Electrostatic Actuation for Gravity Sensor Test Mass Control
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Solution Overview
Problem
Current systems for capturing and controlling test masses in spacecraft lack reliability in positioning and attitude control after release, particularly due to limitations in electrostatic actuation and sensing, which can result in collisions and damage to sensitive equipment during gravitational wave observations.
Innovation Solution
A control system comprising multiple actuation and sensing arrangements within an electrode housing, utilizing a controller to apply electrostatic forces and torques based on real-time position and attitude feedback, allowing precise capture and positioning of test masses without physical contact, employing a higher order electrostatic model for accurate force determination and dynamic voltage allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking mechanism is used to hold the test mass during launch and transfer, then the test mass is protected from damaging movements, but the test mass cannot be released into free fall for gravitational wave measurements
Solution Approach 1:
The locking mechanism is segmented into multiple independent actuators (first and second actuators) that can be selectively activated. This allows the test mass to be held securely during launch while enabling controlled release into free fall for measurements, resolving the contradiction between protection and free fall capability
Solution Approach 2:
The locking mechanism transitions from a static locked state during launch to a dynamic controlled release state. The actuators can adjust their engagement level, allowing the system to switch between protecting the test mass and enabling free fall measurements as needed
2Adaptability or versatility
If the test mass is released into free fall, then gravitational wave measurements can be performed, but the test mass may collide with sensitive equipment causing damage
Solution Approach 1:
Sensors continuously monitor the position of the test mass during free fall and provide feedback to the locking mechanism actuators. This closed-loop control allows real-time adjustment to prevent collisions with sensitive equipment while maintaining free fall conditions for measurements
Solution Approach 2:
The locking mechanism actuators serve as intermediaries between the test mass and the spacecraft structure. They can provide controlled interactions to guide the test mass away from sensitive equipment during free fall without completely isolating the test mass, reducing collision risk
3Measurement precision
If multiple actuators are used to control test mass position, then positioning precision is improved, but the system complexity increases
Solution Approach 1:
The locking mechanism actuators are designed to perform multiple functions: they lock the test mass during launch, release it for free fall, and subsequently control its position during measurements. This multi-functionality reduces the need for separate systems, managing complexity while maintaining precision
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
Enhances the reliability and accuracy of test mass capture and control, reducing the risk of collisions and enabling precise positioning for scientific measurements, while relaxing constraints on test mass release mechanisms and improving ground testing verification.
Implementation Method 1
The actuation and sensing arrangements are configured to apply an electrostatic force to the test mass in response to which the test mass changes its position and/or attitude with respect to the electrode housing
Implementation Method 2
The actuation and sensing arrangements are configured to detect a position and/or an attitude of the test mass in the cavity with respect to the electrode housing
Data Source
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AI summary
Systems and methods for capturing a test mass (50) within an electrode housing (12) of a spacecraft (1) with multiple actuation and sensing arrangements (22) are described. The method includes determining a position and/or attitude of the test mass (50) with respect to the actuation and sensing arrangements (22) and determining a control voltage for moving the test mass (50) into a desired position and/or attitude between the actuation and sensing arrangements (22) by electrostatic forces generated by the actuation and sensing arrangements (22), wherein electrostatic forces required for moving the test mass and the control voltage for moving the test mass (50) into the desired position are determined based on the detected position and/or attitude of the test mass (50) between the actuation and sensing arrangements (22).