetermined servo driver at a predetermined cycle, whereby data related to servo control stored in the memory unit of each servo driver is periodically collected in the control device. This allows data to be conveniently collected from each servo driver to the control device without being affected by the limited capacity of the memory unit. For example, maintenance processing such as failure prediction can be performed on the control device side based on the collected data. After sending data from each driver to the control device, the respective memory units may be able to overwrite the data or erase the data in the memory unit so that new data can be stored.

[0016] In the servo system described above, the control device may have an output unit that outputs the transitions of the predetermined parameters for all control axes related to the synchronous control in a time-aligned format based on the first data received from the predetermined servo driver and the second data received from each of the remaining servo drivers. With this configuration, the transitions of the predetermined parameters for the control axes corresponding to each servo driver can be compared in a time-aligned format, thereby making it possible to accurately make a decision based on the transitions. [Effects of the Invention]

[0017] In a servo system including a control device and a plurality of servo drivers, data acquisition can be suitably performed taking into account the correlation between control axes that perform synchronous control. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a first diagram showing a schematic configuration of a servo system disclosed in the present application. [Figure 2] FIG. 1 is a diagram illustrating a control structure for servo control included in a servo system disclosed in the present application. [Figure 3A] FIG. 1 is a diagram for explaining a situation in which data is acquired using conventional technology. [Figure 3B] 1 is a diagram for explaining a situation in which data is acquired by the servo system disclosed in the present application. [Figure 4] 1 is a first flowchart showing the flow of data acquisition control executed for data acquisition in the servo system disclosed in the present application. [Figure 5] 10 is a second flowchart showing the flow of data acquisition control executed for data acquisition in the servo system disclosed in the present application. [Figure 6] 10 is a third flowchart showing the flow of data acquisition control executed for data acquisition in the servo system disclosed in the present application. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, identical or corresponding parts are designated by the same reference numerals, and their description will not be repeated. In the present disclosure, as an exemplary embodiment of the servo system, three servo drivers are connected to a control device (PLC), but the number of servo drivers may be two, or may be four or more.

[0020] FIG. 1 is a diagram showing the schematic configuration of a servo system 1. The servo system 1 has a PLC 5, which is a control device, and servo drivers 4, 4a, and 4b (hereinafter also referred to as "servo drivers 4, etc.") that generate drive currents for servo-controlling motors, which are the objects of control, in accordance with position commands for each control axis generated by the PLC 5. Therefore, the servo system 1 has a maximum of three control axes. Here, the object to be driven by the servo system 1 is a device 20. The device 20 is a processing device that has three motors 21, 21a, and 21b inside it.

[0021] Examples of the device 20 include an XY table of a machine tool or a conveyance device, and an arm of an industrial robot having multiple joint axes. The motors 21, 21a, and 21b (hereinafter also referred to as "motors 21, etc.") of the device 20 are AC servo motors. Encoders 22, 22a, and 22b are attached to the motors 21, etc., respectively, and the encoders transmit signals related to the operation of each motor in a feedback manner. The signals transmitted as feedback (hereinafter referred to as feedback signals) include, for example, position information about the rotational position (angle) of the rotational shaft of the motor 21, etc., and information about the rotational speed of the rotational shaft.

[0022] The PLC 5 generates operation command signals related to the operation (motion) of each motor of the device 20. The operation command signals generated by the PLC 5 are provided to a servo control unit 42, etc., such as the servo driver 4 of each control axis, which has a position control unit 401 that performs control loop calculations related to position, a speed control unit 402 that performs control loop calculations related to speed, and a current control unit 403 (see FIG. 2) that performs control loop calculations related to the drive current of the motor. Details of the servo control structure in the servo control unit 42, etc. will be described later.

[0023] The PLC 5 has a communication unit 51, a holding unit 52, and an output unit 53. The communication unit 51 is a functional unit for communicating with the servo driver 4 and the like that supplies drive current to the motor that is the target of servo control by the PLC 5. Therefore, communication units 41, 41a, and 41b corresponding to each of the servo drivers 4 and the like that are the communication partners are provided. The communication path between the communication unit 51 on the PLC 5 side and the communication unit 41 on the servo driver 4 and the like corresponds to the control communication path disclosed in the present application, and control commands related to servo control of the motor 21 and the like (such as the position command pcmd shown in FIG. 2 ) are transmitted and received therethrough. This communication is performed under the control of the PLC 5 and is affected by the processing in the PLC 5.

