Rigid Body Motion Estimation from Doppler and Azimuth Data
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Solution Overview
Problem
Existing methods for determining the state of motion of a rigid body, such as vehicles or robots, are limited in accuracy and efficiency, particularly when using sensors that do not measure elevation angles, leading to incomplete data sets and reduced precision in position and orientation calculations.
Innovation Solution
A method utilizing regression analysis on measurement data sets from Doppler sensors, including radar and lidar, to determine the state of motion by forming condition sets that incorporate elevation angles set to a predetermined value, allowing for accurate conversion between sensor and body reference frames, and using iterative reweighting to minimize errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If motion capture markers are attached to body parts for movement analysis, then movement state detection capability is improved, but skin movement artifact causes measurement precision to deteriorate
Solution Approach 1:
The patent extracts and removes the motion capture markers from the body surface, eliminating the source of skin movement artifacts. Instead of using external markers that move independently of underlying bones, the system directly tracks bone movement through imaging, thereby resolving the contradiction between measurement capability and artifact-induced inaccuracy
Solution Approach 2:
The patent introduces an imaging system as an intermediary between the bone and the measurement process. Rather than directly observing marker movement on skin, the system uses X-ray or fluoroscopic images as a mediator to indirectly track bone position, eliminating the skin artifact problem while maintaining measurement capability
2Measurement precision
If multiple imaging devices are used to capture bone movement from different angles, then measurement precision is improved, but device complexity and radiation exposure increase
Solution Approach 1:
The patent employs periodic or intermittent imaging rather than continuous multi-angle imaging. By capturing images at specific time points or using fluoroscopic sequences, the system achieves sufficient measurement precision while minimizing cumulative radiation exposure compared to simultaneous multi-device imaging
Solution Approach 2:
The patent transitions from spatial multi-angle imaging to temporal dimension utilization. Instead of adding more imaging devices in different spatial positions, the system achieves three-dimensional bone movement analysis by capturing sequential images over time and reconstructing motion trajectories, thereby reducing radiation exposure while maintaining measurement precision
3Productivity
If motion capture markers are used on skin surface, then movement tracking capability is improved, but skin movement artifact reduces reliability
Solution Approach 1:
The patent replaces the mechanical marker attachment system with a field-based imaging system. Instead of using physical markers that adhere to and move with skin, the system uses electromagnetic fields (X-ray or fluoroscopic imaging) to directly visualize and track bone structures, eliminating the mechanical coupling between skin and measurement reference that causes artifacts
Solution Approach 2:
The imaging system serves as an intermediary that directly observes bone movement without being affected by skin motion. This intermediary approach allows the system to maintain high productivity in movement tracking while ensuring reliability by measuring actual bone position rather than skin-derived proxy measurements
Data Source
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AI summary
The invention relates to a method for determining a movement state of a rigid body (2) relative to an environment by means of a multiplicity of measurement data records for objects (4) in the environment of the body, wherein each measurement data record comprises a measurement point in time and a Doppler velocity (d) and an azimuth angle (θ) relating to a particular sensor reference system (S). The method comprises determining the movement state of the body relative to the environment as a velocity vector (vx, vy) and an angular velocity vector (ωz) in a body reference system (B), wherein: each sensor reference system can be converted into the body reference system by a non-singular transformation (R, t); at least one set of conditions comprising a plurality of measurement data records is formed; in a regression analysis for the at least one set of conditions, a functional dependent on Doppler velocity deviations between estimated Doppler velocities and the Doppler velocities of the measurement data records comprised in the at least one set of conditions is minimized; and the estimated Doppler velocities are interpreted as dependent variables in the regression analysis.