Servo system and motor

Abstract

To construct a compact servo system while keeping a favorable servo control environment for a motor.SOLUTION: A control device for a servo system includes a first communication part configured to transmit / receive s signal with a motor through wireless communication, and a position / speed control part for performing control loop calculation regarding the position and speed based on a command value to the motor and a first signal which is a feedback signal regarding the operation of the motor and outputting the calculation result to motor side through the first communication part. The motor includes a second communication part configured to transmit / receive a signal with the control device through the wireless communication, a driver circuit for generating a drive current for the motor, and a current control part for performing control loop calculation regarding the drive current based on the calculation result outputted by the position / speed control part and received by the second communication part and a second signal which is a feedback signal relating to the drive current for the motor in the driver circuit and outputting the calculation result to the driver circuit.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a motor and a servo system including the motor and a control device.

Background Art

[0002] In a general servo system, control loop operations regarding position, speed, and current are performed by a servo driver that drives a motor. A position command is issued from a control device (for example, a PLC or the like) on the upper side to the servo driver. Here, for example, in the technique of Patent Document 1, in a servo system that servo-controls a plurality of control axes, in order to provide a positioning device that realizes a robust position control loop, a controller that performs a control loop operation regarding current is arranged in a servo driver corresponding to a motor of each control axis, and a controller that performs a control loop operation regarding the position and speed of all axes is arranged in an upper device of the driver. In addition, Patent Document 2 discloses a technical idea in which, in order to enhance reliability against failures and the like, inside a servo driver, a circuit board constituting a position control loop and a speed control loop and a power module including a current control loop are configured separately.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, a servo system consists of a control device such as a PLC, a servo driver that generates drive current to drive the motor according to position commands received from the control device, and a motor. In addition to the drive circuit (inverter device, etc.) for current generation, the servo driver incorporates a functional unit that performs control loop calculations for servo control in the system. In other words, the servo driver is a device that aggregates control signals and drive currents, and many cables are connected to it. Therefore, when constructing a servo system, careful consideration is required regarding the placement of the servo driver. In particular, in a servo system that drives multiple control axes, the number of servo drivers required will correspond to the number of control axes, and the volume occupied by the servo driver will also increase.

[0005] Furthermore, in order to safely servo-control a motor, it is necessary to suitably position the functional unit that performs the control loop calculations for servo control within the servo system. In particular, if this functional unit is located far away from the motor being controlled, it may interfere with the servo control.

[0006] This invention has been made in view of these problems, and aims to provide a technology for constructing a compact servo system while suitably maintaining the environment for servo control of a motor. [Means for solving the problem]

[0007] A servo system relating to one aspect of the present disclosure is a servo system including a control device and a motor. The control device includes a first communication unit configured to exchange signals with the motor via wireless communication, and a position and speed control unit that performs a control loop calculation for position and speed based on a command value to the motor and a first signal which is a feedback signal related to the operation of the motor, and outputs the calculation result to the motor side via the first communication unit. The motor comprises a second communication unit configured to exchange signals with the control device via wireless communication, a drive circuit that generates a drive current for the motor, and a current control unit that performs a control loop calculation related to the drive current based on the calculation result output by the position / speed control unit and received by the second communication unit, and a second signal which is a feedback signal related to the drive current of the motor in the drive circuit, and outputs the calculation result to the drive circuit.

[0008] In a servo system configured in this way, the position and speed control unit, which performs control loop calculations related to the position and speed of the motor's servo control, is located in the control unit. On the other hand, the current control unit related to the motor's servo control and the drive circuit (e.g., an inverter device) that generates the motor's drive current according to the calculation results of the current control unit are located in the motor. As a result, unlike conventional technology, the position and speed control unit, the current control unit, and the servo driver itself, including the drive circuit, can be omitted, allowing for a more compact servo system. Furthermore, since signals are exchanged between the control unit and the motor via wireless communication between the first and second communication units, the use of cables for signal transmission for servo control can be minimized, reducing the load required to construct the servo system.

[0009] Furthermore, as described above, in the servo system disclosed in this application, the current control unit and drive circuit, which are functional parts related to current control, are located on the motor side, in a configuration equivalent to a conventional servo driver. This means that the part of the functional parts for servo control that has the strongest influence on the motor's behavior is located close to the motor, which is the target of the drive. As a result, although precise control is difficult compared to servo control with a complete set of functional parts including functional parts related to position and speed, simple control such as stopping and continuing motor operation can be sufficiently ensured. Therefore, the arrangement of the current control unit described above makes it possible to construct a compact servo system while ensuring a certain degree of motor controllability.

