Shovel

A shovel comprising:

• a lower traveling body:
• an upper turning body turnably mounted on the lower traveling body;
• an attachment including a boom attached to the upper turning body, an arm attached to an end of the boom, and an end attachment attached to an end of the arm;
• an arm cylinder configured to drive the arm;
• a hydraulic pump configured to supply hydraulic oil to the arm cylinder;
• a relief valve configured to release a pressure of the hydraulic oil in a rod-side oil chamber of the arm cylinder;
• and
• a hardware processor configured to correct a motion of the arm or the end attachment according to a stability of a body of the shovel during aerial motion of the attachment,
• wherein the hardware processor is configured to, in a case of correcting the motion of the arm, correct the motion of the arm to move the arm in a closing direction, in response to identifying a predetermined motion of the shovel that causes the body of the shovel to be in an unstable state,
• the hardware processor is configured to, in response to identifying the predetermined motion of the shovel, cause the relief valve to release the pressure in the rod-side oil chamber of the arm cylinder by discharging the hydraulic oil in the rod-side oil chamber of the arm cylinder to a hydraulic oil tank, to allow the arm to be moved in the closing direction by a weight of the arm during the aerial motion of the attachment,
• a stable range of the attachment where a degree of static stability of the attachment is more than or equal to a predetermined reference is defined around the shovel,
• the stable range is an area surrounding the lower traveling body in a plane in which the lower traveling body is positioned, and an outer edge of the stable range is spaced apart from the lower traveling body, and
• the hardware processor is configured to determine whether a position of the end attachment relative to the lower traveling body is beyond the outer edge of the stable range, and to determine that the body of the shovel is in a static unstable state in response to determining that the position of the end attachment relative to the lower traveling body is beyond the outer edge of the stable range.