Senior Design Week 6: Mark Figueroa

This week I Prioritized finalizing the brush system for the Astraeus rover’s robotic cleaning arm. When I initially designed the robotic arm cleaning system I looked into creating custom brushes. I even reached out to a few brush manufacturers to quote us on a design specific to our needs. But the pricing for low-volume, custom antistatic brushes turned out to be way outside our project’s budget. So I pivoted to a more practical solution using ECOMAID Roomba-compatible side brushes which are commercial aftermarket Roomba brushes.

These three-armed nylon brushes are flexible, lightweight, and already optimized for sweeping fine dust in tight spaces which inevitably made them a solid fit for our use case. Plus, nylon bristles naturally generate a static charge as they rotate, which will help lift and disperse fine dust particles like Martian regolith in future testing like originally intended.

To support these brushes mechanically, I designed a 3D-printed housing that holds them in place exactly as they come out of the package with no modifications needed. I also modeled beveled gears that slot into the brush hubs and transfer torque from a pair of compact N20 gear motors mounted in parallel. The entire frame is held together with a crossbar to maintain structural rigidity and gear alignment.

Figure 1: CAD model of the dual-brush cleaning module, featuring Roomba-style side brushes mounted in a custom 3D-printed housing with beveled gear drive and parallel N20 motors.

As I was making the brush mechanism and having the Roomba brushes in hand to see their size and weight, I realized the arm would need additional reinforcement to support the load effectively. I wanted to build off the success of the double-sheered bicep joint, so I applied the same technique to the forearm, adding a double-shear bracket that significantly improved joint stiffness and reduced the flexing. Additionally to reinforcing the forearm, I designed the outer double-sheared plate to tie together both the forearm and shoulder segments. This is intended to give a more unified structure that helps distribute the weight of the brush assembly across the entire arm to both improve the mechanical stability and reduce the stress on individual joints.

Figure 2: Modified robotic arm with double-shear reinforcement on the forearm and outer plate connecting the shoulder for improved structural support.

Once I finished the assemblies, I was able to combine the brush module as its own subassembly in the CAD model of the robotic arm. It's intended to be powered through the rover's 6V rail and designed to spin both brushes at the same speed for consistent cleaning motion. With the hardware now complete and integrated into the arm, the system is fully ready for wiring and future control testing.

Figure 3: Integrated brush module on the end of the robotic arm within Autodesk Fusion