JP2023152074A - servo system - Google Patents

Abstract

To provide a servo system that can more flexibly connect an optional unit that outputs detected sensor values.SOLUTION: A servo system of the present invention includes a plurality of control units that control a connected electric motor, and a bus that connects the plurality of control units so that they can communicate with each other. An optional unit that broadcasts sensor values related to control of the electric motor to the plurality of control units is detachably connected to the bus.SELECTED DRAWING: Figure 3

Description

The present invention relates to a servo system.

In servo control in a servo system, in addition to feedback signals from a motor, detection values of various sensors such as a fully closed sensor and a pressure sensor are used (see, for example, Patent Documents 1 and 2).

Japanese Patent Application Publication No. 2008-90825 Japanese Patent Application Publication No. 2010-67036

In recent years, so-called building block type servo systems have also been used, in which a plurality of inverter units that control motors are connected to a converter unit that outputs AC power to DC power. It is also conceivable to connect optional units such as various sensors to such a building block type servo system. However, since the option unit and the inverter unit are connected on a one-to-one basis, there is a lack of flexibility in the arrangement of the option units.

One aspect of the disclosed technology is to provide a servo system that can more flexibly connect optional units that output detected sensor values.

One aspect of the disclosed technology is exemplified by a servo system as follows. This servo system includes a plurality of control units that control connected electric motors, and a bus that connects the plurality of control units so as to be able to communicate with each other, and the bus includes sensor values related to control of the electric motors. An optional unit that broadcasts the information to the plurality of control units is detachably connected.

In the above servo system, both the control unit and the option unit are connected to the bus. Then, the option unit outputs the sensor value by broadcasting via the bus. Therefore, the optional unit can transmit sensor values to any of the plurality of control units even if it is placed at an arbitrary position on the bus. Therefore, according to the above servo system, the option unit can be connected to the servo system more flexibly.

The servo system may have the following features. The device further includes a management unit connected to the bus and assigning different identification numbers to each of the plurality of control units and the option unit. According to the above servo system, each unit connected to the bus can be uniquely identified.

The servo system may have the following features. The optional unit broadcasts the sensor value with the identification number assigned by the management unit, and the plurality of control units are notified of the optional unit that is the source of the sensor value to be acquired. The identification number is designated, and the plurality of control units acquire the sensor value to which the designated identification number is attached, and control the electric motor using the acquired sensor value. According to the above servo system, since an identification number is attached to the option unit, the control unit can control the electric motor using the identification number and the sensor value transmitted from the desired option unit.

The servo system may have the following features. The management unit broadcasts a first signal via the bus, and upon receiving the first signal, each of the plurality of control units receives an identification number determined based on the identification number assigned to the own unit. After the delay time has elapsed, a response to the first signal is broadcast via the bus, and upon receiving the first signal, the option unit transmits the delay time determined based on the identification number. After a period of time, the sensor value is broadcast via the bus in response to the first signal. Since the delay time is determined based on the identification numbers assigned to each unit differently, it is possible to suppress the responses from a plurality of units to be output to the bus simultaneously. Furthermore, since the occurrence of collisions on the bus can be suppressed, deterioration in communication efficiency of communication using the bus can be suppressed.

The servo system may have the following features. The management unit recognizes that, among the plurality of control units and the optional units, a unit that does not respond to the first signal has been removed from the bus. By having such a feature, the servo system can recognize removal of the unit from the bus without any additional work by the user.

The servo system may have the following features. The management unit sets a priority for the plurality of control units and the option unit, and each of the plurality of control units and the option unit controls the first control unit at a frequency according to the set priority. Send the above response to the signal. By having such a feature, the servo system described above can preferentially execute communication using a bus for units to which a high priority is set.

The servo system may have the following features. The plurality of control units and the option unit are connected to a host device that outputs a command to the plurality of control units to drive the electric motor, using wiring different from the bus. The option unit drives the electric motor according to a command received from the higher-level device via wiring, and also transmits the sensor value to the higher-level device via the wiring. By having such features, the servo system can allow the host device to monitor the servo system, including changes in sensor values.

According to the disclosed technology, it is possible to provide a servo system in which optional units including sensors can be connected more flexibly.

