Method and apparatus for compensating boom deflection, and method and apparatus for controlling boom

A boom of a construction machine that compensates for boom deflection, the boom comprising:

• a plurality of joints mechanically coupling the construction machine to an end of the boom, wherein the boom is configured to:
• determine a joint angle set for the boom that would place the end at a predetermined target position if the boom were viewed as a rigid body, the joint angle set comprising a joint angle for each joint of the boom;
• determine an actual position reached by the end when the boom is driven to the joint angle set by evaluating a deflection model of the boom that maps elastic deflection to joint angles, the model being generated from sensor-collected operating data for the boom;
• determine a deviation between the predetermined target position and the actual position;
• in response to the deviation not satisfying a predetermined condition, adjust the joint-angle set to obtain an adjusted joint-angle set and, when a deviation determined from the adjusted joint angle set does not satisfy the predetermined condition, continue to adjust the joint-angle set until the deviation satisfies the predetermined condition, wherein each adjustment iteration comprises:
• (i) adjusting a sub-boom composed of at least two joints that are adjacent in sequence and selected in sequence starting from the end while holding all other joints constant;
• and
• (ii) computing an adjustment vector Δq=M·Jsub+·Δe, where Δe is the deviation, Jsub+ is a right pseudo-inverse of a Jacobian of the sub-boom, and M is a predetermined function of a magnitude of the deviation that is strictly decreasing and has a value range less than or equal to 1;
• and
• move the end of the boom to the predetermined target position by controlling at least two of the plurality of joints according to the adjusted joint angle set, the at least two joints being adjacent in sequence in the boom and selected in sequence starting from the end of the boom.