Multi-axis servo driver

Abstract

The invention discloses a multi-axis servo driver, and relates to the technical field of communication. The multi-axis servo driver is used for driving a servo motor and comprises a master control unit and at least one slave control unit, and the master control unit is used for being connected with an upper computer so as to carry out joint debugging on all the control units; the master control unit is in communication connection with each slave control unit; the main control unit outputs a first PWM wave to control a set number of servo motors; each slave control unit outputs a second PWM wave to control the servo motors with the set number; the master control unit sends a chip selection signal to any selected slave control unit at a first period mark point of the first PWM wave so as to jointly debug a servo motor controlled by the selected slave control unit; wherein the first period mark point is any waveform point of the first PWM wave; and the selected slave control unit responds to the chip selection signal to adjust the second PWM wave so as to realize synchronous coordination control of each servo motor.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a multi-axis servo driver. Background Art

[0002] With the development of industrial automation technology, more and more application scenarios need to support one-machine multi-axis (servo motor) drive systems in order to achieve more efficient and flexible production processes. However, the main problem faced by traditional one-machine multi-axis drive systems is how to achieve efficient and synchronous debugging and monitoring between multiple axes. In traditional one-machine multi-axis systems, the debugging software generally requires users to select a specific axis number when connecting. Although this method is relatively simple in the initial design, as the complexity of the multi-axis system increases, it becomes very inefficient to select and debug each axis number one by one, especially when multiple axes need to be debugged, the operation becomes cumbersome and time-consuming.

[0003] In addition, in the traditional one-machine multi-axis control solution, since there is no built-in synchronization mechanism between the axes, their control signals and sampling signals cannot be synchronized. Therefore, in the multi-axis linkage debugging scenario, the debugging software of the host computer cannot continuously collect the motion waveforms of multiple axes, and thus cannot determine the motion deviation between the multiple axes. Summary of the invention

[0004] The main technical problem solved by the present invention is to provide a multi-axis servo driver capable of ensuring coordinated synchronization of various servo motors.

[0005] According to the first aspect, an embodiment provides a multi-axis servo driver for driving a servo motor, comprising a master control unit and at least one slave control unit, wherein the master control unit is used to connect to a host computer to perform joint debugging of the control units; The master control unit and each slave control unit are communicatively connected; The master control unit outputs a first PWM wave to control a set number of servo motors; each slave control unit outputs a second PWM wave to control the set number of servo motors; The master control unit sends a control signal to any selected slave control unit at a first cycle mark point of the first PWM wave to coordinate the servo motor controlled by the selected slave control unit; wherein the first cycle mark point is any waveform point of the first PWM wave; The selected slave control unit adjusts the second PWM wave in response to the control signal to achieve synchronous coordinated control of each servo motor.

[0006] In one embodiment, the waveform point of the selected second PWM wave output from the control unit corresponding to the first cycle mark point is the second cycle mark point; When the second cycle mark point is ahead of the first cycle mark point, the slave control unit extends the cycle of the second PWM wave until the time difference between the second cycle mark point and the first cycle mark point is less than a set value.

[0007] In one embodiment, the waveform point of the selected second PWM wave output from the control unit corresponding to the first cycle mark point is the second cycle mark point; When the second cycle mark point lags behind the first cycle mark point, the slave control unit shortens the cycle of the second PWM wave until the time difference between the second cycle mark point and the first cycle mark point is less than a set value.

[0008] In one embodiment, the first cycle mark point is a zero-crossing point of the first PWM wave, and the second cycle mark point is a zero-crossing point of the second PWM wave.

[0009] In one embodiment, each control unit includes a capture unit, and the capture unit is used to calculate the time difference between the second cycle mark point and the first cycle mark point.

[0010] In one embodiment, the master control unit and the slave control unit communicate with each other through synchronous serial communication and asynchronous serial communication. The master control unit uses the synchronous serial communication to send a control signal to any selected slave control unit; each control unit uses the asynchronous serial communication to send asynchronous communication data to perform asynchronous communication.

