Multi-axis servo control system

Abstract

The present application provides a multi-axis servo control system, comprising a plurality of motors and a plurality of drive control devices. The plurality of drive control devices are connected to each other through an external communication bus. Each of the drive control devices comprises a control unit and a plurality of drive units. The plurality of drive units and the control unit are connected in series through a plurality of local buses to form a serial communication loop capable of sequentially transmitting data. Each of the drive units is used to control at least one of the motors. The control unit receives a multi-axis position command through the external communication bus, and the drive units correspondingly receive the multi-axis command through the local buses to distributively control the motors.

Description

Technical Field

[0001] This invention relates to a multi-axis servo control system, and more particularly to a multi-axis servo control system with distributed control of position commands and current commands. Background Technology

[0002] Please see Figure 1 and Figure 2 As shown, these are schematic diagrams of the first and second types of existing multi-axis servo control systems, respectively. Figure 1 As shown, the first type used is a single independent servo driver controlling the rotation of a single-axis motor, meaning one servo driver controls the rotation of one motor, such as... Figure 1 As shown, this configuration uses three servo drives 100A paired with three corresponding motors 200A. In this type of application, the servo drives 100A are connected in pairs via a field bus 300A. Each servo drive 100A can receive control commands from a host controller (or host computer) to control its corresponding motor 200A. The field bus can be EtherCAT, CANOpen, PROFINET, etc., but is not limited to these. Each servo drive 100A includes at least a controller and a power module. The controller plans and controls the motor speed, and the power module provides the current output to the drive. However, in this type of control system, since each motor 200A is controlled by a corresponding servo drive 100A, synchronization is limited by the communication cycle of the field bus in multi-axis applications, resulting in poor synchronization.

[0003] like Figure 2 As shown, the second type uses a single independent servo driver to control multiple motors, such as... Figure 2 As shown, each servo driver 100A controls three motors 200A, but this is not limited to three. As long as the output current (power) supplied by the servo driver 100A is within the allowable range, the number of motors 200A that can maintain normal operation can be driven and controlled. Similarly, the servo drivers 100A are connected to each other via a communication bus 300A and receive control commands from the host controller via the communication bus 300A. However, due to the limitation of output current (power), the upper limit of the number of motors 200A or the rated output of the motors 200A is limited from the initial design of the servo driver 100A, thus its expandability and replaceability are relatively poor.

[0004] Therefore, how to design a multi-axis servo control system, especially a multi-axis servo control system with distributed control of position command and current command, to solve the problems and technical bottlenecks of the existing technology, is an important research topic for the inventors of this case. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-axis servo control system to solve the problems of the prior art.

[0006] To achieve the aforementioned objectives, the multi-axis servo control system proposed in this invention includes multiple motors and multiple drive control devices. The multiple drive control devices are interconnected via an external communication bus. Each drive control device includes a control unit and multiple drive units. The multiple drive units and the control unit are connected in series via multiple local buses to form a serial communication loop capable of sequentially transmitting data. Each drive unit is used to control at least one of the motors. The control unit receives multi-axis position commands via the external communication bus, and the drive units correspondingly receive multi-axis commands via the local buses, thereby enabling distributed control of the motors.

[0007] In one embodiment, the local bus is a high-speed bus; the local bus starts from an output terminal of the control unit, connects the drive units in series in sequence, and finally feeds back to an input terminal of the control unit to form a series communication loop that can transmit data in sequence.

[0008] In one embodiment, each drive unit includes a processor, and the control unit includes a processor; the serial communication loop includes the processor of the control unit, the output terminal of the control unit, an input terminal of each drive unit, the processor of each drive unit, an output terminal of each drive unit, the input terminal of the control unit, and the processor of the control unit.

[0009] In one embodiment, the control unit includes a command processor and a command synchronizer. The command synchronizer is connected to the command processor.

[0010] In one embodiment, the control unit includes a command generator, a command processor, and a command synchronizer. The command processor is connected to the command generator. The command synchronizer is connected to the command processor.

[0011] In one embodiment, the control unit is a slave controller that provides a slave operation mode for controlling the drive units, which are also drive control devices.

[0012] In one embodiment, the control unit is a master station controller, providing a master station operation mode for controlling the drive units, which are also drive control devices, as well as the control unit and drive units of other drive control devices. The drive unit includes a current loop unit. The current loop unit receives a current command and a current value, and compares the current command and the current value to generate a current control signal.

