US Patent 8731784 Blade control system and construction machine

A blade control system of the present invention includes an angle obtaining part, an open ratio setting part and a lift cylinder controlling part. The angle obtaining part is configured to obtain an angle of a lift frame with respect to a designed surface. The open ratio setting part is configured to set an open ratio based on the angle. The lift cylinder controlling part is configured to open a proportional control valve at the open ratio for elevating the blade when a distance between the designed surface and an edge of a blade is determined to be less than or equal to a threshold.