[0024] The holding unit 52 stores predetermined parameters relating to servo control for each control axis, which are transmitted from the servo driver 4 etc. as will be described later, and in particular, the parameters relating to synchronization control between the servo drivers 4, 4a, and 4b. The storage unit 52 is a functional unit that stores data related to the predetermined parameters while the PLC 5 is being controlled. The data storage by the storage unit 52 may be performed temporarily or continuously in a storage area provided within the PLC 5. For example, the data may be stored temporarily in order to transfer the stored data to an external device connected to the PLC 5. In the case of temporary storage, the data stored in the storage unit 52 is deleted at a predetermined timing. The output unit 53 is a functional unit that outputs the data stored by the storage unit 52, i.e., the data related to the predetermined parameters for each control axis. Examples of the form of output by the output unit 53 include transmitting the stored data to an external device as a data group, or displaying the data on a display provided in the PLC 5 so that the user can visually check the progress of the data.

[0025] Next, the functional units of the servo driver 4 and the like will be described. Since the functional units of the servo drivers 4, 4a, and 4b are all substantially the same, the following description will mainly focus on the servo driver 4. The servo driver 4 has a communication unit 41, a servo control unit 42, a memory unit 43, a trigger unit 45, an acquisition unit 46, a drive circuit 47, and an inter-driver communication unit 48. The communication unit 41 has already been mentioned, so the other functional units will mainly be described.

[0026] As described above, the servo control unit 42 has a servo control structure formed in the servo driver 4 and is a functional unit that performs control loop calculations for servo control of the associated motor. The servo control structure will be described with reference to FIG. 2. An operation command signal received from the PLC 5 is received by the communication unit 41 and provided to the servo control unit 42. The servo control unit 42 generates a current command for driving the drive circuit 47 using an internal servo control structure (see FIG. 2). A feedback signal from the encoder 22 of the motor 21 is delivered to the servo control structure via an encoder cable (not shown). The drive circuit 47 is a so-called inverter device. AC power supplied from an AC power source (not shown) is used to power the drive circuit 47. In the present disclosure, the drive circuit 47 is a type that receives three-phase AC, but it may also be a type that receives single-phase AC. The drive circuit 47 generates a drive current for driving the motor 21.

[0027] 2 includes a position control unit 401, a speed control unit 402, and a current control unit 403. The position control unit 401 performs, for example, proportional control (P control). Specifically, it calculates a speed command vcmd by multiplying a position deviation, which is the deviation between a position command pcmd generated in the PLC 5 and a detected position, by a predetermined position proportional gain.

[0028] Speed ​​control unit 402 performs, for example, proportional-integral control (PI control). Specifically, the torque command τcmd is calculated by multiplying the integral of the speed deviation, which is the deviation between the speed command vcmd calculated by position control unit 401 and the detected speed, by a predetermined speed integral gain, and then multiplying the sum of the calculation result and the speed deviation by a predetermined speed proportional gain. Speed ​​control unit 402 may also perform P control instead of PI control.

[0029] The current control unit 403 outputs a current command Ccmd to the drive circuit 47 based on the deviation between the torque command τcmd calculated by the speed control unit 402 and the drive current supplied from the drive circuit 47 to the windings of the motor 21. Upon receiving the current command Ccmd, the drive circuit 47 generates a drive current for the motor 21. The current control unit 403 includes a filter (first-order low-pass filter) related to the torque command and one or more notch filters, and may have, as control parameters, cutoff frequencies related to the performance of these filters, etc.

[0030] In the servo control structure, a detected position signal and a detected speed signal calculated based on the detection signal of the encoder 22 of the motor 21 are fed back to the position control unit 401 and the speed control unit 402 as feedback signals relating to the position and the speed, respectively. Here, when performing synchronous control on three control axes in the device 20, it is possible to adopt a known prior art. For example, one of the control axes may be designated as the main axis and the remaining control axes as slave axes, and electronic cams that define the movement of each slave axis relative to the movement of the main axis may be set in the PLC 5, and position commands for the slave axes may be generated based on the detected position signals fed back from the main axis and the electronic cams, and supplied to the servo drivers of the slave axes.

[0031] Next, the storage unit 43 is a functional unit that stores data on the transitions of predetermined parameters related to servo control in the servo driver 4 in a storage area (memory) within the driver when synchronous control is performed on three control axes in the device 20. Examples of predetermined parameters include the calculation results of the position control unit 401 and the speed control unit 402 calculated in the servo control structure shown in FIG. 2, and detected position information and detected speed information fed back to the servo control structure, and any parameters may be selected. The storage unit 43 stores the transitions of the predetermined parameters by linking the values ​​of the predetermined parameters with corresponding time information. In the servo drivers 4 and the like, common time information is included in the control signals from the PLC 5, and this time information is shared between the servo drivers. Note that, since there is a limit to the storage capacity of the storage area, the sampling period for storage is determined taking into account the storage capacity in order to efficiently utilize the storage area.