[0013] In one embodiment, the drive unit further includes a command processing unit and a command synchronization unit. The command processing unit receives the current command and processes it. The command synchronization unit, connected to the command processing unit, receives the processed current command and synchronizes it to provide it to the current loop unit.

[0014] In one embodiment, the driving unit further includes a current processing unit. The current processing unit receives the sampled current value and processes the current value to provide it to the current loop unit.

[0015] In one embodiment, the drive unit further includes a feedback processing unit. The feedback processing unit receives a plurality of feedback commands and performs communication packet processing on the feedback commands to provide output to the local bus.

[0016] The proposed multi-axis servo control system achieves the following technical benefits: 1. Through distributed computation achieved by the drive unit processing and controlling current (torque) commands and the control unit processing and controlling position (speed) commands, the computational load of the control unit can be significantly reduced (since the processing and control of current (torque) commands are executed through the drive unit), allowing for the selection of a lower-cost, lower-level controller, and improving the expandability and replaceability of the drive control device; 2. The high-speed local bus achieves a complete communication transmission loop with series feedback through backplane wiring, avoiding data distortion and attenuation; 3. Through the detailed computation of the control unit, the command data is subdivided and then provided to the drive unit controlling each axis motor, enabling the drive unit to precisely control each axis motor; 4. The control unit can operate in slave mode and master mode, thus improving the flexibility and versatility of the control unit.

[0017] To gain a deeper understanding of the techniques, means, and effects employed by this invention to achieve its intended purpose, please refer to the following detailed description and accompanying drawings. It is believed that the purpose, features, and characteristics of this invention can be understood in a thorough and specific manner from these drawings. However, the drawings are provided for reference and illustration only and are not intended to limit the scope of this invention. Attached Figure Description

[0018] Figure 1This is a schematic diagram of the architecture of the first type of existing multi-axis servo control system.

[0019] Figure 2 This is a schematic diagram of the architecture of the second type of existing multi-axis servo control system.

[0020] Figure 3 This is a schematic diagram of the architecture of the multi-axis servo control system of the present invention;

[0021] Figure 4 : This is a schematic diagram illustrating the design of the high-speed local bus of this invention;

[0022] Figure 5 : This is a schematic diagram of the control method of the control unit of the present invention;

[0023] Figure 6 : This is a schematic diagram of the control method of the drive unit of the present invention;

[0024] Figure 7 : This is a schematic diagram of the control unit of the present invention as a slave station;

[0025] Figure 8 : This is a schematic diagram of the control unit of the present invention as the master station.

[0026] Explanation of icon numbers:

[0027] 100: Drive control device

[0028] 200: Motor

[0029] 300: Communication Bus

[0030] 400: Local Bus

[0031] 10: Control Unit

[0032] 20: Drive Unit

[0033] 101: Command Generator

[0034] 102: Command Processor

[0035] 104: Command Synchronizer

[0036] 100A: Servo Driver

[0037] 200A: Motor

[0038] 300A: Communication Bus Detailed Implementation

[0039] The technical content and detailed description of the present invention are explained below with reference to the accompanying drawings.

[0040] Please see Figure 3The diagram shown illustrates the architecture of the multi-axis servo control system of the present invention. The multi-axis servo control system includes multiple motors 200 and multiple drive control devices 100. The multiple drive control devices 100 are interconnected via an external communication bus (field bus) 300. Figure 3 As shown, two sets of drive control devices 100 are used as an example, but the present invention is not limited thereto. In this invention, a multi-axis motor 200 is used, but it is not limited to the fields of mechanical automation operations and robotic arm operations such as conveying and handling devices, pick and place devices, surface mount technology (SMT), positioning devices for vision inspection, spot welding and reciprocating measurement, etc.

[0041] Each drive control device 100 includes a control unit 10 and a plurality of drive units 20. The plurality of drive units 20 are connected in series with each other, and with the control unit 10, via a plurality of local buses 400 to form a serial communication loop capable of sequentially transmitting data. Each drive unit 20 is used to control at least one of the motors 200; however, the number and configuration of the motors 200 controlled by each drive unit 20 are not necessarily sequential. Figure 3 The situation shown is a limitation.

