Development of a Self-Reconfigurable Manipulator with a Spring-Loaded Screw Ring Docking Mechanism Enabling Tight Fitting Insertion IROS 2026 research project Portfolio

IROS 2026 · Research project

Development of a Self-Reconfigurable Manipulator with a Spring-Loaded Screw Ring Docking Mechanism Enabling Tight Fitting Insertion

Toma Arimura · Kunio Kojima · Takuma Hiraoka · Masanori Konishi · Jin Hirai · Hiromi Tada · Ryota Ishikawa · Kei Okada

Graduate School of Information Science and Technology, The University of Tokyo

A spring-compliant, screw-driven dock enables a modular manipulator to align, connect, and disconnect tightly fitted mechanical and electrical interfaces—while keeping heavy shared components away from the moving limbs.

Paper · IEEE link pending Watch the demo Explore the mechanism
System overview Figure 01
Overview of the self-reconfigurable manipulator, the SLSR docking mechanism, module reconfiguration, and a 10-kilogram lifting demonstration
A lightweight modular architecture, robot-operable docking, and high-load manipulation in one system.
Self-reconfiguration in action Video 01
The manipulator uses its own end effector to detach and reconnect a body module.

01 / Motivation

Reconfiguration should not come at the cost of strength.

Self-reconfigurable robots can change their joint arrangement, link length, and reach for different manipulation tasks. Yet conventional modular systems often carry batteries and computers inside moving modules, increasing distal mass as the robot grows.

Our objective is to combine adaptable body configurations with the force capability of a practical multi-joint manipulator.

Architectural opportunity

Centralize heavy components

Placing shared power and computing in a stationary central module reduces the mass carried by the articulated limbs.

Core challenge

The Tight-Fitting Insertion Problem

Power must cross detachable interfaces. Compact connectors and locating pins need precise coaxial alignment, high insertion and extraction forces, and a rigid, low-backlash connection—all at once.

02 / Proposed approach

Compliance for alignment.
Screw feed for force.

The Spring-Loaded Screw Ring (SLSR) separates reliable docking into a forgiving alignment phase and a forceful insertion phase.

Exploded architecture of the Spring-Loaded Screw Ring, including the locating pin, connectors, screw rings, springs, and outer gear
Mechanism architecture. A compliant male screw ring, a rotating female ring, locating geometry, and electrical connectors share one compact interface.

Spring-Loaded Screw Ring

A strong interface the robot can operate by itself.

The robot divides its functions among a central module, actuator-focused joint modules, and an end-effector module. The end effector drives the outer gear on the docking ring, so the robot can operate its own connections.

  • Coarse alignmentA spherical-tip locating pin guides the two modules toward a common axis.
  • Compliant engagementSpring travel keeps the screw rings aligned while their threads begin to engage.
  • Forceful seatingScrew-feed motion generates the axial force needed to insert or release tightly fitted connectors and locating pins.

Mechanism in motion

Two rings, two complementary movements

The end effector rotates the adapter-side ring, while spring-loaded translation on the receptor side maintains contact and alignment.

Continuous close-up animation of the adapter-side female screw ring rotating
Adapter sideFemale screw ring rotationRotation drives thread engagement and converts torque into axial force.
Continuous close-up animation of the receptor-side male screw ring translating along its axis against spring preload
Receptor sideSpring-loaded male ring translationAxial compliance keeps the thread faces in contact during initial alignment.

Docking sequence

From initial contact to a rigid connection

Spring-assisted thread alignment absorbs small positioning errors before screw-generated thrust completes the tight fit.

Two-stage SLSR docking sequence showing spring-assisted screw engagement followed by forceful connector and locating-pin insertion
The same screw motion is reversed to separate the interface during reconfiguration.

03 / Experiments

Validated from docking reliability to high-load manipulation.

The experiments measured the tight-fit load, isolated the contribution of spring compliance, demonstrated module exchange, and tested the strength of a seven-joint configuration.

Experiment A

Docking reliability under tight-fitting constraints

Experiment overview

We first measured the force needed to separate the tightly fitted interface without screw assistance. We then repeated insertion and extraction ten times with and without the push spring to isolate its contribution to thread engagement.

Baseline extraction force
99.3 N average
With push spring
9/10 insertion · 9/10 extraction
Without push spring
0/10 insertion · 10/10 extraction
Repeated attachment trials, shown at 4× speed.
Experimental setup for measuring extraction force and repeated docking, including an example of misalignment without the push spring
Force measurement and spring-ablation setup.

Experiment B

Self-reconfiguration by the robot itself

Experiment overview

In a dual-arm configuration, the left end-effector module operated the docking ring to remove and reconnect the right-arm tip module. This confirms that the robot can manipulate its own interface rather than relying on external tooling.

Operation
Detach and reattach one body module
System response
Data stopped at separation and resumed after reconnection
Robot-driven removal and reconnection sequence.
Sequence of the dual-arm robot detaching and reattaching its right-arm tip module
Self-reconfiguration sequence from the paper.

Experiment C

High-load manipulation with a reconfigured arm

Experiment overview

Five modules formed a seven-joint manipulator with six spatial end-effector degrees of freedom. The resulting arm lifted a 10 kg dumbbell three times to verify that reconfigurability and useful manipulation strength can coexist.

Configuration
Five modules · seven joints
Load test
10 kg lifted three times
10 kg dumbbell lifting demonstration.
Seven-joint robot configuration and sequence of the 10-kilogram dumbbell lifting experiment
Experimental configuration and lifting sequence.

04 / Citation

BibTeX

Publication details will be updated when the final proceedings record becomes available.

BibTeX 
@inproceedings{arimura2026slsr,
  author    = {Arimura, Toma and Kojima, Kunio and
               Hiraoka, Takuma and Konishi, Masanori and
               Hirai, Jin and Tada, Hiromi and
               Ishikawa, Ryota and Okada, Kei},
  title     = {Development of a Self-Reconfigurable Manipulator
               with a Spring-Loaded Screw Ring Docking Mechanism
               Enabling Tight Fitting Insertion},
  booktitle = {2026 IEEE/RSJ International Conference on
               Intelligent Robots and Systems (IROS)},
  year      = {2026}
}