Fig. 5. Reconfigurable modular exterior wall cleaning robot A reconfigurable modular external wall cleaning robot has been successfully developed by Daiko University in Japan, as shown in Figure 5. The robot is composed of a cleaning device, a biped module and a control module. The sequential control based on inverse kinematics and the fifth polynomial interpolation is used to generate the desired step gait. Its main advantage is its modular design, which not only allows for functional expansion, but also saves costs. The experiment has proved that the robot can realize the cycle cleaning of exterior wall surface with 155s.