Timing Correction in Nodal Seismic Units
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Autonomous nodal seismic acquisition units face challenges in maintaining a stable time base due to limited power resources and intermittent access to external time references, leading to power inefficiency and potential distortion in seismic data acquisition.
Innovation Solution
A method and apparatus that utilize a low-power, distributed time base system with intermittent operation of an on-board wireless receiver to access an external precision time base, implementing an open loop control algorithm to correct synchronization errors and drift, and using environmental sensors to estimate and adjust the oscillator frequency, thereby minimizing power consumption and data distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a continuous GPS receiver is used to discipline the VCO for stable timing, then timing stability is improved, but power consumption increases significantly
Solution Approach 1:
The GPS receiver is operated intermittently rather than continuously, updating the VCO frequency at periodic intervals. This allows the system to maintain timing stability through regular corrections while significantly reducing power consumption by allowing the receiver to enter low-power states between updates.
Solution Approach 2:
The system uses environmental sensors to monitor conditions that affect VCO stability and autonomously determines when GPS updates are needed. The open-loop control algorithm predicts drift based on environmental changes and triggers GPS receiver activation only when necessary, enabling the system to self-regulate power consumption while maintaining timing accuracy.
2Use of energy by moving object
If environmental sensors and open-loop control are used to reduce power consumption, then power efficiency is improved, but measurement precision of timing drift deteriorates
Solution Approach 1:
Environmental sensors serve as intermediaries that indirectly measure conditions affecting VCO stability. Instead of directly measuring timing drift continuously (which would require continuous GPS operation), the system uses temperature, humidity, and other environmental parameters as proxies to predict drift and trigger selective GPS updates, maintaining precision while improving power efficiency.
Solution Approach 2:
The system implements feedback through environmental monitoring and drift prediction. When environmental conditions change beyond thresholds that would cause significant drift, the system triggers a GPS update to correct the VCO frequency. This feedback mechanism maintains timing precision without requiring continuous measurement, thereby improving power efficiency.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A wireless seismic data acquisition unit with a wireless receiver providing access to a common remote time reference shared by a plurality of wireless seismic data acquisition units in a seismic system. The receiver is capable of replicating local version of remote time epoch to which a seismic sensor analog-to-digital converter is synchronized. The receiver is capable of replicating local version of remote common time reference for the purpose of time stamping local node events. The receiver is capable of being placed in a low power, non-operational state over periods of time during which the seismic data acquisition unit continues to record seismic data, thus conserving unit battery power. The system implements a method to correct the local time clock based on intermittent access to the common remote time reference. The method corrects the local time clock via a voltage controlled oscillator to account for environmentally induced timing errors. The invention further provides for a more stable method of correcting drift in the local time clock.