The MIRTE Master platform provides a capable but general-purpose starting point for a laboratory cleaning robot. Out of the box, it offers omnidirectional mobility, a four-degree-of-freedom manipulator, and an integrated sensor suite. However, several of its design choices were not well-suited to the specific demands of autonomous waste collection and sorting. This section documents the physical modifications made to the platform: what was changed, why, and how each modification contributes to the overall system’s ability to reliably detect, grasp, and sort laboratory objects.
Original MIRTE Master Platform¶
The original MIRTE Master hardware consists of three main parts:
Mobile base
Electronics
Robotic arm
The mobile base utilizes four geared DC motors with Hall encoders, connected to 97 mm mecanum wheels. This configuration enables omnidirectional movement, which is useful for navigating in small indoor spaces. The base also contains rearward-facing ultrasonic sensors, an IMU, a 2D LiDAR and an RGBD (depth) camera.
The electronics of the original platform are based on an Orange Pi 3B and a Raspberry Pi Pico H, following a two-tier software architecture that separates high-level task logic from low-level execution. The Orange Pi functions as the main computer, handling computationally intensive tasks. The Pico, as the embedded controller, handles lower-level control tasks such as driving the motors and reading lightweight sensor data. The MIRTE Master also includes a custom PCB to connect the motors, sensors, and power system in a structured manner, powered by a 5 Ah 12 V Li-ion Parkside drill battery. No significant changes were made to the electronics for this project.
The robotic arm is mounted on top of the mobile base and has four degrees of freedom, which are driven by four serial bus servo motors of varying strengths. A gripper and RGBD camera are mounted at the end of the arm for object scanning and manipulation.
The original hardware components can be seen in Materials.
Design Goals for the Modified Robot¶
Despite being a capable platform, several aspects of the original design presented practical limitations for this specific use case. The PMMA chassis plates proved brittle under load, cracking during early testing. The RGBD camera, mounted low at the front of the chassis, was too close to the ground to produce reliable depth estimates for small objects on the floor. The gripper’s contact surfaces lacked the friction needed to reliably grasp small, smooth electronic components. Finally, the platform had no provision for storing or separating collected objects. These shortcomings directly motivated the modifications described in the following sections.
The main design goals are:
Increase the stiffness and reliability of the chassis.
Add space for collecting and separating waste.
Mount the camera in a position that enables object detection.
Improve the battery mounting system.
Improve cable management.
Modify the gripper so it can pick up waste objects more reliably.
Chassis Modifications¶
The original MIRTE Master chassis was designed as a general-purpose mobile manipulator base. For this use case, the robot also needed to carry waste bins.
The chassis consists of six side panels and a top and a bottom plate. In the original model, the top and bottom plates were made of clear PMMA. Although PMMA allows the user to see the status of the electronics by looking at the LEDs on the inside, early testing of the MIRTE Master showed that it was not suitable, as attempts to assemble the robot often resulted in shattered plates. The fracture toughness of PMMA (0.7–1.1 MPa·m), which is approximately 30 times lower than that of aluminium (23–35 MPa·m), makes it prone to sudden brittle fracture under mechanical load. Therefore, the PMMA was replaced with aluminium. To still be able to see the status LEDs, the six side panels were 3D-printed using translucent PETG. Two separate waste bins were also added to the rear of the chassis, as they allow the robot to collect, store and separate objects after picking them up.
Gripper Modifications¶
The original MIRTE Master gripper is useful as a general robotic gripper, but the cleanup task requires it to reliably handle objects that vary widely in shape and size.
The original gripper geometry is suitable for holding small and large objects; however, the gripping surface is not. Electronic components tend to have small areas of contact with the gripper, making slippage likely during lifting. To improve gripping performance, the contact patches are layered with soft 83A TPE, coated with an additional layer of Bison Rubber anti-slip coating.
During the initial testing phase of the RGBD camera, it was found that the mounting point was too low for any objects close to the ground to be visible. Although the camera was originally intended to be mounted on the chassis, mounting it on the end of the arm proved beneficial for this project. In addition to the elevated vantage point, this allows for programmable viewing angles. Furthermore, the RGBD camera is now also used for object detection, making the secondary RGB camera unnecessary.
Summary of Hardware Changes¶
| Subsystem | Original design | Modified version |
|---|---|---|
| Chassis | Standard MIRTE Master frame with PMMA | Strengthened top and bottom plates with aluminium |
| Storage | No dedicated cleanup storage | Two separate waste bins added |
| Camera | RGBD camera mounted at the front of the chassis | RGBD camera mounted on the gripper |
| Wiring | Standard cable routing | Slightly improved cable management |
| Gripper | Original MIRTE gripper | Improved gripping surface |
The complete model can be explored using the interactive 3D interface below (Mechanical). The CAD files can be found here.
Source
from IPython.display import HTML
HTML("""
<script type="module" src="https://unpkg.com/@google/model-viewer/dist/model-viewer.min.js"></script>
<model-viewer
src="https://matt-rbt.github.io/Lab-Cleanup-Robot-using-the-Mirte-Master-Platform/models/mirte_masterog3.glb"
camera-controls
auto-rotate
exposure = 0.4
style="width: 640px; height: 640px; background: #1c1917;">
</model-viewer>
""")
# IMPORTANT:
# The model path is an absolute GitHub Pages URL on purpose.
# A relative path like "./models/floor_with_cubes.glb" works locally in VS Code,
# but fails on the deployed MyST site because the page is served from /coverageplanners/.
# Do not change this to a relative path unless you also test the deployed site.