MSM Actuator Spring Unit for Stroke Extension
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Solution Overview
Problem
Magnetic shape memory alloy actuators have limited expansion stroke and effective work due to their design, where the expansion movement is restricted to 3-6% of the crystal's axial extent, and they fail to return to the original position without external restoring means, limiting their universal applicability.
Innovation Solution
The actuator device incorporates a spring unit with a non-linear, degressive or horizontally constant spring force profile that follows the expansion force profile, allowing for increased effective expansion stroke and work by interacting with the shape memory alloy material, using materials like rubber or plastics for non-linear characteristic curves and combining springs with different properties to achieve desired behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a linear-elastic spring is used for restoration, then the crystal can return to the starting position, but the effective expansion stroke is limited to approximately 0.8 mm
Solution Approach 1:
The spring unit is divided into multiple individual springs (first spring, second spring, third spring) with different characteristic curves. Each spring segment contributes differently to the overall restoring force, allowing the system to achieve a non-linear aggregate characteristic that extends the effective stroke while maintaining manageable individual component complexity.
Solution Approach 2:
The spring unit combines springs with different material properties and characteristic curves (linear-elastic, non-linear, degressive) to create a composite spring system. This composite approach allows the aggregate spring unit to provide a tailored non-linear restoring force profile that maximizes effective expansion stroke while ensuring reliable restoration.
2Use of energy by moving object
If the spring force is set to exceed expansion force at all times, then the crystal returns to starting position, but the expansion work is significantly reduced
Solution Approach 1:
The spring unit's characteristic curve is designed to be dynamic rather than static - it provides higher restoring force when needed (during full restoration) but reduces opposition during the expansion phase. The non-linear characteristic allows the spring to adapt its force output based on the expansion state, maximizing expansion work while ensuring complete restoration when required.
Solution Approach 2:
The spring system changes its effective stiffness parameter throughout the stroke range. By using springs with non-linear characteristic curves (particularly degressive curves), the aggregate spring unit provides variable restoring force that is lower during expansion (allowing more work) and higher during restoration (ensuring reliability), thus optimizing both parameters.
3Productivity
If multiple springs with different characteristic curves are combined, then the effective stroke and work are increased, but the device complexity increases
Solution Approach 1:
The spring unit is segmented into multiple functional springs, each with a specific characteristic curve optimized for particular phases of operation. This segmentation allows each spring to contribute its unique strength (linear springs for stability, non-linear springs for stroke extension, degressive springs for work optimization) while maintaining clear functional separation that simplifies design and analysis.
Solution Approach 2:
The spring unit is designed as a multi-functional assembly where different springs serve different purposes: some springs primarily enable restoration, others maximize expansion stroke, and others optimize work output. This multi-functionality allows a single spring unit configuration to simultaneously address multiple performance requirements that would otherwise require separate systems.
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 configuration enhances the usable expansion stroke and work of the actuator device, making it more versatile for various applications by optimizing the interaction between the shape memory alloy and spring units, allowing for multistable positions and improved actuation forces.
Implementation Method 1
magnetic shape memory (MSM) alloy materials for actuator engineering... an MSM crystal body... is exposed to a magnetic field... As a reaction to the exposure to a magnetic field, the crystal body performs an expansion movement
Data Source
AI summary
Actuator device having an expansion unit, which includes a magnetic shape memory alloy material, and a spring unit which interacts therewith in a restoring manner, wherein at least one spring of the spring unit is assigned to the expansion unit, which is designed to perform an expansion movement along an expansion direction, in such a way that the spring can exert a restoring spring force counter to the expansion direction on the expansion unit, and wherein the spring is set up and/or predetermined in its spring characteristic curve properties in such a way that a spring force profile of the spring unit along a stroke range, determined by an expansion force profile of the expansion unit and a restoring spring force profile, of the expansion movement does not form a continuously rising curve, and/or the spring force profile, with respect to a continuously rising curve, extends and/or increases the stroke range.