Keiji Nagatani's research while affiliated with Tokyo University and Graduate School of Social Welfare and other places

Publications (304)

Article
Currently, accidents in which hydraulic excavators mistakenly damage buried pipes are becoming a serious challenge. Although prospecting is required to avoid damage to buried pipes, it is a difficult task for workers, and it increases the period required for construction. In this study, we developed an excavator-avoidance system for buried pipes to...
Article
The autonomous dump truck must judge whether the backhoe is ready for loading the sediment for smooth and safe cooperation with the human-operated backhoes. Analyzing time-series data of the human-operated backhoe loading motion is an effective method to build a prediction model. The transition of several primitive motions enables us to predict the...
Article
Full-text available
Due to the declining birthrate and aging population, the shortage of labor in the construction industry has become a serious problem, and increasing attention has been paid to automation of construction equipment. We focus on the automatic operation of articulated six-wheel dump trucks at construction sites. For the automatic operation of the dump...
Article
Full-text available
In this paper, the socio-economic problems facing the construction industry in Japan are presented, including the COVID19 pandemic, an aging population, aging infrastructure, and severe natural disasters, and a project to tackle the problem is introduced. This project, called ‘Collaborative robots for adaptation of diverse environments and innovati...
Article
Semantic maps are an important tool to provide robots with high-level knowledge about the environment, enabling them to better react to and interact with their surroundings. However, as a single measurement of the environment is solely a snapshot of a specific time, it does not necessarily reflect the underlying semantics. In this work, we propose...
Chapter
When a tracked robot moves in a volcanic environment, the robot often has to climb over unfixed obstacles such as rocks on the loose ground. On the other hand, tracked robots with sub-tracks have been proposed, and the climbing performance of these robots on fixed obstacles can be improved by optimally controlling the sub-tracks. However, the effec...
Chapter
The observation of volcanoes is critical in the estimation of volcanic activities and disaster prevention. Volcanic gas from fumaroles is an effective target for these observations. This is because the gas is highly mobile and quickly transmits underground information to the surface. However, as typical volcanic gas has high temperature and contain...
Article
The volcano exploration mobile robot using a phenomenon of rolling down on slopes was developed in our previous study. However, the robot had a problem that it cannot stop on slopes. In this study, to realize a roll-down mobile robot that can stop on slopes, the roll-down locomotion and stop mechanism using transformation by air pressure of the bod...
Chapter
In Japan, expectations for the automation of construction machines are increasing to solve the labor shortage in the construction industry. In this research, a robotization method by retrofitting a robot to conventional construction machines is introduced to lower the introduction barrier for regional construction companies. The target machine is a...
Article
When a volcano erupts, the area around the volcano's crater is restricted to off-limits areas according to the eruption warning level, which prevents people from conducting a detailed investigation near the crater. Therefore, our research group has been researching and developing sensor devices transported and deployed in the restricted area. Previ...
Article
This paper describes an improvement of pneumatic motor response for autonomous steering of conventional six-wheel dump trucks. Pneumatic motors are robust against overload, so it is considered suitable for the steering actuator of six-wheel dump trucks from the hardware point. However, a disadvantage of the pneumatic motor is the low performance of...
Chapter
By installing omnidirectional measurement light detection and ranging (LiDAR) on a mobile robot, it is possible to acquire the surrounding environment. However, not all measurement areas of LiDAR can be used because of laser rays blocked by the robot’s body. Hence, in this research, the authors aim to expand the measurement area of LiDAR by install...
Article
We develop a large-size dump truck that automatically transports sediments loaded by human-operated backhoes. The dump truck is equipped with a driver robot named SAM and sensors. The driver robot can drive the dump truck remotely and autonomously. However, the difficulty of loading sediments is to decide the suitable dump truck parking location th...
Article
There is an urgent need to automate earthmoving works for large-scale six-wheeled dump trucks. At actual sites, a dump truck stops at a loading position, informed by the backhoe's backet, with its bed facing the backhoe. Therefore, it is necessary to plan a path including a turning back and rapidly replan according to the goal position change. Howe...