[0010] In the servo system described above, the motor may further include a first detection unit that detects abnormalities in wireless communication between the first communication unit and the second communication unit, and an abnormality processing unit that, when an abnormality is detected by the first detection unit, issues a stop command to the current control unit to stop the drive current, thereby stopping the motor. Examples of abnormalities in wireless communication include communication conditions that may adversely affect the optimal servo control of the motor, such as interruption of wireless communication for a predetermined period of time or an increase in noise. Since the motor side has a current control unit, when an abnormality in wireless communication is detected by the first detection unit, the motor can be stopped quickly without being affected by the abnormality by issuing a stop command to the current control unit to stop the drive current. With this configuration, even if a problem occurs in the wireless communication that contributes to the compact servo system, the safety of the servo system can be suitably maintained.

[0011] In the servo system described above, if the abnormality processing unit detects an abnormality by the first detection unit, and the abnormality falls within a predetermined range, it may issue a drive command to the current control unit based on the motor's drive history and continue driving the motor. The predetermined range is the degree of wireless communication abnormality that can be handled by motor control by the current control unit alone. For example, this could include cases where the interruption time of wireless communication between the control unit and the motor is extremely short. In the case of such a minor wireless communication abnormality, it may be possible to infer how to drive the motor from the motor's drive history up to that point. In such cases, the abnormality processing unit may continue operating the motor instead of stopping it due to the wireless communication abnormality. However, if the abnormality subsequently deviates from the predetermined range, it is preferable for the abnormality processing unit to stop the motor as described above.

[0012] Furthermore, in the servo system described above, the second communication unit of the motor may be configured to exchange signals via wireless communication with an emergency stop device that performs an emergency stop on the motor's drive, and the first detection unit of the motor may be configured to detect abnormalities in the wireless communication between the emergency stop device and the second communication unit. When the abnormality processing unit detects an abnormality by the first detection unit, even if the emergency stop device has not sent an emergency stop signal, it may issue a stop command to the current control unit to stop the drive current and stop the motor. In this way, even if an abnormality occurs not only in the wireless communication between the control device and the motor, but also in the wireless communication between the emergency stop device and the motor, a stop command can be issued to the current control unit located on the motor side, allowing the motor to be stopped quickly without being affected by the wireless communication abnormality, thereby enhancing the safety of the servo system.

[0013] Here, the servo system described above may further include other motors. Each of the motors and the other motors has the second communication unit, the drive circuit, and the current control unit, and further has an inter-motor communication unit that exchanges signals with each other via wireless communication. The first communication unit of the control device is configured to exchange signals with the motor and the other motor via wireless communication. The position and speed control unit of the control device may perform a control loop calculation for position and speed based on command values ​​to the motor and the other motor and the first signal, which is a feedback signal related to the operation of the motor and the other motor, and output the calculation results to the motor side and the other motor side, respectively, via the first communication unit. In this way, even when the control device controls multiple motors, by separating the arrangement of the position and speed control unit and the current control unit between the control device side and the motor side, it is possible to construct a compact servo system while suitably maintaining the servo control environment of the motors.

[0014] In the servo system configured in this way, the motor and the other motor may be synchronously controlled by the control device. The motor may further include a first detection unit that detects abnormalities in wireless communication between the first communication unit and the second communication unit, and an abnormality processing unit that, when an abnormality is detected by the first detection unit, issues a stop command to the current control unit of the motor to stop the drive current, and also issues a stop command to the current control unit of the other motor via the inter-motor communication unit to stop the drive current, thereby stopping the motor and the other motor synchronously. With this configuration, when synchronous control is being performed between the motor and the other motor, if an abnormality occurs in wireless communication between the motor and the control device, a stop command can be issued to the current control unit of each motor to suitably stop both while maintaining their synchronous control, thereby suppressing adverse effects caused by the stopping.

[0015] Furthermore, in the servo system described above, each of the motor and the other motor may further have a wireless power supply unit that sends and receives signals for wireless power supply to each other. The motor further includes a second detection unit that detects abnormalities in communication for wireless power supply by the wireless power supply unit, and when the abnormality processing unit detects an abnormality by the second detection unit, it issues a stop command to the current control unit of the motor to stop the drive current, and also issues a stop command to the current control unit of the other motor via the inter-motor communication unit to stop the drive current, thereby stopping the motor and the other motor in a synchronized manner. The wireless power supply unit can, for example, wirelessly supply power from an external source to electrical equipment related to the motor. As an example, wireless power supply is performed to supply drive power to an encoder or a sensor provided on the motor for servo control.

[0016] Even with wireless power supply, if there is a malfunction in the wireless communication, it may become impossible to supply the necessary power to the motor, potentially hindering proper servo control. In particular, if the motor and other components are malfunctioning... When motors are controlled synchronously with each other, the operation of one motor will significantly affect the other. Therefore, by utilizing the motor-to-motor communication unit between the motors, even if an abnormality is detected in the communication for wireless power supply, a stop command can be issued to the current control unit of each motor, just as in the case of an abnormality in wireless communication between the motor and the control unit. This allows both motors to be stopped effectively while maintaining their synchronous control.

