Out-of-Plane Accelerometer Mass with Offset Center of Gravity
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Solution Overview
Problem
Conventional accelerometer designs for out-of-plane acceleration measurements suffer from asymmetrical mass distribution, leading to electrical asymmetry and gas damping issues, which result in sensor reading errors and cross-axis sensitivity, making them less accurate and robust.
Innovation Solution
The design incorporates a mass with closed surfaces and enclosed weight elements of different density, offset from the rotary axis, to minimize cross-axis sensitivity and ensure symmetrical gas damping, allowing for accurate out-of-plane acceleration measurement while maintaining symmetry and optimal gas damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an asymmetrical mass distribution is used to enable out-of-plane acceleration sensing, then the accelerometer can detect out-of-plane accelerations, but cross-axis sensitivity increases and measurement precision deteriorates
Solution Approach 1:
The patent applies asymmetry principle by intentionally creating an unbalanced mass distribution through enclosed weight elements positioned at specific locations within the mass. This asymmetrical configuration generates a torque when subjected to out-of-plane acceleration, enabling the mass to rotate about the in-plane axis. The asymmetrical mass distribution is the key mechanism that converts out-of-plane acceleration into measurable rotational motion while maintaining symmetry in the in-plane directions to minimize cross-axis sensitivity.
2Adaptability or versatility
If an asymmetrical mass configuration is used for out-of-plane detection, then out-of-plane acceleration can be measured, but gas damping becomes unbalanced leading to sensor reading errors
Solution Approach 1:
The patent applies local quality principle by strategically positioning enclosed weight elements with different densities at specific locations within the mass structure. These weight elements are enclosed within cavities at defined positions that create the necessary mass asymmetry for out-of-plane sensing while maintaining overall structural symmetry. The local modification of mass distribution through these enclosed weight elements enables selective sensitivity to out-of-plane acceleration without disrupting the balanced gas damping environment.
3Adaptability or versatility
If electrical asymmetry is introduced to enable out-of-plane sensing, then out-of-plane acceleration detection is achieved, but measurement accuracy decreases due to asymmetry-induced errors
Solution Approach 1:
The patent applies the dimensionality change principle by transitioning the sensing mechanism from in-plane motion to out-of-plane rotational motion. The mass is configured to rotate about an in-plane axis when subjected to out-of-plane acceleration, effectively using rotation in one dimension (out-of-plane) to sense acceleration in that direction. This dimensional transition allows the use of symmetrical in-plane electrode configurations, thereby maintaining electrical symmetry and measurement accuracy while achieving out-of-plane sensing capability.
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 accuracy and robustness of out-of-plane acceleration measurements by minimizing cross-axis sensitivity and maintaining balanced gas damping, allowing for precise detection without compromising surface area usage or increasing complexity.
Implementation Method 1
The spring system deforms elastically so that the mass becomes displaced from the body to an extent that corresponds with the sensed acceleration
Implementation Method 2
The body can include one or more stationary electrodes and the mass acts as a movable electrode and the displacement of the mass changes the capacitance between the stationary and movable electrodes in proportion to the applied acceleration
Implementation Method 3
one or more weight elements disposed between the two closed surfaces and each comprising a substance having a weight per unit volume that is different from a weight per unit volume of the bulk material
Implementation Method 4
the centre of gravity of the mass is offset from the rotary axis in the second in-plane direction
Data Source
AI summary
An accelerometer element is provided that includes a body, a mass and a spring system that couples the mass to the body. The spring system configures the mass to rotate reciprocally about a rotary axis. The mass includes a volume of a bulk material that forms two essentially closed surfaces and incorporates between those two closed surfaces one or more weight elements, each of which is formed of a substance whose weight per unit volume is different from weight per unit volume of the bulk material. The weight elements are incorporated in the mass so that the centre of gravity of the mass is offset from the rotary axis in an in-plane direction and the centre of gravity of the mass and the rotary axis are at the same level within the mass in the out-of-plane direction.