Shu Zhibing (Institute of Motion Control, Nanjing University of Technology, 210009) Abstract: Servo systems are a crucial component of electromechanical products. With the advancement of computer technology, AC servo systems, after extensive application, are developing towards networked control. Based on research into the structure of a field networked control system based on industrial Ethernet, this paper introduces the architecture of an embedded motion controller, summarizes the design and implementation scheme of a networked servo motion control system, and finally introduces the embedded motion controller, control language, and compilation system. Keywords : Embedded controller, AC servo, industrial Ethernet, motion control Currently, commonly used motion controller architectures have many shortcomings, such as excessive size, closed structure, and lack of support for network communication, leading to isolation between motion controllers and significant resource waste during system upgrades. The development of information technologies such as ISP online programmable technology, Internet technology, and embedded real-time operating systems has made modular, networked, embedded, and reconfigurable open intelligent motion controllers an important development direction in the current motion control field. Siemens' Horst Kohlbert's prediction that "embedded Ethernet field devices and embedded Internet servers" will soon become a reality. German company Jetter AG, British company Trio, and Israeli company ELMO have successively released embedded intelligent motion controllers, announcing the arrival of the "network is the controller" era. The characteristics of network servo are: (1) similar to the Internet structure, real-time data transmission does not require programming, and there is no need to consider the network hierarchy; (2) for users, there is only one set of data and one program, all data only needs to be expressed once in the network, and both the program and data can be reused, with the network playing the role of a real server; (3) it can be connected to the Internet to realize global networking of the entire factory; (4) Ethernet is both a system bus connecting various intelligent modules and a field bus connecting field devices. I. Embedded Motion Controller Architecture In foreign countries, factory automation (FA) engineering technology based on industrial LAN technology has made great progress in the last ten years and has shown a good development trend. To adapt to this development trend, the latest servo systems are equipped with standard serial communication interfaces (such as RS-232C or RS-422 interfaces) and dedicated LAN interfaces. The setting of these interfaces significantly enhances the interconnection capability between the servo unit and other control devices. In a motion controller, the most critical part is the control signal generation module, which requires frequent improvement and upgrades. Hardware reconfiguration technology allows the module requiring upgrades to be separated from the system and reconfigured online, thus completing the upgrade operation. In a PC-based motion controller architecture, communication is achieved through a gateway, solving the network communication problem. [IMG=Figure 1 Embedded Motion Controller Architecture]/uploadpic/THESIS/2007/11/2007111310305581748N.jpg[/IMG] Figure 1 shows that the motion controller is divided into two main parts: a network communication module and a motion control module. The network communication module is directly connected to the Internet and obtains control commands from the console according to a pre-defined communication protocol, then passes the commands to the motion control module. The motion control module is directly connected to the motor driver. After analyzing and judging the commands, it generates corresponding motor control signals and transmits them to the motor. Additionally, the result of command execution is returned to the network communication module, which then returns it to the console via the network. II. System Integration of Networked Servo Control 1. System Integration of Network Servo Systems Based on Independent Digital Motion Controllers A network servo system based on an independent digital motion controller (DMC) allows for motion control without relying on a computer or industrial control computer for communication and operation. The control program and the program to be run are directly downloaded to the FLASHROM built into the motion controller itself. The program starts running when triggered by an external trigger signal from the device. The following is a structural block diagram of the system integration of a TRIO-based network servo system: [IMG=Figure 2 Network Servo Structure Based on Multi-Axis Motion Controller]/uploadpic/THESIS/2007/11/2007111310313274180O.jpg[/IMG] Figure 2 Network Servo Structure Based on Multi-Axis Motion Controller In Figure 2, the host computer gains support for the Ethernet bus by connecting a network communication adapter card (100M) supporting the TCP/IP protocol. It is responsible for monitoring and managing the operation and working status of the entire system. After the host computer completes task planning, third-party software develops the user application program and transmits the generated program instructions to the embedded multi-axis motion controller via Ethernet according to the TCP/IP protocol. [IMG=Figure 3 Network Servo Motion Control System Architecture]/uploadpic/THESIS/2007/11/2007111310373451088D.jpg[/IMG] Figure 3 Network Servo Motion Control System Architecture In the network servo motion control system shown in Figure 3, the controller continuously translates and generates updated position commands (motion curves), which are then transmitted to the drivers via the fieldbus. After the bus nodes interpret the commands, they