Robotic system

Abstract

A robot system has a robot including a sensor, can suppress an increase in cost and an increase in the number of wirings, and reduce a delay in acquiring sensor data. The robot system has a robot (10) including a sensor (13), and a robot control device (20) that controls the robot (10), the robot control device (20) connecting a control arithmetic circuit (22) and a servo driver (21) through a high-speed synchronous communication wiring (33) that is a transmission path capable of synchronous data transmission. The servo driver (21) and an encoder (12) in the robot (10) are connected through a multi-point connection wiring (32) having a lower communication speed than the high-speed synchronous communication wiring (33), and the sensor (13) is connected to the multi-point connection wiring (32).

Description

Technical Field

[0001] This invention relates to industrial robots, and more particularly to robot systems having a robot (also known as a robotic arm) and a robot control device for controlling the robot. Background Technology

[0002] Typically, a robot has multiple axes, each equipped with a motor. To control the robot's movements, a robot control unit is used. Each motor in the robot is servo-controlled; therefore, each motor is equipped with an encoder to detect its rotational position. The robot control unit has a servo driver (also called a servo amplifier) ​​for each motor in the robot. The motor position detected by the encoder is fed back to the corresponding servo driver. To control the robot according to externally input commands, the robot control unit includes a control calculation circuit. This circuit calculates the position and speed commands for each axis of the robot based on the external commands and outputs them to the corresponding servo drivers.

[0003] To improve robot control performance, sensors are sometimes installed on the robot to measure vibration, acceleration, temperature, etc., and the measurements from these sensors are used for robot control calculations. When sensors are installed on the robot, data from the sensors needs to be transmitted via wiring, which increases the number of wires inside the robot and connecting the robot to the robot control unit. On the other hand, there is a demand to reduce the number of wires laid inside the robot joints and arms, as well as the number of wires between the robot and the robot control unit. One way to reduce the number of wires and connect multiple devices is through a daisy-chain connection. Another method is a multipoint connection, where multiple devices are connected to a common bus, such as a serial bus. In a multipoint connection, each device can simultaneously receive requests from the host device, thus enabling synchronous data acquisition. RS485 is a communication protocol used to implement multipoint connections.

[0004] Patent Document 1 discloses a method where multiple encoders and sensors are connected via multi-point lines, and data communication is performed between a robot and a robot control device through multi-point transmission. Patent Document 2 discloses a method where a control circuit acts as the master node, and servo drivers, encoders, and sensors act as slave nodes, connected in a daisy-chain configuration. Patent Document 3 discloses a robot whose main body includes multiple analog-to-digital (AD) converters that convert analog signals from sensors fixed to the robot into digital signals, and time-division multiplexes the digital signals generated by these AD converters, transmitting them as serial data to an external monitoring device. Patent Document 4 discloses a method where multiple servo amplifiers are connected to a host device in a daisy-chain configuration based on the EtherCAT (registered trademark) or CC-Link (registered trademark) standard. Patent Document 5 discloses a method where data detected by sensors is sent to an encoder, and sensor data and encoder data are sent together to a servo driver.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: JP2021-30376A

[0008] Patent Document 2: JP2022-141529A

[0009] Patent Document 3: JP2021-102261A

[0010] Patent Document 4: JP2023-176422A

[0011] Patent Document 5: JP2022-141061A Summary of the Invention

[0012] When controlling a robot using vibration or acceleration sensors, the computations required for robot control need to be performed at high speed. Therefore, when the control circuit sends a data request to the sensor, the sensor needs to quickly accept the request and send the measurement data back to the control circuit. When multiple sensors are used, it's necessary to acquire measurement data from multiple sensors without significant time differences. In this case, a connection structure capable of synchronous data transmission is required. While providing dedicated communication wiring for each sensor and connecting it to the control circuit can eliminate the latency required to acquire sensor data, it increases the number of wirings within the robot and connecting the robot to its control unit. On the other hand, when multiple sensors are daisy-chained, data is transmitted sequentially between devices, making synchronous transmission difficult. Consequently, sensors struggle to immediately respond to data requests from the robot control unit and transmit measurement data, resulting in latency in sensor data acquisition. Even with daisy-chain or bus connections, standards such as EtherCAT (registered trademark) or CC-Link (registered trademark) that use synchronous frames for transmission can achieve synchronous data transmission without causing sensor data acquisition latency issues. Data transmission based on the EtherCAT (registered trademark) standard can ensure communication speeds of up to 100 Mbps.