Article
Full-text available
In recent years, aging of bridges has become a growing concern, and the danger of bridge collapse is increasing. To appropriately maintain bridges, it is necessary to perform inspections to accurately understand their current state. Until now, bridge inspections have involved a visual inspection in which inspection personnel come close to the bridg...
Article
In October 2018, a Corporate Sponsored Research Program, called “Construction System Management for Innovation,” was established at the School of Engineering, The University of Tokyo. The purposes of this program are (1) to research and develop a system to realize “i-Construction,” which can improve productivity in the construction sites by utilizi...
Article
In this paper, we propose a visualization system for the teleoperation of excavation works using a hydraulic excavator. An arbitrary viewpoint visualization system is a visualization system that enables teleoperators to observe the environment around a machine by combining multiple camera images. However, when applied to machines with arms (such as...
Article
In the event of a disaster, unmanned construction with remotely operated construction machinery is critical for quick disaster recovery. Those machines can weight up to several tons and can easily sink on inadequate soil. Therefore, it is important to judge the trafficability of remotely operated construction machinery at a disaster site. In this r...
Article
Development of autonomous construction vehicles is needed because of the shortage and aging of skilled workers. Our purpose is to realize motions of loading and unloading sand and gravel by an autonomous dump truck. This paper proposes a path with two waypoints in front of the goal to realize a switchback. As a result, an autonomous dump truck can...
Article
Civil engineering and construction industires have some fatal accidents, and there are more dangeraous situations that do not reach to the accidents. In the latter case, a worker sometimes generates an emotional reaction on-site. To detect such dangerous situations, in this research, a method to detect dangerous scenes automatically by measureing b...
Article
Measuring and recording an action performed by construction machinery is a very effective task for improving productivity of construction sites. However, measuring and recording the action by construction machinery is time consuming and expensive because the construction site managers have to observe and record data manually. Therefore, it is impor...
Article
Automated construction vehicles are required to compensate for the reduction of workers in construction industry. In one of construction works, earthmoving work, a dump truck and backhoe work in cooperation and some researcher have been developing the automation of a dump truck which could transport sediment. However, it is difficult for the automa...
Article
This paper proposes a soil property estimation method for an autonomous excavation in consideration with soil properties. Previous autonomous excavation methods did not consider such properties of target soil, thus they could not increase excavation efficiency against unknown soil. In this research, one of the properties of target soil, the volume...
Article
In volcanoes, there are “unfixed” obstacles like loose rocks. When a tracked robot moves on a volcano environment, it must climb over them. Although it had been revealed that grousers on track belts are effective for climbing over an unfixed obstacle, it was a rough trend. To know it more in detail, additional studies with more parameters and situa...
Article
Light Detection and Ranging (LiDAR) is widely employed in mobile robots to acquire environmental information. However, it has a limited laser irradiation direction and cannot measure the backside of an object. This paper proposes a method to expand the LiDAR measurement range from any direction to any position, using a mirror installed on the manip...
Article
Construction work for disaster recovery is required in Japan where disasters occur frequently. Unmanned construction is a technology that can be utilized for safe construction by remotely operating an unmanned construction machine, without risk of secondary damage or danger to the humans involved in the disaster recovery. However, there exist probl...
Article
In the construction industry of Japan, the number of labors, particularly experienced labors, is decreasing by decreasing birthrate and aging population. In addition, the number of death in the construction industry is one-third of the number in all industries. To resolve the above problems, autonomous construction system has been researched by var...
Article
As part of the Impulsing Paradigm Challenge through Disruptive Technologies Program (ImPACT)’s Tough Robotics Challenge Program, a group of Japanese researchers developed a new concept construction robot for disaster relief situations. This robot has a double swing dual arm mechanism and has drastically improved operability and mobility compared to...
Article
The construction industry has many fatal accidents. In addition, The number of labors is decreasing due to the declining birthrate and an aging population. Particularly, it is serious problem for local small and medium enterprises (SME). Therefore, our research group has been researching the autonomous system of construction machine. In this resear...