[0011] In one embodiment, the asynchronous communication data includes flag data of the servo motors controlled by each control unit; each control unit obtains the asynchronous communication data and determines whether the flag data is consistent with the servo motors controlled by each control unit. If so, the asynchronous communication data is parsed to perform asynchronous communication.

[0012] In one embodiment, the main control unit obtains the feedback signal sent by the selected slave control unit through the synchronous serial communication, and the main control unit verifies the feedback signal. When the feedback signal is abnormal, the main control unit sends a reset signal to the selected slave control unit through the asynchronous serial communication to reset the selected slave control unit.

[0013] In one embodiment, the synchronous serial communication is SPI communication, and the asynchronous serial communication is RS232 communication.

[0014] In one embodiment, the control units are connected in a daisy chain manner to perform RS232 communication.

[0015] According to the multi-axis servo driver of the above embodiment, it includes a main control unit and at least one slave control unit. The main control unit sends a control signal to the selected slave control unit at the first period mark point of the first PWM wave, and the selected slave control unit adjusts the PWM wave of the slave control unit according to the control signal, so as to achieve synchronous coordination of the servo motors controlled by each control unit. The present application synchronizes the PWM waveforms of the main control unit and the slave control unit through period mark points, ensures the coordination and consistency of the control signals and sampling signals of all servo motors, and avoids motion deviations between different servo motors. Moreover, in the case of multiple slave control units, synchronous control through period mark points can make the expansion of the control unit simpler. If more servo motors need to be added, it only needs to be expanded according to the timing control mechanism that the multi-axis servo driver is running, and there is no need to readjust the communication or control architecture of the entire multi-axis servo driver. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the structure of a multi-axis servo driver in an embodiment; Figure 2 A flow chart of a method for RS232 communication in each control unit in an embodiment; Figure 3 A waveform diagram showing that a second period mark point of a second PWM wave leads a first period mark point of a first PWM wave in an embodiment; Figure 4 A waveform diagram showing that a second period mark point of a second PWM wave lags behind a first period mark point of a first PWM wave in an embodiment; Figure 5 Schematic diagram of the structure of the capture unit in each control unit in an embodiment. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below by specific embodiments in conjunction with the accompanying drawings. Wherein similar elements in different embodiments adopt associated similar element numbers. In the following embodiments, many detailed descriptions are for making the present application better understood. However, those skilled in the art can easily recognize that some features can be omitted in different situations, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present application are not shown or described in the specification, this is to avoid the core part of the present application being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0018] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementations. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a required sequence, unless otherwise specified that a certain sequence must be followed.

[0019] The serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings).

[0020] A multi-axis servo drive is a control device used to control a servo motor system with multiple degrees of freedom. Degrees of freedom refer to the ability of a mechanical system to move independently in space. For a six-axis servo system, each axis represents a degree of freedom, and each degree of freedom corresponds to a servo motor. These motors work together to control the movement of the system in different directions. Multi-axis servo drives are usually six-axis servo drives, of which three axes are used to control position (front and back, left and right, and up and down translation), and three axes are used to control direction (pitch, yaw, and roll). Of course, in actual engineering, multi-axis servo drives are not limited to only six axes. The specific number is set according to the actual engineering needs and is not limited here.

[0021] Please refer to Figure 1 In one embodiment, in order to ensure that each servo motor works in coordination and synchronization, the present application provides a multi-axis servo driver 100, including a main control unit 110 and at least one slave control unit 120. The main control unit 110 is used to connect to a host computer and the debugging software installed in the host computer to obtain debugging commands and realize joint debugging of each control unit.

[0022] In one embodiment, since the purpose of each control unit is to control the servo motor, in each control unit, the main control unit 110 outputs a first PWM wave to control a set number of servo motors, and the slave control unit 120 outputs a second PWM wave to also control a set number of motors.

