As earthquakes occur frequently in Japan, aging infrastructures such as bridges, chimneys, power lines and tunnels are extremely dangerous from view point of possibility to collapse due to earthquake shaking. Therefore, it needs to investigate a dangerous point in infrastructures immediately to prevent accident. Usually, inspectors have climbed the attached ladders for inspection of some buildings. However, it is very dangerous, because it uses uncertain ladder and it occurs unpredictable weather and conditions. Therefore, in the previous study, the automatic ladder climbing inspection robot that could climb up and down the ladder by using flexible robot arms without giving damage to the ladder was developed. The previous flexible robot arm that consists of three Extension type Flexible Pneumatic Actuators (EFPAs) that can extend about 2.5 times from its natural length. In this study, in order to investigate a dangerous point in hazardous environments such as inside of a nuclear reactor, we aim to develop a ladder climbing inspection robot that can also move horizontally. To construct the desired robot, we proposed and tested a robot arm/leg that consists of four EFPAs with restraint plates. We confirmed that the arm/leg could bend toward eight radial directions every 45 degrees. We also proposed and tested the automatic ladder climbing inspection robot with horizontal mobile function that consists of four arms/legs. The driving tests of ladder climbing up and down motion were carried out. As a result, we confirmed that the tested robot could climb up and down the ladder. Also, the driving tests of horizontal mobile function of the tested robot was carried out. As a result, we also confirmed that the tested robot could move horizontally toward eight directions every 45 degrees.
