Design and Kinematic Analysis of Tethered Guiding Vehicle (TGV) for façade window cleaning

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To make the task of manually cleaning skyscrapers and façades less dangerous, several window cleaning robots have been developed, each with their own limitations. In this paper, the design and kinematic analysis of a tethered guiding vehicle system (TGV) is presented. The TGV would carry an already available window cleaning robot and transport it over the surface of a building.

As can be seen in the figure, a TGV carries an already existing window cleaning robot. In this case, a Windoro is carried. The TGV can climb by means of a mechanism with nylon ropes. Spinning wheels come into contact with the ropes and as a result of friction the TGV is displaced vertically. The wheels are driven through a gear transmission. When there is wind and the ropes are swinging, the wheels could lose contact to the ropes. To solve this issue, the ropes are guided by linear bearings.

The TGV is modeled by means of modeling software and properties like center of gravity, average density, moments of inertia are determined, etc.. Based on these properties, both the forces acting on the TGV and the required driving forces are calculated. This is done by making a free body diagram of the TGV and applying equilibrium of forces in horizontal and vertical direction. This static part is relatively simple in comparison with the kinematic analysis of the guiding robot.

In the kinematic analysis, a free body diagram of a single wheel is made and driving forces are expressed as function of the friction forces by means of geometry. Important parameters in the kinematic analysis are the angle of inclination, which is dependent on the building structure, the coefficient of friction between the wheel and the rope, and the angle at which the wheel makes contact with the rope. Expressions for the forces needed to climb up and down are found and safety factors are taken into account. When these forces are known, the required torque for the actuator are calculated and an appropriate motor (Johnson DC gear motor) is selected.

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