Abstract : The ring spinning frame adopts programmable logic controller (PLC), frequency converter, AC servo controller and touch screen control, which simplifies the mechanism and improves accuracy. It is conducive to stabilizing spinning tension, reducing yarn breakage and hairiness. According to product requirements, the parameters can be easily adjusted through the human-machine interface. Keywords : PLC; frequency converter; AC servo controller. Yarn spinning is the last process in the spinning process. The performance of the ring spinning frame directly affects the quality of the yarn. In traditional ring spinning frames, the raising and lowering of the spindle, rollers and ring plate are all driven by the main motor. The main motor often uses a dual-speed motor. The slow speed is only used for starting, and the high speed is for normal operation and the speed is constant. This makes the spindle speed constant, and the breakage rate is relatively high during the spinning process. Due to product differences, more changing gears are used between the spindle and drafting roller transmission and between the front and rear drafting rollers to change the yarn twist and draft ratio. The yarn forming and winding are achieved by the raising and lowering of the ring plate through the forming cam and ratchet mechanism. Due to various reasons, the spinning frame has a large number of gears, and the forming cam experiences impact at the tip and pauses at the bottom. Simultaneously, the worm gear mechanism used for step-by-step spinning is prone to wear. Therefore, the quality of spinning and winding is not easily guaranteed, potentially leading to problems such as loop breakage during high-speed unwinding in subsequent processes. With the continuous development of microelectronics and computer technology, programmable logic controllers (PLCs), AC servo controllers, and network technologies have been applied to the control of spinning frames. This has solved the shortcomings of traditional spinning frames, simplified the mechanism, and improved precision. The quality of the processed yarn has been greatly improved. 1. Composition of the Control System The control system consists of a human-machine interface (touchscreen), PLC, AC servo control system, and reducer. The touchscreen and PLC communicate in real-time via MPI. Various parameters can be easily set and modified through the touchscreen. The PLC communicates in real-time with each AC motor and AC servo motor via a vector-type frequency converter and AC servo speed controller through Profibus-DP. The spindle speed is driven by the main motor and adjusted according to the spinning conditions. The rotation speed of the output rollers in the drafting mechanism can be adjusted according to process requirements to meet the needs of different products. The raising and lowering of the ring rail can be selected with appropriate data as required. Synchronization between the frequency converter and the servo controller is achieved using SIMOLINK. [b][align=center]For more details, please click: Application of Frequency Converters and AC Servo Systems in Ring Spinning Machines[/align][/b]