FIG. 1 is a diagram showing an example of a servo system according to an embodiment. FIG. 2 is a diagram schematically showing connections between a converter unit, an inverter unit, and an option unit in the servo system according to the embodiment. FIG. 3 is a diagram illustrating a state in which a converter unit, an inverter unit, and an option unit are connected via an internal bus in the servo system according to the embodiment. FIG. 4 is a diagram showing a schematic configuration of functional units included in the control circuit of the converter unit. FIG. 5 is a diagram showing a schematic configuration of functional sections included in the control circuit of the inverter unit. FIG. 6 is a diagram showing a schematic configuration of a functional section included in the sensor circuit of the option unit. FIG. 7 is a diagram showing an example of a processing flow for detecting a unit newly connected to an internal bus in a servo system. FIG. 8 is a diagram showing an example of a processing flow for detecting removal of a unit connected to an internal bus in a servo system. FIG. 9 is a diagram showing an example of a communication sequence using an internal bus in a servo system.

<Embodiment>
Hereinafter, a servo system according to an embodiment will be described with reference to the drawings. FIG. 1 is a diagram showing an example of a servo system 100 according to an embodiment. The servo system 100 includes a converter unit 1, an inverter unit 2a, an inverter unit 2b, and an option unit 4. A servo motor 3a is connected to the inverter unit 2a, and a servo motor 3b is connected to the inverter unit 2b. When the inverter unit 2a and the inverter unit 2b are not distinguished, they are also referred to as the inverter unit 2. Moreover, when the servo motor 3a and the servo motor 3b are not distinguished, they are also referred to as the servo motor 3. A PLC 5 is connected to the servo system 100 via an industrial network N1.

PLC5 outputs command signals to converter unit 1 and inverter unit 2 of servo system 100 via industrial network N1. The PLC 5 functions, for example, as a monitoring device for the servo system 100 by executing processing according to a program prepared in advance. The industrial network N1 is, for example, a TCP/IP network. The PLC 5 is an example of a "superior device". The industrial network N1 is an example of "wiring".

The servo system 100 is a building block type servo system including a converter unit 1 and a plurality of inverter units 2. In the servo system 100, a plurality of inverter units 2 can be connected to one converter unit 1, and the inverter unit 2 connected to the converter unit 1 can be separated from the converter unit 1. In FIG. 1, the servo system 100 includes three inverter units 2, but the number of inverter units 2 may be two or less, or four or more.

Converter unit 1 and inverter unit 2 receive command signals from PLC 5 via industrial network N1. Converter unit 1 distributes current received from a power source (not shown) to inverter unit 2 . Converter unit 1 is an example of a "management unit".

Inverter unit 2 receives current from converter unit 1 and supplies drive current to servo motor 3 . Inverter unit 2 receives a feedback signal from servo motor 3. Each inverter unit 2 has a servo system that performs feedback control using a position controller, speed controller, current controller, etc. These signals are used to servo control the servo motor 3. drive Furthermore, the inverter unit 2 uses sensor values provided from the option unit 4 for servo control of the servo motor 3. Inverter unit 2 is an example of a "control unit."

The servo motor 3 is, for example, an AC servo motor. The servo motor 3 operates in response to drive current supplied from the inverter unit 2 . The servo motor 3 detects the displacement of the output shaft of the servo motor 3 and outputs a feedback signal indicating the detected displacement to the inverter unit 2. The servo motor 3 is an example of an "electric motor."

The option unit 4 is a unit having sensors such as a temperature sensor, a pressure sensor, a fully closed sensor, and the like. The option unit 4 provides the inverter unit 2 with sensor values detected by the sensors. Option unit 4 is an example of an "option unit."

FIG. 2 is a diagram schematically showing connections among the converter unit 1, inverter unit 2, and option unit 4 in the servo system 100 according to the embodiment. A female type other unit connection port 113 is provided on the side surface of the converter unit 1 . A male upstream connection terminal 221 is provided on the side surface of the inverter unit 2 on the converter unit 1 side (upstream side). Further, a female downstream connection port 222 is provided on the side surface of the inverter unit 2 on the opposite side (downstream side) from the converter unit 1 side. An upstream connection terminal 401 is provided on the upstream side surface of the option unit 4. Furthermore, a downstream connection port 402 is provided on the downstream side of the option unit 4.

