EM Navigation Error Correction Using Inertial Sensor Fusion
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Solution Overview
Problem
Electromagnetic surgical navigation systems face inaccuracies due to metal distortions in the electromagnetic field, leading to errors in positioning and orientation, which can lead to navigation errors, particularly in the presence of metal implants or devices, affecting surgeries such as ENT and cranial procedures.
Innovation Solution
A system utilizing inertial sensors, such as MEMS sensors, as redundant error correction devices to correct for orientation and position errors, enhancing navigation accuracy by integrating with electromagnetic sensors to maintain precise tracking in the presence of metal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GPS signal is used for navigation, then position information can be obtained, but signal availability deteriorates in urban canyons and indoor environments
Solution Approach 1:
The patent combines multiple navigation sensors (GPS receiver, inertial sensors including accelerometers and gyroscopes, and magnetometers) into an integrated navigation system. This fusion allows the system to maintain position availability when GPS signals are blocked by urban canyons or indoor environments, as the inertial sensors continue to provide navigation data through dead reckoning calculations.
Solution Approach 2:
The system dynamically changes operational parameters by switching between GPS-dependent mode and inertial-only mode based on signal availability. When GPS signals are blocked, the system transitions to using only inertial sensor data with updated error correction parameters, allowing continuous navigation operation despite the harmful effect of signal blockage.
2Measurement precision
If multiple sensors are used for navigation, then position accuracy is improved, but error accumulation from sensor drift increases
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors inertial sensor drift errors and adjusts navigation calculations accordingly. By comparing inertial sensor measurements against known reference points or GPS data when available, the system generates correction factors that are fed back into the navigation solution, preventing unbounded error accumulation while maintaining high position accuracy.
Solution Approach 2:
The system dynamically adjusts error correction parameters based on detected drift conditions. When sensor drift is detected, the system modifies the weighting and integration parameters of the inertial data, applying appropriate correction factors to maintain measurement precision while accounting for the accumulated errors from multiple sensors operating over time.
3Duration of action of stationary object
If inertial sensors are used when GPS is unavailable, then position continuity is maintained, but position accuracy deteriorates due to drift errors
Solution Approach 1:
The patent applies preliminary error correction to inertial sensor data by establishing drift correction parameters before GPS signal loss occurs. When GPS is still available, the system characterizes sensor drift behavior and pre-computes correction factors that are then applied during GPS outages, maintaining position accuracy throughout the extended period of GPS unavailability and ensuring navigation continuity.
Solution Approach 2:
The system dynamically adjusts the navigation solution based on the duration and conditions of GPS unavailability. As the outage persists, the system adapts by adjusting sensor fusion weights, applying drift correction models, and modifying integration parameters to maintain both navigation continuity and acceptable position accuracy over extended periods without GPS signals.
Data Source
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Figure 2C
AI summary
A system according to embodiments of the present disclosure includes: an electromagnetic (EM) navigation system including: an EM field generator that generates one or more EM fields; and at least one EM sensor affixed to a tracked object, wherein the EM navigation system determines a pose of the tracked object when the tracked object is within the one or more EM fields; and an independent sensor positioned a first distance relative to the tracked object and that provides a reading indicative of a change in pose of the tracked object, wherein the reading provided by the independent sensor is useful for determining an accuracy of the pose of the tracked object as determined by the EM navigation system.