Lorentz-Force Accelerometer Startup Control for Proof Mass Stability
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Solution Overview
Problem
The initial application of Lorentz forces on the proof mass during the startup of an accelerometer system can cause unintended contact between components, affecting bias stability and scale factor, which reduces the accuracy of acceleration measurements.
Innovation Solution
Reducing the amplitude of electric currents through coils for a threshold period during startup to minimize Lorentz forces and proof mass displacement, followed by increasing current amplitude once the threshold is elapsed to maintain the proof mass at the null position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high amplitude electric currents are applied through coils during startup, then the accelerometer system can quickly reach full functionality, but the proof mass may displace from null position causing unintended component contact
Solution Approach 1:
The patent implements periodic action by applying reduced current amplitude during an initial startup period (first time interval) and then switching to full current amplitude after the proof mass has settled (second time interval). This time-dependent current modulation prevents component contact during startup while maintaining full functionality afterward.
Solution Approach 2:
The patent applies preliminary action by first applying reduced amplitude currents during startup to safely position the proof mass without causing unintended contact, before progressively increasing to full operational current. This preliminary reduced-current phase prevents harmful effects before full operation begins.
2Measurement precision
If electric currents are increased to maintain proof mass at null position, then navigation accuracy is improved, but the risk of component contact increases during startup
Solution Approach 1:
The system periodically transitions from reduced current mode during startup to full current mode after the proof mass settles. This ensures measurement precision is achieved without causing component contact, as full current is only applied after the risk period has passed.
Solution Approach 2:
The patent applies dynamics by making the current amplitude time-dependent rather than static. The current transitions from reduced to full amplitude based on the operational phase, allowing the system to adapt current levels to minimize harmful effects while maintaining measurement precision when safe.
3Productivity
If full current amplitude is applied immediately at startup, then the accelerometer reaches full capability quickly, but bias stability and scale factor are affected
Solution Approach 1:
The patent applies preliminary reduced current during startup before full operational current is applied. This preliminary phase allows the system to initialize without causing unwanted mechanical contact that would affect bias stability and scale factor, while still progressing toward full capability.
Solution Approach 2:
The system uses periodic action with two distinct current amplitude phases: reduced amplitude during startup and full amplitude afterward. This ensures bias stability is maintained during the critical startup period when the proof mass is most vulnerable to displacement-induced errors.
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 approach reduces the risk of component contact and maintains accurate acceleration measurements by ensuring the proof mass remains at the null position, enhancing navigation accuracy.
Implementation Method 1
electric currents flow through the coils within the accelerometer system which, when interacting with Magnetic flux within the accelerometer system, apply Lorentz forces on the proof mass within the accelerometer system
Data Source
AI summary
An accelerometer system comprising: a first magnetic assembly comprising a first pole piece and a first magnet; a second magnetic assembly comprising a second pole piece and a second magnet; a proof mass between the first magnetic assembly and the second magnetic assembly; a first coil disposed around the first pole piece; and a second coil disposed around the second pole piece; and processing circuitry configured to: cause a first current to flow through the first coil to apply a first Lorentz force to the proof mass; cause a second current to flow through the second coil to apply a second Lorentz force to the proof mass; and limit a maximum amplitude of the first current and the second current for at least a threshold period of time.