Other unit connection port 113 of converter unit 1 and upstream connection terminal 221 of inverter unit 2a are connected, and downstream connection port 222 of inverter unit 2a and upstream connection terminal 221 of inverter unit 2b are connected. The upstream connection terminal 401 of the option unit 4 is connected to the downstream connection port 222 of the inverter unit 2b. In the building block type servo system 100, the converter unit 1, inverter unit 2, and option unit 4 are removably connected to each other by connecting the connection terminals and connection ports of each unit in this way.

FIG. 3 is a diagram illustrating a state in which converter unit 1, inverter unit 2, and option unit 4 are connected via internal bus B1 in servo system 100 according to the embodiment. In the converter unit 1, a control circuit 101 that controls the supply of current to the inverter unit 2 and the exchange of information with the inverter unit 2 is connected to an internal bus B1. In the inverter unit 2a, a control circuit 201a that controls the servo motor 3a is connected to the internal bus B1. In the inverter unit 2b, a control circuit 201b that controls the servo motor 3b is connected to the internal bus B1. When the control circuit 201a and the control circuit 201b are not distinguished, they are also referred to as the control circuit 201. In the option unit 4, a sensor circuit 400 that outputs a sensor value detected by the sensor is connected to the internal bus B1. Internal bus B1 is an example of a "bus".

The internal bus B1 is a multi-drop type bus that connects units. Data output by a certain unit connected to internal bus B1 can be received by all other units connected to internal bus B1. That is, the units connected to the internal bus B1 output data by broadcast to the internal bus B1. Examples of the internal bus B1 include RS-485 and CAN buses.

In the servo system 100, the converter unit 1, inverter unit 2, and option unit 4 are connected as illustrated in FIG. 2, so that the internal bus B1 of the converter unit 1, inverter unit 2, and option unit 4 is connected. When the control circuit 101 is connected to the internal bus B1, it becomes possible to supply current to the control circuit 201 and exchange information with the control circuit 201. Moreover, the sensor circuit 400 can output a sensor value detected by the sensor to the control circuit 201 by being connected to the internal bus B1. As described above, since the internal bus B1 is a multi-drop type bus, the sensor circuit 400 outputs sensor values to the internal bus B1 by broadcasting.

<Functional parts of converter unit 1>
FIG. 4 is a diagram showing a schematic configuration of functional sections included in control circuit 101 of converter unit 1. As shown in FIG. The control circuit 101 can be regarded as a computer having an arithmetic unit, a storage device, and the like. The functional units shown in FIG. 4 are realized by executing a predetermined program or the like in the control circuit 101. The control circuit 101 includes a communication control unit 11, a power supply unit 12, a management unit 13, and a storage unit 14, but may include functional units other than these.

The communication control unit 11 outputs a synchronization signal that triggers communication start to the inverter unit 2 and option unit 4 that communicate using the internal bus B1. The power supply section 12 converts an alternating current supplied from an external power source into a direct current, and supplies the DC current to the inverter unit 2 . The synchronization signal is an example of a "first signal."

The management unit 13 detects a unit newly connected to the internal bus B1 based on the response to the synchronization signal from the inverter unit 2 and the option unit 4. The management unit 13 assigns a unique ID among the units connected to the internal bus B1 to the detected new unit. The management unit 13 allocates IDs such that, for example, units connected to the upstream side are assigned a lower number. The assigned ID is stored in the storage unit 14 in association with, for example, the serial number of the unit included in the response that transmitted the response. Furthermore, if there is no response to the synchronization signal from a unit to which an ID has been assigned, the management unit 13 detects that the unit has been removed from the servo system 100. For example, the ID assigned to the unit whose removal was detected is deleted from the storage unit 14. ID is an example of an "identification number."

The storage unit 14 stores IDs assigned to the inverter unit 2 and the option unit 4 by the management unit 13 and information related to processing performed by the control circuit 101. The storage unit 14 is, for example, an EEPROM.

