Acceleration Sensor Latch Circuit for Munition Arming
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Solution Overview
Problem
Mechanical acceleration sensors in projectiles often fail due to faults in switching devices, preventing the arming of munitions, and lack testability, leading to mission losses.
Innovation Solution
A switch circuit using a non-rigid membrane and a switching latch that responds to acceleration forces, producing a signal to activate a squib and energize a battery, with features like diodes to restrict current and allow testability without risk of detonation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical acceleration sensors (g-switches) are used to activate the squib for arming the munition, then the munition can be armed after launch, but the switching device may fail due to high acceleration forces, preventing the squib from activating and resulting in mission loss
Solution Approach 1:
The patent divides the switching function into two separate components: a mechanical g-switch for detecting acceleration and an electronic latch circuit for controlling current flow. This segmentation isolates the fragile switching function from the high-stress acceleration environment, as the latch circuit can be designed to withstand the extreme forces while the g-switch only needs to detect and trigger the sequence.
Solution Approach 2:
The electronic latch circuit serves as an intermediary between the mechanical g-switch and the squib. The g-switch triggers the latch, which then controls the current flow to the squib. This intermediary protects the squib activation system from direct exposure to the harsh mechanical stresses by using the latch as a buffer that can be designed with appropriate force resistance.
2Reliability
If common acceleration sensors are used, then the munition arming function can be implemented, but the devices lack testability, making it difficult to detect faulty switches before mission loss
Solution Approach 1:
The latch circuit incorporates feedback mechanisms that allow the system to report its state. The circuit can be designed to provide test signals or status indicators that show whether the latch is functioning properly and whether the g-switch has been triggered. This feedback enables ground testing of the entire arming sequence without actually arming the munition.
Solution Approach 2:
The system allows for preliminary testing of the switching devices and latch circuits before the actual mission. Test modes can be activated that simulate the acceleration trigger condition and verify that the squib would fire if commanded, without requiring actual launch conditions. This preliminary action detects faulty switches before they cause mission loss.
3Reliability
If the switch circuit allows current flow to activate the squib, then the munition can be armed, but premature activation or unintended current flow could cause dangerous situations
Solution Approach 1:
The latch circuit is designed to be dynamically controllable, allowing it to be set, reset, and tested in different states. The circuit can be configured to require specific conditions (such as a reset signal or specific acceleration profile) before allowing current flow to the squib. This dynamic control prevents premature activation by ensuring the latch is in the correct state before permitting squib firing.
Solution Approach 2:
The latch circuit acts as an intermediary that mediates between the trigger condition and the squib activation. It can be designed to require multiple conditions to be met before allowing current flow, such as verification of proper acceleration profile, timing constraints, or manual safety overrides. This intermediary layer adds safety checks that prevent unintended activation while still allowing reliable arming when conditions are proper.
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
Ensures reliable arming of munitions by accurately sensing high acceleration forces and preventing premature activation, enhancing mission success rates through improved reliability and testability.
Implementation Method 1
The membrane is responsive to acceleration forces and is configured to produce a signal as a result of deflections to the membrane caused by acceleration
Data Source
Figure 1
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Figure 3A
AI summary
Methods and apparatus for sensing acceleration according to various aspects of the present invention comprises a non-rigid membrane and a switching latch electrically coupled to the membrane. The membrane is responsive to acceleration forces and is configured to produce a signal as a result of deflections in the membrane caused by acceleration. The signal is transmitted to the switching latch causing a change in state of the switching latch. This change in state allows a second signal to be sent to an activating device such as a squib.