[0017] In addition, in the servo system described above, the motor may further include a first detection unit that detects abnormalities in wireless communication between the first communication unit and the second communication unit, and an abnormality processing unit that, when an abnormality is detected by the first detection unit, receives a stop command for the drive current issued from the control device via the inter-motor communication unit from the other motor, and stops the motor using the current control unit of the motor in accordance with the received stop command. With this configuration, if an abnormality occurs in wireless communication, the stop command from the control device is delivered to the motor via a path where no abnormality has occurred, that is, via the other motor, thereby issuing a stop command to the current control unit and stopping the motor.

[0018] Here, the present disclosure can be viewed from the perspective of a motor incorporated into a servo system. Specifically, the present disclosure is a motor comprising: a control device having a position / velocity control unit that performs control loop calculations for position and velocity based on a command value to the motor and a first signal which is a feedback signal related to the operation of the motor; a communication unit configured to send and receive signals via wireless communication; a drive circuit that generates a drive current for the motor; and a current control unit that performs control loop calculations for drive current based on the calculation result by the position / velocity control unit and a second signal which is a feedback signal related to the drive current of the motor in the drive circuit, received via wireless communication through the communication unit, and outputs to the drive circuit. The technical concept disclosed for the servo system described above is also applicable to the motor disclosed in the present disclosure, as long as no technical discrepancies arise.

[0019] Furthermore, the motor may include a first detection unit that detects an abnormality related to wireless communication with the control device, and an abnormality processing unit that, when an abnormality is detected by the first detection unit, issues a stop command to stop the drive current to the current control unit and stops the motor. With this configuration, when an abnormality occurs in wireless communication, the abnormality processing unit can stop the motor regardless of the abnormality.

Advantages of the Invention

[0020] While suitably maintaining the servo control environment of the motor, the servo system can be constructed compactly.

Brief Description of the Drawings

[0021] [Figure 1] It is a diagram showing a schematic configuration of a servo system. [Figure 2] It is a diagram showing a control structure for servo control included in the servo system shown in FIG. 1. [Figure 3] It is a first flowchart showing the flow of processing when an abnormality occurs in wireless communication in the servo system disclosed in the present application. [Figure 4] It is a second flowchart showing the flow of processing when an abnormality occurs in wireless communication in the servo system disclosed in the present application. [Figure 5] It is a third flowchart showing the flow of processing when an abnormality occurs in wireless communication in the servo system disclosed in the present application.

Modes for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated. In the present disclosure, as an exemplary form of the servo system, a form in which the number of motors servo-controlled by a control device (PLC) is two is shown, but the number of motors servo-controlled may be one or three or more. in which the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated. In the present disclosure, as an exemplary form of the servo system, a form in which the number of motors servo-controlled by a control device (PLC) is two is shown, but the number of motors servo-controlled may be one or three or more.

[0023] Figure 1 shows a schematic configuration of a servo system. The servo system controls two motors 2 and 2a. Figure 2 shows the servo control structure formed in the servo system. The servo system in Figure 1 includes a PLC (Programmable Logic Controller) 5 as a control device, two motors 2 and 2a, and an emergency stop device 8. The servo system is a system for servo-controlling motors 2 and 2a of each control axis to be controlled so that they follow the operation command signal pcmd generated by the PLC5. In this disclosure, we refer to cases in which motors 2 and 2a are servo-controlled independently, and cases in which motors 2 and 2a are servo-controlled synchronously (synchronous control). Which case to adopt depends on the purpose of driving the device etc. driven by motors 2 and 2a.

[0024] Examples of devices in which motors 2 and 2a are incorporated include XY tables in machine tools and transport devices, and arms of industrial robots with multiple joint axes. Motors 2 and 2a are AC servo motors. Encoders 28 and 28a are attached to motors 2 and 2a, respectively, and signals related to the operation of each motor are transmitted as feedback signals by these encoders. These feedback signals (hereinafter referred to as feedback signals) include, for example, position information regarding the rotational position (angle) of the rotation axis of motors 2 and 2a, and information regarding the rotational speed of that rotation axis.

[0025] Furthermore, the PLC5 generates motion command signals related to the operation (motion) of motors 2 and 2a. In this disclosure, regarding the control structure for servo control of motors 2 and 2a (servo control structure), a position / velocity control unit 52 that performs control loop calculations related to position and velocity is located on the PLC5 side, and current control units 22 and 22a that perform control loop calculations related to the drive current of each motor are located on each of motors 2 and 2a. In other words, in this disclosure, the servo control structure is not located in a single device, but is divided and located on the control device PLC5 and each of the motors. The PLC5 and each motor are configured to exchange information with each other via wireless communication. Details of the servo control structure will be described later.