[0023] It should be noted that in the present application, whether the main control unit 110 or the slave control unit 120 controls two servo motors, then the multi-axis servo drive 100 requires a main control unit 110 and two slave control units 120. In actual engineering applications, the control unit and the number of servo motors controlled by the control unit can be set accordingly according to the number of servo motors and the hardware conditions of the drive. For example, the main control unit 110 and the slave control unit 120 can both control one servo motor or three servo motors, or the main control unit 110 controls one servo motor and the slave control unit 120 controls three servo motors, etc., which are not limited here.

[0024] In one embodiment, in order to ensure that the joint debugging of each control unit can be realized, the master control unit 110 and each slave control unit 120 are connected in communication, and in order to improve real-time performance and reliability, the master control unit 110 and each slave control unit 120 communicate in two different ways: synchronous serial communication and asynchronous serial communication. Synchronous serial communication uses SPI communication, which can exchange data between each control unit at high speed, has strong real-time performance, and transmits data accurately during the communication process. Asynchronous serial communication uses RS232 communication, which has a relatively low transmission speed but better stability and anti-interference ability.

[0025] In one embodiment, in SPI communication, the four-wire system of MOSI (output of the master control unit 110, input of the slave control unit 120), MISO (input of the master control unit 110, output of the slave control unit 120), CLK (clock signal), and CS (chip select signal) is used for communication. The master control unit 110 selects which slave control unit 120 to communicate with by controlling the chip select signal. When the chip select signal is valid, the slave control unit 120 is selected. Therefore, the master control unit 110 can send a control signal to any selected slave control unit 120 using SPI, so that the control command obtained by the master control unit 110 through the host computer can be used by the master control unit 110 and the selected slave control unit 120, thereby coordinating the servo motor controlled by the master control unit 110 and the servo motor controlled by the selected slave control unit 120. Specifically, the master control unit 110 selects the slave control units 120 in sequence, that is, performs SPI communication with the first slave control unit 120, the second slave control unit 120, the third slave control unit 120, etc. in sequence, so as to achieve coordinating all control units.

[0026] It should be noted that, since the master control unit 110 and each slave control unit 120 in the present application use SPI communication, any one of all the control units is set as the master control unit 110, and any one of the control units selected by the master control unit 110 using the chip select signal in the SPI communication corresponds to the slave control unit 120. That is, the master control unit 110 is arbitrarily selected from each control unit, and the slave control unit 120 is selected by the master control unit 110 according to the SPI communication.

[0027] In one embodiment, each control unit adopts a daisy chain mode and is connected by a cable to realize RS232 communication. Each control unit uses RS232 to send asynchronous communication data, thereby performing asynchronous communication. Since in RS232 communication, data is transmitted bit by bit at the sending and receiving ends, which is usually asynchronous, specifically, the sending end converts byte data into a string and transmits it through the TXD (transmit data) signal line; the receiving end receives these bits through the RXD (receive data) signal line and reorganizes them into original data. In order to ensure that each control unit determines that the asynchronous communication data currently transmitted through RS232 is its own data, the asynchronous communication data includes the flag data of the servo motor controlled by each control unit.

[0028] Please refer to Figure 2 In one embodiment, the shaft number information of the servo motor is used as the identification data of the servo motor in this application. Each control unit determines whether asynchronous communication data is received. If asynchronous communication data is received, it is determined according to the shaft number information that it is the shaft number information of the servo motor controlled in its own control unit. If so, the asynchronous communication data is parsed to perform corresponding actions and return response data; if not, the asynchronous communication data is forwarded to the next control unit for judgment.

[0029] In one embodiment, SPI is used for communication between the master control unit 110 and each slave control unit 120, and the data with high real-time requirements transmitted include waveform data, special instructions, hardware signals, etc.

[0030] It should be noted that the waveform data refers to the reference signal of the output signal (such as current, voltage or speed) of the multi-axis servo driver 100, such as the sine wave of the three-phase motor or the reference waveform of the space vector modulation (SVPWM), which is used to generate the PWM signal. These waveform data are transmitted between the control units to ensure the synchronous operation of multiple servo motors.

