Application of the Closed-Loop PI Controller as the Low-Pass Filter

The quality of the measurement signal is often the basis for the reliable operation of the automatic control system. Real measurements are always affected by disturbances and an accuracy of measurements is within a certain range. The reliability of the automatic control system is based on its stable operation in the operating space of the system. Too high disturbance of the measurement signal may destabilize the control system. High frequency disturbances are one of the most common problem. Low-pass filters are used to eliminate high-frequency disturbances. However, these filters introduce a delay in the measurement signal. In control of dynamic systems, the delay of the measurement signal may cause the system destabilization. Such a problem was observed in flight stabilization system of the multi-rotor UAV. The paper proposes a low-pass filter based on PI controller in closed-loop feedback. In this filter, the values of the parameter of the PI controller are automatically changed based on the assessment of external factors. The goal of filtration is to eliminate disturbances while minimizing measurement signals delays. The proposed filter was compared with the traditional known solutions. The obtained results showed that the proposed solution introduces lower signal delays at the similar filtration range.