[0026] Furthermore, each of the motors 2 and 2a is provided with drive circuits 23 and 23a that generate the drive current for each motor according to a current command calculated by the current control units 22 and 22a. The drive circuits 23 and 23a are so-called inverter devices. The power supplied to the drive circuits 23 and 23a is AC power supplied from an AC power source (not shown). In this disclosure, the drive circuits 23 and 23a are of the type that receive three-phase AC, but they may also be of the type that receive single-phase AC.

[0027] Here, with reference to Figure 2, the servo control structure formed across the PLC5 and each motor of the servo system disclosed in this application will be described. In this servo system, a servo control structure corresponding to each control axis is formed. That is, the servo control structure corresponding to motor 2 is formed across both motor 2 and PLC5, and the servo control structure corresponding to motor 2a is formed across both motor 2a and PLC5. Since each servo control structure has substantially the same content, the detailed explanation will focus on the servo control structure corresponding to motor 2. Furthermore, as will be described later, the exchange of signals between PLC5 and motors 2 and 2a is performed via wireless communication. In Figure 2, wireless communication and wired communication are not distinguished, but for example, between PLC5 and motor 2 The transmission and reception of signals, specifically the transmission from the speed control unit 522 to the current control unit 22 and the transmission from the encoder 28 to the PLC 5, are performed via wireless communication.

[0028] The servo control structure corresponding to motor 2 includes a position control unit 521 and a speed control unit 522 on the PLC5 side, and a current control unit 22 on the motor 2 side. The position control unit 521 and the speed control unit 522 correspond to the portion of the position / speed control unit 52 shown in Figure 1 that corresponds to motor 2. Therefore, the position / speed control unit 52 includes the position control unit 521, the speed control unit 522, and the position control unit 521a and speed control unit 522a, which correspond to motors 2 and 2a. The position control unit 521 performs, for example, proportional control (P control). Specifically, it calculates the speed command vcmd by multiplying the position deviation, which is the difference between the position command pcmd generated in the PLC5 and the detected position, by a predetermined position proportional gain.

[0029] The speed control unit 522 performs, for example, proportional-integral control (PI control). Specifically, it calculates the torque command τcmd by multiplying the integral of the speed deviation, which is the difference between the speed command vcmd calculated by the position control unit 521 and the detected speed, by a predetermined speed integral gain, and then multiplying the sum of this calculation result and the speed deviation by a predetermined speed proportional gain. Alternatively, the speed control unit 522 may perform P control instead of PI control. The calculated torque command τcmd is the calculation result of the position / speed control unit 52, and this calculation result is transmitted to the motor 2 side via wireless communication.

[0030] The current control unit 22 outputs a current command Ccmd to the drive circuit 23 based on the difference between the torque command τcmd calculated by the speed control unit 522 and the drive current supplied from the drive circuit 23 to the motor 2 windings, thereby generating the drive current for the motor 2. The current control unit 22 includes a filter (first-order low-pass filter) and one or more notch filters related to the torque command, and may have control parameters such as cutoff frequencies related to the performance of these filters.

[0031] In the servo control structure, the detected position signal and detected speed signal, calculated based on the detection signal of the encoder 28 of the motor 2, are fed back to the position control unit 521 and the speed control unit 522 as position and speed feedback signals, respectively. These feedback signals are also transmitted to the PLC 5 via wireless communication.

[0032] Furthermore, as described above, the servo control structure corresponding to motor 2a also has a position control unit 521a and a speed control unit 522a on the PLC5 side, and a current control unit 22a on the motor 2a side. The position control unit 521a, speed control unit 522a, and current control unit 22a are functional units corresponding to the position control unit 521, speed control unit 522, and current control unit 22, respectively.

[0033] Next, we will describe the other functional parts of the PLC5, motors 2 and 2a, and emergency stop device 8 included in the servo system. First, we will describe the functional parts of the PLC5. The PLC5 has a communication unit 51 and a position / speed control unit 52. The latter has already been described. The former, the communication unit 51, is a functional unit for wireless communication with motors 2 and 2a, which are the targets of servo control by the PLC5. Therefore, communication units 21 and 21a are provided, corresponding to motors 2 and 2a, which are the communication partners. Any wireless communication method can be used for wireless communication between communication unit 51 and communication unit 21, and between communication unit 51 and communication unit 21a. Between communication unit 51 and communication unit 21, the torque command τcmd from the speed control unit 522 shown in Figure 2 to the motor 2 side, and the detected speed signal and detected position signal based on the detection signal of the encoder 28 are transmitted via wireless communication. The same applies to communication unit 51a and communication unit 21a.

[0034] Next, the motor 2 consists of a communication unit 21, a current control unit 22, a drive circuit 23, a detection unit 24, and an abnormality control unit. The system includes a processing unit 25, a motor-to-motor communication unit 26, a wireless power supply unit 27, and an encoder 28. The communication unit 21, current control unit 22, drive circuit 23, and encoder 28 have already been mentioned, so this explanation will mainly focus on the other functional units. The communication unit 21 can also communicate wirelessly with the emergency stop device 8 in addition to the PLC 5. Therefore, a communication unit 81 is provided that is compatible with the emergency stop device 8, which is the communication partner.

