Lead Compensator for Attitude Estimation Latency Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing attitude correction systems for spacecraft instruments face errors due to inadequate attitude measurements from Inertial Reference Units (IRU) and latency in data transfer, which affect the accuracy of line-of-sight control, especially when integrating rate sensor data over short periods.
Innovation Solution
A lead compensator is introduced to correct for rate sensor dynamics and data transfer latency using a transfer function module operating in an open loop mode, coupled with an angular rate sensor and an integrator to provide compensated angular rates, which are then summed with non-compensated attitudes to improve the accuracy of line-of-sight control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rate sensor data are integrated to derive attitude data, then attitude accuracy is improved over short periods, but errors are introduced due to latency in data transfer and IRU dynamics
Solution Approach 1:
The patent applies preliminary action by computing compensation for rate sensor dynamics and data transfer latency before the attitude data is used by the instrument. The lead compensator processes the rate sensor data in advance to predict and correct for the effects of latency and dynamics, rather than attempting to correct errors after they have manifested in the attitude measurement. This allows the system to proactively eliminate sources of error before they degrade measurement accuracy.
Solution Approach 2:
The patent creates a mathematical model (copy) of the rate sensor dynamics and data transfer latency characteristics. By developing a transfer function that replicates the behavior of the rate sensor and latency effects, the system can process this model through the lead compensator to generate corrected attitude data. This copying approach allows error correction without requiring direct modification of the physical sensor or data transfer process.
2Measurement precision
If a lead compensator is used to correct for rate sensor dynamics and data transfer latency, then attitude error is reduced, but system complexity increases
Solution Approach 1:
The patent introduces a lead compensator as an intermediary component between the rate sensor and the instrument that requires accurate attitude data. This intermediary processes the raw rate sensor data through a transfer function that compensates for dynamics and latency effects, producing corrected attitude data without requiring fundamental changes to the existing sensor or instrument architecture. The compensator acts as a mathematical mediator that bridges the gap between imperfect measurements and required accuracy.
Solution Approach 2:
The patent applies parameter changes by modifying the temporal and frequency characteristics of the rate sensor data through the lead compensator. The transfer function adjusts parameters such as phase angle and gain frequency-dependently to counteract the lagging effects of rate sensor dynamics and data transfer latency. By changing these parameters in the frequency domain, the system achieves more accurate attitude measurements without adding physical complexity to the sensor hardware.
Data Source
AI summary
A system includes an angular rate sensor disposed in a vehicle for providing angular rates of the vehicle, and an instrument disposed in the vehicle for providing line-of-sight control with respect to a line-of-sight reference. The instrument includes an integrator which is configured to integrate the angular rates of the vehicle to form non-compensated attitudes. Also included is a compensator coupled across the integrator, in a feed-forward loop, for receiving the angular rates of the vehicle and outputting compensated angular rates of the vehicle. A summer combines the non-compensated attitudes and the compensated angular rates of the to vehicle to form estimated vehicle attitudes for controlling the instrument with respect to the line-of-sight reference. The compensator is configured to provide error compensation to the instrument free-of any feedback loop that uses an error signal. The compensator may include a transfer function providing a fixed gain to the received angular rates of the vehicle. The compensator may, alternatively, include a is transfer function providing a variable gain as a function of frequency to operate on the received angular rates of the vehicle.