Abstract : This paper introduces a linear motor control system based on a Smith predictor used in a piston outer diameter copying lathe for internal combustion engines. The principle of the system is explained, and the real-time response Smith predictor is analyzed. To ensure the system has stable and high-frequency response performance, the adjustment method for matching the position and speed feedback parameters when the system is connected to different linear motors is listed. Keywords : Piston outer diameter machining; Smith predictor; linear motor; stability; high frequency response 0 Introduction The outer diameter of an internal combustion engine piston has a certain ellipticity and special shape, making machining challenging. Traditional machining methods use hard templates, but this cannot meet the requirements of rapid product updates. To meet the rapidly changing market demands, a flexible CNC lathe can be used to machine the piston outer diameter. The machining principle is shown in Figure 1: The piston rotates at a constant speed with the spindle. Under the control of a linear motor control system based on a Smith predictor, the X-axis actuator motor—a linear motor—drives the cutting tool to perform circular interpolation cutting on the piston's outer diameter in the X-axis direction as required. Simultaneously, the X-axis actuator motor—a linear motor—moves in the Z-axis direction as required to complete the machining of the piston's shape. Due to the special shape requirements of the piston, a large amount of X-axis position data needs to be processed at different Z-axis positions. Therefore, one of the key technologies of this equipment is a linear motor control system with high data processing capability, high frequency response, high precision, and no pure hysteresis. This article analyzes and discusses the working principle of a linear motor control system based on a Smith predictor, elaborates on the Smith predictor, and introduces the adjustment method for matching position and speed feedback parameters when the system is connected to different linear motors. [b][align=center]For more details, please click: Linear Motor Control System Based on Smith Predictor[/align][/b]