[0035] The detection unit 24 is a functional unit that detects abnormalities related to wireless communication when the motor 2 communicates wirelessly with a nearby communication partner. In this disclosure, the motor 2 communicates wirelessly with the PLC 5 and the emergency stop device 8. Furthermore, the motor 2 is powered wirelessly by a wireless power supply unit 27, described later, which supplies power to the encoder 28 and other sensors (not shown) mounted on the motor 2 from the power supply device 50. This wireless power supply is also subject to abnormality detection by the detection unit 24. Therefore, the detection unit 24 corresponds to the first and second detection units in this disclosure. Abnormality detection by the detection unit 41 is performed based on various parameters of the signal that is the subject of wireless communication. For example, abnormalities can be detected by using the length of time the signal is interrupted or the magnitude of noise in the signal (S / N ratio). As will be described later, the motor 2 can exchange signals with motor 2a via wireless communication using the motor-to-motor communication unit 26. This wireless communication between motors may also be subject to abnormality detection by the detection unit 24.

[0036] The abnormality processing unit 25 is a functional unit that controls the drive of the motor 2 by issuing a predetermined command to the current control unit 22 when an abnormality in wireless communication is detected by the detection unit 24. If an abnormality occurs in wireless communication, there is a risk that the safety of the drive of the motor 2 may be compromised as a result of the abnormality. Therefore, from the viewpoint of safety regarding the drive of the motor 2, the abnormality processing unit 25 safely controls the drive of the motor 2 by issuing a command related to current control to the current control unit 22. In this disclosure, since the current control unit 22, which is a functional unit related to the servo control of the motor 2, is located on the motor 2 side, even if an abnormality occurs in the wireless communication between the PLC 5 and the motor 2, it is possible to control the drive of the motor 2 to some extent via the current control unit 22. The predetermined command issued to the current control unit 22 by the abnormality processing unit 25 only needs to be a command that can safely control the motor 2, and examples include a command to stop the motor 2 or a command to continue driving the motor 2 within a safe range.

[0037] The motor-to-motor communication unit 26 is a functional unit for wireless communication with the motor 2a. Therefore, a motor-to-motor communication unit 26a that also corresponds to the motor 2a is provided. Next, the wireless power supply unit 27 is a functional unit that receives drive power for driving the encoder 28 and other sensors (not shown) mounted on the motor 2, which is output via wireless communication from an externally provided power supply device 50, and converts the electrical energy of the received signal into DC power for driving the encoder 28, etc. Known technologies can be used for the wireless power supply method between the wireless power supply unit 27 and the power supply device 50, for example, electromagnetic induction methods and magnetic field resonance methods can be exemplified.

[0038] Furthermore, like motor 2, motor 2a also has the following functional units: a communication unit 21a, a current control unit 22a, a drive circuit 23a, a detection unit 24a, an abnormality processing unit 25a, an inter-motor communication unit 26a, a wireless power supply unit 27a, and an encoder 28a. Power is supplied to the wireless power supply unit 27a via wireless communication by a power supply device 50a.

[0039] Next, the emergency stop device 8 has a communication unit 81 and a stop control unit 82. The communication unit 81 has already been described. The stop control unit 82 is a functional unit that outputs an emergency stop signal to the motor 2, which is the wireless communication partner. This emergency stop signal is output when the user presses a switch (not shown) provided on the emergency stop device 8. The output emergency stop signal is transmitted to the motor 2 via the communication unit 81, activating a circuit breaker (not shown) provided on the motor 2, which cuts off the path of the drive current supplied from the drive circuit 23, thereby stopping the motor 2. The motor is brought to an emergency stop. As the emergency stop device 8 is a safety-critical device for the motor 2, it is necessary that wireless communication is always established between the communication unit 81 of the emergency stop device 8 and the communication unit 21 of the motor 2 so that the emergency stop signal is reliably delivered to the motor 2 in an emergency. Therefore, a reference signal is sent from the stop control unit 82 to the motor 2 to confirm the establishment of this wireless communication, and a response signal is sent from the motor 2 to the emergency stop device 8 in response to it. By monitoring the exchange of this reference signal and response signal, it is possible to determine whether wireless communication between the two is maintained. If the exchange is interrupted, the detection unit 24 on the motor 2 side will detect this situation.

[0040] <Safety Control 1> Here, the first safety control performed in motor 2 will be described based on Figure 3. This safety control is repeatedly performed by the cooperation of each functional unit of motor 2 shown in Figure 1. Note that in this safety control, motor 2 and motor 2a are not synchronously controlled. Therefore, this safety control is performed by motor 2 alone.