[0013] However, when data transmission is based on the EtherCAT (registered trademark) standard, each sensor or encoder in the device needs to be connected to a controller, pulse transformer, and a device called the PHY (physical layer processing circuit), resulting in a high-cost structure.

[0014] When multiple connections are made and RS485 is used as the communication protocol, the maximum communication speed is around 10 Mbps. When many devices are connected to a single bus, the communication cycle lengthens. This increased communication cycle for transmitting sensor and encoder data leads to a decrease in the robot's control performance.

[0015] When using daisy-chain or multi-point connections to connect encoders and sensors to the robot control unit, the wiring for each device (encoder and sensor) within the robot is arranged in a single-stroke manner. While this wiring method may seem simple at first glance, it can become a complex wiring arrangement with long cable lengths when considering the actual wiring conditions in robots or manipulators, such as when the robot moves back and forth within the arm.

[0016] The purpose of this invention is to provide a robot system having a robot including sensors, which can suppress the increase in the number of wiring, thereby suppressing the increase in cost, and can ignore the delay in acquiring sensor data.

[0017] One aspect of the robot system includes a robot and a robot control device for controlling the robot, wherein the robot includes: a motor provided for each axis of the robot; an encoder provided for and connected to each motor; and one or more sensors; the robot control device includes: a servo controller provided for each motor and performing servo control on the respective motor; and a control computing circuit provided in a common manner with respect to servo drives and controlling the robot, the control computing circuit being connected to the servo drives via a first wiring, the first wiring being a transmission path capable of synchronous data transmission; for each servo drive, the servo drive and the encoder connected to the respective motor are connected via a second wiring, the second wiring enabling multi-point connection; the sensors are connected to the second wiring via multi-point connection; the communication speed of the first wiring is faster than the communication speed of the second wiring.

[0018] According to the present invention, a robot system having a robot including sensors can be obtained, which can suppress the increase in the number of wiring and the rise in cost, and can ignore the delay in acquiring sensor data. Attached Figure Description

[0019] Figure 1 This is a block diagram illustrating the structure of a robot system according to one embodiment.

[0020] Figure 2 This is a block diagram representing another structure of the robot system. Detailed Implementation

[0021] Next, embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 The structure of a robot system according to one embodiment is shown.

[0022] The illustrated robot system consists of a robot (manipulator) 10 and a robot control unit 20 that controls the robot 10. The robot 10 typically has multiple axes. For each axis of the robot 10, a motor 11 and an encoder 12 are provided. The encoder 12 is mechanically connected to the motor 11 and is used to detect the rotational position of the motor 11. In addition, the robot 10 is equipped with one or more sensors 13 for detecting vibration, acceleration, temperature, sound, etc. The sensors 13 can be gyroscope sensors, etc. The robot control unit 20 includes: a servo driver 21 that is configured with and drives each motor 11 in the robot 10; and a control calculation circuit 22 shared with the servo driver 21. The control calculation circuit 22 executes calculations for controlling the robot 10 based on externally input instructions and generates internal instructions as position or speed instructions for each axis of the robot 10. The internal instructions for each axis of the robot 10 are sent to the corresponding servo driver 21, and the servo driver 21, having received the internal instructions, performs servo control on the motor 11 of the corresponding axis according to the internal instructions. The servo driver 21 and the corresponding motor 11 are connected via motor power wiring 31.

[0023] The control circuit 22 and the servo driver 21 are connected via a high-speed synchronous communication cable 33. The high-speed synchronous communication cable 33 is physically daisy-chained or bus-connected, with the control circuit 22 as the master device and each servo driver 21 as a slave device. The high-speed synchronous communication cable 33 is a transmission path capable of synchronous data transmission, for example, configured to transmit data according to the EtherCAT (registered trademark) standard protocol. For the servo driver 21 to perform servo control on the motor 11, the rotational position of the motor 11 needs to be fed back from the encoder 12 connected to the motor 11. The servo driver 21 and the corresponding encoder 12 are connected via a multi-point connection cable 32, and the sensor 13 is also connected to this multi-point connection cable 32. The multi-point connection cable 32 is a transmission path capable of multi-point communication, for example, configured to use the RS485 standard as the protocol. In the multi-point connection cable 32, for example, master / slave communication is performed with the servo driver 21 as the master device and the encoder 12 and sensor 13 as slave devices. As a transmission path, the high-speed synchronous communication wiring 33 has a higher communication speed than the multi-point connection wiring 32. The maximum communication speed of the high-speed synchronous communication wiring 33 is, for example, 100 Mbps, while the maximum communication speed of the multi-point connection wiring 32 is, for example, several Mbps to 10 Mbps. The high-speed synchronous communication wiring 33 corresponds to the first wiring, and the multi-point connection wiring 32 corresponds to the second wiring.