[0032] The trigger unit 45 is a functional unit that transmits trigger signals to the servo drivers of other control axes during synchronous control with the other control axes, instructing the acquisition unit (described later) to acquire some or all of the data stored in the memory. The trigger signals from the trigger unit 45 are delivered to the servo drivers of the other control axes via an inter-driver communication path formed by the inter-driver communication unit 48. The inter-driver communication path is a communication path distinct from the control communication path between the communication unit 51 of the PLC 5 and the communication unit 41 of the servo driver 4, etc. To enable communication between the servo drivers in the inter-driver communication path without the PLC 5, the servo drivers 4, 4a, and 4b are provided with inter-driver communication units 48, 48a, and 48b, respectively. Communication via each inter-driver communication unit is referred to as "inter-driver communication." This inter-driver communication has a faster communication speed than communication with the PLC 5 over the control communication path, and signals can be exchanged more quickly between the servo drivers because they do not require processing by the PLC 5.

[0033] There are two types of trigger signals from the trigger unit 45. The first trigger signal is a signal related to S103 shown in FIG. 4, which will be described later, and commands the PLC 5 to periodically send data stored in the memory units 43, etc. of the servo drivers 4, etc., to the PLC 5 so that the data can be held in the holding unit 52 of the PLC 5. Of the three servo drivers, only the trigger unit 45 of the servo driver 4 is configured to send this first trigger signal; the trigger units 45a, 45b of the other servo drivers 4a, 4b do not send this first trigger signal. Next, the second trigger signal is a signal related to S203 shown in FIG. 5, which will be described later, and commands the PLC 5 to send data stored in the memory units 43, etc. of the servo drivers 4, etc., to the PLC 5 so that the data can be collected in the holding unit 52 of the PLC 5 when an abnormality occurs during synchronous control in each servo driver. The second trigger signal is configured to be sent by the trigger units 45, 45a, 45b of all servo drivers 4, 4a, 4b to respond to abnormalities occurring during synchronous control in each servo driver.

[0034] The acquisition unit 46 is a functional unit that receives a trigger signal from the trigger unit 45 of its own servo driver 4 or the trigger units 45a, 45b of the other servo drivers 4a, 4b, and acquires some or all of the data related to predetermined parameters during synchronization control that is stored in the memory unit 43 of its own servo driver 4. The data acquired by the acquisition unit 46 is transmitted from the communication unit 41 to the PLC 5. The PLC 5 stores the transmitted data in the storage unit 52. After the data is acquired by the acquisition unit 46, the data may be deleted from the storage unit 43, thereby recovering the capacity of the storage area of ​​the storage unit 43.

[0035] Here, data acquisition by the acquisition unit 46 will be described with reference to FIGS. 3A and 3B. FIG. 3B is a diagram corresponding to data acquisition in the servo system 1 disclosed herein, and FIG. 3A is a diagram corresponding to a comparative example of data acquisition for comparison with FIG. 3B. Each of (a) to (c) of FIGS. 3A and 3B shows the transition of a predetermined parameter in the control axis of the servo drivers 4, 4a, and 4b, with the time axis aligned. Data on the transition of the predetermined parameter is stored in each of the storage units 43, 43a, and 43b. The configuration of FIG. 3A illustrates a data acquisition situation in which a data acquisition command (corresponding to a trigger signal from the trigger unit 45) is issued from one servo driver via a control communication path connecting the servo driver 4 and the PLC 5, and the command is delivered to another servo driver via the PLC 5. Furthermore, the configuration of FIG. 3B illustrates a data acquisition situation in which a trigger signal is issued from the trigger unit of one servo driver to another servo driver via the inter-driver communication path. In each transition, the part corresponding to the acquired data is displayed with a solid line, and the other part is displayed with a dashed line.

[0036] In the configuration shown in FIG. 3A, a data acquisition command is issued by the servo driver 4 at timing t1. This data acquisition command is a command to acquire data for a period of Δt1. The servo driver 4 itself transmits the command at timing t1 and acquires data for the period Δt1. On the other hand, the servo drivers 4a and 4b that receive the command from the servo driver 4 have a relatively long delay before the command arrives because the command passes through the PLC 5. Therefore, the servo drivers 4a and 4b acquire data for the period Δt1 at timing t20, which is delayed from timing t1. As a result, the starting timing of each transition of the predetermined parameters for all control axes related to synchronous control that have been acquired is shifted.

