Just1

Build around the documented power and parts choices

The hardware guide selects an 8 GB Pi 4, four TT motors, two L298N drivers and 60 mm mecanum wheels. It separates the Pi's 5 V, 3 A power bank from the six-AA motor battery holder. A rechargeable motor supply is mentioned as a future alternative, not a fully specified replacement configuration. The repository includes a STEP assembly, printable STL components and wiring diagrams, but their presence is not a fit or electrical test. [S004] [S005] [S006]

The $250 headline comes from a March 2025 US parts table. That table assumes access to free chassis printing and lists screws, wires, spacers and a switch separately. A builder should price the chosen camera, printing, accessories, batteries and delivery before treating it as a complete budget. No current delivered build total was verified here. [S006]

Follow the selected software route

The setup guide targets Ubuntu Server 24.04 and ROS 2 Jazzy, with RTAB-Map, Nav2, the Madgwick filter and Foxglove bridge. Its camera setup builds libcamera and libcamera-apps from source. Those clone instructions do not pin dependency revisions, so preserving this project commit alone does not preserve the complete installation. No installation commands were run in this review. [S002] [S007]

The launch file provides manual, diagnostics and autonomous modes. In autonomous mode, Foxglove is used to inspect the map and publish navigation goals. There is an important optional-camera detail: the hardware guide calls the camera optional, but the launch file starts the camera node in both manual and autonomous modes. Omitting the camera therefore calls for checking and adapting that launch configuration; this review does not claim a tested camera-free setup. [S005] [S007] [S010]

Read wheel commands and odometry differently

The autonomous motor controller converts velocity commands into wheel RPM using fixed wheel radius and chassis dimensions, then converts those RPM values to bounded motor percentages. Its wheel_speeds message contains calculated RPM commands, not encoder feedback. Adding wheel encoders is still listed as a future improvement in the overview. [S001] [S009]

The node documentation describes lidar scan matching and IMU data as the input to ICP odometry. Consequently, a wheel command does not demonstrate that the robot actually moved at that speed. The provided diagnostics mode can help a builder check individual wheels and movements, while sensor transforms must match the physical installation. This commissioning sequence is an editorial recommendation, not a test performed here. [S008] [S009] [S010]

Upstream reports that the lidar placement misses obstacles below 20 cm. It also reports high CPU utilization during navigation, with RTAB-Map, Nav2 and the camera contributing load. Those observations are useful constraints for an indoor experiment, but this review does not establish collision avoidance reliability, achieved speed or available computing margin. [S001] [S007]

What the source release covers

The root license is MIT for software and associated documentation. Third-party driver code and dependencies retain their own terms. The archive includes STEP, STL and wiring artifacts, but this review did not establish a separate hardware-design grant or complete source for the purchased electronics. No printed assembly, power system, calibration or navigation test was performed. [S003] [S004] [S005]