Article
When teleoperating mobile robots, there is a danger that the robots tumble due to uneven terrain. It is important to avoid tumble because it will cause stagnation of works. In this study, a method to avoid tumbles during traveling in uneven terrain is proposed. This method enables the robots to avoid the tumbles by deciding the robot’s stability an...
Article
The objective of this paper is to model and predict the behavior of backhoe when working cooperatively with autonomous dump trucks. Specifically, this paper focuses on predicting when the backhoe operator is ready to load sand or gravel onto the dump truck. We employ Non-Parametric Bayes Hidden Markov Model to model the behavior of a human backhoe...
Article
By installing omnidirectional measurement type LiDAR(Light Detection And Ranging) on a mobile robot, although it is possible to acquire the surrounding environment, not all measurement areas of LiDAR can be used; therefore and a blind spot occurs. In this research, we aim to expand the measurement area of LiDAR by installing mirrors at this blind s...
Article
When a volcano erupts, it is too dangerous for humans to observe the volcano from close to it. Therefore, a UAV-UGV robotic observation system was developed by the authors’ research group. In this system, UGV (unmanned ground vehicle) is transported to a landing point by UAV (unmanned aerial vehicle), and the UGV moves to observation points by remo...
Article
We propose a planar omnidirectional crawler mobile mechanism for the mobile basis of search and rescue robots. One of the advantages of the planar omnidirectional crawler mechanism is that it allows the robot to move in any direction without causing large slippage on soft ground because it does not require a turning motion when the robot switches i...
Article
When a natural disaster occurs, investigation and restoration are necessary to prevent damage spread. However, disaster scenarios always have a risk of secondary disasters, making it difficult to send in human for a response. In such situations, it is common to use unmanned construction machines. Moreover, recently, intelligent construction machine...
Article
When a tracked robot explores a volcanic environment, it faces difficulty in climbing over unfixed obstacles such as loose rocks on the ground. Such unfixed obstacles sometimes cause the sliding-down or tipping-over of the robot. Although such phenomena should be avoided for the success of the mission, they have not been sufficiently studied yet. T...
Chapter
In disaster areas, operating heavy construction equipment remotely and autonomously is necessary, but conventional remote-controlled heavy equipment has problems such as insufficient operability, limited mobility on slopes and stairs, and low work efficiency because of difficult remote control. As part of the ImPACT-TRC Program, a group of Japanese...
Article
Investigation of active volcanoes by robots is required to grasp their situation. Considering that volcanic environments are rough terrain, tracked robots are suitable for the investigation. When a tracked robot travels on a volcanic environment, it must climb over obstacles. The obstacles on a volcanic environment can be roughly divided into “fixe...
Article
As part of the Impulsing Paradigm Challenge through Disruptive Technologies Program (ImPACT)'s Tough Robotics Challenge Program, a group of research leaders at Osaka University, Kobe University, Tohoku University, Tohoku University, The University of Tokyo and Tokyo Institute of Technology developed a construction robot for disaster relief in order...
Article
This paper proposes a method to visualize running stability of robots in its surrounding terrain. The stability should be evaluated by taking account of the physical interaction between a robot and terrain. In this study, the dynamics of the robot behavior in the terrain is calculated in advance with a dynamic simulator, and the stability is assess...
Article
Fumaroles investigation is an effective method for prediction of a volcanic eruption. However, some fumaroles are located in places where humans are not able to reach, such as steep slopes or depressions. In this research, we propose a tether-towing 2-wheeled robot to enable investigation of fumaroles located on steep slopes. To confirm the validit...
Article
We propose teleoperation using aerial video taken by multi-rotor UAV to increase operability of the remote control construction machine. Outside view camera commonly using in remote construction is fixed on the ground, thus the viewpoints are limited, but our method provides free views. On the other hand, there are no examples that are using an aer...
Article
In recent years, Japanese general contractors have two problems: poor working environments and reduction of laborer due to a declining birthrate and an aging population. Particulary, this problem becomes serious in local small and medium-sized enterprises(SME). Therefore, our research group has been conducting research aiming at realization of auto...