[0042] The control unit 10 receives multi-axis position commands (or multi-axis speed commands) through the external communication bus 300, and the drive units 20 receive multi-axis commands correspondingly through the local bus 400, so as to control the motors 200 in a distributed manner. Details will be provided later.

[0043] like Figure 3 As shown, this invention provides a multi-axis servo control system (servo drive design for multi-axis motor control), which decentralizes traditional multi-axis motor control, consisting of a control unit 10, a drive unit (or servo unit, servo drive unit) 20, a local bus 400, and a motor 200, each independently composed of a single external communication bus 300. The characteristics of this control system architecture are:

[0044] 1. The high-speed local bus has 400 input and output connections, which will be described in detail later.

[0045] 2. The control unit 10 is responsible for the synchronous control of the position and speed of each axis motor 200 and the motion process of each axis, which will be described in detail later.

[0046] 3. The drive unit 20 is responsible for the current control, current sampling, and position feedback of the motor 200. One drive unit 20 controls more than one motor 200; therefore, by simply replacing it with a drive unit 20 that provides greater output power, it can drive and control more or greater rated power motors 200 without affecting the operation of the whole machine. Therefore, it has good expandability and replaceability.

[0047] 4. The control unit 10 can function as both a master and a slave, providing command control for each axis motor 200. In master mode, it can actively control other servo drives (i.e., drive control devices 100) and multiple motors 200 connected to its own servo drives via the external communication bus 300. In slave mode, it controls the multiple motors 200 connected to its own servo drives and passively receives commands from the external bus, as will be detailed later.

[0048] Please see Figure 4 The diagram shows a schematic of the high-speed local bus design of this invention. The high-speed local bus 400 of this invention, combined with hardware design (e.g., implemented via backplane wiring in this embodiment), employs a series feedback method (the local bus 400 within the left drive control device 100 is an extension of the local bus 400 within the right drive control device 100). Starting with the control unit 10, data is transmitted to the input terminal in (or input module in) of the first serial drive unit 20. The received data is processed by the processor 402 and transmitted to the input terminal in of the second serial drive unit 20 via the output terminal out (or output module out). This process continues sequentially to the input terminal in of the last serial drive unit 20. Finally, the data is output from the output terminal out of the last serial drive unit 20 to the other input terminal in of the previous drive unit 20, returning sequentially to the other input terminal of the control unit 10, thus forming a complete communication transmission loop. Therefore, by using a series feedback method for data communication transmission, data distortion and attenuation can be avoided.

[0049] Please see Figure 5The diagram illustrates the control method of the control unit of the present invention. The control unit 10 receives multi-axis command data (commands for the first axis, the second axis, ..., the Nth axis) transmitted via the external communication bus 300. This multi-axis command data is provided by the host controller and includes position, speed, torque, etc. In this embodiment, the control unit 10 includes a command processor 102 and a command synchronizer 104. After receiving the multi-axis command data, the control unit 10 processes the data using the command processor 102, including command smoothing and command interpolation. Then, the processed command data is synchronized by the command synchronizer 104 and transmitted to the first drive unit 20 via the high-speed local bus 400. Command data for each drive unit 20 is then transmitted sequentially via the local bus 400, finally returning the command data to the control unit 10. The control unit 10 then processes the status information of each axis and sends the processed information back to the communication bus 300. In other words, the timing schedule for controlling each axis motor 200 is executed by the control unit 10. Therefore, the multi-axis command data provided by the upper-level controller is refined through the command processor 102 and command synchronizer 104 of the control unit 10, subdividing command data at the second or millisecond (ms) level into commands at the microsecond (µs) or even nanosecond (ns) level, and provided to the drive unit 20 controlling each axis motor 200, enabling the drive unit 20 to precisely control each axis motor 200. In this embodiment, the control unit 10 only needs to process the command data, while the current control of each axis motor 200 is handled by its corresponding drive unit 20, achieving distributed computing efficiency.

[0050] It is worth mentioning that the control unit 10 has position command control and current command control, where the position command corresponds to the speed command and the current command corresponds to the torque command. In existing conventional control mechanisms, position (speed) command control and current (torque) command control are usually processed by the same processor or controller. However, in this invention, the processing and control of the current (torque) command is executed by the drive unit 20, while the processing and control of the position (speed) command is executed by the control unit 10. In other words, due to the modularity of this invention, the current (torque) command and the position (speed) command can be executed by different processors or controllers (i.e., drive unit 20 and control unit 10). This not only significantly reduces the computational load of the control unit 10 (since the processing and control of the current (torque) command is executed by drive unit 20), allowing for the selection of a lower-cost, lower-level controller, but also improves the expandability and replaceability of the drive control device 100.

