Modeling, identification, and real-time control of bucket hydraulic system for a wheel type loader earth moving equipment

摘要

The earth moving equipment industry is quickly gearing up to achieve great gains in efficiency.performance, safety, and operator comfort by the rapid deployment of recent digital controltechnology in its products. There are two major types of earth moving equipment operating in largenumbers: excavators and wheel type loaders. Excavators have received much attention by theindustry recently. The wheel type loader product studied in this paper is another example of a highvolume versatile machine at the opposite end of the configuration spectrum. A state of the artelectro-hydraulic open centered non-pressure compensated valve control system is studied toevaluate the potential gains by implementing digital velocity servo control. The control objectives areto (1) meet operator perceived response requirements, (2) meet operator perceived smoothnessrequirements, (3) create a sub-system that could accept commands from an autonomous high levelplanning controller. Closed loop digital velocity control is successfully implemented in the racking motion of a wheelloader using a standard proportional-integral (PI) and a dynamic valve transform algorithm. Thedynamic valve transform is a function of hydraulic flow rate which is a function of engine speed androd end cylinder pressure. Robustness of performance was verified through extensive systemmodeling, validation, and hardware tests on a large Caterpillar wheel loader model 990.