Recently, the ratio of the Japanese elderly became more than 26 % in 2020. Under these circumstances, various assisting and rehabilitation devices to help welfare work for the elderly and disabled using pneumatic soft actuators have been actively developed. A pneumatic soft actuator is useful for, not only power assisted system but also a rehabilitation device. In the previous study, the Extension type Flexible Pneumatic Actuators (we call it “EFPA” for short) that could extend 2.5 times of its original length was proposed and tested. W. Tian developed the Tetra hedral shaped Soft Actuator (we call it “TSA” for short) for wrist rehabilitation. Usually, a pneumatic actuator was often used for wearable and rehabilitation devices because it has an advantage of compliance based on air com pressibility. Especially, a pneumatic soft actuator is more suitable because it has more advantages such as lighter weight and more compliance based on flexibility. Based on this concept, K. Hase developed the mobile robot using six TSAs for core training and amusement. The mobile robot consists of six TSAs. The control system that consists of the tested robot and 18 on/off valves was also developed. The sequential driving pattern for moving forward and rotating in clock-wise and counter clock-wise was investigated. As a result, it could be confirmed that the tested robot can move toward six directions and rotate toward both clock-wise and counter clockwise. In the report, in order to increase the carrying force per unit plane area of the robot, a miniaturized Tetrahedral shaped Flexible Pneumatic Actuator (TSA) was proposed and tested. The generated lifting force of the improved TSA with miniaturization was investigated. As a result, it can be confirmed that the generated lifting force of the improved TSA increase because of improved stiffness based on miniaturization and increasing setting angle of EFPA. A small-sized six-legged mobile robot using improved TSAs and a compact pneumatic drive system were also proposed and tested. As a result, it can be confirmed that the tested small-sized mobile robot can translate and rotate smoothly even if the lifting force of the robot is increased compared with the previous one. In addition, due to confirm mobility of the robot, the experiment to overcome obstacles using the robot was carried out. As a result, it can be confirmed that the robot can overcome the step with height of 14.5 mm.
