System, Valve Assembly, and Methods for Oscillation Control of a Hydraulic Machine

A hydraulic system comprising:

• a source of fluid;
• a reservoir of fluid;
• a hydraulic cylinder actuator having a head-side chamber and a rod-side chamber;
• an accumulator;
• and
• a valve assembly comprising:
• a housing comprising:
• (i) an accumulator fluid passage fluidly coupled to the accumulator, (ii) a supply fluid cavity fluidly coupled to the source of fluid, (iii) a reservoir fluid cavity fluidly coupled to the reservoir of fluid, (iv) a head fluid cavity configured to be fluidly coupled to the head-side chamber, and (v) a rod fluid cavity configured to be fluidly coupled to the rod-side chamber,
• a main spool that is axially-movable within the housing between an unactuated axial position, a first axial position, and a second axial position, and
• a balancing spool that is axially-movable within the housing based on an axial position of the main spool, wherein (i) when the main spool is at the unactuated axial position, the balancing spool allows the supply fluid cavity to be fluidly coupled to the accumulator fluid passage, (ii) when the main spool is at the first axial position, the balancing spool is subjected to opposing fluid forces by fluid from the head fluid cavity and fluid from the accumulator fluid passage, thereby causing pressure level of the accumulator to be balanced with pressure level in the head-side chamber, and (iii) when the main spool is at the second axial position, the main spool allows the accumulator fluid passage to be fluidly coupled to the head fluid cavity and the rod fluid cavity to be fluidly coupled to the reservoir fluid cavity.

A method comprising:

• operating a valve assembly in an unactuated state, wherein the valve assembly comprises:
• (i) a housing having:
• an accumulator fluid passage fluidly coupled to an accumulator, a supply fluid cavity fluidly coupled to a source of fluid, a reservoir fluid cavity fluidly coupled to a reservoir of fluid, a head fluid cavity configured to be fluidly coupled to a head-side chamber of a hydraulic actuator, and a rod fluid cavity configured to be fluidly coupled to a rod-side chamber of the hydraulic actuator, (ii) a main spool that is axially-movable within the housing, and (iii) a balancing spool that is axially-movable within the housing based on an axial position of the main spool, wherein operating the valve assembly in the unactuated state comprises the main spool being at an unactuated axial position, causing the balancing spool to allow the supply fluid cavity to be fluidly coupled to the accumulator fluid passage;
• operating the valve assembly in a first actuated state, wherein the main spool moves to a first axial position, causing the balancing spool to be subjected to opposing fluid forces by fluid from the head fluid cavity and fluid from the accumulator fluid passage, thereby causing pressure level of the accumulator to be balanced with pressure level in the head-side chamber;
• and
• operating the valve assembly in a second actuated state, wherein the main spool moves to a second axial position, causing the accumulator fluid passage to be fluidly coupled to the head fluid cavity and the rod fluid cavity to be fluidly coupled to the reservoir fluid cavity.