The construction industry is one of the largest economical sectors in developed countries. The economical contribution of the construction industry is comparable with the contribution of the manufacturing industry. However, the construction industry is one of the most unfamiliar areas of R&D in the robotics community. The first ideas for construction robots appeared in the 1970s in Japan. Due to quality problems of construction works, lack of skilled labor, low productivity, numerous accidents and fatalities and high construction demand, the first prototypes of construction robots were developed towards the end of the 1970s. Since then more than 200 construction robots and service robots for buildings have been developed, but only about 10% of them have been successfully introduced to the construction market. The development of on-site robots in the 1980s peaked with the development of integrated automated building construction sites in the 1990s. In the beginning of the 21st century humanoid robots were researched and tested. In the future we will see robots that care for the elderly and handicapped as a further development of construction robots.

This issue gives an overview on the state of art of robotic technologies in construction. The introductory article also relates the construction robotics development to the industrial robotics technology in the prefabrication sector of the 1970s, gives examples of various construction robotics developments of the 1980s, the integrated automated building construction sites since the 1990s, and the humanoid construction robotics developments and integrated industrialization efforts of recent date. Robotic subtechnologies such as programming, sensors, kinematics, teleoperation, navigation, human-robot interaction are presented to the reader. During the last years much effort has been devoted to the application of robots and robotics technology in construction works. Most of them are for out-door application, where the tasks are developed in complex unstructured environments and under hazardous conditions. The construction robots introduced during the last years have dramatically improved labor conditions, productivity and quality levels, and also have increased the safety conditions for operators. The nowadays construction robotics technology tries to take advantage of the last developments for control, navigation, localization, human-machine interface or sensor use. However robotics in construction is still a very challenging topic in order to clarify many unsolved R&D issues.

The purpose of this special issue is to provide a review of open issues and new developments in robotics in construction, ranging from major construction engineering projects to residential building construction:

• Robotics for building construction.

• Robotics for civil engineering: roads, bridges, earth moving, etc.

• Inspection, maintenance and infrastructures robots.

• Navigation, mapping and localization of robots in construction environments.

• Technology components for construction robots: 3D sensors, end-effectors, HMI, control strategies, cooperation, safety, etc.

The following article reviews past and current tendencies and derives and describes opportunities for construction robotics and automation. There substantial evidence in the construction industry, that conventional construction methodology has reached its limits. Although approaches of construction robotics are still in an innovation or seed phase, it can be expected that with continuous effort put into research and development these approaches may soon enter a growth phase and encounter adoption on way larger scales. Furthermore, the article describes the different application of construction robotics, proving the ability and efficiency of robot systems in diverse fields. Currently, it can already be observed that single task construction robots, on-and-off site construction robots and automated construction sites are becoming even more and more crucial factors, in order to enhance the overall construction efficiency and building sustainability.

Population projections for Japan suggest that the production-age population, ages 15 to 64, will be 70% or less in 2045 than that of today. In the field of construction, such rapid reductions in the production-age population will bring about a severe reduction in the number of workers as well as budget cuts in infrastructure investment due to the decrease of tax revenue. At the same time, infrastructure, which has already been constructed, is now due for maintenance and approaching its renewal dates. Therefore, the task of stably providing infrastructure for society into the future will be more difficult than ever. In the field of construction, more complex projects will have to be carried out with limited manpower and budgets. This problem will be addressed, not by an extension of existing means, but by innovations in construction technology. ICT (Intelligent Construction Technology) is expected to be a promising tool to meet these future needs. This article discusses current conditions and future prospects for a new construction model utilizing ICT in Japan.

Human workforce working at the Fukushima Daiichi Nuclear Power Plant face severe health and safety risks owing to the presence of radioactive obstacles and debris caused by the accident and the subsequent shutdown of the plant. Under such circumstances, various robots are deployed to undertake many tasks, however, it is not easy for robots to realize smooth locomotion and efficient operation because radioactive debris and architectural structures such as steps and doors tend to hinder their movement. In addition, installable sensors and actuators are restricted in such an environment. To overcome these difficulties, we propose an automated construction system with modularized rail structure for robot locomotion and operation. The structure is anchored to walls or floors and enables working robots to reach a specific destination. This paper describes the development of a rail structure supporting mechanism. The developed mechanism applies resin foam to three different components: the actuator, adhesive material, and structural material. To our knowledge, these multi-modal applications of resin foam are quite unique and novel. Basic experiments were conducted using the developed prototype. Experimental results verified the feasibility of pillar expansion, anchoring, and fixation motions, and they also revealed the impact of the components’ properties on the performance of the supports.