<Functional parts of inverter unit 2>
FIG. 5 is a diagram showing a schematic configuration of functional sections included in the control circuit 201 of the inverter unit 2. As shown in FIG. The control circuit 201 can be considered as a computer having an arithmetic unit, a storage device, and the like. The functional units shown in FIG. 5 are realized by executing a predetermined program or the like in the control circuit 201. The control circuit 201 includes a control section 21, an acquisition section 22, a communication section 23, and a storage section 24, but may include functional sections other than these.

The control unit 21 servo-controls the servo motor 3 according to instructions from the PLC 5. In the servo control by the control unit 21, for example, sensor values acquired by the acquisition unit 22 may be used.

The acquisition unit 22 acquires sensor values output from the option unit 4 via internal bus B1 by broadcast. For example, the acquisition unit 22 stores the ID of the option unit 4 designated by the user or the like in the storage unit 24, and acquires the sensor value transmitted from the option unit 4 with the ID stored in the storage unit 24. Good too.

Communication section 23 outputs a response signal according to the synchronization signal from converter unit 1 to converter unit 1 via internal bus B1. The response signal may include, for example, the serial number of the own unit. The communication section 23 may determine the transmission timing of the response signal based on the ID assigned to the inverter unit 2. For example, the communication unit 23 may transmit the response signal after a time period obtained by multiplying the ID assigned to the own unit by a predetermined response time after receiving the synchronization signal. The predetermined response time may be stored in the storage unit 24 in advance, for example.

The storage unit 24 stores information related to processing performed by the control circuit 201. The storage unit 24 is, for example, a nonvolatile storage unit such as an EEPROM.

<Functional parts of option unit 4>
FIG. 6 is a diagram showing a schematic configuration of functional units included in the sensor circuit 400 of the option unit 4. As shown in FIG. The sensor circuit 400 can be regarded as a computer having a calculation device, a storage device, and the like. The functional units shown in FIG. 6 are realized by executing a predetermined program or the like in the sensor circuit 400. The sensor circuit 400 includes a measurement section 41, a communication section 42, and a storage section 43, but may include functional sections other than these.

The measurement unit 41 performs measurement using a sensor included in the option unit 4. For example, if the sensor included in the option unit 4 is a temperature sensor, the measurement unit 41 measures the temperature. Further, for example, if the sensor included in the option unit 4 is a pressure sensor, the measurement unit 41 measures pressure. Option unit 4 may include multiple sensors. When the optional unit 4 has a plurality of sensors, the measurement section 41 may perform measurement using each sensor.

The communication unit 42 transmits the sensor value measured by the measurement unit 41 via the internal bus B1 in response to the synchronization signal from the converter unit 1. Transmission via the internal bus B1 is performed by broadcast, as described above. For example, the serial number of the optional unit 4 may be attached to the sensor value.

The communication unit 42 may determine the transmission timing of the response signal based on the ID assigned to its own unit. For example, the communication unit 42 may transmit the sensor value to the internal bus B1 after a time period obtained by multiplying the ID assigned to the own unit by a predetermined response time after receiving the synchronization signal. The predetermined response time may be stored in the storage unit 43 in advance, for example.

The communication unit 42 may further transmit the sensor value to the PLC 5 via the industrial network N1. Transmission via the industrial network N1 may be performed by specifying the PLC 5 as the destination device.

The storage unit 43 stores information related to processing performed by the sensor circuit 400. The storage unit 43 is, for example, a nonvolatile storage unit such as an EEPROM.

FIG. 7 is a diagram showing an example of a processing flow for detecting a unit newly connected to the internal bus B1 in the servo system 100. An example of a processing flow for detecting a unit newly connected to the internal bus B1 will be described below with reference to FIG. 7. It is assumed that the communication control section 11 of the converter unit 1 outputs a synchronization signal to the internal bus B1 at predetermined intervals.

In S1, the management section 13 of the converter unit 1 determines whether or not a response to the synchronization signal outputted by the communication control section 11 at predetermined intervals has been received. If received (YES in S1), the process proceeds to S2. If not received (YES in S2), the process proceeds to S1.