[0051] Please see Figure 6The diagram illustrates the control method of the drive unit of the present invention. In one embodiment, the drive unit 20 can perform current loop control via a control chip. The drive unit 20 of the present invention includes a current sampling unit 21, a current processing unit 22, a command processing unit 23, a command synchronization unit 24, a current loop unit 25, a pulse width modulation (PWM) unit 26, and a feedback processing unit 27. The current sampling unit 21 receives the current feedback signal and samples it, for example, using Delta-Sigma (Δ-Σ) modulation. The current processing unit 22 receives the sampled current feedback signal and processes it. The command processing unit 23 receives command data input from the local bus 400 and provides local high-speed command data processing. The command synchronization unit 24 provides a command synchronization timing mechanism to synchronize the command data. The current loop unit 25 receives the synchronized command data provided by the command synchronization unit 24 and the feedback current information provided by the current processing unit 22 to perform current loop control. The PWM unit 26 generates a control PWM signal output based on the current loop control of the current loop unit 25, thereby controlling the actual current of the motor 200. The feedback processing unit 27 is used to receive encoder feedback, end optical ruler feedback, and pressure (force) sensor feedback for encoder communication packet processing.

[0052] Specifically, the drive unit 20 receives command data from the control unit 10 and performs position control loop, speed control loop, and encoder position processing for the motor 200. The command data includes, but is not limited to, current commands, electrical angles, speed, and communication delay compensation amounts, and its transmission and reception are equipped with error detection and correction mechanisms.

[0053] Because each time the drive unit 20 is interrupted, it will transmit the current command, electrical angle and communication delay compensation to the drive units 20 of other axes, the command synchronization unit 24 is required to perform a time synchronization mechanism on each axis drive unit 20 to ensure that the encoder sampling, current feedback sampling and PWM activation time are synchronized between multiple axes.

[0054] By sampling current feedback, the feedback data is decoded by the current processing unit 22 and then, with the help of a self-designed sync filter architecture, the current feedback information is transmitted back to the current loop for control. The current sampling method includes, but is not limited to, Delta-Sigma (Δ-Σ), ADC, etc.

[0055] The current loop control of current loop unit 25 includes PI (differential-integral) control, dq-axis (direct-to-quadrature) current conversion, SVPWM control, voltage decoupling, and dead time compensation. The current loop control of current loop unit 25 uses the comparison value calculated by SVPWM control to realize the six-bridge control of IGBT through PWM unit 26.

[0056] Feedback processing unit 27 receives encoder feedback signals, end encoder signals, and pressure sensor signals. These communication formats all include ECC (error correcting code) functionality. After decrypting the communication packets, feedback processing unit 27 transmits the data back to control unit 10 via local bus 400 communication, thereby performing full closed-loop control of position and torque.

[0057] In this invention, the control unit 10 can operate in two modes: slave mode and master mode. Please refer to [link / reference]. Figure 7 The diagram illustrates the control unit 10 as a slave station. When the control unit 10 acts as a slave station, multi-axis command data is provided by a host controller, a programmable logic controller (PLC), or a motion controller. Therefore, the drive unit 20 receives this multi-axis command data and can further drive and control each axis motor 200. In slave mode, the control unit 10 passively receives the multi-axis command data provided by the host controller and refines the command data through the command processor 102 and command synchronizer 104, enabling the drive unit 20 to precisely control each axis motor 200.

[0058] Figure 7 The master station device shown on the right (which can be a third-party upper-level master station controller) plans the commands for each axis and transmits them to each slave device via the communication bus 300. Relevant slave information is also transmitted back to the third-party upper-level master station controller via the communication bus 300. For each slave device, each slave device provides multi-axis command information to the third-party slave device, allowing the third-party slave device to control each axis motor 200 within its own device.

