Recessed Electromagnetic Coil Accelerometer for Hysteresis Reduction
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Solution Overview
Problem
Accelerometers using electromagnetic forces to counteract proof mass displacement are affected by hysteresis, which is exacerbated by material boundaries and the presence of magnets in the magnetic circuit assembly, leading to performance degradation and navigation errors.
Innovation Solution
The accelerometer system incorporates a magnetic circuit assembly with reduced material boundaries and uses electromagnetic coils instead of magnets, housed in recesses formed by modular excitation rings to minimize hysteresis and protect electronic circuitry from harmful environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a magnetic circuit assembly includes multiple pieces of metal alloy material connected by adhesive materials, then the structural integrity and assembly flexibility are improved, but the hysteresis effect increases due to different coefficients of thermal expansion between adhesive and metal alloy
Solution Approach 1:
The magnetic circuit assembly is divided into multiple discrete metal alloy pieces rather than using a single monolithic structure. This segmentation allows each piece to be independently manufactured and assembled, reducing the overall hysteresis effect while maintaining assembly flexibility through controlled joints between segments.
Solution Approach 2:
Different regions of the magnetic circuit assembly have different properties - the metal alloy pieces provide magnetic flux pathways with specific permeability characteristics, while the adhesive materials provide structural bonding. By optimizing the local properties of each material and their interface, the design achieves both manufacturability and reduced hysteresis.
2Device complexity
If a magnet is included in the flux path of the magnetic circuit assembly, then the magnetic flux generation is simplified, but the hysteresis effect increases compared to systems without magnets in the flux path
Solution Approach 1:
The magnet is extracted from the flux path of the magnetic circuit assembly. Instead of having the magnet embedded within the flux path where it would create hysteresis losses, the design positions the magnet externally or in a location that generates magnetic flux without requiring it to pass through the magnetic circuit assembly material, thereby eliminating the hysteresis effect while maintaining the ability to generate the required magnetic flux.
3Ease of manufacture
If adhesive materials are used to connect metal alloy pieces in the magnetic circuit assembly, then the assembly ease and flexibility are improved, but the thermal expansion mismatch increases hysteresis effect
Solution Approach 1:
The magnetic circuit assembly is segmented into multiple metal alloy pieces that are connected by adhesive materials. This segmentation approach allows for easier assembly and manufacturing flexibility while the careful selection and design of adhesive joints minimizes the impact of thermal expansion mismatch on measurement precision.
Solution Approach 2:
The design optimizes parameters such as the coefficient of thermal expansion matching between adhesive and metal alloy materials, the geometry of adhesive joints, and the thermal management of the assembly to reduce thermal expansion effects. By controlling these parameters, the hysteresis effect from thermal expansion mismatch is minimized while maintaining assembly ease.
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 hysteresis-related errors and enhances accuracy by optimizing magnetic softness and shielding electronic components, allowing precise acceleration measurement even in harsh conditions.
Implementation Method 1
an electromagnetic coil configured to generate a magnetic field that flows through the magnetic circuit assembly
Implementation Method 2
a magnetic circuit assembly that includes one or more pieces of metal alloy material... generate a magnetic field that flows through the magnetic circuit assembly
Implementation Method 3
The excitation ring may be made of materials that protect the electronic circuitry from harmful environments
Implementation Method 4
adhesive materials that connect pieces of metal alloy material may have a different coefficient of thermal expansion (CTE) than the metal alloy. This means that when the accelerometer device is exposed to high temperatures, the adhesive material may expand at different rates than the metal alloy, increasing the effect of hysteresis
Data Source
AI summary
In some examples, an accelerometer system includes a first excitation ring comprising: a first housing; and a first cover removably attached to the first housing, wherein the first housing and the first cover define a first recess. The accelerometer system also includes a second excitation ring comprising: a second housing; and a second cover removably attached to the second housing, wherein the second housing and the second cover define a second recess. The accelerometer system also includes a proof mass assembly; and processing circuitry located within one or both of the first recess and the second recess, wherein the first excitation ring and the second excitation ring shield the processing circuitry from harmful levels of radiation existing outside of the accelerometer system, and wherein the processing circuitry is configured to maintain a proof mass of the proof mass assembly in a null position.