Fiber Optic Shape Sensor Navigation with IMU Error Correction
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Solution Overview
Problem
Conventional fiber optic shape sensors experience significant errors in measuring the position and shape of optical fibers, especially with long lengths, due to imperfections in calibration and noise in measurement data, and are inaccurate during rapid changes in fiber shape or strain.
Innovation Solution
Combining a distributed fiber optic shape sensor with one or more localized position sensors, such as inertial measurement units, to correct for errors in orientation measurements, using a state estimation unit like a Kalman filter to improve the accuracy of position and shape determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the length of the optical fiber is increased to extend the measurement range, then the coverage area is improved, but the measurement precision deteriorates due to accumulated errors
Solution Approach 1:
The patent divides the long optical fiber into multiple segments by placing localized position sensors at different positions along the fiber. Each segment's position is measured independently by its corresponding localized sensor, preventing error accumulation across the entire length. The estimating unit integrates measurements from all segments to determine the overall shape and position of the long fiber accurately.
2Device complexity
If conventional fiber optic shape sensors are used without localized position sensors, then the device complexity is reduced, but the measurement precision deteriorates during rapid changes in fiber shape
Solution Approach 1:
The patent merges the advantages of distributed spatial sensing with localized position sensing by combining fiber optic shape sensors with inertial measurement units at strategic positions. The distributed sensor captures continuous shape information while the localized sensors provide accurate orientation and position data during rapid movements. The estimating unit fuses these complementary measurements to achieve high precision during dynamic conditions.
3Device complexity
If distributed spatial sensors alone are used for navigation, then the device complexity is minimized, but the reliability deteriorates due to time-dependent drift in inertial navigation
Solution Approach 1:
The patent implements feedback by using the distributed spatial sensor to continuously monitor the actual position and shape of the optical fiber, then feeding this information back to correct drift in the inertial navigation system. The estimating unit compares the fiber's actual configuration with the inertial navigation estimate and applies corrections to maintain long-term accuracy without requiring frequent stationary periods for zero-velocity updates.
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 reduces errors in position measurements to as low as 0.1% of the fiber length, providing accurate navigation even with long optical fibers and during rapid changes in fiber shape, and is suitable for various applications including medical procedures and underwater exploration.
Implementation Method 1
Some fiber optic shape sensors obtain these measurements by using one or more fiber cores and an optical frequency domain reflectometer that transmits light to and receives reflected light from the optical fiber cores. In this way, the FOSS can measure the distributed strain on the fiber cores, which can be used to determine the position and shape of the optical fiber.
Implementation Method 2
An IMU determines the acceleration of an object and changes in the orientation of the object based on measurements provided by one or more accelerometers and/or gyroscopes physically connected to the object.
Data Source
AI summary
Systems and methods for determining the shape and/or position of an object are described. A fiber optic shape sensor (FOSS) may be used in combination with one or more inertial measurement units (IMUs) to mutually cross-correct for errors in the sensors' measurements of position and/or orientation. The IMU(s) may be attached to the FOSS's optical fiber, such that each IMU measures the orientation of a corresponding portion of the optical fiber. The position and shape of the optical fiber can then be determined based on the measurements obtained from the IMU(s) and the measurements obtained from the FOSS. For example, the FOSS measurements and the IMU measurements can be provided to a state estimation unit (e.g., a Kalman filter), which can estimate the position and/or shape of the optical fiber based on those measurements. In some embodiments, the estimates of position are used for navigation of tethered mobile devices.