Floating photovoltaic (FPV) systems experience continuous attitude variations under wave excitation, and accurate laboratory reproduction of such motion is essential for evaluating electrical and mechanical performance. However, push-rod actuators typically used in FPV simulators suffer from asymmetric dead-zone voltages during direction reversal, causing stagnation, phase lag, and peak clipping when controlled with conventional PID. This letter identifies this overlooked limitation and proposes a lightweight nonlinear PID controller with direction-dependent bias compensation that forces the PWM output to instantaneously surpass the dead-zone thresholds. Implemented on an STM32F407, the method eliminates reversal-induced pauses and enables smooth sinusoidal tracking. Experiments show that the proposed controller reduces phase lag from 0.176 s to 0.061 s (65.3%) and the sum of squared errors from 12.75 to 1.37 (89.3%), representing a substantial improvement over linear PID. The approach is computationally inexpensive and broadly applicable to actuator systems exhibiting dead-zone characteristics.