Robot Tool Calibration Using Sphere and Distance Sensors
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Solution Overview
Problem
Current robot calibration methods, whether manual or automatic using vision sensors, are inefficient and time-consuming, especially when the end execution tool is frequently replaced, due to errors in determining the tool's center and requiring recalibration.
Innovation Solution
An automatic calibration method using a ball-rod member with distance sensors around a target point, allowing the robot to move a sphere to accurately determine transformation matrices without relying on visual identification, thereby streamlining the calibration process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual visual examination method is used to determine whether the end execution tool reaches the target point, then the operator can visually judge the position, but the calibration process is time-consuming and error-prone
Solution Approach 1:
The patent replaces the manual visual examination method with an automatic distance sensing system. Distance sensors automatically measure the position of the sphere center relative to the target point, eliminating the need for operator visual judgment. This substitution of mechanical/visual inspection with automated sensing technology resolves the contradiction by providing both high precision measurement and rapid data acquisition.
Solution Approach 2:
The calibration system performs self-measurement through the distance sensors that automatically detect the sphere position. The robot controls the end execution tool to move the sphere, and the distance sensors automatically record the measurements without requiring operator intervention for position determination. This self-service mechanism eliminates manual time consumption while maintaining measurement accuracy.
2Extent of automation
If vision sensor is used to identify the center of the end execution tool, then automatic calibration is achieved, but the calculation amount is very large and identifying speed decreases
Solution Approach 1:
The patent extracts the center identification function from the complex end execution tool by attaching a simple sphere with known geometric parameters. Instead of using vision sensors to identify the complex tool center, the system uses distance sensors to measure the sphere center position. This extraction of the identification target to a simple geometric form eliminates heavy calculation requirements while maintaining automation.
Solution Approach 2:
The patent introduces a simple, inexpensive sphere as a temporary calibration artifact that is easier to measure than the actual end execution tool. The sphere serves as a surrogate object for calibration purposes, allowing rapid measurement with distance sensors without the computational complexity of analyzing the real tool's geometry through vision systems.
3Adaptability or versatility
If the end execution tool is frequently replaced, then the robot system can handle different tools, but recalibration is required after every replacement which is troublesome and time-consuming
Solution Approach 1:
The patent creates a universal calibration reference system using the sphere that can be used with any end execution tool. The sphere serves as a common measurement reference that remains unchanged regardless of tool replacement. By calibrating the robot system relative to this universal sphere reference rather than each specific tool, the system achieves adaptability to different tools without requiring recalibration when tools are exchanged.
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 method significantly reduces calibration time and effort by accurately determining transformation matrices without the need for frequent recalibration when the end execution tool is replaced, enhancing the efficiency of the robot system.
Implementation Method 1
providing distance sensors around a target point, and sensing an actual distance from each of the distance sensors to the sphere
Data Source
AI summary
An automatic calibration method of a robot system comprises providing a ball-rod member including a connection rod and a sphere connected to the connection rod, fixing the connection rod to an end execution tool mounted on a flange of a robot, providing distance sensors around a target point, and sensing an actual distance from each of the distance sensors to the sphere. The robot is controlled to move a center of the sphere to the target point in different poses based on the actual distances sensed by the distance sensors. A first transformation matrix of the center of the sphere with respect to a center of the flange is calculated based on pose data of the robot at the target point. A second transformation matrix of a center of the end execution tool with respect to the center of the flange is calculated based on the first transformation matrix.