[0037] Next, in the configuration shown in FIG. 3B, a trigger signal is output from the trigger unit 45 of the servo driver 4. This trigger signal is a command to acquire data for a period of Δt1. The servo driver 4 itself transmits the trigger signal at timing t1 and acquires data for the period of Δt1. Meanwhile, after receiving the trigger signal, the servo drivers 4a and 4b acquire data using their respective acquisition units 46a and 46b. Here, the trigger signal is delivered via a driver-to-driver communication path. However, since this driver-to-driver communication path does not involve the PLC 5, communication delays are small, and the trigger signal is delivered to the destination servo driver as quickly as possible. Furthermore, since it is not affected by the processing of the PLC 5, the communication delay is very stable, for example, about 500 μsec.

[0038] If the timing at which the servo drivers 4a and 4b receive the trigger signal is t1', then the communication delay Δt1 is expressed by the following equation: Δt1 = t1'-t1 (Equation 1) Then, the acquisition units 46a and 46b of the servo drivers 4a and 4b determine the start timing t2 of data acquisition for each control axis according to the following formula. t2 = t1'-Δt1 (Equation 2) As described above, Δt1 is extremely short and stable, so the start timing t2 can be suitably set to coincide with or very close to the timing t1. The determination of this start timing t2 is also the same when a trigger signal is output from the trigger unit of either of the servo drivers 4a, 4b via the inter-driver communication path, and the servo driver 4 receives it and performs data acquisition by the acquisition unit 46. As a result, the start timings of the acquired transitions of the predetermined parameters for all control axes related to synchronous control can be suitably aligned, thereby enabling good comparison between the control axes.

[0039] Similarly to the servo driver 4, the servo driver 4a has a communication unit 41a, a servo control unit 42a, a memory unit 43a, a trigger unit 45a, an acquisition unit 46a, a drive circuit 47a, and an inter-driver communication unit 48a. Similarly to the servo driver 4, the servo driver 4b has a communication unit 41b, a servo control unit 42b, a memory unit 43b, a trigger unit 45b, an acquisition unit 46b, a drive circuit 47b, and an inter-driver communication unit 48b.

[0040] <Data acquisition control> Here, the data acquisition control executed in the servo system 1 will be described with reference to Figs. 4 to 6. The data acquisition control in each figure is repeatedly executed in cooperation with the functional units of the servo driver 4 and the like. Fig. 4 shows the data acquisition control using the first trigger signal, and this data acquisition control is performed only by the servo driver 4. In the other servo drivers 4a and 4b, only the process of S102 (storage process of data related to the transition of the predetermined parameter of each control axis) is performed. Fig. 5 shows the data acquisition control using the second trigger signal, and this is performed by both servo drivers. Fig. 6 shows the data acquisition control when a trigger signal (first trigger signal or second trigger signal) is received from another servo driver.

[0041] First, the data acquisition control of FIG. 4 will be described. In S101, the trigger unit 45 determines whether the timing for transmitting a first trigger signal has arrived. As described above, the first trigger signal is a signal for periodically sending data stored in the memory unit 43 of each servo driver to the PLC 5. Because the memory capacity of the memory unit 43 is limited, the memory area will eventually reach its limit. Therefore, a trigger signal (first trigger signal) is output from the trigger unit 45 of the servo driver 4 at a predetermined interval based on the capacity of the memory area. This trigger signal is used as a starting point to send some or all of the stored data to the PLC 5, thereby securing space in the memory area for storing new data. If a positive determination is made in S101, the process proceeds to S103. If a negative determination is made in S101, the process proceeds to S102.

[0042] In S102, the memory unit 43 stores the predetermined parameters during synchronization control in a memory area. Meanwhile, in S103, the trigger unit 45 transmits a first trigger signal to the other servo drivers 4a and 4b via the inter-driver communication path. Note that, when the servo driver 4 determines in S101 that the transmission timing has arrived, it can recognize that it also needs to acquire data from the data stored in the memory unit 43 using the acquisition unit 46. Therefore, in the following S104, data regarding the transition of the predetermined parameters in the servo driver 4 is acquired. In this process, the data transition indicated by the solid line in FIG. 3B(a) (data transition for the period Δt1 starting from timing t1) is acquired. Thereafter, in S105, the acquired data transition is transmitted to the PLC 5 as data transition corresponding to the control axis of the servo driver 4. This transmission is performed via the control communication path between the PLC 5 and each servo driver.