are converted into digital pulse signals to control the AC servo motors, thus completing the positioning required by the command. In a multi-axis system, one controller can control multiple motor drivers. The servo motor is the main actuator, performing the specific actions. The motion controller in Figure 3 can be an independent motion controller such as the MC206, MC224, or Euro205 from Trio Corporation in the UK. These controllers use the latest industrial-grade 32-bit, 120MHz-150MHz microprocessor technology, integrating the latest control theory and network control technology. Different controllers can be selected to control 1-24 axes. A servo motor can be controlled using a closed-loop control system with analog voltage outputs of 0 to +/-10V and encoder feedback. It can also control stepper motors, frequency converters, pneumatic servos, hydraulic servos, or any combination thereof. Trio has programmable I/O and can be expanded as needed (up to 512 I/Os). 2. Open control systems based on touchscreens and independent digital controllers: In some assembly line production equipment or batch processing equipment, it is necessary to modify certain processing data or monitor equipment operating data. For example, in cutting equipment, the cutting length needs to be modified according to different processes and products. Because touchscreens are convenient to operate and inexpensive (much cheaper than industrial PCs), they are used to modify data or display the data that needs to be monitored, such as processing speed and output. Independent digital motion control controllers such as Trio and ELMO have communication ports with Modbus and Ethernet protocols, allowing direct data exchange with various touchscreens, such as HITECH, Schneider, and EasyView. Its control principle block diagram is the same as that of an open CNC system integration based on a stand-alone digital motion controller, except that a touch screen is connected to the communication port of the digital motion controller. As shown in Figure 3, the distributed intelligent control system based on the touch screen consists of an industrial touch screen, a multi-axis motion controller, AC servo drives, and AC servo motors. This paper uses the PWS6600 series from Quanyi Company. Its feature is that the multi-axis motion controller is connected to the industrial touch screen via Modbus or Ethernet, the AC servo drives are connected to each other and to the multi-axis motion controller via fieldbus, and the output of the AC servo drive is connected to the AC servo motor. [IMG=Figure 4 Distributed Servo System Architecture]/uploadpic/THESIS/2007/11/2007111310382833784B.jpg[/IMG] Figure 4 Distributed Servo System Architecture The PWS6600 (hereinafter referred to as PWS) panel adopts a high-resolution STN LCD display module and meets the IP65/NEMA 4 waterproof and dustproof design level. It can store 255 images. Each image can be composed of text, graphics and specified internal system data. Designers only need to edit various images to display device status, operation instructions, parameter settings, action flow, statistical data, alarm signals, simple reports, etc. 3. System Integration of Open CNC Systems Based on PC + Digital Motion Control Card: For some equipment, due to the load of the controlled engineering and processed parts, the previous two system integration methods cannot meet the requirements of the equipment and processing technology. It is necessary to combine a computer with a digital motion controller, using dedicated control or dynamic link libraries of the array motion controller, and secondary development using high-level languages ​​such as VB and VC to create a dedicated or general-purpose control system to control the motion process of the equipment. Trio's PCI208 product is a PC-based digital motion control card using the PCI bus. This control card adopts the latest industrial-grade 32-bit floating-point 50MHz DSP microprocessor technology, improving computing speed and processing power. It integrates the latest control theory and network control technology, and can control 2 to 8 axes, including servo motors, stepper motors, frequency converters, pneumatic/hydraulic servo cylinders, or any combination thereof. In addition, it has 20 input points and 10 output points, as well as 2 CAN bus expansion ports, which can expand I/O and 16-bit analog input voltage modules via the CAN bus. III. Dedicated Control Languages ​​and Compilation Systems for Motion Controllers Motion control languages ​​are the primary means of communication between human control intentions and the controller. Programs written in motion control languages ​​must be compiled or interpreted for the motion controller to execute. Therefore, the motion control language and its compiler or interpreter directly affect the ease of use, the strength of the motion controller's functions, and the speed of its response. High-level motion control languages ​​are still rarely studied in China. Foreign motion control languages ​​generally adopt a high-level language format and then add instructions suitable for motion control for expansion. This article mainly introduces the ELMO-like VC language ELMO Studio and the TRIO-like VB language trioBASIC. Motion control languages ​​such as ELMO Studio and trioBASIC use high-level languages, with concise, easy-to-understand, and easy-to-remember instructions, simple programming, and basic PLC and motion control functions. The implementation of PLC and motion control functions uses a unified programming language, simplifying program writing. Languages ​​like ELMO Studio and trioBASIC use a host computer compiler to analyze the source program's lexical, syntactic, and semantic aspects. The compiler then generates intermediate code, which is downloaded to the embedded motion controller (lower-level device) for interpretation. The