Method and system for on-line system identification

An active noise or vibration control system with on-line system identification for identifying the response of a physical system, said control system comprising

• control means producing control signals, said control means including control adaption means responsive to residual signals,
• test signal generating means for generating test signals, wherein the test signal generating means includes means for delaying or inverting a fixed test signal of length determined by the response time of the physical system, including actuator means and sensing means,
• said actuation means responsive to a combination of the control signals and the test signals and producing a canceling noise or vibration, one component of which counters or partially counters an unwanted first noise or vibration,
• said sensing means responsive to the combination of said canceling noise or vibration and said first noise or vibration and producing input signals,
• compensation filter means responsive to said test signals and producing compensation signals, said compensation filter means including a filter adaption means responsive to said test signals and said residual signals and configured to minimize the correlation between the residual signals and the test signals,
• signal subtraction means for subtracting said compensation signals from said input signals to produce said residual signals,
• characterized in that the compensation signals substantially cancel the components of the input signal due to the test signals.