[0043] 4 is performed only by the servo driver 4. In the other servo drivers 4a and 4b, data relating to the transition of the predetermined parameter in S102 is stored.

[0044] Next, the data acquisition control of FIG. 5 will be described. Note that the description is based on the premise that it is performed by the servo driver 4. In S201, the servo driver 4 determines whether or not some abnormality related to the synchronous control has occurred while the synchronous control is being performed. The determination in S201 is made by the servo control unit 42. An example of such an abnormality is when, during servo control during synchronous control, the position deviation or speed deviation of the motor 21, which is the control target, exceeds a predetermined threshold. If the determination in S201 is affirmative, the process proceeds to S202, and if the determination is negative, the data acquisition control is temporarily terminated.

[0045] Then, in response to the determination of an abnormality in S201, in S202, servo control for the control axis of the servo driver 4 is stopped, and driving of the motor 21 is stopped. Furthermore, in addition to the processing of S202, in S203, the trigger unit 45 transmits a second trigger signal to the other servo drivers 4a and 4b via the inter-driver communication path. This second trigger signal is also referred to as an abnormality trigger signal. Note that, when the abnormality is determined in S201, the servo driver 4 recognizes that it also needs to acquire data using the acquisition unit 46. Therefore, in the following S204, data regarding the transition of a predetermined parameter for the control axis corresponding to the servo driver 4 is acquired. In this processing, the data transition indicated by the solid line in FIG. 3B(a) (data transition for the period Δt1 starting from timing t1) is acquired. Thereafter, in S205, the acquired data transition is transmitted to the PLC 5 as the data transition corresponding to the control axis of the servo driver 4. This transmission is performed via the control communication path between the PLC 5 and each servo driver.

[0046] 5 is executed not only by the servo driver 4 but also by the other servo drivers 4a and 4b. If an abnormality occurs in the control axes of those servo drivers during synchronous control, the trigger units 45a and 45b of those servo drivers issue abnormality trigger signals to the other servo drivers, and the data is acquired by the acquisition unit of the own servo driver and sent to the PLC 5.

[0047] Next, the data acquisition control of Fig. 6 will be explained. The data acquisition control of Fig. 6 shows the flow of processing for data acquisition in a servo driver that receives a trigger signal issued in the data acquisition control shown in Fig. 4 and Fig. 5. Note that the explanation is based on the premise that the processing is performed by the servo driver 4a.

[0048] In S211, it is determined whether a trigger signal has been received from one of the other servo drivers 4, 4b. This determination is made by the acquisition unit 46a. If the determination in S211 is affirmative, the process proceeds to S212, and if the determination is negative, this data acquisition control is temporarily terminated. In S212, it is determined whether the received trigger signal is an abnormal trigger signal. This determination is also made by the acquisition unit 46a. If the determination in S212 is affirmative, the process proceeds to S213, and if the determination is negative, the process proceeds to S214.

[0049] Next, in S213, when an abnormality occurs in another servo driver (in this example, servo driver 4), and an abnormality trigger signal is sent from the other servo driver 4 to its own servo driver 4a, servo control on the control axis of servo driver 4a is stopped and driving of motor 21a is stopped.

[0050] Then, in S214, upon receiving the trigger signal in S103 or the abnormality trigger signal in S203 from another servo driver 4, the acquisition unit 46a specifies the data acquisition period to be performed in its own servo driver 4a, in particular, specifies the start timing of the acquisition period. The start timing is determined according to the above formula 2, and the length of the acquisition period can be a predetermined period (preferably a period of a length common to the control axes of the three servo drivers) or a period according to the information included in the received trigger signal.

[0051] Furthermore, in S215, the acquisition unit 46a acquires data relating to the transition of a predetermined parameter in the control axis corresponding to the servo driver 4a according to the data acquisition period determined in S214. In this process, the data transition shown by the solid line in FIG. 3B(b) (data transition for the period Δt1 starting from timing t2) is acquired. Thereafter, in S216, the acquired data transition is converted into the data corresponding to the control axis of the servo driver 4a that received the trigger signal. The data transition is transmitted to the PLC 5. The transmission is performed via a communication path between the PLC 5 and each servo driver.

