An Online Open-Loop S-Curve Velocity Profile Control Method for Stepping Motors on FPGA

Velocity profiles, particularly S-curves, are widely used in open-loop stepper motor control to reduce step missing and overshoot. However, because offline methods are inflexible and require a large amount of storage space, and online methods require a high level of discretization speed, open-loop control of stepper motors is difficult to achieve both high flexibility and low oscillation. As a result, this article proposes a hybrid S-curve velocity profile theory for stepper motors and its online control using an FPGA platform. The proposed theory includes a fully mathematical analytical formula for pulse interval sequence (PIS), which significantly improves calculation speed in direct solution while avoiding quantization or sampling errors in approximate solution. The comparative analysis shows that this system's online solution speed can reach 67.595 ns per step, which is faster than other similar literature. Comparative experiments show that the proposed system has the same positioning accuracy, speed tracking accuracy, and low oscillation performance as traditional S-curves. Among them, the online control accuracy of the proposed theory can reach the level of the traditional five-segment S-curve, and the offline control accuracy can reach the level of the traditional cosine S-curve.