Isotropic Vibration Damping in Inertial Measurement Units
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Solution Overview
Problem
Existing inertial measurement units (IMUs) suffer from vibration-induced malfunctions and vibration rectification errors due to anisotropic mechanical filter characteristics, which affect measurement accuracy across different axes.
Innovation Solution
The IMU incorporates a sensor unit with a case and first fixing part, an elastic member with distinct damping properties in different directions, a second fixing part, and a fixing member that secures the sensor unit and elastic member to the second fixing part, achieving an isotropic filter characteristic across the X, Y, and Z axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gel bushings are arranged with axial directions parallel to each other along the same direction, then vibration in the axial direction (Z-axis) is restrained, but vibrations in other directions (X and Y-axis directions) are restrained to a lesser extent, resulting in anisotropic filter characteristics
Solution Approach 1:
The patent applies asymmetry by arranging elastic members with different axial directions rather than parallel arrangements. Specifically, the elastic members are configured with axial directions oriented at different angles (e.g., 0°, 45°, 90°, 135°) to create isotropic filter characteristics that uniformly restrain vibrations in all directions, eliminating the anisotropic effect where only axial vibrations were effectively restrained.
Solution Approach 2:
The patent transitions from one-dimensional vibration restraint (axial direction only) to three-dimensional isotropic restraint by distributing elastic members with axial directions spanning multiple spatial dimensions. This multi-directional arrangement ensures uniform vibration attenuation across all three axes (X, Y, Z), enabling accurate acceleration measurements in any direction.
2Device complexity
If gel bushings are arranged parallel to each other, then the device structure is simple, but the combined filter characteristic is anisotropic making it difficult to evaluate acceleration using three axes
Solution Approach 1:
The patent uses asymmetric arrangement of elastic members with different axial orientations (0°, 45°, 90°, 135°) to achieve isotropic filter characteristics. This asymmetric configuration ensures that the combined filter response is uniform across all three acceleration axes, enabling accurate vector acceleration evaluation while maintaining a relatively simple device structure.
3Ease of manufacture
If elastic members have anisotropic filter characteristics, then manufacturing is simpler, but vibration rectification error (VRE) restraining effect is lower in directions with lower filter characteristic
Solution Approach 1:
The patent segments the vibration restraint function by using multiple elastic members with different axial directions instead of a single isotropic damper. Each elastic member segment handles specific directional vibrations, and their combined effect provides uniform VRE restraint across all directions. This segmentation approach maintains ease of manufacture while achieving reliable isotropic vibration control.
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 effectively dampens vibrations at specific frequencies in multiple directions, reducing vibration rectification errors and enhancing measurement accuracy by achieving an isotropic filter characteristic across all axes.
Implementation Method 1
an elastic member having a first elastic member mainly damping a vibration at a predetermined frequency in a first direction
Implementation Method 2
a second elastic member mainly damping a vibration at a predetermined frequency in a second direction that is different from the first direction
Implementation Method 3
a fixing member fixing the sensor unit and the elastic member to the second fixing part. The fixing member has a first fixing member penetrating the sensor unit and the first elastic member and pressing the first elastic member
Data Source
AI summary
An inertial measurement unit includes: a sensor unit including an inertial sensor, a case accommodating the inertial sensor, and a first fixing part having the case fixed thereto; an elastic member having a first elastic member mainly damping a vibration at a predetermined frequency in a first direction and a second elastic member mainly damping a vibration at a predetermined frequency in a second direction that is different from the first direction; a second fixing part where the sensor unit and the elastic member are arranged; and a fixing member fixing the sensor unit and the elastic member to the second fixing part.