Application of a MIMO-PID Controller for a Hydraulic Excavator Considering the Velocity of CoM

Abstract

There are many machines that require human operation in industry, and high operational skills are required to operate these machines efficiently. However, the number of highly skilled workers is decreasing due to the recent trends of falling birthrate and population aging. This decline is particularly pronounced in the construction industry, while the demand for construction workers remains high owing to the increasing number of developed infrastructures. To reduce this mismatch between the supply and the demand, it is important to achieve high efficiency in tasks using hydraulic excavators, because these machines can greatly increase the productivity at construction sites. Accordingly, it is necessary to improve productivity even if unskilled operators use hydraulic excavators. This paper proposes a control system that achieves efficient motions based on the velocity of the center of mass (CoM) of the hydraulic excavator’s attachments, which reflects the characteristics of skilled workers’ operations. The motions of multiple attachments give rise to interference terms owing to the characteristics of the hydraulic system. A two-input two-output control system, in which the input consists of the lever input and the output is the CoM velocity is constructed. The fictitious reference iterative tuning (FRIT) method is used to calculate the controller parameters. The proposed method was verified by comparing the results of a simulated digging motion and an experiment with an actual hydraulic excavator operated by an unskilled operator.