In recent years, the working population in the construction industry has been declining. However, the number of construction works projects is increasing because of the increase in development and infrastructure maintenance. Therefore, it is necessary to meet this increasing demand with limited resources. Productivity at construction sites is significantly improved through the extensive use of hydraulic excavators. However, productivity is affected by the skill of excavator operator. In addition, it is difficult and time-consuming to learn the operation of the machines required to achieve an efficient level of work. Therefore, novice operators need support to achieve high productivity. In this study, the behavior of the combined center-of-mass of the excavator attachment as an index that expresses the difference in operating characteristics of operators for hydraulic excavators is focused. In addition, a control system that assists the operation in excavation work based on the velocity of the combined center-of-mass of the attachment is proposed. Furthermore, the database-driven control is applied to correspond to the nonlinear characteristics of a hydraulic excavator. The proposed method is implemented on a hydraulic excavator and its effectiveness is verified.

No abstract

In recent years, there has been strong focus on sustainable development goals (SDGs). In Japan, Society 5.0, which is proposed as a future vision to be achieved towards the realization of SDGs, is being promoted by various organizations. In particular, “i-Construction” is being promoted in the construction industry. As a result, hydraulic excavators are becoming increasingly automated and semi-automated. Furthermore, if operators achieve high productivity, it helps them maintain a sense of accomplishment and motivation to work. In this study, a control system that results in the desired output is proposed for a hydraulic excavator; in this system, the degree of interference depends on the human input and controller input. Attachments on hydraulic excavators cause interference owing to the characteristics of the hydraulic system. Therefore, a control system that can adaptively adjust the controller input to the human operation, considering the interference with information caused by human operation stored in the database, was constructed. The proposed method was implemented on a hydraulic excavator and its effectiveness was verified.

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.

The fictitious reference iterative tuning method is used to design Proportional-Integral-Derivative (PID) controllers to achieve desired performance for industrial machines. However, the desired control performance cannot be obtained by this method, if the system characteristics changed in steady state. In this paper, design method of a PID controller using the Fictitious Exogenous Signal is proposed. The change of system characteristics is considered as an impulse-like virtual disturbance. The Fictitious Exogenous Signal to calculate PID parameters is obtained from a set of operational data. The effectiveness of the proposed method has been verified by numerical examples.