[0041] First, in S101, it is determined whether or not an abnormality has occurred in the wireless communication between the communication unit 51 of the PLC5 and the communication unit 21 of the motor 2. This determination is made by the detection unit 24. For example, if the communication unit 21 is unable to receive the calculation result (i.e., torque command τcmd) of the position / speed control unit 52 (position control unit 521 and speed control unit 522) of the PLC5 for a predetermined period of time or longer, an abnormality can be detected. Alternatively, if the noise ratio in the signal of the calculation result detected by the communication unit 21 is higher than a predetermined threshold, an abnormality can also be detected. The determination of whether or not an abnormality in communication has occurred should be made appropriately, taking into consideration the location where the servo system shown in Figure 1 is installed, and the presence of obstacles (including fixed and movable ones) between the PLC5 and the motor 2. If the determination in S101 is positive, it is determined in S102 that an abnormality has been detected in the wireless communication. If the determination in S101 is negative, the process proceeds to S106.

[0042] After an anomaly is detected in S102, S103 determines whether the detected anomaly is minor. Minor anomaly here means that although an anomaly has occurred in wireless communication, the current control unit 22 of the motor 2 is expected to be able to maintain the motor 2's operation state relatively safely. As described in S105 below, if the anomaly is minor, the anomaly processing unit 25 attempts to continue driving the motor 2 using the current control unit 22. Therefore, the determination of whether the anomaly is minor is made by considering whether the processing in S105 is possible. For example, if the period during which wireless communication was unavailable is shorter than 1.5 times the predetermined period used in the determination in S101, it can be determined that the motor 2 can continue driving through the processing by the anomaly processing unit 25 in S105. In such a case, this "period shorter than 1.5 times the predetermined period" can be used as the threshold for determining minor anomaly in S103. If the result in S103 is negative, the process proceeds to S104; if the result is positive, the process proceeds to S105.

[0043] In S104, the abnormality processing unit 25 outputs a command to the current control unit 22 to stop the drive current, i.e., a stop command, in order to stop the motor 2. If there is an abnormality in wireless communication, the motor 2 will not be under servo control by the PLC 5. However, the processing in S104 allows the motor 2 to be stopped while maintaining a certain level of control using the current control unit 22 that remains on the motor 2 side. This configuration is extremely useful from the standpoint of motor 2 safety and suitably reinforces wireless communication between the PLC 5 and the motor 2 in the servo system. After the completion of S104, the safety control is repeated again.

[0044] Furthermore, in S105, the abnormality processing unit 25 uses the current control unit 22 to control the motor 2 The process of continuing to drive the motor is performed. If the wireless communication abnormality is minor, even though the motor 2 is not under servo control by the PLC 5, it is possible to control the operation of the motor 2 to some extent using current control by the current control unit 22, and therefore adverse effects from minor abnormalities can be safely avoided. Specifically, the abnormality processing unit 25 uses information on the past drive history of the motor 2 to output a command to the current control unit 22 to continue driving the motor 2. For example, in situations where the rotational speed of the motor 2 does not change much, or when the rotational speed is constant, the required drive current is relatively small, so the drive torque corresponding to the rotational speed at the time of the abnormality is calculated from the drive history information and a command corresponding to the drive torque is output to the current control unit 22. As a result, even if there is an abnormality in wireless communication with the PLC 5, the motor 2 can be controlled to some extent, and the frequency of stopping the motor 2 can be reduced. After the completion of S105, the safety control is repeated again.

[0045] If a negative result is obtained in S101, the process proceeds to S106. In S106, it is determined whether or not an abnormality has occurred in the wireless communication between the communication unit 81 of the emergency stop device 8 and the communication unit 21 of the motor 2. This determination is made by the detection unit 24. As described above, a reference signal and a response signal are exchanged between the emergency stop device 8 and the motor 2. When the detection unit 24 detects that this signal exchange has been interrupted, it can detect that an abnormality has occurred in the wireless communication between the two. If a positive result is obtained in S106, it is determined in S107 that an abnormality has been detected in the wireless communication. If a negative result is obtained in S106, the safety control is repeated again.

[0046] The emergency stop device 8 is a device of high importance for the safety of the motor 2. Therefore, if an abnormality occurs in the wireless communication with the emergency stop device 8, it is preferable to stop the motor 2 promptly from the viewpoint of ensuring safety. Thus, after an abnormality is detected in S107, the process proceeds to S104, and the motor 2 is stopped by outputting a stop command to the current control unit 22 as described above.

[0047] As shown in Figure 3, with the safety control system, a servo system is configured such that a position / speed control unit 52 and a current control unit 22 are placed on the PLC 5 and motor 2 respectively, and information can be exchanged between them via wireless communication. Even if a malfunction occurs in the wireless communication, the operation of the motor 2 can be controlled while keeping it under a certain degree of control. As a result, it becomes possible to achieve both a compact servo system and safe motor operation.

