Mechanics

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General Description

Fejemis is a three wheels mobile robot. The front part in yellow and black is a commercial brush for industry floor. The manual handle has been replaced with the Fejemis drive system. The front wheel can be lowered to allow the brush to be lifted when not in use.

It has been modeled in the cad program OnShape, as you can see in the next figure.

The drawings can be accessed here: https://cad.onshape.com/documents/c3f44096b0f5e4646ed48e3f/w/670467f68cac02b087631e3d/e/e591dbcff8879adc4528ee2b

Main Mechanical Parts

Front Wheel

The front wheel plays an important role in the robot’s movement and overall cleaning performance. It helps guide and steer the robot as it moves through the environment, allowing it to turn, follow paths, and navigate around obstacles while cleaning. As a result, the stability and rigidity of the front wheel directly affect both motion accuracy and mapping quality.

Previous Design

The original front wheel assembly was one of the main mechanical weaknesses of the robot. Its low rigidity caused wobbling during motion, which negatively affected odometry and reduced movement stability. This introduced drift in the generated map and lowered the overall quality of localization and navigation.

Current Design

The wheel assembly was redesigned by adding ball bearings, increasing the infill of the 3D-printed parts, and mounting the magnetic encoder more securely. These changes improved rigidity, produced steadier motion, and reduced map drift.

The updated design is available at this link: https://cad.onshape.com/documents/d35a3b26eb917ad7000d2d0c/w/821c3ada1e18c2055d92ea08/e/35b8a6b1c67d3640704aa6e7 as a downloadable ZIP file for future modification and improvement.

Future Work

Although the redesigned front wheel performs better, the current structure still relies on plastic components that may loosen, deform, or wear over time during repeated use. Future work should evaluate whether a tighter mechanical design, a stronger filament material, or a different material altogether would provide better long-term rigidity and durability.

Another component that should be improved is the support that attaches the linear actuator to the robot. This part should be reprinted with higher infill and thicker side walls to increase its strength and reduce flex during operation. Future team members can assess whether these further changes are necessary based on long-term use and observed wear.