[0031] Special instructions refer to control commands that need to be shared or coordinated between multiple control units, such as synchronization instructions, mode switching instructions, and emergency stop instructions. Synchronization instructions are used to trigger the simultaneous start, stop, or change of mode of multiple axes. Multiple servo motors may operate in different modes (such as position control, speed control, or torque control), and other slave control units 120 need to be notified to switch modes through SPI communication. When the master control unit 110 detects a fault (such as limit triggering, current overload), an emergency stop instruction is immediately broadcast through SPI communication.

[0032] Hardware signals refer to sensor data or feedback signals that need to be transmitted in real time, such as encoder feedback, current / voltage sampling values, limit / safety signals, and temperature data. Encoder feedback means that each servo motor may be equipped with a rotary encoder to sample position or speed data in real time. The main control unit 110 needs to obtain the encoder data of all servo motors for global coordination. The current / voltage sampling values ​​are used to feedback current and voltage information in real time for closed-loop control and protection. Limit / safety signals refer to the limit trigger signals of each servo motor transmitted to the main control unit 110 via SPI communication for centralized processing. Temperature data means that if the temperature of the driver of a servo motor is too high, the main control unit 110 needs to be notified via SPI communication for protection processing.

[0033] In one embodiment, in order to ensure the accuracy of these data, the main control unit 110 needs to verify the feedback signal when obtaining the feedback signal including these data sent by the selected slave control unit 120. If the feedback signal is abnormal, the main control unit 110 sends a reset signal to the selected slave control unit 120 via RS232 to reset the SPI communication of the selected slave control unit 120.

[0034] It should be noted that if there is a serious anomaly in SPI communication (such as timing problems, bus conflicts), the module for SPI communication of the slave control unit 120 may not be able to receive data or respond to instructions normally. At this time, sending the reset signal again through SPI may fail. RS232 communication is independent of SPI communication and can reliably convey the reset signal to the slave control unit 120, avoiding the risk of SPI communication failing to reset.

[0035] In one embodiment, when checking the feedback signal, CRC check is used. CRC (Cyclic Redundancy Check) is an error detection technology used to detect whether an error occurs during data transmission or storage. The basic principle of CRC check is to calculate a check code through polynomial division and append the check code to the end of the data for verification.

[0036] In one embodiment, although SPI communication itself is a high-speed synchronous serial communication protocol, it can be used in combination with a variety of communication protocols to support different application requirements, such as Modbus, CAN communication, I2C and Ethernet protocols.

[0037] In one embodiment, after the communication between the master control unit 110 and the slave control unit 120 is completed, in order to ensure the synchronization of the control units controlling the servo motor, the master control unit 110 sends a control signal to any selected slave control unit 120 at the first cycle mark point of the output first PWM wave to coordinate the servo motor controlled by the selected slave control unit 120. The selected slave control unit 120 adjusts the second PWM wave corresponding to the selected slave control unit 120 in response to the control signal, thereby realizing synchronous coordinated control of the servo motor.

[0038] It should be noted that the control signal in the present application is a chip select signal, and the selected slave control unit 120 adjusts its own PWM wave in response to the obtained chip select signal sent by the master control unit 110. In order to ensure the synchronization of the PWM waves of each control unit, the master control unit 110 starts to communicate at a fixed time within a cycle of the PWM wave, that is, the chip select signal is pulled down at the first cycle mark point of the first PWM wave. When the selected slave control unit 120 obtains the chip select signal, the time difference between the moment of the chip select signal and the second cycle mark point in the selected slave control unit 120 is calculated. If the time difference is within the set value, it means that the PWM waves of the master control unit 110 and the slave control unit 120 are synchronized. If the time difference exceeds the set value, then the second PWM wave of the selected slave control unit 120 needs to be adjusted.

[0039] In one embodiment, the first cycle mark point of the first PWM wave and the second cycle mark point of the second PWM wave can be any waveform point on the PWM wave. For example, if the first cycle mark point is at the 1 / 3 waveform point of the cycle of the first PWM wave, then the second cycle mark point is also at the 1 / 3 waveform point of the cycle of the second PWM wave. However, for the convenience of engineering practice, the first cycle mark point and the second cycle mark point are respectively the zero-crossing point of the first PWM wave and the zero-crossing point of the second PWM wave.

