Abstract:

Stepper motors play a key role in the workflow of automatic sputum smear slide preparation and staining. During the startup and shutdown processes of a motor, the rapid changes experienced by the motor speed necessitate excellent motor startup and shutdown control algorithms. First, the overload phenomenon caused by the excessive torque required during the sudden high-speed startup of the motor should be avoided to protect the motor from damage. Second, during deceleration, sudden stoppage of the high-speed rotating motor should be prevented to reduce the inertial impact on the motor and minimize the resulting motion deviation. This study aimed to optimize the startup and shutdown control algorithms for stepper motors. During the startup and shutdown stages, an S-shaped curve was adopted to achieve smooth changes in motor speed. This S-shaped speed change curve was designed based on the Logistic function, to ensure smooth changes in motor speed during startup and shutdown, thereby avoiding the impact caused by sudden acceleration or deceleration. A 7-segment acceleration and deceleration optimization algorithm was employed to achieve effective control of the motor overall motion. Simulation experiments were conducted to verify the effectiveness of the algorithm. The stepper motor exhibited an S-shaped change in its speed-time curve during the startup and shutdown intervals, ensuring smooth startup and shutdown of the motor. Actual test results show that after adopting the S-shaped acceleration and deceleration startup and shutdown control algorithm, the positional error was within ±0.05 mm, a significant reduction compared to the ±0.9 mm caused by the trapezoidal control algorithm. This demonstrates that the S-shaped acceleration and deceleration startup and shutdown control algorithms achieve remarkable results in reducing positional errors.

Key words: stepper motor, start-stop control, 7-segment S-shaped acceleration and deceleration control algorithm, positional error