1. Introduction Rockwell's MCC (Centerline Motor Control Centers) products are fieldbus-based motor control centers. To highlight the principles and emphasize the demonstration effect, this paper mainly focuses on controlling the 1305 AC inverter. The 1305 AC inverter is a microprocessor-controlled AC inverter used for three-phase motor control, generating three-phase PWM signals, regulating output frequency and voltage, and controlling motor speed and torque. It boasts unparalleled reliability. Under any load condition, it can adjust to bring the motor to its optimal operating state, with smooth start-up, low impact, high torque boost, and reliable operation. The controller in the MCC is the ControlLogix 5550, a processor that integrates Ethernet modules, device network modules, power supplies, processors, and I/O. Rockwell's software is powerful, including network communication, network configuration, logic programming, and human-machine interface configuration functions. The RS-Linx software establishes communication between AB's programmable controllers and various Rockwell application software. RS-NetWorx for DeviceNet is a 32-bit graphical network configuration tool supporting software, providing the network positioning view and the information and tools needed for device network configuration. RS-Logix 5000 software is a ladder logic programming software for ControlLogix series controllers. PanelBuilder is a Microsoft Windows-based software package used to design control panel applications for PanelView terminals (touchscreens). RS-Linx establishes a communication channel, connecting the computer to the ControlLogix 5550 controller via an RS232 communication channel. Ladder logic programs are written using RS-Logix 5000 software and downloaded to the controller. Simultaneously, the control panel application written using PanelBuilder is downloaded to the PanelView terminal. The 1305 AC inverter is controlled via the PanelView terminal to control the motor. 2. Hardware Structure and Configuration: The MCC internally uses a DeviceNet fieldbus structure, internally distributing various frequency converters, overcurrent protection devices, terminal monitoring devices, and power monitors. DeviceNet requires an external 24V power supply. The computer and programmable logic controller (PLC) communicate using RS232, connecting the computer's COM port to the ControlLogix 5550's COM port. The basic system hardware structure is shown in Figure 1. [align=center] Figure 1 System Hardware Structure Diagram[/align] In Figure 1, the 1203-GK5 communication module connects the 1305 AC inverter to DeviceNet, mapping the device's I/O addresses to the 1756-DNB's I/O, providing a direct, digital connection to DeviceNet for the underlying devices. The network communication baud rate is 125kbps. The DIP switches SW2.7-SW2.8 of the 1203-GK5 communication module are all set to 0. To allow communication on datalink channels A, B, C, and D, DIP switches SW1.1-SW1.4 are all set to 1. The RS-Linx software is started, and the network channels are configured. The RS232 driver is loaded, and online browsing is used to locate the ControlLogix 5550-4 slot processor and the various device network nodes connected to it. Start the rsnetworx for devicenet software and configure the network devices. Configure the parameters of the 1305 inverter: (1) To enable the 1305 inverter to accept remote control, set the second bit (adapter 2, i.e., remote i/o) in the mask group logic mask to 1 (allow). Set the second bit of the corresponding start mask, stop mask, jog mask, reference mask, accel mask, deccel mask, fault mask, and direction mask to 1 as well. (2) To achieve remote control, set freq select 1 in the frequency setup group to adapter 2 (remote i/o). Configure the scanlist of the 1756-dnb module. Map the i/o addresses of each device (1305, paneiview) to the i/o of the 1756-dnb, thereby realizing the data transmission and control functions. In this way, the operation of the 1305 inverter can be directly controlled through the operation on the paneiview. 3. Software Design and Implementation The 20 input bytes of the 1305 frequency converter include 2 logic command bytes, 2 frequency reference bytes, and 16 data link channel bytes. The motor is controlled by controlling the logic command bytes and frequency reference bytes. The definition of each bit of the input logic command byte is shown in Table 1 (Table 1 only lists some bits used in the program). [align=center]Table 1 Meaning of Logic Command Bytes of 1305 Frequency Converter[/align] The frequency reference byte consists of 2 bytes (16 bits) and is used to input the target voltage frequency value. Because the 1305 controls the motor speed by adjusting the voltage frequency, the lower 9 bits are the fractional part, and the higher 7 bits are the integer part. Start the rslogic5000 software and write the logic control program. The basic idea of ​​the logic control ladder diagram program is shown in Figure 2. [align=center]Figure 2 Logic Control Schematic[/align] The initialization program performs the following functions: To enable the 1756-dnb to work, the input statusregister.run bit and the output commandregister.run bit of the 1756-dnb module must be set to 1. Bits 12, 13, and 14 of the logic command byte corresponding to the 1305 frequency converter are set to 0, 0, and 1 respectively, i.e., the speed prompt selection is set to freq select 1, which is already set to adapter 2 (remote i/o) in the network configuration. Bit 6 is then set to 1, i.e., panel control is disabled, because performing panel control while remote control will cause errors. The direct input speed prompt subroutine performs the following functions: To enable direct input of motor speed in the panelview terminal, a notification label and a handshake label must be set for the input label when writing the ladder diagram; otherwise, it can only be input once and will not work again. When the operator presses the Enter key, the notification label is set to 1. The input tag remains open until the controller program checks that the value has been written to the tag address, then sets the handshake tag to 1. After the controller sets the handshake bit, the terminal automatically clears the notification bit. The controller program then clears the handshake tag to 0. The controller ladder logic must set the handshake bit before a timeout occurs. The default handshake timeout is 4 seconds. The basic principle of the direct input speed prompt subroutine is shown in Figure 3. [align=center] Figure 3 Direct Input Speed ​​Prompt Subroutine Block Diagram[/align] Start the PanelBuilder software and configure the terminal control interface according to the I/O mapping relationship definition (see Table 2). The terminal control interface is shown in Figure 4. [align=center] Figure 4 PanelView Terminal Control Interface Diagram[/align] [align=center] Table 2 I/O Mapping Relationship Definition Table[/align] Download the configuration program to the PanelView terminal, run the monitoring interface, and realize remote motor start, stop, reverse, acceleration, deceleration, and speed setting through the PanelView terminal. This system has been successfully run in the Rockwell Laboratory at Shanghai Jiao Tong University. The frequency conversion range is 0–60 Hz (selectable), the speed range is 0–1736 r/min, and the acceleration and deceleration times are adjustable. Frequency conversion via acceleration and deceleration buttons is highly accurate, with an error not exceeding 0.033%; the error via manual frequency setting is also less than 0.34%, with the error mainly occurring in the decimal input portion. The no-load output voltage is 7–407 V (rated voltage 460 V); the maximum no-load power consumption is 3% (rated power 1.5 kW). The experimental results are satisfactory. 4. Conclusion Based on the DeviceNet fieldbus, a communication channel was established using RS-Linx, a ladder logic program was written using RS-Logix 5000, and a control interface was developed using PanelBuilder. By controlling a 1305 frequency converter, remote control of the motor was achieved. The equipment involved in this paper includes a controller, frequency converter, communication module, and touchscreen terminal, basically covering typical MCC equipment. These are very helpful in establishing a complete set of methods for analyzing and researching commonly used MCCs, laying a solid foundation for future in-depth and complex research on MCCs. References [1] Rockwell Automation Technology Center, Zhejiang University. Programmable Logic Controller Systems [M]. Hangzhou: Zhejiang University Press, 2000.