Abstract This paper analyzes the characteristics and message structure of DeviceNet network. Through the study of peer I/O communication principles, a design scheme for a multi-motor synchronous control system based on DeviceNet network and frequency converter speed regulation is proposed, and the hardware and software implementation is given. Keywords DeviceNet, frequency converter, peer I/O , multi-motor synchronization I. Introduction In recent years, AC speed regulation has developed rapidly, and frequency converter speed regulation control systems have been widely used in various industries such as machinery, metallurgy, and chemical industry. As the core control component of the frequency converter speed regulation system, the frequency converter initially worked as a single unit. However, various large and medium-sized automated production lines now require complex control systems such as synchronous control and proportional control composed of multiple frequency converters, which must coordinate with each other to form a continuous production line speed regulation control system. This paper designs a new system for centralized monitoring and control of multi-motor distributed drive mechanism based on DeviceNet network, realizing synchronous and proportional control of multiple motors with minimal hardware equipment and simple wiring connections. Compared to the previous synchronous control method that involved setting operating parameters via a PLC and then sending speed commands to the frequency converter via a D/A conversion module (0-10VDC or 4-20mA), this method significantly reduces system costs, increases signal transmission distance, and enhances anti-interference capabilities, making it particularly suitable for long-distance, multi-motor control systems. II. System Design Using DeviceNet for integrated motor control offers several advantages, such as: ① Support for hot-swapping of devices, allowing for live replacement of network nodes and online modification of network configurations, facilitating system expansion and upgrades. ② Device installation on the network is more cost-effective than traditional I/O cabling, especially when devices are distributed over a distance of several hundred meters, further reducing installation costs. ③ RSNetwork for DeviceNet allows for convenient configuration, testing, and management of network devices. The network devices display their operating status graphically, providing a clear overview. At present, many network adapters of frequency converters on DeviceNet support the transmission of peer I/O connection messages, such as 20-comm-D (PowerFlex series frequency converter), 1203-GU6 (1305, 1336 series frequency converter), and 1336-GM6 built-in adapter (1336 series frequency converter). The multi-motor control system designed in this paper uses peer I/O messages for data transmission between the master and slave adapters of the frequency converter [1]. The system realizes the synchronous start-stop, steering, jogging, proportional following and other control requirements of multiple frequency converters through master-slave communication with one frequency converter as the master station. [align=center][IMG=Multi-motor synchronous control system based on DeviceNet network]/uploadpic/THESIS/2008/1/2008012816274111501I.jpg[/IMG][/align] The system hardware structure is shown in Figure 1. PowerFlex 70 frequency converter is used to control the operation of AC motor. The PowerFlex 70 inverter has 5 serial ports, each corresponding to a different communication device. The inverter can be directly connected to the device network via the DPI port and the connected 20-COMM-D device network adapter [2]. The PC configures, writes software and monitors the DeviceNet network online through the external device network adapter 20-COMM-D. Master adapter: [IMG=Multi-motor synchronous control system based on DeviceNet network]/uploadpic/THESIS/2008/1/2008012816274959610A.jpg[/IMG] Slave adapter: [IMG=Multi-motor synchronous control system based on DeviceNet network]/uploadpic/THESIS/2008/1/200801281627566311521G.jpg[/IMG][align=left][/align] The parameters of the master and slave inverters and adapters are set using DriveExplorer software, as shown in Figure 2. [IMG=Multi-motor Synchronous Control System Based on DeviceNet Network]/uploadpic/THESIS/2008/1/2008012816280814588P.jpg[/IMG] III. Communication Implementation After the master-slave adapters are initialized, the field control requirements can be met by setting the parameters of the master and slave frequency converters. For example, the control logic value of the master frequency converter can be sent out through data link A1, and the speed reference value can be sent out through data link A2. Multiple master and slave frequency converters can be started, stopped, reversed, and jogged simultaneously through the human-machine interface of the master frequency converter. By adjusting the speed reference ratio of the master and slave frequency converters, the running speed of the slave frequency converter relative to the master frequency converter can be adjusted, so that the slave motor follows the master motor at a certain speed ratio. Its online speed adjustability is particularly suitable for motors in the entire line to run at speeds different from the master equipment. Each motor can also independently adjust its parameters according to control requirements. Similarly, other parameters of the master inverter, such as acceleration and deceleration times, can be transmitted via data link B, thereby enabling more precise control of the slave inverter's following performance. The connection and data exchange between the master and slave inverters are shown in Figure 3. [IMG=Multi-motor Synchronous Control System Based on DeviceNet Network]/uploadpic/THESIS/2008/1/20080128162820966230E.jpg[/IMG] IV. Conclusion This paper proposes a multi-motor synchronous control system based on DeviceNet network and using variable frequency speed regulation. It achieves various control requirements, such as synchronous start/stop, steering, jogging, and proportional following, by using one inverter as the master station and controlling multiple other inverters through master-slave communication. Experiments show that the system operates reliably, and the following motor accurately and synchronously follows the traction motor speed according to the set ratio based on process requirements. The system has a simple structure, low cost, and convenient control. Furthermore, the system has scalability and great flexibility; power-matching inverters can be selected according to the actual site conditions to form single-master or multi-master systems to meet different control requirements. References: [1] DeviceNet selection guide. Rockwell Automation company. [2] PowerFlex DeviceNet Adapter 20-COMM-D User Manual. Rockwell Automation company