[0040] Please refer to Figure 3In one embodiment, the master control unit 110 pulls down the chip select signal at the first cycle mark point of the first PWM wave, that is, the zero-crossing point of the first PWM wave, that is, sends the chip select signal to the selected slave control unit 120 at point T, and the second cycle mark point of the second PWM wave of the selected slave control unit 120 leads the first cycle mark point of the first PWM wave, that is, the zero-crossing point of the second PWM wave leads the zero-crossing point of the first PWM wave. Therefore, in order to ensure the synchronization of the first PWM wave and the second PWM wave, it is necessary to extend the cycle length of the second PWM wave until the difference between the zero-crossing point of the first PWM wave and the zero-crossing point of the second PWM wave is less than the set value.

[0041] It should be noted that the chip select signal sent by the master control unit 110 is sent in a loop. When the chip select signal is sent to the first slave control unit 120, it is sent to the second slave control unit 120, and the cycle is repeated. After the cycle is completed, the chip select signal is sent to the first slave control unit 120 again. Then, the selected slave control unit 120 can calculate the time difference between the first cycle mark point of the first PWM wave and the second cycle mark point of the second PWM wave each time the chip select signal is obtained, until the time difference is less than the set value. The adjustment value for the extension of the period of the second PWM wave can be set according to engineering practice. Figure 3 As a schematic diagram, in the third cycle 3T, the cycle of the second PWM wave is extended from T1 to T1', so that the first cycle mark point of the first PWM wave and the second cycle mark point of the second PWM wave are synchronized.

[0042] Please refer to Figure 4 In one embodiment, the second cycle mark point of the second PWM wave selected from the control unit 120 may also lag behind the first cycle mark point of the first PWM wave, that is, the zero-crossing point of the second PWM wave lags behind the zero-crossing point of the first PWM wave. Therefore, in order to ensure the synchronization of the first PWM wave and the second PWM wave, it is necessary to shorten the cycle length of the second PWM wave until the difference between the zero-crossing point of the first PWM wave and the zero-crossing point of the second PWM wave is less than the set value. The adjustment value for the extension of the cycle of the second PWM wave can be set according to engineering practice. Figure 4 As a schematic diagram, in the third period 3T, the period of the second PWM wave is extended from T2 to T2', and in the third period 3T, the first period mark point of the first PWM wave and the second period mark point of the second PWM wave are synchronized.

[0043] Please refer to Figure 5 In one embodiment, in order to calculate the time difference between the second cycle mark point and the first cycle mark point, a capture unit is provided in each control unit, and the chip select signal is expanded to be sent to the capture unit. The capture unit can be used to directly obtain the first cycle mark point of the first PWM wave, that is, Figure 3 and Figure 4 The cap point in is the first cycle mark point, and the selected slave control unit 120 knows the second cycle mark point of its own second PWM wave, so the time difference between the second cycle mark point and the first cycle mark point can be calculated.

[0044] It should be noted that the capture unit (CAP) is usually a peripheral module inside the control unit, which is part of the timer / counter unit and is specifically used to capture the edge event of the input signal. Since each slave control unit 120 obtains the first cycle mark point of the first PWM wave to adjust its own second PWM wave, the capture unit only needs to be set in each slave control unit 120. SPI communication activates the slave control unit 120 through the falling edge of the chip select signal and ends the communication through the rising edge. The capture unit can quickly and accurately detect the edge event of the chip select signal, thereby determining the time of the first cycle mark point.

[0045] In this way, the multi-axis servo driver 100 provided by the present application can solve the problem that multiple servo motors cannot be debugged at the same time, and the communication data in the entire communication process is divided into high real-time data and low real-time data, and transmitted respectively through SPI communication and RS232 communication, avoiding the blocking of low real-time data to high real-time data. In addition, the main control unit can obtain various data of other slave control units through SPI communication, and the host computer can obtain various data of all control units only with the main control unit. In addition, when the servo motors of each control unit are controlled, the chip select signal is pulled down at the cycle mark point to achieve synchronization of each servo motor.

