Haptic Actuator Flexure with Reduced Material Medial Portions
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Solution Overview
Problem
Haptic actuators face challenges in maintaining desired stress and stiffness metrics within confined spaces, leading to potential fatigue fractures and unwanted oscillations due to high stress and inadequate design in non-travel directions.
Innovation Solution
The design incorporates flexures with diverging arms having reduced material medial portions defined by arcuate recesses or openings, which distribute strain uniformly and reduce maximum stress, while maintaining equivalent spring constants in the travel direction, thereby enhancing stiffness in orthogonal directions and reducing unwanted oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional flexure design with uniform material distribution is used, then the structure provides adequate support, but high stress concentrations occur leading to fatigue fractures
Solution Approach 1:
The flexure structure transitions from uniform material distribution to non-uniform distribution with varying cross-sectional areas. The reduced material medial portions create localized variations in stiffness and stress distribution, concentrating flexibility where needed while maintaining strength at critical locations, thereby reducing stress concentrations and preventing fatigue fractures
2Volume of moving object
If confined space design is implemented, then the haptic actuator fits within size constraints, but stress and stiffness metrics deteriorate
Solution Approach 1:
The flexure is segmented into distinct portions with different material distributions - reduced material medial portions alternating with adjacent end portions. This segmentation allows each section to be optimized for its specific function: reduced material sections provide flexibility for compact packaging, while adjacent end portions maintain structural integrity and stiffness, achieving both size constraints and performance metrics
3Stability of the object's composition
If adequate stiffness is provided in all directions, then structural stability is improved, but unwanted oscillations in non-travel directions increase
Solution Approach 1:
The flexure structure implements directional stiffness variation through reduced material medial portions that are strategically positioned. These portions reduce stiffness specifically in non-travel directions to minimize oscillations, while the overall structure and adjacent end portions maintain adequate stiffness in the travel direction, achieving selective directional properties that eliminate harmful oscillations without compromising structural stability
4Reliability
If material is reduced to lower stress, then fatigue life increases, but manufacturing precision requirements increase
Solution Approach 1:
The reduced material medial portions are defined by arcuate recesses with curved geometries rather than sharp corners or complex shapes. This curvature simplifies manufacturing by avoiding stress concentration at geometric discontinuities, reduces the number of precise dimensional controls needed, and allows for more robust manufacturing tolerances while still achieving the stress reduction necessary for improved fatigue life
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 design reduces stress and fatigue while maintaining desired stiffness, increasing the life and reliability of the haptic actuator with minimal manufacturing cost increase, and effectively minimizes unwanted vibrations by optimizing stiffness in non-travel directions.
Implementation Method 1
a field member having opposing first and second sides... reciprocally movable within the housing responsive to the at least one coil
Implementation Method 2
Each flexure may include two diverging arms joined together at proximal ends and having spaced distal ends operatively coupled between adjacent portions of the field member and the housing. The two diverging arms may each include a proximal segment having a reduced material medial portion relative to adjacent end portions
Data Source
AI summary
A haptic actuator may include a housing, at least one coil carried by the housing, and a field member having opposing first and second sides. The haptic actuator may also include a respective at least one flexure mounting each of the first and second sides of the field member to be reciprocally movable within the housing responsive to the at least one coil. Each flexure may include two diverging arms joined together at proximal ends and having spaced distal ends operatively coupled between adjacent portions or the field member and the housing. The two diverging arms may each include a proximal segment having a reduced material medial portion relative to adjacent end portions, and a distal segment, being canted with respect to the proximal segment, and having a reduced material medial portion relative to adjacent end portions.