Several infrastructures, such as bridges and tunnels, require periodic inspection and repair to prevent collapse. There is a strong demand for practical bridge inspection robots to reduce the cost and time associated with the inspection of bridges by an inspector. Bridge inspection robots are expected to pass through obstacles such as bolted splice part and right-angled routes. The aim of this study involved developing a bridge inspection robot that can travel on a right-angle path as well as splicing parts. A two-wheel-drive robot was developed and equipped with two rimless wheels as driving wheels. A neodymium magnet was provided at the tip of each spoke. Non-driving wheels were attached at the rear as a rotatable caster. The robot can turn on the spot to avoid the bolt on the splicing part. Experiments were conducted to check the performance of the robot. The results confirmed that the robot passed through the internal right-angle paths in a laboratory and in an actual environment that corresponds to a box girder of a bridge. It is extremely difficult to manually control a robot on the splicing part. Therefore, a camera and an LED (light emitting diode) were attached to autonomously control the robot. The results indicate that the newly developed robot could run through the splicing part without hitting the nuts.

Robotic fish are ideal for surveying fish resources and performing underwater structural inspections. If a robot is sufficiently fishlike in appearance and does not use a screw propeller, real fish will not be easily surprised by it. However, it is comparatively difficult for such a robot to determine its own position in water. Radio signals, such as those used by GPS, cannot be easily received. Moreover, sound ranging is impractical because of the presence of rocks and waterweed in places where fish spend a lot of time. For practical applications such as photographing fish, a robotic fish needs to follow the target fish without losing awareness of its own position, in order to be able to swim autonomously. We have developed a robotic fish named FOCUS (FPGA Offline Control Underwater Searcher) which is equipped with two CMOS cameras and a field-programmable gate array (FPGA) circuit board for data processing. The forward-facing camera is used to track red objects, since this is the color of the fish of interest. In addition, using visual information obtained with the bottom-facing camera, the robot can estimate its present position. This is achieved by performing real-time digital image correlation using the FPGA. However, until now, the position estimation accuracy has been poor due to the influence of yaw and roll. In the present study, the position estimation method has been greatly improved by taking into account the yaw and roll values measured using gyro sensors.

Many social infrastructures and buildings are aging. Therefore, inspections to find deteriorated parts to prevent accidents are important. However, significant costs and inspection time are required for the current technologies. Therefore, inspection methods using robots are attracting attention. As the most appropriate option to traverse freely on concrete bridges and building walls is by traversing with lift force from propellers, a robot called HORNET has been developed that can run along a wall with two rotors. However, the floating-type robot with propellers could drop from a wall if hit by strong wind. Therefore, a gyro sensor was installed in the robot to detect its posture and adopted a simple maneuvering assist control to reduce the above-mentioned issue. In this study, the motion of HORNET was analyzed and a simple control system was designed to realize the maneuvering assist control. It was confirmed that the resistance of HORNET to the crosswind was improved by adding the control system.

Underwater robots are often used to investigate marine animals. Ideally, such robots should be in the shape of fish so that they can easily go unnoticed by aquatic animals. In addition, lacking a screw propeller, a robotic fish would be less likely to become entangled in algae and other plants. However, although such robots have been developed, their swimming speed is significantly lower than that of real fish. Since to carry out a survey of actual fish a robotic fish would be required to follow them, it is necessary to improve the performance of the propulsion system. In the present study, a small robotic fish (SAPPA) was manufactured and its propulsive performance was evaluated. SAPPA was developed to swim in bodies of freshwater such as rivers, and was equipped with a small CMOS camera with a wide-angle lens in order to photograph live fish. The maximum swimming speed of the robot was determined to be 111 mm/s, and its turning radius was 125 mm. Its power consumption was as low as 1.82 W. During trials, SAPPA succeeded in recognizing a goldfish and capturing an image of it using its CMOS camera.

Terrestrial hermit crabs which are a type of hermit crabs live on land, whereas typical hermit crabs inhabit the sea. They have an ability of climbing a tree vertically. Their claws allow them to hang on the tree. In this study, an outer-pipe inspection robot was developed. Its locomotion mechanism was developed in imitation of the terrestrial hermit crab’s claws. It is equipped with two rimless wheels. Each of the spokes is tipped with a neodymium magnet, which allows the robot to remain attached to even a vertical steel pipe. Moreover, the robot has a mechanism for adjusting the camber angle of the right and left wheels, allowing it to tightly grip pipes with different diameters. Experiments were conducted to check the performance of the robot using steel pipes with different diameters, placed horizontally, vertically, or obliquely. The robot attempted to move a certain distance along a pipe, and its success rate was measured. It was found that the robot could successfully travel along pipes with vertical orientations, although it sometimes fell from oblique or horizontal pipes. The most likely reason for this is identified and discussed. Certain results were obtained in laboratory. Further experiments in actual environment are required.