Kumar UtkarshRobotics · ROS 2

SCARA conveyor pick-and-place

Hardware + digital twinJun – Aug 2026· Solo project

I started from an open SCARA design and built everything else around it: the URDF from CAD, MoveIt 2 planning, a ros2_control hardware interface, a depth-camera pipeline in OpenCV, a conveyor, and a digital twin that runs next to the real arm. The final demo picks only the colour you ask for.

What it does

  • A 4-DOF SCARA arm watches a conveyor of randomly coloured boxes.
  • A fixed depth camera with OpenCV finds boxes by colour and depth.
  • The arm picks only the selected colour and places it, ignoring everything else.
  • A Gazebo digital twin runs alongside the physical arm.
  • A manual control GUI and conveyor control run through ROS 2.

How it is built

Mechanical
An open SCARA design, adapted and 3D-printed; stepper motors and lead screws.
Firmware
Arduino with a CNC shield driving the steppers.
ROS 2
URDF from the Fusion 360 assembly, MoveIt 2 for planning, a C++ ros2_control hardware interface.
Perception
Fixed depth camera; OpenCV colour and depth detection.
Simulation
A Gazebo world that mirrors the physical cell.
Simulation only
Hand-gesture control (OpenCV + MediaPipe, Part 7) and voice control (speech-to-text, an LLM for task understanding, text-to-speech, MoveIt; Part 9).

The hard part

Moving from hardcoded coordinates to picking from live camera data. I first tried a camera mounted on the robot, then chose a fixed camera as the simpler and more reliable design. On hardware, the work was syncing the twin with the physical arm and validating each subsystem on its own (control GUI, conveyor, camera detection, hardware interface) before the full run.

Gripper above the conveyor
Gripper over the conveyor
The SCARA gripper holding a green block above the conveyor
Block held in the gripper, Aug 2026
SCARA arm with its digital twin shown in an inset
Arm and twin in sync

Status and limits

  • The mechanism is adapted from an open SCARA model, credited in Part 2. My work is the ROS 2 integration, simulation, planning, perception, conveyor cell, electronics and twin.
  • The steppers run without encoders, so closed-loop positioning is not shown.
  • Gesture and voice control were demonstrated in simulation only.
  • I haven't published a measured success rate.

Related

Manipulation in simulation, the arm work that came before this · the 3-DOF arm digital twin · the industrial robotic arm program built on this cell (in preparation).

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