External recognition is important for underwater machinery works. However, acquisition of external field information from optical camera images may not be possible, owing to muddiness of water caused by such work. Furthermore, in order to improve the workability of machines in the scenario of their remote operation, it is important to know the positional relation information between a target object and the end effector. To solve these problems, an acoustic video camera was developed and performance test experiments were conducted at a caisson dockyard. In the experiments, a prototype of acoustic video camera was used to measure and to recognize a target objects and an underwater construction machine. And the feasibility of monitoring for underwater construction using the acoustic videos was evaluated. As a result, it was found that despite the lower accuracy of shape recognition on account of a resolution problem, the positional relation could be recognized satisfactorily since the video images could be presented from an arbitrary viewpoint.

Slope shaping is important for the prevention of and recovery from sediment disasters. Because of the danger of direct operation at disaster scenes, teleoperation is the most efficient method for slope shaping. In this paper, we propose a support system for the teleoperation of slope shaping using a construction robot. The system is composed of two sub-systems: an Augmented Reality (AR) finishing stake system and a system for evaluating finished shape deviation. The former is an AR system which presents a virtual finishing stake to the operator of a construction robot. The latter is an evaluation system which measures the actual shape of the slope in 3D and presents its deviation from the planned shape. Moreover, we developed multiple Computer Graphics (CG) patterns of the virtual finishing stake. In this study, first, we verified the usefulness of a real finishing stake quantitatively via subjective experiments. Then we verified the effectiveness of our proposed systems and identified the optimal CG pattern of the virtual finishing stake via the experiments. Based on the results, we discuss the usefulness of the finishing stake and the effectiveness of our system for slope shaping using a teleoperated construction robot.

This paper presents a method of planning trajectories for the motions of building robots according to the given points of support on the basis of a two-level interpolation. This method features the calculation of speeds at the intermediate points of the trajectory, while duly accounting for the limitations for controlling moments. The combination of analytical and searching methods of calculation makes it possible to obtain a solution during the interval of control.

The Wireless Positioning System (WPS) has gained increasing attention for mobile robot applications in indoor environments over conventional on-board sensors. This is mainly due to their cost effectiveness as well as adaptability for future use. Many literatures on WPS adapted existing wireless infrastructures such as WiFi for mobile robot usage, resulting in relatively impractical accuracy for mobile robot application. A systematic technique must be sought in order to place the wireless nodes where coverage could be maximized and be suitable for a mobile robot positioning system via fingerprinting technique. We propose an effective and simple means to optimize wireless access point (AP) placement. Simulation results by ITU-R P.1238 MWF signal propagation model with automatic wall crossing computation have ensured the maximum coverage for human users using a minimum number of wireless nodes as possible. The mobile robot positioning error employing the weighted k-nearest neighbor algorithm (WKNN) with the average signal strength as fingerprint database yielded significant results when the proposed placements are used over symmetrical placements.

In recent years, unmanned construction based on the teleoperation of construction equipment has increasingly been used in disaster sites or mines. However, operations based on teleoperation are based on 2D images, in which the lack of perspective results in considerably lower efficiency when compared with on-board operations. Previous studies employed multi-viewpoint images or binocular stereo, which resulted in problems, such as lower efficiency, caused by the operator’s need to evaluate distances by shifting his or her line of sight, or eye fatigue due to binocular stereo. Thus, the present study aims to improve the work efficiency of teleoperation by superimposing a 3D model of the terrain on the on-board operator’s view image. The surrounding terrain is measured by a depth image sensor and represented as a digital terrain model, which is generated and updated in real time. The terrain model is transformed into the on-board operator’s view, on which an artificial shadow of the bucket tip and an evenly spaced grid projected to the ground surface are superimposed. This allows the operator to visually evaluate the bucket tip position from the artificial shadow and the distance between the excavation point and bucket tip from the terrain grid. An experiment was conducted investigating the positioning of the bucket tip by teleoperation using a miniature excavator and the terrain model superimposed display. The results showed that the standard deviations of the positioning errors measured with the superimposed display were lower by 30% or more than those obtained without the superimposed display, while they were approximately equal to those acquired using binocular stereo. We thus demonstrated the effectiveness of the superimposed display in improving work efficiency in teleoperation.

Since the industrial age began, increasing numbers of manufacturing plants have been set up to serve economic growth demand. More bridges were built simultaneously to connect cities and to make transportation more convenient. As these facilities have aged, regular maintenance has increased. The limb mechanism project we started almost 20 years ago was to deliver new types of inspection and maintenance to industrial fields. Our first prototype, a six-limb robot called Asterisk, included such capabilities as walking on ceilings, climbing and descending stairs and ladders, walking tightropes, and transversing rough terrain. Asterisk’s latest version uses electromagnets to work in antigravity environments such as steel structures. Unfortunately, this presented a major danger, requiring that we replace electromagnets with electropermanent magnets (EPMs). Limitations on EPMs, however, required a new control strategy. We propose and compare three control methods – open-loop control, closed-loop control using torque feedback, and closed-loop control using angle feedback – in the sections that follow. Our objective is to determine the best control for inspection robots having electropermanent magnets but not using additional sensors.

