Magnetic Torsion Spring for Miniature Robot Joints

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing magnetic torsion spring designs for small-scale robots are limited in their ability to produce customizable torsional stiffness responses and are difficult to assemble below 10 mm, often resulting in sinusoid-like stiffness and limited equilibrium points, which restricts the gripping and prying strength and control of robotic manipulators.

Innovation Solution

The design incorporates magnetic material embedded in adjacent links connected by a pin joint, allowing for adjustable stiffness and magnetic actuation, with the size, position, and orientation of the magnetic material determining the spring's torque curve and susceptibility to external magnetic fields, enabling customizable torque-displacement responses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If multiple magnets are mounted concentrically or on concentric rings to create magnetic torsion springs, then the spring can provide restoring forces and energy storage, but the assembly becomes difficult to assemble on a scale below 10 mm

Engineering Contradiction:

Improverestoring forceVSAvoidassembly difficulty

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The magnetic torsion spring is segmented into two separate links, each containing a single magnet. This segmentation eliminates the need for complex concentric mounting of multiple magnets, enabling assembly at scales below 10 mm while maintaining the restoring force capability through magnetic interaction between the separated magnets.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The pin joint serves as an intermediary element that connects the two links containing magnets. This intermediary structure enables the transmission of magnetic forces between the separated magnets while facilitating easier assembly compared to direct concentric mounting, resolving the contradiction between maintaining restoring force and reducing assembly difficulty.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If existing magnetic torsion spring designs are used, then the spring can provide sinusoid-like stiffness response, but the stiffness profile cannot be controlled precisely and only one stable equilibrium is achieved

Engineering Contradiction:

Improvestiffness responseVSAvoidstiffness profile control

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The magnetic torsion spring design enables dynamic control of the stiffness profile through adjustable parameters including magnet size, position, and orientation. This dynamic adjustability allows precise control over the stiffness response and the creation of multiple stable equilibrium points, moving beyond the fixed sinusoid-like response of conventional designs.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention utilizes parameter changes in magnet configuration (size, position, orientation) to precisely control the stiffness profile. By varying these parameters, the system can achieve desired torque curves and multiple stable equilibria, resolving the limitation of fixed stiffness profiles in existing designs.

Inventive Principle:

Principle #35Parameter changes

3Strength

If elastic compliant joints are used in millimeter-scale robot manipulators, then the joints can provide restoring torque for decoupled control, but buckling occurs making motion prediction difficult and limiting gripping strength

Engineering Contradiction:

Improverestoring torqueVSAvoidmotion predictability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The invention replaces traditional elastic compliant joints with a magnetic torsion spring system. This substitution eliminates mechanical buckling by using magnetic fields to provide restoring torque, ensuring predictable motion and maintaining gripping strength without the structural limitations of elastic materials.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables versatile and precise control of torsional stiffness in miniature robots, allowing for wireless actuation and improved gripping and prying capabilities, overcoming the limitations of existing designs by providing customizable torque-displacement relationships and stable equilibrium points.

Implementation Method 1

Magnetic interaction scales with decreasing distance between magnets, so magnetic springs are applicable to small-scale robots

Methodology Applied

Scientific EffectMagnetic interaction: Magnetism

Implementation Method 2

Magnetic fields can penetrate physical barriers to apply forces and torques wirelessly to magnetic robotic devices in small confined environments

Methodology Applied

Scientific EffectMagnetic actuation: Magnetic Field

Data Source

PatentUS20240238963A1Magnetic torsion spring for a magnetically actuated mechanism and method for forming the spring

Publication Date: 2024.07.18 THE GOVERNING COUNCIL OF THE UNIV OF TORONTO

AI summary

A magnetic torsion spring for a magnetically actuated mechanism, the spring having first and second links of the mechanism rotatably connected at a joint of the mechanism, the first link provided with a first magnet spaced from the joint and the second link provided with a second magnet spaced from the joint generating a spring effect, the spring defined by a torque curve with respect to spring deflection, the torque curve defined by spring type, dimensionless characteristic length ratio of the spring, and an amplitude constant, and the length ratio has a value between 0 and 1.