[0048] <Safety Control 2> Here, a second safety control performed in motor 2 will be described based on Figure 4. In this safety control, motor 2 and motor 2a are controlled synchronously, and during this control, the safety control is repeatedly executed in cooperation with the respective functional units of both motors.

[0049] In S201, it is determined whether or not an abnormality has occurred in the wireless communication between the communication unit 51 of the PLC 5 and the communication unit 21 of the motor 2. The processing in S201 is essentially the same as the processing in S101. If the result in S201 is positive, the process proceeds to S202, where it is determined that an abnormality has been detected in the wireless communication. If the result in S201 is negative, the process proceeds to S205.

[0050] After an abnormality is detected in S202, in S203, the abnormality processing unit 25 outputs a command to stop the drive current, i.e., a stop command, to the current control unit 22 of motor 2 in order to stop motor 2 and motor 2a synchronously. At the same time, it also outputs a stop command to the current control unit 22a of motor 2a, which is the target of synchronous control. The stop command to the current control unit 22a is delivered via the inter-motor communication units 26 and 26a. By using this method, the stop command can be reliably delivered to motor 2a without being negatively affected by wireless communication malfunctions between PLC5 and motor 2. As a result of the processing in S203, both motors can be stopped synchronously by the current control unit 22 in motor 2 and by the current control unit 22a in motor 2a (processing in S204). After the completion of S204, the safety control is repeated again.

[0051] If a negative determination is made in S201, the process proceeds to S205. In S205, it is determined whether or not an abnormality has occurred in the wireless communication for wireless power supply between the supply device 50 and the wireless power supply unit 27 of the motor 2. This determination is made by the detection unit 24. As described above, the drive power for the encoder 28 and the like is wirelessly supplied between the supply device 50 and the wireless power supply unit 27, and if this wireless power supply stops, it becomes difficult to drive the motor 2, so in such cases it is preferable to stop the motor 2. For example, if the power per unit time sent from the supply device 50 via the wireless power supply unit 27 falls below a predetermined threshold, it can be detected that an abnormality has occurred in the wireless communication for wireless power supply. If a positive determination is made in S205, it is determined that an abnormality has been detected in the wireless communication in S202. If a negative determination is made in S205, the safety control is repeated again.

[0052] As shown in Figure 4, with the safety control described above, in a servo system where the position / speed control unit 52 and current control units 22 and 22a are located on the PLC 5 and motors 2 and 2a respectively, and information can be exchanged between them via wireless communication, even if a malfunction occurs in the wireless communication, motors 2 and 2a, which are under synchronous control, can be safely stopped while remaining under a certain degree of control. As a result, it becomes possible to achieve both a compact servo system and safe motor operation.

[0053] <Safety Control 3> Here, a third safety control performed in motor 2 will be described based on Figure 5. In this safety control, motor 2 and motor 2a are not synchronously controlled, but the functional units of both motors cooperate to repeatedly execute the safety control.

[0054] In S301, it is determined whether or not an abnormality has occurred in the wireless communication between the communication unit 51 of the PLC 5 and the communication unit 21 of the motor 2. The process in S301 is essentially the same as the process in S101. If the result in S301 is positive, the process proceeds to S302, where it is determined that an abnormality has been detected in the wireless communication. If the result in S301 is negative, the safety control is repeated.

[0055] After an anomaly is detected in S302, in S303, a stop command to stop motor 2, generated by PLC5, is received via motor 2a, which has normal wireless communication with PLC5. Specifically, motor 2a receives the stop command from PLC5 addressed to motor 2, and then motor 2 receives the same stop command via motor-to-motor communication units 26 and 26a. Then, in S304, the anomaly processing unit 25 passes the received stop command to the current control unit 22, and motor 2 is stopped. As a result, even if an anomaly occurs in the wireless communication between PLC5 and motor 2, motor 2 can be stopped safely. After the completion of S304, the safety control is repeated.

[0056] As shown in Figure 5, in a servo system where a position / speed control unit 52 and a current control unit 22 are placed on the PLC 5 and motor 2 respectively, and information can be exchanged between them via wireless communication, even if a malfunction occurs in the wireless communication, the operation of the motor 2 can be controlled while keeping it under a certain degree of control. As a result, it becomes possible to achieve both a compact servo system and safe motor operation.

[0057] <Note 1> A servo system including a control device (5) and a motor (2), The control device (5) is A first communication unit (51) is configured to exchange signals with the motor (2) via wireless communication, A position and speed control unit (52) performs a control loop calculation related to position and speed based on the command value to the motor (2) and a first signal which is a feedback signal related to the operation of the motor (2), and outputs the calculation result to the motor side via the first communication unit. It has, The motor (2) is A second communication unit (21) is configured to exchange signals with the control device (5) via wireless communication, A drive circuit (23) that generates the drive current for the motor (2), A current control unit (22) performs a control loop calculation related to the drive current based on the calculation result output by the position / velocity control unit (52) and received by the second communication unit (21), and a second signal which is a feedback signal related to the drive current of the motor (2) in the drive circuit (23), and outputs the calculation result to the drive circuit. A servo system having the following features.