[0024] Data indicating the rotational position of motor 11 is detected by encoder 12 as encoder data and fed back to the corresponding servo driver 21 via multi-point connection wiring 32 for servo control of motor 11. Furthermore, protocol conversion is performed in servo driver 21 and transmitted to control processing circuit 22 via high-speed synchronous communication wiring 33. Measurement data from sensor 13 is also transmitted to servo driver 21 as sensor data via multi-point connection wiring 32, where protocol conversion is performed and transmitted to control processing circuit 22 via high-speed synchronous communication wiring 33.

[0025] In this embodiment, a multi-point connection wiring 32 is provided for each servo driver 21 to connect the servo driver 21 to the corresponding encoder 12, and the sensor 13 is also connected to the multi-point connection wiring 32. Figure 1 In this circuit, a sensor 13 is connected to a multipoint connection wiring 32, which is connected to an encoder 12. However, the number of sensors 13 connected to a multipoint connection wiring 32 is not limited to this. If more than one sensor 13 is installed in the robot 10, there can be multipoint connection wiring 32 without any sensor 13 connected, or there can be multipoint connection wiring 32 with more than two sensors 13 connected. However, considering the time required for the robot control device 20 to send a data request command to the sensor 13 and for the sensor 13 to send the sensor data corresponding to the command to the robot control device 20, the number of sensors 13 that can be connected to the multipoint connection wiring 32 is limited. Therefore, if the communication speed is f and the number of devices connected to a multipoint connection wiring 32, i.e., the total number of encoders 12 and sensors 13, is N, then assuming that the data length of the data request command sent to all devices without distinguishing between devices is 1 byte and the data length returned from the devices is L bytes, the time T required to collect data from N devices can be expressed by formula (1).

[0026] T = (8 + 8 × L × N) / f (1)

[0027] When using an RS485-based transmission path to implement multi-point connection wiring 32, the commonly used communication speed is around 2.5 Mbps. Therefore, if the communication speed f is 2.5 Mbps, the number of devices N is 8, and the data length L sent by the devices is 6 bytes, then T is 156.8 microseconds. The time T shown in formula (1) does not include the time required for the device receiving the request command to start transmitting data, so the actual time required will be slightly longer. Compared with the control cycle used in the robot control device 20, the value of approximately 160 microseconds calculated here is not negligible, which may lead to a decrease in the control performance of the robot 10. The time T is preferably at most less than 100 microseconds, and more preferably less than 75 microseconds. When the communication speed f is 2.5 Mbps, the data length L is 6 bytes, and the encoder 12 and two sensors 13 are connected to a multi-point connection wiring 32, that is, when N=3, according to formula (1), T is 60.8 microseconds. Since the number N includes the number of encoders 12, it can be known that if the communication speed f is 2.5 Mbps and the data length A sent by the device is 6 bytes, the number of sensors 13 connected to a multi-point connection wiring 32 is preferably two or less. On the other hand, in the high-speed synchronous communication wiring 33 used to connect the control operation circuit 22 and the servo driver 21 in the robot control device 20, for example, when using the EtherCAT (registered trademark) standard as the protocol, data transmission is usually carried out at a maximum communication speed of 100 MHz. Therefore, even if the number of axes or the number of sensors 13 in the entire robot system increases, there will be no delay that would cause a decrease in the control performance of the robot 10.

[0028] To control robot 10, data needs to be sent from encoder 12 according to a predetermined control cycle, and encoder 12 needs to have a high response speed. Conversely, the response of sensor 13 may sometimes be slower than that of encoder 12. In this case, the data to be transmitted by a set of sensors 13 can be transmitted through multiple data transmissions from encoder 12. Even so, there will be no delay that would degrade the control performance of robot 10. Figure 2 This illustrates another example of a robot system. Here, a certain axis of robot 10 is equipped with, for example, three sensors 13. These sensors 13 are connected to a multi-point connection wiring 32, which connects the encoder 12 and the servo drive 21 of the aforementioned axis. In the figure, the three sensors 13 are represented as sensor A, sensor B, and sensor C, respectively. Consider a case where the required response speed for sensors A to C is less than one-third of the required response speed for encoder 12. In this case, three types of data request commands corresponding to sensors A to C are prepared.

