Application of H/sub /spl infin// control with eigenvalue perturbations to stabilize a transonic compressor

Robust linear control is used to stabilize the flow field perturbations which lead to rotating stall and surge in a transonic single-stage axial compressor. As in previous low-speed compressor control experiments with uniform inlet flow, a separate control is implemented for each of the decoupled spatial harmonics of the pre-stall perturbations. However, due to compressibility effects in a high-speed compressor, there are multiple lightly damped modes for each of the pre-stall harmonics which are not present in the low-speed case. Therefore, constant gain proportional control, which is effective in low-speed applications, cannot extend the operating range of this highspeed compressor at design speed. Instead, H _∞ control laws are implemented to stabilize the flow field perturbations. Standard transfer function weightings are incorporated into the design to address actuator saturation and bandwidth limitations. Additionally, an eigenvalue perturbation technique, developed by Smith (1995) and Smith et al. (1994) is included to allow for a range of dominant eigenvalue locations and thus addresses model uncertainty and changing eigenvalue locations with varying compressor mass flow. Results are presented which demonstrate control effectiveness along the design-speed compressor characteristic as well as the ability to reject large amplitude transient disturbances.