Output-feedback inclination control of directional drilling systems

Directional drilling techniques, based on rotary steerable systems, are used to generate complex curved boreholes. In practice, however, boreholes drilled with such systems often show instability-induced borehole spiraling, which negatively affects the borehole quality and increases drag losses while drilling. As a basis for controller synthesis, we present a directional drilling model in terms of delay differential equations characterizing the evolution of the borehole inclination. Next, the problem of curved well-bore generation is formulated as a tracking problem and an output-feedback control strategy is developed, solving this tracking problem while guaranteeing the prevention of borehole spiraling.