Blade control device and blade control method

1. A blade control device comprising:

a processor configured to perform the following:

acquiring a design surface indicating a target shape of an excavation object to be excavated by a blade supported by a vehicle body of a work vehicle, the design surface including a first surface present in front of the work vehicle and a second surface having a slope different from a slope of the first surface;

acquiring an observed pitch angle indicating an inclination angle of the vehicle body in a longitudinal direction;

in a state in which at least a part of the vehicle body is positioned on the first surface and the blade is positioned above the second surface, calculating a planned pitching angle indicating a deviation between the observed pitch angle and a design surface pitch angle indicating an inclination angle of the second surface;

correcting the observed pitch angle based on the planned pitching angle and calculating a corrected pitch angle of the vehicle body;

acquiring a target height of the blade, the target height being calculated based on the design surface;

correcting the target height based on the corrected pitch angle, and generating a corrected target height,

based on the corrected pitch angle, calculating a target cylinder speed of a hydraulic cylinder that adjusts a height of the blade,

calculating a corrected target height variation based on the corrected target height,

calculating a target cylinder speed correction value based on the planned pitching angle and the corrected target height variation, and

determining a correction gain for the corrected target height variation based on a correction table and the planned pitching angle,

wherein the correction table includes correlation data indicating a relationship between the planned pitching angle and the correction gain to be given to the corrected target height variation.

2. The blade control device according to claim 1 , further comprising the following steps performed by the processor:

searching for an inflection position indicating a boundary between the first surface and the second surface on the design surface; and

calculating the planned pitching angle based on the inflection position.

3. The blade control device according to claim 1 , further comprising the following steps performed by the processor:

acquiring a position of the vehicle body;

acquiring an operation amount of the hydraulic cylinder;

calculating the height of the blade based on the position of the vehicle body, the inclination angle of the vehicle body, and the operation amount of the hydraulic cylinder; and

calculating the target cylinder speed such that a deviation between a height of a cutting edge of the blade and the corrected target height becomes small.

4. The blade control device according to claim 3 , further comprising the following steps performed by the processor:

calculating the target cylinder speed based on the corrected target height;

adding the target cylinder speed and the target cylinder speed correction value to each other and calculates a corrected cylinder speed; and

outputting a control command to control the height of the blade based on the corrected cylinder speed.

5. The blade control device according to claim 1 ,

wherein an angle formed by the first surface and the second surface is larger than 180[°] on the design surface.

6. A blade control method comprising:

acquiring a design surface indicating a target shape of an excavation object to be excavated by a blade supported by a vehicle body of a work vehicle, the design surface including a first surface present in front of the work vehicle and a second surface having a slope different from a slope of the first surface;

acquiring an observed pitch angle indicating an inclination angle of the vehicle body in a longitudinal direction;

calculating a planned pitching angle indicating a deviation between the observed pitch angle and a design surface pitch angle indicating an inclination angle of the second surface in a state in which the vehicle body is positioned on the first surface and the blade is positioned above the second surface;

correcting the observed pitch angle based on the planned pitching angle and calculating a corrected pitch angle of the vehicle body;

acquiring a target height of the blade, the target height being calculated based on the design surface;

correcting the target height based on the corrected pitch angle, and generating a corrected target height;

calculating a target cylinder speed of a hydraulic cylinder that adjusts a height of the blade, based on the corrected pitch angle;

calculating a corrected target height variation based on the corrected target height;

calculating a target cylinder speed correction value based on the planned pitching angle and the corrected target height variation; and

determining a correction gain for the corrected target height variation based on a correction table and the planned pitching angle;

wherein the correction table includes correlation data indicating a relationship between the planned pitching angle and the correction gain to be given to the corrected target height variation.