Computing device and computing method

A computing device of a work machine including a work implement, the computing device calculating a weight of a load conveyed by the work implement, the work machine including

• a vehicular body,
• a boom bottom pin supported by the vehicular body,
• a boom rotatably coupled to the vehicular body by the boom bottom pin,
• a boom top pin attached to a tip end of the boom,
• an attachment rotatably coupled to the boom by the boom top pin, and
• a pivot member supported by the boom and being rotatable together with the attachment with respect to the boom, wherein
• the computing device calculates the weight of the load based on two equilibrium equations of an equation of moment equilibrium around the boom bottom pin and an equation of moment equilibrium around a center of rotation of the pivot member.

A computing device of a work machine including a work implement, the computing device calculating a weight of a load conveyed by the work implement, the work machine including

• a vehicular body,
• a boom bottom pin supported by the vehicular body,
• a boom having one end rotatably coupled to the vehicular body by the boom bottom pin,
• a boom top pin attached to the other end of the boom,
• an arm having one end rotatably coupled to the other end of the boom by the boom top pin,
• an arm top pin attached to the other end of the arm,
• an attachment having one end rotatably coupled to the other end of the arm by the arm top pin,
• a boom hydraulic cylinder that drives the boom to rotationally operate,
• an arm hydraulic cylinder that drives the arm to rotationally operate,
• an attachment hydraulic cylinder that drives the attachment to rotationally operate,
• a pressure sensor including at least two sensors of a boom pressure sensor that is attached to the boom hydraulic cylinder and outputs hydraulic oil pressure information of the boom hydraulic cylinder, an arm pressure sensor that is attached to the arm hydraulic cylinder and outputs hydraulic oil pressure information of the arm hydraulic cylinder, and an attachment pressure sensor that is attached to the attachment hydraulic cylinder and outputs hydraulic oil pressure information of the attachment hydraulic cylinder, and
• a boom position sensor that outputs boom information for obtaining a position of the boom with respect to the vehicular body, an arm position sensor that outputs arm information for obtaining a position of the arm with respect to the boom, and an attachment position sensor that outputs attachment information for obtaining a position of the attachment with respect to the arm, wherein
• the computing device calculates the weight of the load in conveyance of the load based on any two relational expressions of a first relational expression generated from the hydraulic oil pressure information of the boom hydraulic cylinder and the boom information, a second relational expression generated from the hydraulic oil pressure information of the arm hydraulic cylinder and the arm information, and a third relational expression generated from the hydraulic oil pressure information of the attachment hydraulic cylinder and the attachment information, and
• the pressure sensor includes at least two sensors corresponding to the two relational expressions.

A computing method of calculating a weight of a load conveyed by a work implement, for a work machine including the work implement, the work implement including as members, a boom that pivots around a first center of rotation, an arm that pivots around a second center of rotation, and an attachment that pivots around a third center of rotation, the computing method comprising:

• establishing, for the members, relational expressions of a motion around any two centers of rotation of the first center of rotation, the second center of rotation, and the third center of rotation;
• obtaining a weight and a position of a center of gravity of each of the members;
• obtaining positions of the members in conveyance of the load;
• obtaining thrust corresponding to the motion in the relational expressions;
• computing horizontal distances between the positions of the centers of gravity of the members in conveyance of the load and corresponding ones of the first center of rotation, the second center of rotation, and the third center of rotation based on the positions of the centers of gravity and the positions of the members, respectively;
• and
• computing the weight of the load conveyed by the work implement based on the relational expressions, the obtained information, and the computed information.