MEMS Sequencer Barrier Displacement Threshold
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Solution Overview
Problem
Existing pyrotechnic sequencers are prone to accidental triggering due to sensitivity to vibrations and spurious control signals, compromising safety and reliability in firing safety devices.
Innovation Solution
A MEMS-based sequencer with a mobile barrier that requires specific displacement conditions to be met before allowing channel opening, ensuring the barrier moves only after the movable member, and only if the displacement threshold is exceeded, thus preventing accidental releases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple inertial lock structure is used, then the device complexity is reduced and manufacturing cost is lowered, but the reliability decreases due to sensitivity to vibrations and spurious control signals
Solution Approach 1:
The safety device is segmented into two independent control paths: a primary control path for normal operation and a secondary control path for verification. The barrier is controlled by a movable member that requires both a control signal AND a validation signal to disengage, creating sequential segmentation of the release mechanism that prevents accidental triggering while maintaining structural simplicity
Solution Approach 2:
A movable member acts as an intermediary between the control signal and the barrier. This intermediary component requires dual validation (control signal + validation signal) before allowing barrier movement, thereby mediating the control process to eliminate sensitivity to spurious signals while keeping the overall structure simple and manufacturable
2Reliability
If a complex dual-validation system is implemented, then the reliability of triggering control is improved, but the device complexity increases
Solution Approach 1:
The control signal path and validation signal path are merged into a single mechanical control sequence through the movable member. Both signals converge at the movable member which, when both conditions are met, allows the barrier to move. This merging approach achieves dual-validation reliability without requiring separate complex mechanical systems
Solution Approach 2:
The movable member automatically sequences the control process by requiring the barrier to move a threshold distance before accepting the validation signal. This self-service mechanism eliminates the need for external complex control logic, as the mechanical structure itself enforces the dual-validation requirement through its geometric constraints and movement sequence
3Speed
If the barrier is highly sensitive to control signals, then the response time is reduced, but the reliability deteriorates due to accidental triggering from spurious signals
Solution Approach 1:
The control signal initiates a preliminary action by moving the barrier a threshold distance, which prepares the system for rapid response but does not complete the release. This preliminary movement must be followed by the validation signal to fully disengage the movable member and release the barrier, thereby maintaining fast response while preventing accidental triggering from spurious signals alone
Solution Approach 2:
The system dynamically transitions through distinct states: locked state, partially released state (after control signal), and fully released state (after validation signal). This dynamic state progression allows the barrier to respond quickly to valid control signals while requiring additional validation to complete the release, thereby balancing response speed with reliability against spurious signals
4Reliability
If a displacement threshold mechanism is added, then the reliability is improved by preventing premature release, but the device complexity increases
Solution Approach 1:
The system uses a displacement threshold parameter to control the release sequence. The barrier must move a specific threshold distance before the validation signal can take effect. This parameter-based control achieves reliable release timing without complex mechanical switches or sensors, as the threshold is inherently defined by the mechanical geometry of the movable member and barrier interaction
Data Source
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AI summary
Sequencer for a secure firing device forming a microelectromechanical system, comprising: - a transmission channel (1); - a barrier (2) capable of moving in translation between a rest position totally blocking the channel (1) and a position of total release of the channel; and - a movable member (3) cooperating with the barrier (2) and capable of moving, under the action of a validation signal, between an initial locking position prohibiting the movement of the barrier (2) until the total release position and an unlocking position allowing the movement of the barrier (2) until its total release position.The sequencer further comprises: - a first set (A, A') of mechanical means capable of preventing the movement of the moving part (3) to its unlocked position when the movement of the barrier (2) is initiated before that of the moving part (3), and this as long as the movement of the barrier (2) from the rest position to the total release position is less than a displacement threshold; and - a second set (B, B') of mechanical means capable of preventing the movement of the moving part (3) to its unlocked position when the moving part (3) is actuated prior to the movement of the barrier (2) to the release position.