Centripetal Acceleration Estimation in IMU Kinematic Chains
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Solution Overview
Problem
Inertial measurement units (IMUs) face challenges in accurately calculating angles between coupled bodies due to non-gravitational accelerations, such as centripetal accelerations, which degrade the accuracy of angle measurements.
Innovation Solution
A method is developed to determine centripetal accelerations of IMUs on rigid bodies in kinematic chains by using angular velocity, angular acceleration, global angular velocity skew matrices, and positional information relative to pivot points, allowing for improved angle calculations between coupled rigid bodies without relying on earlier bodies in the series for input data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If IMUs are used to measure motion of rigid bodies in kinematic chains, then motion information can be obtained, but non-gravitational accelerations (centripetal accelerations) degrade the accuracy of angle calculations
Solution Approach 1:
The patent converts the harmful effect of non-gravitational accelerations into a beneficial solution by using the measured acceleration data to calculate and compensate for centripetal acceleration components. The algorithm separates gravitational and non-gravitational components, using the latter to correct angle measurements, thereby turning the degrading factor into an improvement mechanism.
Solution Approach 2:
The patent implements a feedback mechanism where angle measurements are continuously refined by incorporating acceleration data. The system calculates centripetal acceleration from measured accelerations and uses this information to correct subsequent angle calculations, creating a closed-loop improvement process that enhances measurement precision iteratively.
2Measurement precision
If centripetal accelerations are accounted for to improve angle calculation accuracy, then measurement precision improves, but calculation complexity increases
Solution Approach 1:
The patent segments the acceleration measurement into distinct components: gravitational acceleration and non-gravitational (centripetal) acceleration. By separating these components and processing them through different calculation paths, the system manages complexity while improving accuracy. The segmentation allows each component to be handled with appropriate computational methods.
Solution Approach 2:
The patent applies partial action by selectively compensating for centripetal acceleration effects rather than attempting to model all possible motion artifacts. The algorithm focuses on the dominant non-gravitational component (centripetal acceleration) while making reasonable approximations for other effects, achieving improved accuracy without the full computational burden of complete physical modeling.
3Measurement precision
If iterative estimation methods are used to determine centripetal accelerations, then angle calculation accuracy improves, but computation time increases
Solution Approach 1:
The patent performs preliminary calculations of centripetal acceleration components using available measurement data before final angle determination. By pre-computing acceleration corrections from IMU measurements and propagating these through the kinematic chain, the system reduces the computational burden during iterative refinement stages, optimizing the balance between accuracy and computation time.
Data Source
AI summary
A method for determining centripetal accelerations of pivotally coupled rigid bodies arranged in a series, where the series includes a rigid body arranged between a previous rigid body and a next rigid body, includes determining the centripetal acceleration of the next rigid body and the centripetal acceleration at an inertial measurement unit (IMU) coupled to the next rigid body based on measurements and calculated parameters from the rigid body and the next rigid body. The centripetal acceleration of the next rigid body and the centripetal acceleration at the IMU coupled to the next rigid body are determined without using measurements or calculated parameters from the previous rigid body.