With the spread of skyscrapers with large areas of glass windows, robotic cleaners, which can replace and so protect people from the risk of falling, have been seen as a viable option as robotic technology becomes more and more advanced. Various kinds of adhesion, actuation and locomotion systems exist for the different needs of climbing robots enabling them to work in different circumstances with different abilities, both on ferrous-magnetic and non-ferrous- magnetic surfaces, ground and walls and with slow or fast motion. Today there are many types of adhesion: magnetic, vacuum and dry, etc. Likewise, different sorts of locomotion are popular: legged locomotion, tracked locomotion and wheeled locomotion. However, there are increasing problems using climbing robots, such as complex structures, stepping over obstacles and high price. Some of these limitations are gradually being solved.

This thesis develops a robotic structure, named Hubbot. It will achieve a combined set of motions, consisting of linear motion, rotational motion, leg extension/retraction motion and interference avoidance motion. It has a simple and light weight structure. From the perspective of a simple design, a hub will be presented as well as some symmetrical legs instead of a multi- joint legged moving structure. From the perspective of reducing the weight, a rack and pinion gear is driven by a hung, reversible motor. From the perspective of operating savings, Electric Linear Actuators (ELA) are suggested to replace pneumatic cylinders.

A literature review described drawbacks of common locomotion mechanism, such as more complicated structure in legged locomotion mechanism than other mechanisms, especially translation locomotion mechanism. With respect to actuation mechanisms, ELA has the obvious advantages of light weight and high force and a simple structure among all actuators, even alternative to pneumatic actuator. Likewise, with comparison to other adhesion mechanisms, vacuum suction mechanisms present the simpler structure as well as flexible working terrains, but they could not work on rough or cracked surface. (A table makes the comparisons clearer and much more.)

Requirements for a window cleaning robot, such as light weight and working conditions, are presented. To address the problems mentioned before, the potential design using a hub is described. The rack and pinion gears mentioned above that are separately mounted to the two modules drive them to linearly move successively using one servo motor. However, the rack must totally separate from the pinion before each module is driven to rotate respect to each other by another servo motor. These reduce the number of motors needed. Those symmetrical pillars may avoid a complicated Degree of Freedom (DOF) as well as help the robot move and overcome barriers flexibly via 4 ELAs and 4 fixed legs. Further, the four position arrangements of these legs are proposed and compared as well as the assembly of these legs and solenoid valves. (A table makes the comparisons clearer.) Most importantly, based on the working situations of this robot, the kinematic and dynamic analysis regarding its velocity and acceleration, adhesion force and motor force, are performed.

Furthermore, a structural optimization of the rotational mechanism is shown by three different bearing arrangements. The aim is to choose the best one to ensure the rigidity of the shaft and reduce the cost of the robot. Also, the method of attaching these kinds of bearings is indicated and compared by 3D CAD models. (A table makes the comparisons clearer.)

Finally, a functional embodiment design is presented as well as its whole structure’s exploded view, consisting of three mechanisms: locomotion, adhesion and actuation. The four motions are highlighted showing in detail through their sequence formulations.