Vertical error control for the façade-cleaning robot equipped on a gondola

As many high-rise buildings have been constructed in recent years, the demand for cleaning and managing their façades has been naturally increased. In response to such demand, various façade-cleaning robots have been developed to protect human workers from danger. For the reliable operation of façade-cleaning robot on the buildings, it is essential not only to overcome obstacles like window frames but also to clean the exterior walls of building effectively. Among existing façade-cleaning robots, the gondola-mounted façade-cleaning robot has the advantages of good obstacle overcoming, structural simplicity, excellent cleaning ability and easy installation. However, it is frequently observed that areas around the obstacle remain uncleaned due to the limited motion of cleaning unit installed at the gondola and disturbances like the swing of gondola caused by the wind. In this study, a z-axis manipulator (ZAM) is suggested for the gondola-mounted façade-cleaning robot to minimize the uncleaned areas around obstacles. To this end, a laser sensor and a light sensor are tactfully combined to detect the obstacle. Also, the H-infinity (H∞) control method is adopted to ensure the good cleaning performance of proposed manipulator against disturbances like the wind. The simulations and experiments using the proposed z-manipulator show that the magnitude of wind disturbance acting on the manipulator is suppressed from 9.579 mm to about 3.94 mm and the width of uncleaned area around the obstacle is significantly reduced from 31 mm to 6.5 mm.