In S2, the management unit 13 determines whether the response received in S1 is a response from a unit to which no ID has been assigned. The management unit 13 determines whether the response is from a unit to which no ID has been assigned, based on whether the serial number included in the response received in S1 is stored in the storage unit 14, for example. If the response is from a unit to which no ID has been assigned (YES in S2), the process proceeds to S3. If the response is not from a unit to which no ID has been assigned (NO in S2), the process proceeds to S1.

In S3, the management unit 13 assigns an ID to the source unit of the response received by the converter unit 1. For example, the management unit 13 associates the assigned ID with the serial number included in the response received in S1 and causes the storage unit 14 to store the associated ID.

FIG. 8 is a diagram showing an example of a processing flow for detecting removal of a unit connected to internal bus B1 in servo system 100. An example of a processing flow for detecting removal of a unit connected to internal bus B1 in servo system 100 will be described below with reference to FIG. 8. It is assumed that the communication control section 11 of the converter unit 1 outputs a synchronization signal to the internal bus B1 at predetermined intervals.

In S11, the management unit 13 determines whether responses to the synchronization signal have been confirmed from all units to which IDs have been assigned. If responses from all units to which IDs have been assigned are confirmed (YES in S11), the process in S11 is repeated. If responses from at least some of the ID-assigned units are not confirmed (NO in S11), the process proceeds to S12.

In S12, the management unit 13 deletes from the storage unit 14 the ID of the unit whose response was not confirmed in S11.

FIG. 9 is a diagram showing an example of a communication sequence using the internal bus B1 in the servo system 100. In FIG. 9, it is assumed that an ID is assigned to each unit. An example of a communication sequence using internal bus B1 in servo system 100 will be described below with reference to FIG. In the example of FIG. 9, it is assumed that among the inverter units 2, the inverter unit 2a uses the sensor value from the option unit 4.

In FIG. 9, it is assumed that time passes from top to bottom. In FIG. 9, the converter unit 1 is written as "CONV", the inverter unit 2a is written as "INV1", the inverter unit 2b is written as "INV2", and the option unit 4 is written as "OPT". Further, in FIG. 9, solid line arrows illustrate actual signal transmission. A solid arrow with "BROADCAST" at the end exemplifies a signal transmitted by broadcast. Moreover, the dotted arrow extending from the broadcast exemplifies the receiving destination of the signal transmitted by the broadcast.

At T1, converter unit 1 broadcasts a synchronization signal to internal bus B1. The synchronization signal broadcasted at T1 is received by the inverter unit 2a, the inverter unit 2b, and the option unit 4, as exemplified by V1, V2, and V3.

At T2, the inverter unit 2a broadcasts a response to the synchronization signal transmitted at T1 to the internal bus B1. The response broadcasted at T2 is received by the converter unit 1, as illustrated at V4.

At T3, inverter unit 2b broadcasts a response to the synchronization signal transmitted at T1 to internal bus B1. The response broadcasted at T3 is received by the converter unit 1, as illustrated at V5.

At T4, the option unit 4 broadcasts the sensor value onto the internal bus B1 in response to the synchronization signal transmitted at T1. The sensor values broadcasted at T4 are received by the converter unit 1 and the inverter unit 2a, as illustrated at V6 and V7.

<Actions and effects of embodiments>
In this embodiment, both the inverter unit 2 and the option unit 4 are connected to the internal bus B1. The data output to the internal bus B1 is then transmitted by broadcast. Therefore, the option unit 4 can transmit sensor values to both inverter units 2a and 2b even if it is placed at any position. Therefore, according to this embodiment, the option unit 4 including the sensor can be connected to the servo system 100 more flexibly.

In this embodiment, the converter unit 1 assigns different IDs to each of the inverter unit 2 and the option unit 4. Therefore, according to this embodiment, each unit can be uniquely identified. Further, according to the present embodiment, the ID of the option unit 4 is attached to the sensor value transmitted from the option unit 4, so that the inverter unit 2 can use the sensor value sent from the desired option unit 4. The servo motor 3 can be controlled.

In this embodiment, after receiving the synchronization signal from the converter unit 1, the inverter unit 2 and the option unit 4 output a response after delaying by a delay time corresponding to the assigned ID. Such a configuration prevents a plurality of units from simultaneously outputting responses to the internal bus B1. Furthermore, since it is possible to suppress the occurrence of collisions on the internal bus B1, a decrease in communication efficiency of communication using the internal bus B1 is suppressed.

