Resolver to digital conversion-based sliding mode tracking control for oscillating valve pulser with disturbances

The oscillating-valve pulser (OVP) creates pressure signals through the rotor oscillation to transfer downhole data while drilling. However, the performance of the OVP is susceptible to state acquisition, parameter uncertainties, and periodic mud disturbances in harsh downhole conditions. In this article, the problem of OVP control with resolver-to-digital conversion (RDC) feedback is investigated. First, a novel sliding-mode reaching dynamics with approximately fixed-time stability is proposed, and a new angle estimation algorithm used in RDC is developed on this basis. Then, a dual-loop structure is established, and the outer loop is designed by the super-twisting sliding mode (STA) and a finite-time disturbance observer (FTDO). The stability of the whole closed-loop dynamics is proven via Lyapunov analysis. A set of simulation comparisons is performed to verify the proposed RDC method, and it will be used to provide the feedback information for the STA, FTDO, and inner loop. Next, the designed control scheme is validated by two modulation formats, demonstrating its ability to produce clear pressure signals.