Active control of unsteady motion phenomena in turbomachinery

In a turbomachine, a control system for actively controlling the dynamics of at least one mode out of a plurality of modes of at least one unsteady motion phenomenon associated with the blading of said turbomachine, said control system having a control bandwidth which is at least partly coextensive with the bandwidth of said unsteady motion phenomenon and comprising:

• (a) an array of sensors located in said turbomachine in predetermined relationship to said unsteady motion phenomenon for continuously producing from each of said sensors sensor signals related to said unsteady motion phenomenon;
• (b) signal processing means connected to receive said sensor signals from each of said sensors and having a plurality of channels for continuously processing said sensor signals and continuously outputting control signals, said plurality of channels being at least equal in number to said plurality of modes,
• (c) an array of actuator means in said turbomachine in predetermined relationship to said unsteady motion phenomenon, said actuator means being adapted to be continuously driven by said control signals, said actuator means including means for introducing local perturbation of the flow through the turbomachine about a mean value;
• wherein said signal processing means comprises means (V) for obtaining a set of independent measures of said plurality of modes by obtaining a plurality of differentially weighted sums of said sensor signals, means (D) for differentially weighting said set of independent measures of said plurality of modes, and means (UO for differentially weighting said differentially weighted set of independent measures thereby producing said control signals, whereby said actuator means have outputs which are weighted with respect to each other thereby to counter said at least one mode without causing said other modes to become unstable.