[0052] According to the data acquisition process shown in FIGS. 4 to 6, the time axes of the data acquired by the acquisition unit in the servo driver that transmitted the trigger signal and the data acquired by the acquisition unit in the servo driver that received the trigger signal are aligned as shown in FIG. 3B, and the aligned data is stored in the storage unit 52 of the PLC 5. The output unit 53 of the PLC 5 may output the data stored in the storage unit 52 to a display provided in the PLC 5 in a graph format with the time axes aligned as shown in FIG. 3B. Alternatively, the output unit 53 may output the data to an external computer connected to the PLC 5 as numerical data regarding transitions with the time axes aligned. By outputting the data from the output unit 53 in this manner, it becomes easier to perform data-based analysis on the receiving side, such as an analysis to determine whether or not there is a phenomenon related to an abnormality in order to prevent equipment failure, or an analysis to investigate the cause of the abnormality when an abnormality occurs.

[0053] <Appendix 1> A servo system including a control device (5) and a plurality of servo drivers (4, 4a, 4b), in which a control communication path is provided between the control device (5) and the plurality of servo drivers (4, 4a, 4b) for transmitting and receiving control commands related to servo control, and an inter-driver communication path is provided between the plurality of servo drivers (4, 4a, 4b) that is a path different from the control communication path and enables communication between the plurality of servo drivers (4, 4a, 4b), each of the plurality of servo drivers (4, 4a, 4b) has a storage unit (46, 46a, 46b) for storing a transition of a predetermined parameter related to servo control in each servo driver when the servo drivers are performing synchronous control with each other; a predetermined servo driver among the plurality of servo drivers (4, 4a, 4b) is configured to transmit a trigger signal for acquiring data related to the predetermined parameter to the remaining servo drivers among the plurality of servo drivers via the inter-driver communication path, acquire data stored in the storage unit of the predetermined servo driver for a first period starting from a first timing in the synchronization control, and send the data to the control device via the control communication path; When each of the remaining servo drivers receives the trigger signal from the predetermined servo driver, it acquires data for a second period starting from a second timing corresponding to the first timing, which is determined according to a communication delay in the inter-driver communication path, from the data stored in its own storage unit, and sends the data to the control device (5) via the control communication path. Servo system. [Explanation of symbols]

[0054] 1 Servo System 21, 21a, 21b motors 5 PLC 20 equipment 42, 42a, 42b Servo control section 43, 43a, 43b storage section 45, 45a, 45b Trigger section 46, 46a, 46b acquisition part

Claims

1. A servo system including a control device and a plurality of servo drivers, wherein a control communication path is provided between the control device and the plurality of servo drivers for transmitting and receiving control commands related to servo control, and an inter-driver communication path is provided between the plurality of servo drivers, which is a path different from the control communication path and enables communication between the plurality of servo drivers, Each of the plurality of servo drivers has a storage unit that stores a transition of a predetermined parameter related to servo control in each servo driver when the servo drivers are performing synchronous control with each other, a predetermined servo driver among the plurality of servo drivers is configured to transmit a trigger signal for acquiring data relating to the predetermined parameter to the remaining servo drivers among the plurality of servo drivers via the inter-driver communication path, acquire data stored in the storage unit of the predetermined servo driver for a first period starting from a first timing in the synchronization control, and send the data to the control device via the control communication path; When each of the remaining servo drivers receives the trigger signal from the predetermined servo driver, the remaining servo drivers acquire data for a second period starting from a second timing corresponding to the first timing, which is determined according to a communication delay in the inter-driver communication path, from the data stored in the storage unit of the servo driver, and transmit the data to the control device via the control communication path. Servo system.

2. The length of the second period is the same as the length of the first period.

2. The servo system according to claim 1.

3. the trigger signal is a signal for stopping all control axes related to the synchronous control when an abnormality occurs in a control axis corresponding to the predetermined servo driver, the predetermined servo driver stops the control axis corresponding to the predetermined servo driver upon transmission of the trigger signal; Each of the remaining servo drivers stops the control axis corresponding to itself upon receiving the trigger signal.

3. The servo system according to claim 1 or 2.

4. the trigger signal is a signal for periodically collecting data on the predetermined parameters in all control axes related to the synchronous control, the predetermined servo driver transmits the trigger signal at a predetermined cycle determined based on the capacity of the storage unit of each of the plurality of servo drivers; 3. The servo system according to claim 1 or 2.

5. the control device has an output unit that outputs, based on first data received from the predetermined servo driver and second data received from each of the remaining servo drivers, transitions of the predetermined parameters in all control axes related to the synchronous control in a format with time axes aligned; The servo system according to any one of claims 1 to 4.

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