Work machine and method for controling work machine

A work machine comprising:

• a boom;
• a work tool configured to drive with respect to the boom;
• a cylinder configured to drive the work tool;
• a sub-link attached to the boom, the sub-link being configured to transmit driving force of the cylinder to the work tool;
• a sensor configured to detect a stroke of the cylinder;
• and
• a controller including a processor, the controller being configured to control the cylinder based on a posture of the sub-link with respect to the boom,
• the controller being further configured to calculate a first cylinder drive command and a second cylinder drive command and issue the larger of the first cylinder drive command and the second cylinder drive command as a target cylinder drive command,
• the first cylinder drive command being based on a difference between the posture of the sub-link and a limit posture of the sub-link and
• a second cylinder drive command being based on a difference between the stroke and an end position of the cylinder,
• the end position of the cylinder being a maximum value of the stroke of the cylinder or a minimum value of the stroke of the cylinder, and
• the limit posture of the sub-link being a posture of the sub-link at a tilt end of the work tool or a posture of the sub-link at a dump end of the work tool.

A method for controlling a work machine having a boom, a work tool, a sub-link, and a cylinder arranged to drive the work tool with respect to the boom, the method comprising:

• controlling the cylinder based on a posture of the sub-link with respect to the boom, the sub-link being configured to transmit a driving force of the cylinder to the work tool to drive the work tool with respect to the boom,
• the controlling the cylinder including
• calculating a first flow rate limit amount based on a difference between the posture of the sub-link and a limit posture of the sub-link, the limit posture corresponding to a mechanism limit of the sub-link that is different from an end position of the cylinder,
• calculating a second flow rate limit amount based on a difference between the stroke and the end position of the cylinder,
• determining a larger of the first flow rate limit amount and the second flow rate limit amount,
• setting the larger of the first flow rate limit amount and the second flow rate limit amount as a flow rate limit amount, and
• controlling the flow rate of the hydraulic fluid supplied to the cylinder such that the flow rate does not exceed a difference between a maximum flow rate and the flow rate limit amount.