Development of Rail Camera for Bridge inspection with Attitude Control using Thrust of Rotors

A lot of concrete structures are deteriorating to dangerous levels throughout Japan. These concrete structures need to be inspected regularly to ensure they are safe enough to be used. According to national standards, a visual inspection of the bridge is required once every five years. In the visual inspection, the worker checks the bridge with their own eyes directly. So, it is necessary to set up scaffolding to access the bridge's underside for visual inspection. Alternatively, it is an essential aerial work platform. However, setting up of scaffolding and aerial work platforms is not economical in time and money. So, we developed an inspection device for the check of bridges called a Rail camera. This inspection device connects a rod and a rail and the connection has a rotational degree of freedom. Rotors are attached to the tip of the rod and it can be attitude controlled by thrust of rotors. So, half of the device's weight is lifted by the thrust of the rotors. And it can be taken with a camera mounted on an electric slider on the rail. The worker on the bridge can check the underside of the bridge safely by holding the rod with one hand and operating the rail camera with another hand. The rail camera developed had a rail length of 2 m and a weight of 2.5 kg. Magnesium was used for the rail and rod to reduce weight. Coaxial rotors were used to cancel the counter-torque caused by the rotation of the propeller. To verify the performance, a visual inspection was performed on the bridge. As a result, it was confirmed that the horizontal attitude was maintained by the rotor thrust.