Article
When a volcano erupts, molten rocks, ash, pyroclastic flow, and debris flow can cause disasters. Debris flow is responsible for enormous damage across large areas. This makes debris flow simulations a crucial means of determining whether to issue an evacuation warning for area residents. For safety purposes, restricted areas are designated around v...
Article
Multi-rotor unmanned aerial vehicles (UAVs) are used in various applications because they can hover and take off and land vertically. Although they are useful for civilian applications, their cruise flight speeds are limited owing to the generation of a pitching moment in a uniform flow. However, aerodynamic forces acting on multi-rotor UAVs have n...
Article
Full-text available
Multi-rotor unmanned aerial vehicles are unstable in headwind because of nose-up pitching moment generation and thrust degradation. Reducing the pitching moment generation could enhance the tolerance of the unmanned aerial vehicles to wind and improve cruise flight speed. In this study, a canted rotor configuration was proposed to reduce the moment...
Article
Small multirotor unmanned aerial vehicles (UAVs) are convenient for multiple applications because they can hover and vertically take off and land. However, their posture in landing motion is unstable because of ground effect. However, ground effect on small quadrotor UAVs has been unclear compared to that of an isolated rotor. To examine the ground...
Article
Recently, the devices tethered on 10m and longer string to micro unmanned aerial vehicles (MUAV) are used in sample return, remote area exploring, or transportation to remote place missions. However, because of the pendulum effect and the lack of movement dumping in the air, the tethered object starts to oscillate uncontrollably, fails to land safe...
Article
Up to now, we have constructed a system that makes it easy to control general construction machine remotely. In this research, we describe a camera system using a Tether Powered Multirotor, which is a system for shooting a construction machine from the outside in the system. As a result of conducting practical tests on the Tether Powered Multi-roto...
Article
In 2015, Field Robotics Laboratory at Tohoku University had joined a competition named “ARGOS” which stands for Autonomous Robot for Gas and Oil Sites. It is a challenge to develop a robot that can autonomously patrol and inspect a gas and oil plant site. During the second competition at the competition site, the robot “AIRK” had a problem that it...
Article
As part of the Impulsing Paradigm Challenge through Disruptive Technologies Program (ImPACT)'s Tough Robotics Challenge Program, a group of research leaders at Osaka University, Kobe University, Tohoku University, Tohoku University, The University of Tokyo, Tokyo Institute of Technology, and Komatsu Ltd. developed a construction robot for disaster...
Article
When a natural disaster occurs, it is necessary to perform emergency restoration work using an unmanned construction machine. To support the work, the authors are considering a method using wired Micro Unmanned Aerial Vehicles (MUAV) to obtain an external viewpoint for remotely controlling a construction machine. For MUAV's autonomous flight in var...
Article
When an eruptive activity began in active volcanoes, it is difficult to enter the volcano area. Therefore, expectations for robotic exploration are increasing to get information for observing the status of volcanos. Tracked vehicles have high terrainability, so it is suitable for exploring volcanic environments. However, when such a vehicle travels...
Article
Full-text available
Odometry is widely used to localize wheeled and tracked vehicles because of its simplicity and continuity. Odometric calculations integrate the wheel or track’s rotation speed. The accuracy of position thus calculated, is affected by slippage between the ground and the wheel or track. When traveling on a loose slope, the localization accuracy of th...
Article
Full-text available
In search-and-rescue missions, multi-degrees-of-freedom (DOF) tracked robots that are equipped with subtracks are commonly used. These types of robots have superior locomotion performance on rough terrain. However, in teleoperated missions, the performance of tracked robots depends largely on the operators’ ability to control every subtrack appropr...
Conference Paper
In Japan, several types of natural disasters such as floods, earthquakes, and volcanic eruptions have occurred and will likely occur in the future. Therefore, civil engineering works are required for restoration after such natural disasters, and teleoperated construction machines have been developed to facilitate such works. Dur- ing the operation...