Efficient economical test methods are widely needed worldwide. One target of this is to develop climbing robots that check for defects in concrete. These concrete-wall-climbing robots generally use suction cups to support themselves and test apparatus, but the danger exists of this expensive equipment falling. This may occur due to one of two reasons. The first is inadequate ring-seal decompression in suction cups and the second is suction cup slippage. We have added claws to suction cups to help prevent slippage. The claws we developed are attached to the suction cups to help grip the wall. In the sections below, we discuss the scratch tests we performed to test claw effectiveness in improving suction cup grip. We then prove through tests under actual conditions that the estimated grip force matched that of an actual suction cup’s grip force with the claw.

This paper presents a test methodology for evaluating the safety of mobile manipulators (robot arms mounted on mobile bases). This methodology addresses the safety concerns relevant to modern, agile, manufacturing practices in which mobile manipulators will play a significant role. We consider 1) the unique capabilities and anticipated uses of mobile manipulators and 2) the potential exemptions and special cases in which their behavior may be unpredictable or otherwise contrary to the safety requirements. Finally, we define metrics for assessing compliance with functional safety requirements and anticipated performance.

The accuracy of efficient flight simulation depends on the quality of the aerodynamic data used to simulate aircraft dynamic motion. The accuracy of such data prediction depends strongly on motion variables, aerodynamic derivatives, and the coefficients used when the complete global aerodynamic database is being building. A surrogate model applied as a prediction method based on several measured points (exact function) used to predict unknown points of interest helps reduce time taken by the experiment or computation. Latin hypercube sampling searches the solution space for aerodynamic data to optimize the experimental design, so the key objective is to develop an aircraft’s efficient digital flight motion by solving equations of motion and predicting aerodynamic data using a surrogate model. To realize these goals, we use sample surrogate model data, acquired from empirical model USAF Stability and Control DATCOM. The database was built for two main variables, the angle of attack and the Mach number, along the longitudinal and lateral axes. Exact and predicted functions were compared by calculating the mean squared error (MSE). The digital flight was validated through mode motion analysis and a flight quality scale to prove flight mission capabilities. A comparison between results predicted by the surrogate model and the exact function showed that flight simulation analysis and prediction ability of the surrogate model are useful in future analyses.

Under the effects of surroundings such as gravitational force, ambient temperature, and chemical substances, each animal has acquired an optimized body structure through its evolution. For example, vertebrate land animals have a sophisticated musculoskeletal structure including not only monoarticular muscles but also multiarticular muscles to support their weight against gravitational force. Many researchers have developed musculoskeletal robots with a biarticular muscle mechanism that enables them to execute physical tasks similar to the mimicked animal. However, the developmental process of the musculoskeletal structure has not been examined in detail in past studies. In this study, we developed a musculoskeletal robot with redundant air cylinders to investigate the developmental process of the body structure of the animal. We proposed a switching mechanism between several muscle structures called the actuator network system (ANS). In the ANS, the selection of mutually interconnected, simultaneously activated air cylinders is changed by switching the interconnections. The experimental results indicate that by changing the connection of the cylinders and the inner pressure of the connected cylinders, i.e., the strength of the connection, the response of the robot to external forces can be modified, thus demonstrating the feasibility of our approach.

Visual recognition of previously visited places is a basic cognitive skill for a wide variety of living beings, including humans. This requires a method to extract relevant cues from visual input and successfully match them to memories of known locations, disregarding environmental variations such as lighting changes, viewer pose differences, moving objects and scene occlusion. Interest point correlation is a visual place recognition method inspired by results from neuroscience and psychology; specifically, it addresses those challenges by converting raw visual inputs to a low-variance representation, selecting regions-of-interest for representation matching, and identifying consistent matching trends. Real-world experiments employing a mobile robot demonstrate that interest point correlation is robust to visual changes, suggesting its founding principles are sound.

We propose a method for conveying human knowledge to home and office assistance robots by teaching them how to perform the process of grasping objects with a custom-made tool. Specifically, we propose a semi-direct teaching method that respects the limitations of the hardware on the robot while utilizing human experience for intuitive teaching. We specify the information necessary for grasping objects through the generation of teaching data, which include the grasping force, relative position, and orientation. To respect the hardware limitations and at the same time allow inexperienced users to perform the teaching process easily, we used a teaching tool that possesses the same mechanism as the end effector of the robot. To simplify the teaching, we developed a sensing system that would reduce the teaching time with accurate measurements. Subsequently, the robot would use the teaching data to grasp the object. Experiments conducted using volunteers demonstrated the validity of the proposed method, wherein the teaching data for three different tasks were generated in less than 30 s each and accurate measurements were obtained for both the grasping position and force for grasping the objects.