Sealed Apogee Detection Module Using Inertial Sensor Fusion
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Solution Overview
Problem
Existing apogee detection systems for ballistic projectiles are unreliable due to their reliance on external environmental data, such as barometric pressure, which leads to inaccurate detection and prediction of apogee, and are also larger and heavier than desired.
Innovation Solution
A self-contained apogee detection system that uses a combination of sensors, including three-axis accelerometers, gyroscopes, and magnetometers, to predict and detect apogee without relying on external environmental data. This system employs a quaternion extended Kalman filter to fuse and filter sensor signals in real-time, providing accurate state and orientation information about the projectile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If barometric pressure sensors are used for apogee detection, then detection capability is provided, but the system becomes larger, heavier, and less reliable due to dependence on external environmental data
Solution Approach 1:
The patent extracts and eliminates the dependency on external barometric pressure sensors, removing the harmful reliance on environmental data. The system uses only internal inertial sensors (accelerometers, gyroscopes, magnetometers) to detect apogee, thereby reducing weight and improving reliability by eliminating the vulnerable pressure sensing component.
Solution Approach 2:
The patent replaces the barometric pressure sensing mechanism with an inertial measurement system. Instead of using pressure sensors that require external environmental interaction, the system uses accelerometers, gyroscopes, and magnetometers with signal processing algorithms to detect apogee, achieving the same function with improved reliability and reduced weight.
2Measurement precision
If barometric pressure sensors are used for apogee detection, then detection capability is provided, but measurement accuracy deteriorates due to environmental data dependence
Solution Approach 1:
The patent implements feedback through signal processing algorithms that continuously monitor and analyze data from multiple inertial sensors. The system uses filtering and fusion algorithms to process accelerometer, gyroscope, and magnetometer signals, providing feedback control that enhances measurement precision and compensates for individual sensor errors, thereby improving both accuracy and reliability.
Solution Approach 2:
The patent combines multiple sensor types (accelerometers, gyroscopes, magnetometers) into a composite sensing system. This multi-sensor fusion approach leverages the strengths of each sensor type while compensating for their individual weaknesses, achieving superior measurement precision and reliability compared to single-sensor barometric systems.
3Reliability
If self-contained inertial sensors are used, then system weight is reduced and reliability is improved, but detection accuracy must be maintained through complex signal processing
Solution Approach 1:
The patent makes the inertial sensor system multi-functional by using the same accelerometer, gyroscope, and magnetometer for both navigation/attitude determination and apogee detection. This universal approach consolidates functionality, reducing the need for separate dedicated components and thereby managing complexity while maintaining reliability.
Solution Approach 2:
The system performs self-service through autonomous signal processing and fusion algorithms that automatically process raw sensor data without external assistance. The onboard computer independently fuses data from multiple sensors, detects apogee conditions, and triggers appropriate actions, eliminating the need for external barometric references and reducing system complexity.
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
The system achieves accurate and reliable detection and prediction of apogee, enabling timely initiation of mission-critical actions such as fuze arming, propulsion ignition, and control surface deployment, while being compact and lightweight.
Implementation Method 1
at least one three-axis accelerometer
Implementation Method 2
at least one gyroscope
Implementation Method 3
at least one magnetometer
Implementation Method 4
a quaternion extended Kalman filter to fuse and filter sensor signals
Data Source
AI summary
A closed, self-contained ballistic apogee detection module for use in a projectile, such as a rocket, mortar round, or artillery round, fuses data from multiple built-in sensors, such as an accelerometer, a magnetometer, and a gyroscope, and processes the data using a microprocessor through a custom quaternion extended Kalman filter to provide accurate state and orientation information about the projectile so as to accurately predict apogee. The module outputs a signal indicating apogee detection or prediction which they projectile uses to initiate fuze arming, targeting control, airbody transformation, maneuvering, flow effector deployment or activation, payload exposure or deployment, and/or other mission activity. Because the system and method of the invention does not rely on external environmental data to detect apogee, it need not use a pressure sensor and can be completely sealed in and closed without requiring access to air from outside the projectile for barometric readings.