Nonlinear PID Control Based on the Fal Function of an Elastic Cable Winch System Using dSPACE

In cable-driven mechanisms, cable elasticity degrades linear controller performance, causing oscillations and reducing positioning accuracy. The main novelty of this study is the real-time experimental application of a nonlinear PID (NPID) controller based on the fal function to effectively suppress these oscillations in an elastic cable winch system. The fal function enables dynamic gain adaptation based on error magnitude. The experimental setup was driven by a dSPACE DS1104 board with a sampling time of 0.001 s, utilizing a five-cycle periodic trapezoidal reference to evaluate all operating conditions in a single run. Compared to a conventional PID tuned under identical hardware conditions, the proposed NPID reduced the maximum absolute error by 57%, accumulated error by 42%, average error amplitude by 40%, and total control effort by 26%. Ultimately, the NPID significantly improves tracking accuracy and actuator efficiency in flexible electromechanical systems without deviating from the familiar PID structure.