Pneumatic Stepper Motor Layout for MRI-Compatible Robotic Actuation

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Solution Overview

Problem

Current pneumatic stepper motors for MRI-compatible applications are either too bulky, complex to manufacture, or lack the necessary power and precision, particularly in MRI-guided robotic systems where metal-free and lightweight actuators are required.

Innovation Solution

A lightweight, metal-free pneumatic stepper motor design featuring a housing with a rack and two pistons, where the pistons are arranged to cooperate with the rack, allowing for easy assembly and manufacture, and can be customized for specific applications, using rapid prototyping techniques like 3D printing and laser-cutting.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If electromagnetic stepper motors are used for MRI-compatible applications, then power and precision are improved, but metal-free requirement and MRI compatibility are compromised

Engineering Contradiction:
Improvepower outputVSAvoidMRI compatibility
Core Design Contradiction:
PowerVSObject-affected harmful factors

Solution Approach 1:

The patent replaces electromagnetic actuation with pneumatic actuation. The pneumatic stepper motor uses pressurized air to drive pistons that move along a rack with gear elements, eliminating all metal components and electromagnetic fields while maintaining sufficient power output for MRI-guided robotic systems

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs pneumatic principles by using compressed air to drive the pistons. The pneumatic tube supplies air to drive the pistons in reciprocating movement, which then engage with the rack's gear elements to produce controlled rotational or linear motion, achieving both MRI compatibility and adequate power output

Inventive Principle:
Principle #29Pneumatics and hydraulics

2Weight of moving object

If complex pneumatic stepper motors are designed for MRI compatibility, then metal-free and lightweight properties are improved, but manufacturing complexity and component quantity increase

Engineering Contradiction:
ImproveweightVSAvoidmanufacturing complexity
Core Design Contradiction:
Weight of moving objectVSDevice complexity

Solution Approach 1:

The patent merges multiple components into integrated structures. The housing accommodates the rack and pistons in a compact arrangement, and the rack combines the rack structure with integrated gear elements, reducing the total number of separate components while maintaining functionality

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The rack serves multiple functions simultaneously: it provides the structural framework, contains the gear elements for engagement with pistons, and acts as the output mechanism for rotational or linear motion. This multi-functionality reduces the need for separate components

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Ease of manufacture

If pneumatic stepper motors are simplified for easy manufacture, then ease of manufacture is improved, but power output and precision may deteriorate

Engineering Contradiction:
Improveease of manufactureVSAvoidpower output
Core Design Contradiction:
Ease of manufactureVSPower

Solution Approach 1:

The patent optimizes critical parameters such as the dimensions of the rack, the geometry of the gear elements, and the size of the pistons to maximize power output. By carefully selecting these parameters, the motor achieves high force and torque outputs while maintaining a simple, manufacturable design with minimal components

Inventive Principle:
Principle #35Parameter changes

4Volume of moving object

If compact pneumatic stepper motors are designed, then volume and weight are improved, but force and torque output may be reduced

Engineering Contradiction:
ImprovevolumeVSAvoidforce output
Core Design Contradiction:
Volume of moving objectVSForce

Solution Approach 1:

The patent transitions from linear piston movement to rotational output through the rack's gear elements. This dimensional change allows the compact motor to generate rotational torque, which is often more useful in robotic applications, while maintaining a small volume

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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

The design achieves high force and torque outputs while being compact and easy to manufacture, with improved specifications and manufacturability, suitable for demanding applications such as MRI-guided robotic systems and high-voltage switchgear.

Implementation Method 1

at least one pneumatic tube connected to said housing that is arranged to supply air to the housing in order to drive said pistons in a reciprocating movement

Methodology Applied
Scientific EffectPneumatics: Pressure Gradient

Implementation Method 2

a rack comprising a plurality of gear elements, and two pistons, each comprising at least two teeth, said pistons being arranged to cooperate with said rack

Methodology Applied
Scientific EffectRack and pinion mechanism: Rack and Pinion

Data Source

PatentEP3504445B1Pneumatic stepper motor and device comprising at least one such pneumatic stepper motor
Publication Date: 2022.10.05 MACHNET MEDICAL ROBOTICS BV
  • EP3504445B1 patent drawingFigure 1A~1B
  • EP3504445B1 patent drawingFigure 1C~2
  • EP3504445B1 patent drawingFigure 3A~3B

AI summary

The invention relates to a pneumatic stepper motor, comprising: - a housing, said housing accommodating at least part of: - a rack or geared axle comprising a plurality of gear elements; and - two pistons, each comprising at least two teeth, said pistons being arranged to cooperate with said rack or geared axle. The racks may either be straight or curved. The pistons are preferably double-acting pistons. The invention also relates to a device, comprising at least one, and preferably a plurality of, such pneumatic stepper motor (s). The device may in particular be an MRI-compatible robotic system, more in particular for example an MRI-guided breast biopsy device.