[0029] If these commands are set as data requests a to c, then when the robot control device 20 sends data request a, in response, each sensor 13 acquires data synchronized with data request a, and the robot 10 transmits encoder data a and sensor data of sensor A to the robot control device 20. Encoder data a is encoder data synchronized with data request a. Similarly, in response to data request b, encoder data b and sensor data of sensor B are transmitted; in response to data request c, encoder data c and sensor data of sensor B are transmitted. Encoder data b and c are encoder data synchronized with data requests b and c, respectively. In this case, for encoder data, each time a data request is sent, encoder data synchronized with that data request is sent. In contrast, sensor data a to c are sensor data of sensors A to C synchronized with the initial data request, i.e., data request a. In this way, by transmitting data from the three sensors 13 in three separate transmissions, sensor data can be acquired from the three sensors 13, and the communication cycle can be equivalent to the case where N=2 in formula (1), i.e., the case where only one sensor 13 is set.

[0030] When a sensor 13 for measuring vibration and acceleration is installed on robot 10, its purpose is typically to measure the vibration and acceleration of the axis driven by motor 11 when it is driven, thereby enabling more precise control of robot 10. In this case, the sensor 13 for measuring vibration and acceleration is installed on the arm of the target axis, and therefore necessarily close to the motor 11 of the target axis, and also close to the encoder 12 of that axis. Therefore, when the sensor 13 is installed to measure the vibration or acceleration associated with a certain axis of robot 10, the total wiring length can be shortened by connecting the sensor 132 to the multi-point connection wiring 32 connected to the encoder 12 of that axis. Furthermore, by connecting the sensor 13 to the multi-point connection wiring 32 in this way, when using the measurement results of vibration and acceleration to diagnose each axis, such as estimating the lifespan of the motor 11 of that axis, the vibration and acceleration data can be obtained through the multi-point connection wiring 32 in the servo driver 21 that servo controls the motor 11, and each axis can be diagnosed by the servo driver 21 instead of the control calculation circuit 22. The same applies when sensor 13 is used as a temperature sensor to detect the degree of heating in motor 11, or as a sound sensor to detect abnormal sounds or other sounds generated by motor 11.

[0031] In the robot system of the above embodiment, data transmission within the robot control device 20 uses a high-speed synchronous communication cable 33, which enables high-speed synchronous data transmission via a transmission path based on, for example, the EtherCAT (registered trademark) standard. Data transmission between the servo driver 21 of the robot control device 20 and the encoder 12 and sensors 13 in the robot 10 uses, for example, a multi-point connection cable based on the RS485 standard. The high-speed synchronous communication cable 33 is expensive, but its use is limited to within the robot control device 20, thereby suppressing cost increases. On the other hand, by providing a multi-point connection cable 32 for each axis of the robot 10 and connecting the encoder 12 and several sensors 13 to this cable 32, the generation of delays in transmitting sensor data can be suppressed through a low-cost structure. Therefore, the robot system according to this embodiment can reduce the delay in acquiring sensor data while suppressing cost increases and the increase in the number of cables.

[0032] The above describes an example of a structure for implementing the present invention, but the above technology can also be implemented using the following structure.

[0033] [1] A robot system, comprising a robot and a robot control device for controlling the robot, The robot includes: a motor for each axis of the robot; an encoder for each motor and connected to that motor; and one or more sensors. The robot control device includes: a servo driver configured for each of the motors and providing servo control to the corresponding motors; and a control processing circuit configured in a shared manner with respect to the servo drivers and controlling the robot. The control and computing circuit and the servo driver are connected via a first wiring, which is a transmission path capable of synchronous data transmission. For each of the servo drives, the servo drive and the encoder connected to the corresponding motor are connected via a second wiring harness, which enables multi-point connections. The sensor is connected to the second wiring via a multi-point connection. The communication speed of the first wiring is faster than that of the second wiring.