[0059] Please see Figure 8The diagram illustrates the control unit of this invention acting as a master station. In master mode, the control unit 10 functions as a master controller, meaning that in addition to controlling the local drive unit 20, the control unit 10 can also generate command information via the command generator 101 and transmit it to other slave devices via the communication bus 300, thereby controlling the other slave devices. In other words, when the control unit 10 itself can act as a master controller, a third-party upper-level master controller is not required. Therefore, the planning, interpolation, and synchronization processing of command data for each axis can all be completed in the control unit 10. In one embodiment, through program programming, users can be provided with programs to control external or internal axes. By downloading the programmed program to the control unit 10, the control unit 10, operating in master mode, controls the motors 200 of the external and / or internal axes according to the programmed program.

[0060] In summary, the present invention has the following features and advantages:

[0061] 1. The distributed operation achieved by the drive unit 20 in processing and controlling the current (torque) command and the control unit 10 in processing and controlling the position (speed) command can not only significantly reduce the computational load of the control unit 10 (since the processing and control of the current (torque) command is executed through the drive unit 20), but also allows for the selection of a controller with lower cost and lower function, and improves the expandability and replaceability of the drive control device 100.

[0062] 2. The high-speed local bus achieves a complete communication transmission loop through series feedback via backplane routing, which avoids data distortion and attenuation.

[0063] 3. Through the detailed calculation of the control unit 10, the command data is subdivided and then provided to the drive unit 20 that controls each axis motor 200, so that the drive unit 20 can precisely control each axis motor 200.

[0064] 4. The control unit 10 can be operated in slave mode and master mode, thus increasing the flexibility and versatility of the use of the control unit 10.

[0065] The above description is merely a detailed description and accompanying drawings of preferred embodiments of the present invention. The features of the present invention are not limited thereto and are not intended to limit the present invention. The entire scope of the present invention should be determined by the following claims. All embodiments that conform to the spirit of the claims of the present invention and similar variations thereof should be included in the scope of the present invention. Any variations or modifications that can be easily conceived by those skilled in the art within the field of the present invention can be covered by the following patent scope.

Claims

1. A multi-axis servo control system, comprising: Multiple motors; and Multiple drive control devices are interconnected via an external communication bus, and each drive control device includes: Control unit; and Multiple drive units are connected in series with the control unit via multiple local buses to form a serial communication loop that can transmit data sequentially; each drive unit is used to control at least one of the multiple motors. in, The control unit receives multi-axis position commands through the external communication bus, and the multiple drive units receive multi-axis commands correspondingly through the local bus to control the multiple motors in a distributed manner. The control unit is a slave controller, which provides a slave operation mode to control the plurality of drive units that are also the drive control device; Alternatively, the control unit is a master station controller, providing a master station operation mode to control the multiple drive units that are also the drive control device, as well as the control unit and the multiple drive units of other drive control devices; The local bus mentioned therein is a high-speed bus; The local bus starts at the output of the control unit, connects the multiple drive units in series, and ends at the input of the control unit, forming a series communication loop that can transmit data in sequence.

2. The multi-axis servo control system according to claim 1, wherein each of the drive units includes a processor, and the control unit includes a processor; The serial communication loop includes the processor of the control unit, the output terminal of the control unit, the input terminal of each of the drive units, the processor of each of the drive units, the output terminal of each of the drive units, the input terminal of the control unit, and the processor of the control unit.

3. The multi-axis servo control system according to claim 1, wherein when the control unit is a slave controller, the control unit comprises: Command processor; and A command synchronizer, connected to the command processor.

4. The multi-axis servo control system according to claim 1, wherein when the control unit is the master station controller, the control unit comprises: Command generator; Command processor, connected to the command generator; and A command synchronizer, connected to the command processor.

5. The multi-axis servo control system according to claim 1, wherein the drive unit comprises: The current loop unit receives a current command and a current value, and compares the current command and the current value to generate a current control signal.

6. The multi-axis servo control system according to claim 5, wherein the drive unit further comprises: The command processing unit receives the current command and processes the current command; and The command synchronization unit is connected to the command processing unit, receives the processed current command, and synchronizes the current command to provide it to the current loop unit.

7. The multi-axis servo control system according to claim 5, wherein the drive unit further comprises: The current processing unit receives the sampled current value and processes the current value to provide it to the current loop unit.

8. The multi-axis servo control system according to claim 5, wherein the drive unit further comprises: The feedback processing unit receives multiple feedback commands and performs communication packet processing on the multiple feedback commands to provide output to the local bus.

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