Tool Pose Estimation via Material Property Signal Correlation
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Solution Overview
Problem
Current machining systems face challenges in accurately estimating the spatial position of a tool within an object, particularly in inhomogeneous bodies like human bones, due to incorrect registration processes and lack of adequate feedback mechanisms, leading to potential errors in surgical or machining operations.
Innovation Solution
A system that uses a sensor coupled to the machining tool to generate output signals based on material properties, comparing these signals with pre-determined candidate signals to determine the tool's spatial position through correlation analysis, allowing for real-time adjustment and alignment with planned trajectories.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If registration is performed using landmark correlation, then the object can be referenced with the model, but incorrect identification of landmarks leads to incorrect registration and false manipulation
Solution Approach 1:
The system continuously monitors tool position and orientation during machining, comparing actual positions with planned positions. When deviations are detected, the system provides feedback to adjust the tool path, ensuring accurate machining despite registration errors. This closed-loop control compensates for initial registration inaccuracies by real-time correction.
Solution Approach 2:
The system transforms the problem from attempting perfect initial registration to accepting registration as an approximation and instead focuses on real-time parameter adjustments during machining. By changing from a static registration approach to a dynamic compensation approach, the system achieves high precision without requiring perfect landmark identification.
2Measurement precision
If additional landmarks are used for verification of registration transformation, then registration accuracy can be improved, but the complexity of the registration process increases
Solution Approach 1:
The system extracts the verification function from the registration process itself and separates it into a continuous monitoring phase during machining. Instead of performing all verification during initial registration, the system extracts position verification to occur continuously during the machining operation, using the tool's interaction with the workpiece as the verification mechanism.
Solution Approach 2:
The machining process itself serves as the verification mechanism. As the tool machines the workpiece, the actual material removal and tool engagement provide self-verification of position and orientation, eliminating the need for separate verification landmarks or procedures.
3Measurement precision
If traditional position sensors are used to estimate tool pose, then the system can track tool position, but the system lacks adequate feedback mechanisms for inhomogeneous bodies leading to potential errors
Solution Approach 1:
The system merges traditional position sensing with material property sensing by integrating force/torque sensors that detect both mechanical contact position and material characteristics. This combination provides simultaneous information about tool location and material properties, eliminating the information loss that occurs when using position sensors alone on inhomogeneous materials.
Solution Approach 2:
The system introduces material property feedback as an intermediary between the tool and control system. By sensing material properties such as density variations through force measurements, the system gains additional information about the workpiece that complements position data, enabling more accurate tool path adjustment for inhomogeneous materials.
Data Source
AI summary
The invention relates to a system for estimating the spatial position (pose) of a tool (2) within an object (1), particularly in the form of a human bone that is to be machined with said tool, comprising: a sensor (21) being designed to be coupled to said tool (2), which sensor (21) is further designed to generate an sensor output signal (31) upon machining of said object (1) along an actual trajectory (30), which sensor output signal (31) depends on a material property of said object along said actual trajectory (30), an analyzing means being designed to determine a correlation between said sensor output signal (31) upon machining said object (1) and a plurality of pre-determined candidate output signals (42), each candidate output signal (42) being generated in beforehand using said material property along an associated model trajectory (40) in a model of said object (1), and wherein said analyzing means is designed to estimate a spatial position of the tool (2) within the object (1) using the model trajectory (40) whose associated candidate output signal (42) has the highest correlation with the sensor output signal (31), for instance. The invention further relates to a method for estimating the pose of the tool (2), as well as a computer program product.