[0046] Those skilled in the art will appreciate that all or part of the functions of the various methods in the above-mentioned embodiments can be implemented by hardware or by computer programs. When all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program can be stored in a computer-readable storage medium, and the storage medium can include: read-only memory, random access memory, disk, optical disk, hard disk, etc., and the program is executed by a computer to implement the above-mentioned functions. For example, the program is stored in the memory of the device, and when the program in the memory is executed by the processor, all or part of the above-mentioned functions can be implemented. In addition, when all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program can also be stored in a storage medium such as a server, another computer, disk, optical disk, flash disk or mobile hard disk, and can be downloaded or copied and saved in the memory of the local device, or the system of the local device is updated, and when the program in the memory is executed by the processor, all or part of the functions in the above-mentioned embodiments can be implemented.

[0047] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art, according to the concept of the present invention, some simple deductions, modifications or substitutions can be made.

Claims

1. A multi-axis servo driver for driving a servo motor, characterized in that: It includes a main control unit and at least one slave control unit, wherein the main control unit is used to connect to a host computer to perform joint debugging of the control units; The master control unit and each slave control unit are communicatively connected; The master control unit outputs a first PWM wave to control a set number of servo motors; each slave control unit outputs a second PWM wave to control the set number of servo motors; The master control unit sends a control signal to any selected slave control unit at a first cycle mark point of the first PWM wave to coordinate the servo motor controlled by the selected slave control unit; wherein the first cycle mark point is any waveform point of the first PWM wave; The selected slave control unit adjusts the second PWM wave in response to the control signal to achieve synchronous coordinated control of each servo motor.

2. The multi-axis servo driver according to claim 1, characterized in that: The waveform point of the selected second PWM wave output from the control unit corresponding to the first cycle mark point is the second cycle mark point; When the second cycle mark point is ahead of the first cycle mark point, the slave control unit extends the cycle of the second PWM wave until the time difference between the second cycle mark point and the first cycle mark point is less than a set value.

3. The multi-axis servo driver according to claim 1, characterized in that: The waveform point of the selected second PWM wave output from the control unit corresponding to the first cycle mark point is the second cycle mark point; When the second cycle mark point lags behind the first cycle mark point, the slave control unit shortens the cycle of the second PWM wave until the time difference between the second cycle mark point and the first cycle mark point is less than a set value.

4. The multi-axis servo driver according to claim 2 or 3, characterized in that: The first cycle mark point is a zero-crossing point of the first PWM wave, and the second cycle mark point is a zero-crossing point of the second PWM wave.

5. The multi-axis servo driver according to claim 4, characterized in that: Each control unit includes a capture unit, and the capture unit is used to calculate the time difference between the second cycle mark point and the first cycle mark point.

6. The multi-axis servo driver according to claim 1, characterized in that: The master control unit and the slave control unit communicate with each other through synchronous serial communication and asynchronous serial communication. The master control unit uses the synchronous serial communication to send a control signal to any selected slave control unit; each control unit uses the asynchronous serial communication to send asynchronous communication data to perform asynchronous communication.

7. The multi-axis servo driver according to claim 6, characterized in that: The asynchronous communication data includes the flag data of the servo motor controlled by each control unit; each control unit obtains the asynchronous communication data and determines whether the flag data is consistent with the servo motor controlled by each control unit. If it is consistent, the asynchronous communication data is parsed to perform asynchronous communication.

8. The multi-axis servo driver according to claim 7, characterized in that: The main control unit obtains the feedback signal sent by the selected slave control unit through the synchronous serial communication, and the main control unit verifies the feedback signal. When the feedback signal is abnormal, the main control unit sends a reset signal to the selected slave control unit through the asynchronous serial communication to reset the selected slave control unit.

9. The multi-axis servo driver according to claim 8, characterized in that: The synchronous serial communication is SPI communication, and the asynchronous serial communication is RS232 communication.

10. The multi-axis servo driver according to claim 9, characterized in that: The control units are connected in a daisy chain to perform RS232 communication.

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