![]() ![]() However, the system will also have quite a lot of internal friction. The classical stepper motor NEMA-17 should be able to provide this. To calculate the minimal needed torque, a mass of 2.5 kg is assumed for the robot as well as a drum radius of 3 cm and an angle of 30° between the robot and the building. In order to make sure the stepper will provide enough torque for the movement part of the robot, a gear reduction is added. The results of these calculations can be found in the following section.Ģ- Design process & Considerations of material and manufacturing choices This force will depend on the mass of the robot and the angle between the robot and the building, which will be largest near the top of the building. This force depends on the frictional constant (static at first then dynamic when the roller gets moving) and the normal force with which the robot pushes against the window. The torque will depend on the frictional force between the rollers and the window. The minimal torque needed will also depend on the angle under which the robot hangs on the building.Ĭoncerning the cleaning part, the determination of the minimal torque is more difficult. This torque depends on the mass the robot will have and on the radius of the drum that will be used to roll up the cable. Regarding the movement part, a minimal amount of torque will be needed at the place where the drum is located. Most of the parts of the robot were laser-cut and 3D-printed from self-made models. In this first subsection, the mechanical designs are discussed. In this section, the initial and final designs of the two subsystems - moving and cleaning subsystems - are discussed, including the mechanical designs, the electronic circuits and the Arduino code that are used to actuate each subsystem. The use of servo motors allows high torque and easy placement in the robot. Each roller is connected to a servo motor that has been modified to turn 360 degrees. The second subsystem is the cleaning part composed of two cleaning rollers. Cables attached around the drums also pass through cable guides to make sure they always leave the robot in the same place and to improve its performance. The first subsystem is the moving part and it contains two drums, each connected to a stepper motor by a set of two gears. The initial prototype consisted of two subsystems. Then, various additions and changes were made to solve this problem leading to a second and final prototype that successfully lifts up itself. However, during the first tests made on this first prototype, an important problem was encountered: the torque provided by the two stepper motors was not sufficient to lift up the robot. An initial prototype was designed based on theoretical considerations (datasheets information, calculations, CAD model). To achieve the desired performance for the robot, two prototypes were built. ![]()
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