Compensation of time and amplitude discretization by applying feedback modulator for motion control of electric railway

A discrete control input system called notch is commonly used for motion control of a railway rolling stock in Japan. The coarse time and amplitude discretization cause large sampling and quantization errors and deteriorate the control performance when a controller is designed in a continuous-time continuous-amplitude system and then digitally redesigned. The application of a feedback modulator (FBM) provides high-precision positioning close to that of continuous control for conventional electric rail vehicle drives that the traction input is limited to a finite number of steps. It is shown by the numerical simulation that the application of an FBM to a PID controller significantly reduces the tracking error compared to simple discretization by zero-order hold.