Compliant Isolator for Detector Assembly Drift Mitigation
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Solution Overview
Problem
Imaging vehicles face challenges in accurately measuring line-of-sight (LOS) error due to drift and noise in inertial measurements, particularly from secondary inertial sensors, which affect the precision of 6-axis position and attitude determination for guidance, navigation, and control (GNC) maneuvers.
Innovation Solution
The solution involves partially isolating the detector assembly from the vehicle frame using a compliant isolator, separating main 6-axis inertial measurements from secondary inertial rate measurements, and processing these measurements to estimate and remove drift and noise errors. This is achieved by mounting the detector assembly on a compliant isolator that couples low-frequency rigid body motion while isolating high-frequency attitude noise, using a main IMU as a truth reference, and employing secondary rate sensors to measure angular rate changes in pitch and yaw, with a computer processing these measurements to correct for drift and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If secondary inertial rate sensors are used to measure angular rate changes in the isolated detector assembly, then measurement capability is improved, but drift and noise errors increase
Solution Approach 1:
The system divides inertial measurement into two separate segments: a main IMU mounted on the vehicle frame for stable reference measurements, and secondary rate sensors mounted on the isolated detector assembly for capturing relative motion. This segmentation allows each sensor to perform its specialized function while mitigating the weaknesses of the other.
Solution Approach 2:
The computer processes measurements from both the main IMU and secondary rate sensors, using the main IMU's stable reference to detect and compensate for drift in the secondary sensors. The system continuously compares measurements and applies corrective algorithms to remove drift and noise errors from the secondary sensor data.
2Object-affected harmful factors
If the detector assembly is mechanically isolated from the vehicle frame, then shock and vibration environment is improved, but mechanical coupling is reduced
Solution Approach 1:
A compliant isolator is introduced as an intermediary element between the vehicle frame and the detector assembly. This isolator mechanically decouples the assembly from high-frequency vibrations and shocks while maintaining sufficient coupling to transmit low-frequency rigid body motions needed for accurate inertial measurement.
3Object-affected harmful factors
If compliant isolator is used to isolate detector assembly, then vibration isolation is improved, but low-frequency motion coupling must be maintained
Solution Approach 1:
The compliant isolator is designed with specific mechanical parameters that create a frequency-dependent coupling characteristic. The isolator's stiffness and damping properties are tuned to block high-frequency vibrations while maintaining adequate compliance to transmit low-frequency rigid body motions, effectively filtering the mechanical transmission spectrum.
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
This approach provides a more accurate and stable measurement of the detector assembly's position and attitude, reducing LOS error and improving image alignment accuracy by mitigating the effects of drift and noise, thereby enhancing the overall precision of GNC operations.
Implementation Method 1
Mechanical isolation is commonly used to mechanical low-pass filter the vibrations and body motion observed by the main IMU
Implementation Method 2
The compliant isolator isolates the detector assembly from high-frequency attitude noise while coupling the low-frequency rigid body motion of the vehicle frame to the detector assembly
Data Source
AI summary
The 6-axis position and attitude of an imaging vehicle's detector assembly is measured by mounting the detector assembly on a compliant isolator and separating the main 6-axis IMU on the vehicle from a secondary IMU comprising at least inertial rate sensors for pitch and yaw on the detector assembly. The compliant isolator couples low-frequency rigid body motion of the vehicle below a resonant frequency to the isolated detector assembly while isolating the detector assembly from high-frequency attitude noise above the resonant frequency. A computer processes measurements of the 6-axis rigid body motion and the angular rate of change in yaw and pitch of the isolated detector assembly to mitigate the drift and noise error effects of the secondary inertial rate sensors and estimate the 6-axis position and attitude of the detector assembly.