Abstract: To address the nonlinear friction element in a turntable position servo system, a friction-compensating sliding mode controller is designed. This controller treats friction as a bounded disturbance of the system and compensates for friction using sliding mode control, given only the upper bound of the friction torque. Simulation results show that the controller effectively suppresses the influence of friction torque, achieving high-precision position tracking with strong robustness. Keywords: Sliding mode control, turntable, friction. In mechanical systems with relative motion, friction is a crucial factor limiting system performance. For turntable servo systems, especially vertical turntables, the mechanical structure results in large friction dead zones in the outer and inner rings. Frictional resistance is the main nonlinear interference in the low-frequency band. Because the controlled object exhibits nonlinearity, it causes "flat-top" phenomena in position tracking and "dead zones" in velocity tracking, making it difficult to achieve high-precision control using traditional control methods. The existence of these nonlinear dynamics introduces parameter uncertainties into the turntable servo system design, leading to significant steady-state errors and reduced position tracking accuracy. To improve the system's control accuracy, friction compensation is necessary. Currently, many control technologies are applied to friction compensation, such as adaptive control, observer technology, neural networks, and sliding mode control. One common method is friction model-based compensation control, which requires establishing a mathematical model of the friction element and using the model output as the compensation signal. However, in practice, it is difficult to establish an accurate mathematical model of friction. Another method is to use adaptive methods or disturbance observers to obtain the friction torque value and introduce it into the control to counteract the influence of the friction torque. There are also many studies applying sliding mode variable structure control to friction compensation, such as the design method of sliding mode control for servo systems under friction model conditions proposed in references [2-3]. For details, please click to download: Design of Sliding Mode Controller for Flight Simulation Turntable Servo System.