A method and apparatus for dithering hydraulic valves to mitigate static friction (“stiction”) associated with the hydraulic valves. A first hydraulic valve and a second hydraulic valve are dithered to mitigate stiction associated with those valves. The dithering of the first and second hydraulic valves also cause dithering of a main hydraulic valve associated with the first and second hydraulic valves. Accordingly, stiction of three hydraulic valves of a hydraulic system is mitigated.

A pressure wave generator with dynamic reflector of pressure impulse is disclosed which comprises an outer fixed and an inner coaxially-rotating cylindrical elements with the given profiled openings of the given shapes and sizes in the solid walls and a dynamic reflector of pressure impulse, configured in the solid wall of the inner rotating cylindrical element having a longitudinal radial-azimuthal variable-concave surface. Such concave surface provides a decomposition of the reflected pressure impulse to a radial and azimuthal component, especially important on the stage of decrease of the pressure amplitude from a maximal value to zero. Variation of the curvature of the radial-azimuthal shape of the concave surface provides a maximal azimuthal component and a minimal radial component of the mechanical reaction of the shaft of the pressure wave generator. The helicoidally-shape of the inner surface of a collector add an azimuthal motion to reflected pressure impulse.

An improved servovalve for a seismic vibrator or vibration machine which includes a left additional passageway conducting a portion of sampled pressure from a left cylinder pressure chamber to only a portion of the right end drive surface of the spool, wherein the portion of the right end drive surface is less that of the entirety of the right end drive surface; and a right additional passageway conducting a portion of sampled pressure from a right cylinder pressure chamber to only a portion of the left end drive surface of the spool, wherein the portion of the left end drive surface is less that the entirety of the left end drive surface; thereby providing at least two additional passageways configured to provide linear proportional pressure feedback in spool movement control.

A vortex-controlled variable flow resistance device ideal for use in a backpressure tool for advancing drill string in extended reach downhole operations. The characteristics of the pressure waves generated by the device are controlled by the growth and decay of vortices in the vortex chamber(s) of a flow path. The flow path is designed to produce alternating primary and secondary vorticesone clockwise and one counter-clockwisewhere the primary vortex is stronger and produces higher backpressure than the secondary vortex. This in turn generates alternating weak and strong pressure pulses in the drill string. The weak pulses may be barely perceptible so that the effective frequency of the pulses is determined by the stronger primary vortices.

A vortex-controlled variable flow resistance device ideal for use in a backpressure tool for advancing drill string in extended reach downhole operations. The characteristics of the pressure waves generated by the device are controlled by the growth and decay of vortices in the vortex chamber(s) of a flow path. The flow path is designed to produce alternating primary and secondary vorticesone clockwise and one counter-clockwisewhere the primary vortex is stronger and produces higher backpressure than the secondary vortex. This in turn generates alternating weak and strong pressure pulses in the drill string. The weak pulses may be barely perceptible so that the effective frequency of the pulses is determined by the stronger primary vortices.

A hydraulic propulsion system converts heat or thermal energy into hydraulic energy, and such hydraulic energy into mechanical work. The hydraulic propulsion system includes a thermal unit, a hydraulic cylinder with pistons and springs mounted therein, one or more hydraulic motors, one or more hydraulic accumulators, and one or more electrical energy generators, as well as a plurality of flow control valves to control the flow of hydraulic fluid between the various components. The hydraulic propulsion system may be enhanced by a sonic transmission unit including a sonic wave generator.

A hydraulic propulsion system converts heat or thermal energy into hydraulic energy, and such hydraulic energy into mechanical work. The hydraulic propulsion system includes a thermal unit, a hydraulic cylinder with pistons and springs mounted therein, one or more hydraulic motors, one or more hydraulic accumulators, and one or more electrical energy generators, as well as a plurality of flow control valves to control the flow of hydraulic fluid between the various components. The hydraulic propulsion system may be enhanced by a sonic transmission unit including a sonic wave generator.

A fluidic component having a flow chamber allowing a fluid flow to flow through, said fluid flow entering the flow chamber through an inlet opening of the flow chamber and emerging from the flow chamber through an outlet opening of the flow chamber, and which flow chamber has at least one means for changing the direction of the fluid flow at the outlet opening in a controlled manner. The flow chamber has a main flow channel, which interconnects the inlet opening and the outlet opening, and at least one auxiliary flow channel as a means for changing the direction of the fluid flow at the outlet opening in a controlled manner. The inlet opening has a larger cross-sectional area than the outlet opening or the inlet opening and the outlet opening have cross-sectional areas that are equal in size.

A fluidic component having a flow chamber allowing a fluid flow to flow through, said fluid flow entering the flow chamber through an inlet opening of the flow chamber and emerging from the flow chamber through an outlet opening of the flow chamber, and which flow chamber has at least one means for changing the direction of the fluid flow at the outlet opening in a controlled manner. The flow chamber has a main flow channel, which interconnects the inlet opening and the outlet opening, and at least one auxiliary flow channel as a means for changing the direction of the fluid flow at the outlet opening in a controlled manner. The inlet opening has a larger cross-sectional area than the outlet opening or the inlet opening and the outlet opening have cross-sectional areas that are equal in size.

A fluidic device for providing analogue output control includes a main channel, a first control channel, a second control channel, a comparator which receives respective input fluid flows from the main, the first and the second control channels. The first control channel is configured such that the input fluid flow therefrom carries an oscillating pressure wave signal, the second control channel includes a flow regulator controllable to vary the mass flow rate of the input fluid flow from the second control channel, and the main channel is configured such that the input fluid flow therefrom is at a reference mass flow rate. The comparator is configured such that the input fluid flows from the first control and the second control channels act in combination on the input fluid flow from the main channel to produce an output fluid flow from the comparator having a PWM mass flow rate characteristic.