Projectile Roll Estimation via Gravity Vector De-rolling
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Solution Overview
Problem
Guided projectiles face challenges in accurately estimating their roll orientation with respect to the gravity vector during flight, due to continuous changes caused by roll, perturbations, and noise in measurement units, which affects their ability to navigate to a target.
Innovation Solution
A guided projectile system that includes a measurement unit to measure rotation rates about orthogonal axes, a controller to process these signals, and control surfaces to adjust flight path, using methods such as filtering and adaptive filtering to estimate and correct for roll orientation, allowing for precise navigation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods are used to estimate roll orientation, then the system structure remains simple, but measurement precision deteriorates due to perturbations and noise
Solution Approach 1:
The patent applies preliminary action by pre-integrating roll rate signals to obtain preliminary roll orientation estimates before applying filtering corrections. This allows the system to establish a baseline estimation that can then be refined, improving overall measurement precision while managing complexity through staged processing
Solution Approach 2:
The patent implements feedback by using adaptive filtering that continuously adjusts filter coefficients based on estimated roll orientation and rate measurements. This feedback mechanism compensates for perturbations and noise in real-time, significantly improving roll orientation estimation accuracy without requiring a complete redesign of the measurement system
Solution Approach 3:
The patent introduces an intermediary filtering process that acts as a mediator between raw measurement signals and final roll orientation estimates. The filter serves as an intermediate processing stage that removes noise and perturbations while preserving the essential roll orientation information, thereby improving measurement precision without directly modifying the sensor hardware
2Measurement precision
If roll orientation is continuously corrected during flight, then navigation accuracy improves, but loss of time increases due to continuous processing
Solution Approach 1:
The patent applies periodic action by updating roll orientation estimates at discrete time intervals rather than continuously. The filter processes measurements at scheduled update rates, maintaining navigation accuracy while avoiding the computational overhead of truly continuous processing, thus reducing time loss
Solution Approach 2:
The patent uses preliminary integration of roll rate to obtain quick initial roll orientation estimates before applying more computationally intensive filtering. This preliminary action provides timely navigation corrections without waiting for full filter convergence, reducing processing time while maintaining accuracy
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
Enables accurate estimation and correction of roll orientation, improving the projectile's ability to follow a guided trajectory and reach the target effectively by reducing the impact of perturbations and noise.
Implementation Method 1
a measurement unit to measure rotation rates about orthogonal axes
Implementation Method 2
filter the time-sequential gravity vector estimates to reduce the effects of perturbations and noise
Implementation Method 3
integrate the roll rate signals to produce a cumulative roll estimate
Data Source
AI summary
An apparatus and method for estimating a roll angle of a projectile may include a measurement unit outputting roll rate, yaw rate, and pitch rate signals indicative of rotation rates about substantially orthogonal roll, yaw, and pitch axes, the roll axis substantially aligned with a longitudinal axis of the projectile. A controller may sample the roll rate, yaw rate, and pitch rate signals to obtain time sequential roll rate, yaw rate, and pitch rate samples; calculate time sequential cumulative roll estimates by summing the roll rate samples; calculate time sequential gravity vector estimates from the corresponding yaw rate and pitch rate samples; de-roll each gravity vector estimate based on the corresponding cumulative roll estimate; filter the de-rolled gravity vector estimates to determine a filtered initial roll estimate; and add the filtered initial roll estimate to the current cumulative roll estimate to provide a current roll angle estimate.