MEMS IMU Position Verification With Physiological Drift Reset
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Solution Overview
Problem
Existing IMU systems, particularly MEMS IMUs, suffer from drift issues that lead to inaccurate position and orientation measurements over time, compromising the precision of robotic surgical procedures due to cumulative errors, especially when attached to a patient's anatomy.
Innovation Solution
The system employs a MEMS IMU attached to a patient's anatomical feature, such as a vertebra, and utilizes physiological cues like the end-of-expiration coinciding with the diastole period to periodically reset the IMU's zero reference, compensating for drift, combined with vibration analysis to monitor surgical tool interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a MEMS IMU is used for tracking anatomical features, then the device size and complexity are reduced, but measurement precision deteriorates due to drift over time
Solution Approach 1:
The patent applies periodic action by using physiological cues (end-of-expiration and diastole) to trigger periodic resets of the IMU zero reference. This periodic reset mechanism compensates for cumulative drift errors without requiring continuous complex calibration systems, thus maintaining measurement precision while keeping the device simple.
Solution Approach 2:
The system implements feedback by monitoring physiological signals (respiration and heartbeat) and using them to detect when drift compensation should occur. The feedback loop closes by resetting the IMU reference at optimal physiological moments, ensuring continuous accuracy without adding complex hardware.
2Measurement precision
If the IMU zero reference is continuously adjusted to compensate for drift, then measurement precision is maintained, but device complexity and energy consumption increase
Solution Approach 1:
Instead of continuous adjustment, the system uses periodic resets triggered by physiological events. This approach maintains tracking accuracy by compensating for drift at critical moments without requiring continuous active correction, thereby reducing system complexity and energy consumption.
Solution Approach 2:
The system leverages the patient's own physiological signals (breathing and heartbeat) to automatically determine when drift compensation is needed. This self-service mechanism eliminates the need for external complex calibration systems or continuous manual intervention.
3Measurement precision
If physiological cues are used to reset IMU drift, then measurement precision is maintained over time, but the system requires additional sensing capabilities
Solution Approach 1:
The patent merges the drift compensation function with existing physiological monitoring systems. By combining IMU tracking with standard respiratory and cardiac monitoring, the system achieves long-term accuracy without adding separate complex sensing subsystems, as the physiological cues are already captured by routine surgical monitoring equipment.
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 maintains accurate tracking of anatomical features and surgical tools, ensuring precise robotic surgery by correcting drift and detecting bone density changes, thus enhancing surgical precision and safety.
Implementation Method 1
An inertial measurement unit (IMU) is an electronic device that measures and reports orientation, velocity, and gravitational forces through the use of accelerometers and gyroscopes
Implementation Method 2
An inertial measurement unit (IMU) is an electronic device that measures and reports orientation, velocity, and gravitational forces through the use of accelerometers and gyroscopes
Implementation Method 3
combined with vibration analysis to monitor surgical tool interactions
Data Source
AI summary
Systems and methods for accurate determination of the position of an anatomic part of a subject in robotic assisted image-based surgery, using an inertial measurement unit (IMU) to determine the position and orientation of the anatomical part of the subject. The intrinsic drift of the IMU, which would make the IMU position measurements inaccurate, can be reset to zero regularly, at points of time when the subject's body is stationary. This can be achieved when motion from the subject's breathing and from the heartbeat are essentially zero. Such positions occur respectively when the respiratory signal shows the position of the breathing cycle to be at the end of the expiration phase, and the heartbeat signal represents a time in the diastole period of the subject's electrocardiographic cycle. When these two signal moments coincide, the IMU is essentially stationary, and its drift reset to zero.