Stepper motors are widely used in economical CNC machine tools due to their ease of use. However, to fully utilize their advantages, it is necessary to address the issues of step loss and overshoot that easily occur during stepper motor startup and shutdown. This paper selects a high-performance ARM microprocessor and uses a method of continuously correcting the initial value of the timer to change the timing interrupt pulse rate to control the startup and shutdown process of the stepper motor. Good control results were achieved, and specific calculation formulas and software implementations are provided. Keywords: ARM, stepper motor, acceleration/deceleration control pulse. With industrial development, embedded technology is becoming increasingly widespread and mature. Embedded processors, as high-performance, low-power PISC chips, support multiple operating systems, have high clock speeds, strong processing capabilities, and are compatible with 360-bit devices. They can also carry massive amounts of low-cost microdata storage. They have gained favor across various industries and have demonstrated powerful functionality and significant commercial value. They are especially widely used in the control field. The development of motion control systems using embedded microprocessors with ARM cores has broad development prospects. In some motion control systems requiring low cost, stepper motors are frequently used as actuators. The biggest advantage of stepper motors in this application is that they can be controlled in an open-loop manner without feedback to control position and speed. However, precisely because there is no feedback from the load position to the control circuit, the stepper motor must respond correctly to every change in excitation. If the excitation frequency is not selected properly, the motor cannot move to the new position, resulting in a permanent error between the actual load position and the position expected by the controller, i.e., step loss or overshoot. Therefore, in the open-loop control system of a stepper motor, preventing step loss and overshoot is crucial for the normal operation of the open-loop control system. Stepper Motor Acceleration and Deceleration Control Principle Step loss and overshoot occur during the start-up and stop of the stepper motor, respectively. Generally, the system's maximum starting frequency is relatively low, while the required operating speed is often relatively high. If the system starts directly at the required operating speed, it cannot start normally because this speed exceeds the maximum starting frequency. This can result in anything from missed steps to complete stalling. After the system starts running, if the pulse train is stopped immediately upon reaching the endpoint, the stepper motor rotor will rotate to the next equilibrium position near the endpoint due to system inertia and stop there, resulting in overshoot. Therefore, acceleration and deceleration control are required when the stepper motor starts or stops. Acceleration and deceleration control is mostly implemented in software and is divided into three stages: acceleration, constant speed, and deceleration. The control curve is shown in Figure 1. Acceleration and Deceleration Control Method Using a microprocessor to control the acceleration and deceleration of the stepper motor essentially involves changing the time interval of the output pulses. During acceleration, the pulse frequency gradually increases, and during deceleration, the pulse frequency gradually decreases. A constant acceleration algorithm is used, which is easy to operate and has good results. As shown in Figure 2, when the change of adjacent pulses is completed within a time interval Δt[sub]m[/sub], the stepper motor has rotated one step. Therefore, the shaded area in Figure 2 is 1. Let the m-th frequency of the motor's acceleration be F_m, and the m-1-th frequency be f_m. Let the acceleration be the slope of F, denoted as a. Then, in software implementation, when controlling the motor speed using a timer interrupt, the timer's loaded value is continuously changed. The ARM chip's timing pulse is issued by the S3C4510 timer, so the timer's overflow frequency should be twice the control pulse frequency. The implementation function is as follows: where fo is the initial pulse frequency, fmax is the maximum pulse frequency when reaching uniform speed, tran is the number of transition pulse steps during acceleration or deceleration, and steep is the total number of pulse steps in this program segment. Conclusion Using a microprocessor with a core that has a high clock frequency and fast instruction execution speed, it can generate a higher pulse frequency. By employing acceleration/deceleration control methods to control the stepper motor, it can achieve smooth and high-speed operation. Therefore , it is very suitable for use in economical CNC machine tools, replacing the original PC-based CNC machine tools and reducing costs. Another point to note is that the development of embedded CNC systems is generally based on embedded real-time operating systems, such as UC/OS-11. The operating system itself relies on timer interrupts as the basis for scheduling. Special care must be taken when porting the operating system and selecting the timer to control the stepper motor. The two should not conflict or affect each other, otherwise the whole system will crash. About the author: Liu Yanshuang, female teacher. Main research direction: CNC, stepper motion control. References [1] Ma Zhongmei, Ma Guangyun, Xu Yingcu, et al. ARM Embedded Processing Circuit Structure and Application Fundamentals Beijing University of Aeronautics and Astronautics Press, 2002 [2] Yang Houchuan, Liang Wei, eds. Machine Tool CNC System and Application Beijing University Press, 2005 [3] Wang Tianmiao Embedded System Design and Example Development Beijing Tsinghua University Press, 2003 [4] Zhou Ligong, et al. ARM Controller Fundamentals and Practice Beijing University of Aeronautics and Astronautics Press, 2003