[0058] <Note 2> A control device (5) having a position / velocity control unit (52) that performs a control loop calculation for position and velocity based on a command value to the motor (2) and a first signal which is a feedback signal related to the operation of the motor, and a communication unit (21) configured to send and receive signals via wireless communication, A drive circuit (23) that generates the drive current for the motor (2), A current control unit (22) performs a control loop calculation related to the drive current based on the calculation result from the position / velocity control unit received wirelessly via the communication unit (21) and a second signal which is a feedback signal related to the drive current of the motor (2) in the drive circuit (23), and outputs it to the drive circuit. A motor equipped with a motor. [Explanation of symbols]

[0059] 2, 2a motor 5 PLC 21, 21a Communication Department 22, 22a Current control unit 23, 23a Drive Circuit 24, 24a Detection unit 25, 25a Anomaly Processing Unit 26, 26a Inter-motor communication section 27, 27a Wireless power supply section 28, 28a encoder 50 Feeding device 51 Communications Department 52 Position and Speed ​​Control Unit

Claims

1. A servo system including a control device and a motor, The control device is A first communication unit configured to exchange signals with the motor via wireless communication, A position and speed control unit performs a control loop calculation related to position and speed based on the command value to the motor and a first signal which is a feedback signal related to the operation of the motor, and outputs the calculation result to the motor side via the first communication unit. It has, The aforementioned motor is A second communication unit configured to exchange signals with the control device via wireless communication, A drive circuit that generates the drive current for the motor, A current control unit performs a control loop calculation related to the drive current based on the calculation result output by the position / speed control unit and received by the second communication unit, and a second signal which is a feedback signal related to the drive current of the motor in the drive circuit, and outputs the calculation result to the drive circuit. It has, The servo system further includes other motors, Each of the aforementioned motors and the other motors has the second communication unit, the drive circuit, and the current control unit, and further has an inter-motor communication unit that sends and receives signals to each other via wireless communication. The first communication unit of the control device is configured to exchange signals with the motor and the other motors via wireless communication. The position and speed control unit of the control device is configured to perform a control loop calculation related to position and speed based on command values ​​for the motor and the other motor, and the first signal which is a feedback signal related to the operation of the motor and the other motor, and to output the calculation results to the motor side and the other motor side, respectively, via the first communication unit. Servo system.

2. The aforementioned motor is A first detection unit for detecting abnormalities in wireless communication between the first communication unit and the second communication unit, When the first detection unit detects an abnormality, the abnormality processing unit issues a stop command to the current control unit to stop the drive current and stops the motor. The servo system according to claim 1, further comprising the following:

3. Even when the first detection unit detects an abnormality, if the abnormality falls within a predetermined range, the abnormality processing unit issues a drive command to the current control unit based on the motor's drive history and continues driving the motor. The servo system according to claim 2.

4. The second communication unit of the motor is further configured to exchange signals via wireless communication with an emergency stop device that emergency stops the motor's operation. The first detection unit of the motor is further configured to detect abnormalities in wireless communication between the emergency stop device and the second communication unit. When the abnormality is detected by the first detection unit, even if no emergency stop signal is issued from the emergency stop device, the abnormality processing unit issues a stop command to the current control unit to stop the drive current and stops the motor. The servo system according to claim 2 or claim 3.

5. The aforementioned motor and the other motor are synchronously controlled by the control device. The aforementioned motor is A first detection unit for detecting abnormalities in wireless communication between the first communication unit and the second communication unit, When the first detection unit detects an abnormality, the abnormality processing unit issues a stop command to the current control unit of the motor to stop the drive current, and also issues a stop command to the current control unit of the other motor via the motor-to-motor communication unit to stop the drive current, thereby stopping the motor and the other motor in a synchronous manner. The servo system according to claim 1, further comprising the following:

6. Each of the aforementioned motors and the other motors further includes a wireless power supply unit that sends and receives signals for wireless power supply to each of them. The aforementioned motor is The system further includes a second detection unit for detecting abnormalities related to communication for wireless power supply by the wireless power supply unit, When the abnormality processing unit detects an abnormality by the second detection unit, it issues a stop command to the current control unit of the motor to stop the drive current, and also issues a stop command to the current control unit of the other motor via the motor-to-motor communication unit to stop the drive current, thereby stopping the motor and the other motor in a synchronous manner. The servo system according to claim 5.

7. The aforementioned motor is A first detection unit for detecting abnormalities in wireless communication between the first communication unit and the second communication unit, When an abnormality is detected by the first detection unit, an abnormality processing unit receives a drive current stop command issued by the control device from the other motor via the motor-to-motor communication unit, and stops the motor using the current control unit of the motor in accordance with the received stop command. The servo system according to claim 1, further comprising the following:

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