Design of stepping motor acceleration and deceleration controller for engraving machine

1 Introduction
  For decades, the rapid development of digital technology, computer technology and permanent magnet materials has opened up a broad prospect for the application of stepper motors. The open-loop CNC system consisting of stepper motor and drive circuit is very simple, inexpensive and very reliable. In addition, stepper motors are also widely used in applications such as printers, engraving machines, plotters, embroidery machines and automation instruments. Because of the wide application of stepper motors, more and more research on the control of stepper motors is more and more. If the stepping pulse changes too fast during start-up or acceleration, the rotor will follow the change of the electric signal due to inertia, resulting in blockage. Turning or losing step; overstepping may occur during stop or deceleration for the same reason. In order to prevent stalling, out of step and overstep, and increase the working frequency, the stepping motor should be controlled by the speed. This article describes a stepper motor speed-up controller for an automatic edger that can be used in other applications due to its versatility.
  From the moment frequency characteristics of the stepping motor, the output torque of the stepping motor decreases with the increase of the pulse frequency. The higher the starting frequency, the smaller the starting torque, the worse the ability to drive the load, and the loss will occur when starting. Steps, and overshoot will occur when stopped. For the stepper motor to quickly reach the required speed without losing step or overshoot, the key is to make the torque required by the acceleration during the acceleration process fully utilize the torque provided by the stepping motor at each operating frequency. Can not exceed this torque. Therefore, the operation of the stepping motor generally has to undergo three stages of acceleration, uniform speed and deceleration. The acceleration and deceleration process time is required to be as short as possible, and the constant speed time is as long as possible. Especially in the work requiring fast response, the time required to run from the start point to the end point is short, which requires a short process of acceleration and deceleration, and a high rate at constant speed. In the past, most of the speed up and down speeds were chosen to be in a straight line. When this method is used, its pulse frequency has a constant acceleration. Under the condition that the stepping motor does not lose the step, the acceleration of the driving pulse frequency variation is proportional to the angular acceleration of the stepping motor rotor. When the torque of the stepping motor is kept constant with the rise of the pulse frequency, the straight-line speed is the ideal speed-up and down-speed curve, and the torque of the stepping motor decreases with the increase of the pulse frequency, so the straight line is not ideal. Lifting speed curve. Therefore, the method of raising and lowering speed according to the straight line is simple, but it cannot guarantee that the angular acceleration of the stepping motor rotor is adapted to the change of its output torque during the speed of the lifting and lowering, and the acceleration performance of the motor cannot be maximized. . This system seeks a discrete control algorithm based on FPGA control and exponentially speeds up and down. After several runs, it achieves the expected goal.