COMPREHENSIVE MIXED-SENSITIVITY ON-BLADE CONTROL FOR VIBRATION REDUCTION OF THE EC-145 ROTOR

摘要

In this work, we further investigate the use of H_∞ control design for On-Blade Control (OBC). Mixed-Sensitivity H_∞ is an advanced control method developed when reliable Linear-Time-Invariant representations exist and is especially suited for multivariable control problems. The method allows the designer to specify robustness and performance demands and existing optimisation algorithms would provide a controller which optimises over such design objectives. Alotaibi and Morales recently applied the methods to an analytical and validated model available for the EC-145 helicopter. Their work showed that the method is successful in reducing significantly all 4/rev hub loads while controlling directly the rotor thrust only. In this work, we extend this approach to control directly the remaining 4/rev components of the rotor hub loads. This comprehensive approach is compared to the simpler case (thrust control only) and we outweigh benefits and disadvantages. A key outcome from this work is that the performance can be improved by pursuing the comprehensive approach, achieving a further 21% vibration reduction in average across the flight envelope. However the comprehensive approach requires further implementation requirements, such as additional sensors and increased computational power, and more controller parameters to tune which can limit its applications. Both schemes provide the benefit of having a single controller operating over the wide flight envelope, ensuring higher reliability in terms of robustness properties without the performance being too compromised.