[0034] According to the structure [1], in a robot system consisting of a robot and a robot control device, the increase in cost and the increase in the number of wiring can be suppressed, while the delay in acquiring sensor data can be reduced.

[0035] [2] According to the robot system described in [1], wherein, The sensor that performs measurements associated with a specific axis is connected to the second wiring corresponding to that specific axis.

[0036] [3] According to the robot system described in [1] or [2], wherein, The sensor is a sensor that measures any one of vibration, acceleration, temperature, and sound.

[0037] Since the sensor that performs measurements related to a specific axis is usually located inside the robot near the motor of that axis, i.e. near the encoder, the structure [2] can shorten the connection distance between the sensor and the second wiring, thereby shortening the wiring length inside the robot. In particular, when the sensor is a sensor that measures any of vibration, acceleration, temperature and sound, as specified in [3], defects related to that axis can be detected early when measuring a specific axis.

[0038] [4] According to the robot system described in [1] or [2], wherein, The first wiring is configured in a daisy chain or a bus configuration.

[0039] [5] According to the robot system described in [4], wherein, The first wiring configuration is a transmission path based on the EtherCAT (registered trademark) standard.

[0040] According to the structure [4], the wiring length of the first wiring can be shortened, and as specified in [5], a transmission path based on the EtherCAT (registered trademark) standard can be used as the first wiring, thereby enabling data transmission at a particularly high speed of 100 Mbps and also accommodating the increase in the number of robot axes.

[0041] [6] The robot system according to any one of [1] to [5], wherein, The second wiring configuration is a transmission path based on the RS485 standard.

[0042] [7] The robot system according to any one of [1] to [6], wherein, The encoder and the sensor are respectively designated as devices, and an upper limit is specified for the number of sensors connected to the second wiring, such that for each second wiring, the time required to send a common data request to the device connected to the second wiring and to receive data corresponding to the data request from each device is less than 100 microseconds.

[0043] According to structure [6], the second wiring can be constructed at a lower cost, and according to structure [7], the number of sensors connected to the second wiring can be determined so as not to reduce the control performance of the robot.

[0044] [8] The robot system according to any one of [1] to [6], wherein, In the servo driver, protocol conversion is performed between data transmitted via the first wiring and data transmitted via the second wiring.

[0045] Based on the structure [8], robot systems can be constructed with more flexible network structures.

[0046] Symbol Explanation

[0047] 10...robot; 11...motor; 12...encoder; 13...sensor; 20...robot control device; 21...servo driver; 22...control and computing circuit; 31...motor power wiring; 32...multi-point connection wiring; 33...high-speed synchronous communication wiring.

Claims

1. A robot system comprising a robot and a robot control device for controlling the robot, characterized in that, The robot includes: a motor for each axis of the robot; an encoder for each motor and connected to it; and one or more sensors. The robot control device includes: a servo driver configured for each of the motors and providing servo control to the corresponding motors; and a control processing circuit configured in a shared manner with respect to the servo drivers and controlling the robot. The control and computing circuit and the servo driver are connected via a first wiring, which is a transmission path capable of synchronous data transmission. For each of the servo drives, the servo drive and the encoder connected to the corresponding motor are connected via a second wiring harness, which enables multi-point connections. The sensor is connected to the second wiring via a multi-point connection. The communication speed of the first wiring is faster than that of the second wiring.

2. The robot system according to claim 1, characterized in that, The sensor that performs measurements associated with a specific axis is connected to the second wiring corresponding to that specific axis.

3. The robot system according to claim 1 or 2, characterized in that, The sensor is a sensor that measures any one of vibration, acceleration, temperature, and sound.

4. The robot system according to claim 1 or 2, characterized in that, The first wiring is configured in a daisy chain or a bus configuration.

5. The robot system according to claim 4, characterized in that, The first wiring configuration is a transmission path based on the EtherCAT standard.

6. The robot system according to claim 1 or 2, characterized in that, The second wiring configuration is a transmission path based on the RS485 standard.

7. The robot system according to claim 6, characterized in that, The encoder and the sensor are respectively designated as devices, and an upper limit is specified for the number of sensors connected to the second wiring, such that for each second wiring, the time required to send a common data request to the device connected to the second wiring and to receive data corresponding to the data request from each device is less than 100 microseconds.

8. The robot system according to claim 1 or 2, characterized in that, In the servo driver, protocol conversion is performed between data transmitted via the first wiring and data transmitted via the second wiring.

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