In this embodiment, if there is a unit that does not respond to a synchronization signal among the ID-assigned units, the converter unit 1 detects removal of that unit from the servo system 100 (or internal bus B1). Furthermore, upon receiving a response to the synchronization signal from a unit to which no ID has been assigned, converter unit 1 detects the connection of that unit to servo system 100 . That is, according to the present embodiment, connection and disconnection of units can be easily detected without any additional work by the user.

In this embodiment, the option unit 4 is connected to the PLC 5 by an industrial network N1. The option unit 4 can output the sensor value to the PLC 5 via the industrial network N1. Therefore, according to this embodiment, for example, it is possible to cause the PLC 5 to monitor the servo system 100 including changes in sensor values.

<Modified example>
The converter unit 1 may set priorities to the inverter unit 2 and the option unit 4. Then, the inverter unit 2 and the option unit 4 may determine the response frequency to the synchronization signal according to the set priority. For example, a unit set with a high priority may transmit a response every time it receives a synchronization signal. Further, for example, a unit to which a low priority is set only needs to transmit a response once when receiving a synchronization signal twice. By setting the frequency of responses to the synchronization signal in accordance with the priority in this manner, it is possible to effectively use the internal bus B1 for units that prefer to transmit responses at a high frequency.

<Additional note 1>
a plurality of control units (2) controlling connected electric motors (3);
a bus (B1) that communicably connects the plurality of control units (2);
An optional unit (4) that broadcasts sensor values related to control of the electric motor (3) to a plurality of control units (2) is removably connected to the bus (B1).
Servo system (100).

1... Converter unit 2... Inverter unit 2a... Inverter unit 2b... Inverter unit 3... Servo motor 3a... Servo motor 3b... Servo motor 4... Option unit 5... PLC
DESCRIPTION OF SYMBOLS 11..Communication control part 12..Power supply part 13..Management part 14..Storage part 21..Control part 22..Acquisition part 23..Communication part 24..Storage part 41..Measurement part 42..Communication Part 43... Storage part 100... Servo system 101... Control circuit 113... Other unit connection port 201... Control circuit 201a... Control circuit 201b... Control circuit 221... Upstream side connection terminal 222... Downstream side Connection port 400...Sensor circuit 401...Upstream connection terminal 402...Downstream connection port B1...Internal bus N1...Industrial network

Claims (7)

a plurality of control units that control connected electric motors;
a bus that connects the plurality of control units to each other in a communicable manner;
An optional unit that broadcasts sensor values related to control of the electric motor to a plurality of control units is removably connected to the bus;
servo system. further comprising a management unit connected to the bus and assigning different identification numbers to each of the plurality of control units and the option unit;
The servo system according to claim 1. The optional unit broadcasts the sensor value with the identification number assigned by the management unit,
The plurality of control units are designated with the identification number of the optional unit that is the source of the sensor value to be acquired,
The plurality of control units acquire the sensor values to which the specified identification numbers are attached, and control the electric motor using the acquired sensor values.
The servo system according to claim 2. the management unit broadcasting a first signal via the bus;
Upon receiving the first signal, each of the plurality of control units transmits a response to the first signal via the bus after a delay time determined based on the identification number assigned to the own unit has elapsed. and send it by broadcast,
When the optional unit receives the first signal, the optional unit broadcasts the sensor value via the bus as a response to the first signal after the delay time has elapsed.
The servo system according to claim 2. The management unit recognizes that, among the plurality of control units and the optional units, a unit that does not respond to the first signal has been removed from the bus;
The servo system according to claim 4. The management unit sets priorities for the plurality of control units and the option unit,
Each of the plurality of control units and the option unit transmits the response to the first signal at a frequency according to the set priority;
The servo system according to claim 4. The plurality of control units and the option unit are connected to a host device that outputs a command for driving the electric motor to the plurality of control units by wiring different from the bus,
The plurality of control units drive the electric motors according to commands received from the host device via the wiring,
The optional unit also transmits the sensor value to the host device via the wiring.
A servo system according to any one of claims 1 to 6.

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