In an oil / gas reservoir the oil essentially floats on water and the gas floats on oil. The top seal prevents the oil and gas escaping giving rise to the pressure configuration as shown. The "pressure kick" at the top seal (1) is contained when drilling by the drilling mud. (c) Co...
This paper presents a disturbance-observer-based sliding mode control strategy for an underwater electro-hydrostatic actuator, particularly considering that electro-hydrostatic actuators (EHAs) significantly suffer from sea pressure disturbance, which makes it hard to achieve high-precision position control....