Hydraulic Excavator Operation

[Malene Mederios]

Wedeveloped a system to evaluate the skill of operating a hydraulic excavator. The system employs a remotely controlled (RC) excavator and virtual reality (VR) technology. We remodeled the RC excavator so that it can be operated in the same manner as a real excavator and proceeded to measure the excavator's state. To evaluate the skill of operating this system, we calculated several indices from the data recorded during excavation work and compared the indices obtained for expert and non-expert operators. The results revealed that it is possible to distinguish whether an expert or non-expert is operating the RC excavator. We calculated the same indices from the data recorded during excavation with a real excavator and verified that there exists a high correlation between the indices of the RC excavator and those of the real excavator. Thus, we confirmed that the indices of the real excavator and those of the simulator exhibited similar trends. This suggests that it is possible to partly evaluate the operation characteristics of a real excavator by using an RC excavator with different dynamics compared with a real excavator.

Copyright 2020 Sekizuka, Ito, Saiki, Yamazaki and Kurita. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

On February 21, 2006, a 47-year-old equipment operator, who was working for an excavating company, died after he was pinned to a tree by the cab of the hydraulic excavator he was operating (See Figure 1). At the time of the incident, the victim had been directed by the company owner to use the excavator to move dirt, clear debris, and fill a trench with sand at a residential building site. At approximately 1 p.m., the owner left the site for 20 minutes. When he came back, the owner saw that the excavator was parked over the trench and the victim had been pinned to the tree and crushed by the excavator. The excavator had a lock lever which locked the movements of the boom, arm, and excavating bucket as well as the swing function of the excavator; but the lock had not been activated. The owner immediately went to the other side of the tree, reached into the excavator and pushed the left joystick. Because the lock lever was not activated, the owner was able to turn the excavator to free the victim. As the excavator swung to free the victim, its cab pinned the owner to the other side of the tree. The owner yelled for help. Meanwhile, he was able to push the control to turn the excavator to free himself before other workers arrived. One worker called 911 and emergency medical services (EMS) arrived in minutes. The victim was pronounced dead at the scene. The owner suffered broken ribs and a punctured lung, and was taken by a helicopter to a hospital trauma center. He recovered and returned to work one month later.

At approximately 1 p.m., the owner left the site in his pickup truck to get sand for the victim to fill the trench. The owner came back approximately 20 minutes later and, from a distance, saw the excavator parked over the trench and the victim standing on the excavator treads next to a tree. As the owner got closer, he saw that the cab door was open and the victim pinned to the tree by the excavator. His back was facing the cab, as if he were exiting the cab. The excavating bucket had not been lowered to the ground and the lock lever had not been set in the locked position. The excavator was located approximately 6 inches from the tree. It appeared that when the victim was exiting the cab, he inadvertently bumped the left control joystick with his leg causing the excavator to rotate counter-clockwise and pin him against the tree (Figure 1).

The owner immediately went to the other side of the tree, reached into the excavator and pushed the left joystick. Because the lock lever was not activated, the owner was able to turn the excavator to free the victim. As the excavator swung to free the victim, it pinned the owner to the other side of the tree. The owner yelled for help. Meanwhile, he was able to push the joystick a second time, swinging the excavator away and freeing himself before his son and employee arrived. The employee called 911 and EMS arrived in minutes. The victim was pronounced dead at the scene. The owner was taken by a helicopter to a hospital trauma center, having suffered broken ribs and a punctured lung. He recovered and returned to work a month later.

Recommendation #1: Employers should ensure that equipment operators fully understand and strictly follow the safe operating procedures required by manufacturers including, but not limited to lowering the excavator bucket to the ground and activating the swing lock before exiting the machine.

Recommendation #2: Employers should conduct a job site survey during the planning phases of any construction project to identify potential hazards and develop and implement appropriate control measures to protect workers.

Discussion: In this case, the section of Safety and Operation containing safe operating procedures and precautions was not listed in the table of contents of the excavator operation and maintenance manual; although it was found at the end of the manual. The requirement of activating the swing lock when parking or leaving the machine first appeared in the manual on page 24; it was incorporated into the section of Instruments and Controls.

The Fatality Assessment and Control (FACE) program is one of many workplace health and safety programs administered by the New York State Department of Health (NYS DOH). It is a research program designed to identify and study fatal occupational injuries. Under a cooperative agreement with the National Institute for Occupational Safety and Health (NIOSH), the NYS DOH FACE program collects information on occupational fatalities in New York State (excluding New York City) and targets specific types of fatalities for evaluation. NYS FACE investigators evaluate information from multiple sources. Findings are summarized in narrative reports that include recommendations for preventing similar events in the future. These recommendations are distributed to employers, workers, and other organizations interested in promoting workplace safety. The FACE program does not determine fault or legal liability associated with a fatal incident. Names of employers, victims and/or witnesses are not included in written investigative reports or other databases to protect the confidentiality of those who voluntarily participate in the program.

Simlog has also developed a USB-ready Replica Controls Pedal Unit with the very same shape and toe-down/heel-down action of real hydraulic excavator pedals. Having these pedals will enhance the overall effectiveness of your excavator operator training program and reduce your training costs, by helping trainees learn the hands-and-feet coordination required to operate real hydraulic excavators. (If you choose to not have pedals, the joysticks alone can be used as travel levers.)

Possible Setups

Here are three possible arrangements, one with a single display in front that is wall-mounted, one with three displays in landscape mode and one with three displays in portrait mode.

To support such programs, Simlog customers create multi-purpose simulation stations that combine multiple Personal Simulators by using the same computer, the same displays, the same speakers, and especially the same simulator controls.

The simulation software puts you at the controls of a modern hydraulic excavator at work in a typical construction site with both simulated dirt and large boulders, in interaction with an articulated dump truck. Both SAE and Backhoe-Loader joystick patterns are available, and changing the point of view during the simulation is easy with joystick buttons, keyboard function keys and mouse controls.

Through the application of the Operator Assist System, mine sites will benefit from reduced operator burden, improved mine site safety, increased productivity and reduced fuel consumption. The conducting of testing on a site operated by the mining giant will demonstrate the practical application of the Operator Assist System and will help to improve the accuracy of the system going forward.

Mines producing iron ore, copper and other mineral resources are required to provide stable operations 24 hours a day, 365 days a year and the operators of ultra-large hydraulic excavators at these sites are tasked with efficiently digging material and repeatedly loading them onto dump trucks, while carefully avoiding contact and collisions with surrounding machinery. Therefore, developing solutions which proactively support operators by reducing their workload, while enhancing site safety and productivity is a critical issue for the mining industry to explore.

Based on the verification at the mining site and through insights gained via collaboration with customers, such as through this partnership with Rio Tinto, Hitachi Construction Machinery aims to achieve practical application of the Operator Assist System in stages from 2025.

All of the functions of the Operator Assist System enable retrofitting support for the EX-7 series of ultra-large hydraulic excavator models EX2000-7 through to EX8000-7 (operation weight of 200 to 800 tons), backhoe front specification machines to provide added value to customers for machines that they already own.

The Digging Assist function assesses the situation from the load on the hydraulic cylinder and the operation of the front attachment, detected by sensors to automatically improve control of the hydraulic excavator operation according to the situation.

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