lower-level interpreter uses a loop structure to read and interpret the motion control program downloaded to the motion controller's user program area, thus achieving motion control and PLC control. ELMO Studio (a VC-like language) and trioBASIC (a VB-like language) are subsets of VC and VB respectively, with corresponding control instructions extended for motion control and PLC logic control. They both support multiple data structures, including integer, floating-point, and Boolean types. The overall program structure consists of functions, with execution starting from the main function. Control structures include loops (for and while statements), selection branches (if statements), and unconditional jumps. Supported operations include arithmetic, logical, and relational operations. IV. Embedded Servo Motion Control Systems and SOPC Technology Currently, most embedded systems utilize devices containing ARM or microcontroller processor cores. While these systems offer powerful functionality, to achieve greater flexibility, completeness, and adaptability to a wider range of tasks, numerous interface devices are typically required to form a complete application system. These include, in addition to standard SRAM, DRAM, and Flash memory, network communication interfaces, serial communication interfaces, USB interfaces, VGA interfaces, PS/2 interfaces, or other dedicated interfaces. This increases the overall system size and power consumption, while reducing reliability. The emergence of Programmable On-Chip (SOPC) technology effectively solves these problems. First proposed by Altrear in 2000, SOPC is a System-on-a-Chip (SoC) based on FPGA solutions. Compared to ASIC-based SoC solutions, SOPC systems and their development technologies offer more unique features, and there are several ways to construct an SOPC. V. SOPC Systems Based on Embedded IP Soft Cores in FPGAs Currently, the most representative soft-core processors are Altera's Nios and Nios II cores, and Xilinx's MicroBlaze core. The Nios system, in particular, is a user-configurable and buildable 32-bit/16-bit instruction set and data channel embedded microprocessor IP core. It uses an Avalon bus architecture communication interface and features enhanced memory, debugging, and software functions; it also includes a JTAG-based on-chip device (OCI) core developed by First Silicon Solutions (FS2). Furthermore, the user-editable Nios core based on the Quartus II platform contains many configurable interface module cores, including: a configurable cache module, an RS232 communication port, an SDRAM controller, a standard Ethernet protocol interface, DMA, timers, and coprocessors. Before embedding it into an FPGA, users can use Quartus II and SOPC Builder to build the Nios and its peripheral systems according to design requirements, ensuring that the embedded system fully meets the user's system design requirements in terms of hardware structure, functional characteristics, and resource consumption. Of particular note is that, through Matlab and DSP Builder, or directly using hardware description languages ​​such as VHDL, users can design various accelerators for Nios embedded processors and add them to the Nios instruction set as instructions, thus becoming an interface device for the Nios system and integrating it with the entire on-chip embedded system. For example, users can build their own DSP processor system freely according to the specific requirements of the design project, without being limited to the limited models of DSP processors already on the market from other DSP companies. VI. SOPC System Based on HardCopy Technology HardCopy technology is a brand-new SOC-level ASIC design solution. First, the system model is successfully implemented on a HardCopy FPGA using Quartus II, and then it helps designers seamlessly migrate programmable solutions to low-cost ASIC implementations. In this way, HardCopy devices combine the flexibility of high-capacity FPGAs with the market advantages of ASICs, avoiding the difficulties of directly designing ASICs. From prototyping to product manufacturing, the design from FPGAs can be easily ported to HardCopy devices, achieving the goal of reducing costs and accelerating time-to-market. HardCopy ASICs are built directly on top of the Altera PLD architecture, employing a "sea of ​​logic cells" core for efficient area utilization. Essentially, HardCopy devices are precise replicas of FPGAs, eliminating programmability, dedicated configurations, and the use of metal interconnects for wiring. This results in a smaller silicon area, lower cost, and improved timing characteristics. VII. Conclusion The emergence of SOPC (Single-on-Chip) technology has enabled motion controllers to be reduced to the size of a single integrated circuit chip, which can be embedded into the control system of the motor it controls. This has led to modular, networked, embedded, and reconfigurable open intelligent motion controllers. Simultaneously, SOPC technology simplifies motion control programming, reduces the complexity of maintenance and debugging, and makes the system more stable and reliable. The 21st century is a new century, and it will undoubtedly be a century of rapid development in various science and technology. With the rapid development of materials technology, power electronics technology, control theory technology, computer technology, and microelectronics technology, as well as the gradual improvement of motor manufacturing processes, and the continuous upgrading of the manufacturing industry and the rapid development of "flexible manufacturing technology," servo drive technology, one of the core technologies of "flexible processing and manufacturing technology," will undoubtedly usher in another great development opportunity. (Proceedings of the 2nd Servo and Motion Control Forum and the 3rd Servo and Motion Control Forum)