Modular Hardware for Humanoid Robots

Abstract

As humanoid robots advance into real-world deployment, modular hardware design is emerging as a foundational strategy for scalable production, maintainability, and autonomy. For self-replicating humanoids, modularity is not a luxury—it is a necessity.
This white-paper surveys the rationale, design principles, industrial implementations, and open research questions for modular humanoid architectures. We show how physical modularity, paired with intelligent software abstraction, enables fast assembly, field repair, incremental upgrades, and ultimately robotic self-construction in constrained or remote environments. Drawing on biological, mechanical, and cyber-physical inspirations, we argue that modularity is the linchpin of the next era in humanoid robotics.

1 Introduction

Humanoid robots—systems that mimic the kinematic structure of the human body—promise impact across caregiving, logistics, manufacturing, search-and-rescue, construction, and off-Earth exploration. Yet widespread deployment is bottlenecked by complexity, fragility, and high cost.

At Teragon Robotics we pursue self-replicating humanoids: machines able to fabricate and assemble copies of themselves from modular components. Traditional monolithic architectures (sensors, electronics, and actuators hard-wired into the chassis) hamper this goal: they are hard to assemble in low-resource settings, introduce single points of failure, and resist iterative upgrades.
In contrast, modular hardware decomposes the robot into interchangeable, self-contained units that can be swapped, replaced, or produced independently [1].

2 Motivation for Modularity

2.1 Complexity & Maintainability

State-of-the-art humanoids contain O(30–40) active joints and hundreds of sensors. A burned motor bearing in a monolithic knee may require partial disassembly of the torso, forcing technician intervention. For true field autonomy robots must be

• fast to assemble from kit-like parts,
• diagnosable & repairable by non-experts (or other robots),
• functionally flexible, and
• incrementally upgradable.

2.2 The Biological Analogy

Vertebrates reuse modular skeletal segments—vertebrae, limb bones, digits—while the nervous system applies hierarchical control. Evolution edits modules without rewriting the whole body plan [2]. Robotic design can do the same.

3 Defining Hardware Modularity

A modular humanoid robot consists of physical or cyber-physical units that

1. execute a specific function (sense, actuate, compute);
2. include their own power conditioning and protection;
3. attach to a standard backbone (mechanical, electrical, software);
4. can be added, removed, or re-configured by robots or humans with minimal tooling.

Typical interface layers:

• Mechanical – keyed dovetail rails, conical self-centering pins, snap-fit or magnetic docking.
• Electrical – shared 48 VDC bus, pogo-pin or sprung RF coax, Smart-Power over CAN-FD.
• Software – plug-and-play firmware, auto-discovery over ROS 2 DDS, hot-reloadable drivers.

A well-modularised system follows high cohesion, low coupling principles [3].

4 Functional Partitioning

4.1 Macro-modules

• Head – vision, audio, user-interface LEDs, edge-compute SoC.
• Arms – upper arm, elbow capsule, forearm, wrist/end-effector.
• Legs – thigh, knee, calf, ankle/foot.
• Torso Core – battery, system computer, power & comms backbone.
• Spine – passive carbon-fiber truss or actuator-rich series elastic chain.

Each macro-module owns a micro-controller, diagnostics, and isolated power regulation.

4.2 Micro-modules

• Smart joint actuators – BLDC motor + planetary gearbox + driver + encoder in one capsule.
• Sensor pods – plug-in IMU, 3D LiDAR, or tactile tiles.
• End-effectors – quick-release grippers, suction, or tool-changers.

5 Design Principles

5.1 Standardisation

Success hinges on clearly specified interfaces:

5.2 Hot-swappability

Live replacement demands reverse-polarity protection, inrush current limiting, and dynamic node-ID assignment.

5.3 Robot-friendly Manipulation

Modules need graspable chamfers, magnetic alignment funnels, and captive fasteners sized for two-finger grippers.

6 Industrial Implementations

7 Challenges

• Mass & Volume Overhead – capsule casings add 5–15 % weight; mitigate via carbon-fiber composite shells and shared wall design.
• Joint Stiffness – modular flanges introduce compliance; use conical pins + pre-load fasteners to keep backlash <0.1 mm.
• Signal Integrity – long CAN stubs raise reflections; prefer daisy-chain topology, differential pairs, and FEC-enabled protocols.

8 Modularity for Self-Replication

• Assembly-aware geometry – asymmetric tabs to prevent mis-mating, passive chamfers for ±2 mm positional error.
• In-situ fabrication – FDM printing of polymer link shells + off-the-shelf motor cartridges; minimise post-process machining.
• Autonomy stack – REP-2008 compliant ROS 2 hardware-acceleration layer allows newly attached modules to advertise capabilities (power budget, DoF, firmware hash) [8].

9 Software Backbone

• Middleware – ROS 2 Galactic+ with DDS-XRCE for tiny MCUs; QoS automatically downgraded over lossy radio links.
• Simulation – Isaac Sim or MuJoCo for full-robot + module-in-crate kinematics.
• Firmware – each module exposes boot-loader, health topic, and OTA update slot.

10 Beyond Replication

Modular humanoids unlock:

• one-person field servicing (swap a 6-kg arm in <5 min),
• upgrade cycles (e.g., replace Jetson Xavier with Orin without chassis redesign),
• research hacking (configure same platform for gait vs. manipulation studies).

11 Research Frontiers

• Soft modular actuators – electro-hydrostatic or dielectric-elastomer capsules.
• Self-healing connectors – magnetically guided pogo-pins with conductive elastomer.
• Assembly-aware planners – LLM-driven task-and-motion planners generating build trees.
• Co-evolutionary design – generative models that jointly optimise morphology and module inventory.

12 Conclusion

Modular hardware is the catalyst for scalable humanoid robotics: enabling mass production, field repair, incremental evolution, and eventually true self-replication. Teragon Robotics is investing in robust, field-ready modular architectures to realise adaptable, resilient robots that do not just serve humanity—but sustain themselves.

References

1. Yim M. et al. "Modular Self-Reconfigurable Robot Systems," IEEE Robotics & Automation Magazine 14 (1):43–52, 2007.
2. Lipson H., Pollack J.B. "Automatic Design & Manufacture of Robotic Lifeforms," Nature 406:974–978, 2000.
3. Murata S., Kurokawa H., Kokaji S. "Self-Assembling Machine," Proc. IEEE ICRA, pp. 441–448, 1994.
4. Diftler M.A. et al. "Robonaut 2: The First Humanoid Robot in Space," IEEE ICRA, 2011.
5. Apptronik. "Apollo Humanoid Robot," product page, accessed May 2025.
6. Unitree Robotics. "GO-M8010-6 Integrated Joint Motor," datasheet, 2024.
7. Unitree Robotics. "H1 Full-Size Humanoid Robot," product page, accessed May 2025.
8. ROS 2 Hardware Acceleration Working Group. "REP-2008: ROS 2 HW Acceleration Architecture & Conventions," 2023.