Fine grading system and method for a work machine with a box blade grading attachment

A method of controlling a grading box relative to a frame of a work machine to fine grade a ground surface, the method comprising:

• detecting, via a first hydraulic sensor coupled to a pair of pitch hydraulic actuators, a first output signal corresponding to a grading pressure of the pitch hydraulic actuators relative to the ground surface;
• detecting, via a second hydraulic sensor coupled to a pair of boom hydraulic actuators, a second output signal corresponding to a grading pressure of the boom hydraulic actuators relative to the ground surface;
• setting a target grading pressure;
• lowering the grading box relative to the frame within a defined lift range via the pitch hydraulic actuators and the boom hydraulic actuators to engage the ground surface;
• automatically controlling a proportional relief valve to maintain the target pressure as a function of the first output signal and the second output signal to maintain the target pressure.

A fine grading system for a work machine, the system comprising:

• a frame supported by a plurality of ground-engaging units, the ground-engaging units configured to support the frame on a surface;
• a boom assembly coupled to the frame, the boom assembly having a pair of boom arms pivotally coupled to the frame and movable relative to the frame by a pair of boom hydraulic actuators;
• an attachment coupler coupled to a distal portion of the pair of boom arms, the attachment coupler movable relative to the frame by a pair of pitch hydraulic actuators;
• a grading box coupled to the attachment coupler, the grading box extending transversely to the frame;
• an upper attachment frame portion having an upper attachment frame length extending forward of the grading box;
• a ground-engaging stabilizer wheel coupled to a distal portion of the upper attachment frame portion;
• a stabilizer wheel hydraulic actuator is coupling the stabilizer and further coupled to and orthogonally oriented to the upper attachment frame portion,
• a positioning unit configured to at least raise or lower the grading box relative to the frame via the boom hydraulic actuators and the pitch hydraulic actuators,
• a hydraulic circuit communicatively coupled to a controller, the hydraulic circuit including
• a hydraulic pump coupled to the boom hydraulic actuators and the pitch hydraulic actuators, the hydraulic pump delivering fluid through a plurality of flow paths, the plurality of flow paths coupled the boom hydraulic actuators, the pitch hydraulic actuators, and at least one proportional relief valve;
• a first hydraulic sensor coupled to the pitch hydraulic actuators and configured to generate a first output signal, the first output signal corresponding to a grading pressure of the pitch hydraulic actuators;
• a second hydraulic sensor coupled to the boom hydraulic actuators and configured to generate a second output signal corresponding to a grading pressure of the boom hydraulic actuators;
• a third hydraulic sensor coupled to the stabilizer wheel actuator and configured to generate a third output signal corresponding to a grading pressure of the stabilizer wheel actuator;
• and
• the controller functionally linked to the first sensor, the second sensor, and the positioning unit, and configured to selectively adjust the at least one proportional relief valve as a function of the first output signal, the second output signal and the third output signal corresponding to the grading pressure to be generated by the pitch hydraulic actuators, the boom hydraulic actuators, and the stabilizer wheel actuator to position the grading box with respect to the ground surface;
• the controller automatically controlling the at least one proportional relief valve to maintain the target pressure.