Robust direct acoustic impedance control using two microphones for mixed feedforward-feedback controller

This paper presents an impedance control architecture for an electroacoustic absorber combining both a feedforward and feedback microphone-based system on a current driven loudspeaker. Feedforward systems enable good performance for direct impedance control. However, inaccuracies in the required actuator model can lead to a loss of passivity, which can cause unstable behaviors. The feedback contribution allows the absorber to better handle model errors and still achieve an accurate impedance. Numerical and experimental studies were conducted to compare this new architecture against a state-of-the-art feedforward control method.