Robot Wrist Calibration via Target Imaging and Noncontact Measurement
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Solution Overview
Problem
Calibrating the mechanical parameters of a robot's wrist part is challenging, especially when replacing the wrist part entirely, as existing methods fail to maintain positioning precision due to unknown camera or target positions, making it difficult to calculate the origin error and calibrate the wrist part's mechanical parameters effectively.
Innovation Solution
A calibration system and method using a target attached to the robot's hand and an imaging device around the robot to generate preliminary positions, detect the target's position and distance, and calculate mechanical parameters through optimization of nonlinear functions, allowing for precise calibration of the wrist part's mechanical model without requiring extensive workspace or manual intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If a wrist part is replaced in a robot, then the robot can be maintained or upgraded, but the positioning precision deteriorates due to changes in mechanical parameters
Solution Approach 1:
The patent measures actual mechanical parameters (link lengths, origin positions) of the replaced wrist part and inputs these measured values into the robot control system to update the mechanical model. This parameter update process restores positioning precision after replacement by compensating for manufacturing tolerances and assembly variations through software-based parameter adjustment rather than mechanical reconfiguration.
2Ease of operation
If the mark reference method is used to calibrate mechanical parameters, then the calibration process becomes simpler, but it is ineffective when the wrist part is completely replaced because the marks are on old components
Solution Approach 1:
The patent extracts the calibration function from component-specific marks and implements it through a target attached to the robot hand. By measuring the target's position and posture at multiple robot positions, the system calculates mechanical parameters without relying on marks on the wrist part itself, making the calibration method universally applicable whether the wrist part is replaced or not.
Solution Approach 2:
The patent introduces a target as an intermediary object between the imaging device and the wrist part. The target's known geometry and measurable position/posture serve as a mediator to indirectly determine the wrist part's mechanical parameters, enabling calibration without direct access to or dependence on marks on the wrist part components.
3Productivity
If existing calibration methods are used after wrist part replacement, then the calibration can be performed, but the mechanical parameters of the wrist part cannot be accurately calculated due to unknown camera or target positions
Solution Approach 1:
The patent employs an iterative feedback process where the robot moves to multiple predetermined positions, the imaging device captures target images, and the system calculates both the target's position/posture and the wrist part's mechanical parameters simultaneously. The calculated parameters are then used to update the mechanical model, and the process repeats with refined measurements until convergence, ensuring high accuracy while maintaining efficiency through automated iteration.
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
Enables quick and reliable calibration of the wrist part's mechanical parameters, reducing the need for manual marking and workspace, maintaining precision, and ensuring worker safety by using visual feedback for noncontact measurements, thus preventing a drop in positioning accuracy.
Implementation Method 1
an imaging device set around the robot, the calibration system including a preliminary position generating part using a position of the robot when arranged at a position where the target is included in a field of vision of the imaging device
Data Source
AI summary
A calibration system able to calibrate mechanical parameters of a wrist part by a simpler manner is provided. The calibration system utilizes a target fastened at a predetermined position with respect to the joint closest to a hand of a robot and an imaging device set around the robot so as to calibrate the parameters of a mechanical model representing the wrist part of the robot. The posture of the target is changed from a predetermined initial position to generate a plurality of preliminary positions. Using these preliminary positions as starting points, the end point position of the robot whereby the target becomes a predetermined positional relationship with respect to the imaging device on the image obtained by capturing an image of the target is calculated. The calibration system uses the calculated end point position as the basis to calibrate the mechanical parameters of the wrist part.