City-Climber: Development of a Novel Wall-Climbing Robot

This article describes a novel mobile wall-climbing robot named City-Climber that has the capabilities to move on the ground, climb walls, walk on ceilings, and transit between different surfaces. Unlike the traditional climbing robots using magnetic devices and vacuum suction techniques, and the robots inspired by the gecko foot, the City-Climber robot is based on aerodynamic attraction which achieves good balance between strong adhesion force and high mobility, and can carry a large payload. Since our robots do not require perfect sealing as the vacuum suction technique does, the City-Climber robots can move on virtually any kind of smooth or rough surfaces. We envision that the City-Climber robots will be used in urban environments with potential applications in inspection of high-rise buildings, search and rescue operations, reconnaissance and surveillance. kEyWordS: Mobile robots, suction, wall-climbing robot, aerodynamic attraction IntroductIon In the last few decades, the field of mobile robotics has developed from theoretical research to practical applications. Consumers can now buy a Roomba robotic vacuum cleaner from iRobot Inc. to clean their floors or a Robomow from Friendly Robotics Inc. to mow their lawn. Hospitals have started using mobile robots to deliver lab specimens and the oil industry uses mobile robots to inspect oil pipelines. The military also uses mobile robots to perform various dangerous tasks such as disarming improvised explosive devices and landmines. All of these robots have one thing in common —they all operate in a 2-D space. The City-Climber is part of a new generation of mobile robots that are capable of operating in three dimensions. The ability to move up walls and across ceilings allows these robots to operate in areas that would otherwise be inaccessible and perform tasks that would otherwise be expensive or impossible. These robots can be used for building, aircraft and bridge inspections, tasks which would otherwise require expensive scaffolding and place human workers at risk. Consumer applications of wall-climbing robots include window cleaning and painting; public safety and military applications include surveillance, search and rescue. The Biomimetics Dextrous Manipulation Laboratory at Stanford University has developed a gecko-like wall climbing robot, “Stickybot,” which uses the van der Waals force to adhere to surfaces. Stickybot moves quickly on smooth surfaces, but its current design appears to have a limited payload and the directional adhesive may have trouble operating on dirty or rough surfaces. Michigan State University has produced two wall climbing robots, Flipper and Crawler, which adhere to the walls using micro-pumps to generate suction. The articulated design of these robots allows them to transition easily between two planar surfaces with relatively heavy payload . The downside of the design of these robots is their slow speed and inability to work on rough surfaces such as brick walls. The wall-climbing robot manufactured by Clarifying Technologies Inc. is a commercially available four-wheeled robot capable of quickly driving up rough surfaces; it uses a vortex suction mechanism to adhere to walls. The payload for this robot, however, is limited to about one pound. The goal of our research is to overcome the limitation of these robots by producing the City-Climber robot which is small, lightweight, and be capable of non-destructive adhesion on both smooth and rough surfaces, with strong attraction force to carry a significant payload and sufficient mobility for travel on various planar surfaces and the ability to transit between them. MEchAnIcAl dESIGn The mechanical design of the City-Climber is divided into three main areas; the adhesion mechanism, the drive system and the