Genetic programming control of quasiperiodic thermoacoustic oscillations*

We use genetic programming (GP) to discover model-free control laws for the suppression of two-frequency quasiperiodic oscillations in a prototypical self-excited thermoacoustic system. Starting from an initial generation of control laws, we rank their performance based on a predefined cost function that quantifies the trade-off between pressure amplitude reduction and actuation cost. We then breed subsequent generations of control laws via a tournament algorithm in which direct forwarding of elitism individuals occurs alongside genetic operations such as mutation, replication and crossover. We implement this GP control strategy in both closed-loop and open-loop formats, and we benchmark these against conventional open-loop control involving harmonic forcing. We find that all three control strategies can deliver similar levels of amplitude reduction, but that GP closed-loop control requires the least actuation effort. We also find that GP closed-loop control can reveal novel actuation mechanisms, offering useful insight into the interactions between the pressure and heat-release-rate fields.