Abstract : This paper introduces a technical improvement project using closed-loop control with speed feedback. The development of the technical improvement work was aided by the use of the Weifu software simulator for programming, compilation, and simulation. Keywords : Open-loop, Closed-loop, Motor, Encoder, Frequency Converter, Optocoupler, Microcontroller 1 Introduction In our company's textile section, several texturing machines use a single frequency converter to control one motor in an open-loop manner. During production, as the motor load increases, the corresponding motor speed inevitably decreases, leading to a decline in product quality. This is because the production process requires a settable motor speed that remains essentially constant throughout production. Using a single frequency converter to control one motor in an open-loop manner, before each machine start-up, the process engineer must set the operating frequency corresponding to the required motor speed based on past experience. After startup, the process engineer must use a stroboscope to measure the motor speed. If the motor speed does not meet the process requirements, the set value of the operating frequency must be adjusted until it does. During production, the increase in motor load is gradual (due to the gradual increase in the winding bobbin). In situations involving sudden changes (operator-operated rollers, yarn cake extraction), open-loop motor speed control only stabilizes after the speed change, not maintains a constant speed. However, appropriate closed-loop control effectively maintains the motor speed at the set value and reduces the workload of process engineers. Since one inverter controls one motor in a closed loop, only a required motor speed needs to be set before startup, eliminating the need for repeated adjustments after startup. Currently, most inverters used in texturing machines in the post-spinning workshop are Emerson EV series inverters, all equipped with closed-loop control functionality. By simply adding a speed encoder, a connector between the motor shaft and the speed encoder, and a cable connecting the encoder and the inverter, closed-loop control can be achieved using the inverter's function, making the most of the equipment. The following details a speed closed-loop control modification project for the motor used on one side of a texturing machine. [b]2. Speed ​​Closed-Loop Control System Hardware[/b] [b][align=center]For details, please click: Modification Project of Converting Motor Speed ​​Open-Loop Control to Closed-Loop Control[/align][/b]