A negative pressure wall-climbing robot is a special robot for climbing vertical walls, which is widely used in construction, petrochemicals, nuclear energy, shipbuilding, and other industries. The mobility and adhesion of the wheel-track wall-climbing robot with steering-straight mode are significantly decreased on the cylindrical wall, especially during steering. The reason is that the suction chamber may separate from the wall and the required driving force for movement increases, during steering. In this paper, a negative pressure wall-climbing robot with omnidirectional movement mode is developed. By introducing a compliant adjusting suction mechanism and omni-belt wheels, an omnidirectional movement mode is formed instead of the steering-straight mode, and the performances of adhesion and mobility are improved. We establish the safety adhesion model for the robot on a cylindrical wall and obtain the safety adhesion forces. We designed and manufactured an experimental prototype based on the analysis. Experiments showed that the robot has the ability of full maneuverability in cylindrical walls.

Motivated by practical applications of inspection and maintenance, we have developed a wall-climbing robot with passive compliant mechanisms that can autonomously adapt to curved surfaces. At first, this paper presents two failure modes of the traditional wall-climbing robot on the variable curvature wall surface and further introduces the designed passive compliant wall-climbing robot in detail. Then, the motion mechanism of the passive compliant wall-climbing robot on the curved surface is analyzed from stable adsorption conditions, parameter design process, and force analysis. At last, a series of experiments have been carried out on load capability and curved surface adaptability based on a developed principle prototype. The experimental results indicated that the wall-climbing robot with passive compliant mechanisms can effectively promote both adsorption stability and adaptability to variable curvatures.

A novel wall-climbing robot with multiple attachment modes is proposed. For uneven surfaces, the mechanical model of a spine wheel is brought out to grab the surfaces with its multi-spines. For smooth surfaces, an adhesive belt is obtained by the industrial synchronous belt and the polyurethane material to adhere to the surfaces. To avoid the robot overturning, an adsorption device with flexible skirt edge is presented. In addition, the normal force and motor torque are evaluated respectively. Finally, the prototype of the wall-climbing robot is manufactured and tested, and the experimental results show that the robot could climb the wall surface 0–360° with a maximum load of 0.5 kg.

In this paper, wall-climbing robots with a single suction cup are studied. The robots mainly consist of three parts: A vacuum pump, a sealing mechanism and a driving mechanism. Basic conditions that the robots can adhere to and move reliably on a vertical surface are first established, then the sealing mechanism with an air spring and regulating springs is analyzed, and the synthetic rigidity formula for the sealing loop is obtained. Finally, two application examples are given: One for the ultrasonic inspection of cylindrical stainless steel nuclear storage tanks, and the other for cleaning high-rise buildings.