Robot Coordinate Calibration for Non-Perpendicular Z-Axis Deviation
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Solution Overview
Problem
Existing hand-eye calibration methods for industrial robots fail when the z-axis of the effector coordinate system is not perpendicular to the workbench, leading to errors in transformation relationships between coordinate systems.
Innovation Solution
A method and apparatus that involve photographing a target object from three positions around the actual effector coordinate system's z-axis, merging these positions, determining the center of a circle formed by the target object's positions, and calculating the deviation of the z-axis from the theoretical effector coordinate system by measuring the distance and position of the effector's contact point with the workbench.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the z-axis of the effector coordinate system is not perpendicular to the workbench, then the robotic arm cannot perform accurate operations, but requiring precise perpendicularity increases calibration complexity and parameter settings
Solution Approach 1:
The patent replaces complex mechanical calibration procedures with a visual measurement method. Instead of using精密 mechanical alignment tools and multiple parameter adjustments, the system uses a camera to photograph the workbench and target object, then calculates the deviation angle through image processing and coordinate transformation. This substitutes mechanical alignment with optical measurement, significantly simplifying the calibration process while maintaining high precision.
Solution Approach 2:
The system enables the robotic arm to automatically determine its own coordinate system deviation through self-photographing. The camera mounted on the effector photographs the workbench and target object, and the system automatically calculates the z-axis deviation angle through coordinate transformation algorithms. This self-calibration approach eliminates the need for external calibration equipment and complex parameter settings, allowing the system to correct its own positioning errors autonomously.
2Reliability
If traditional hand-eye calibration methods are used, then coordinate transformation can be determined, but the method fails when the z-axis is not perpendicular to the workbench
Solution Approach 1:
The patent introduces a deviation angle parameter to characterize the non-perpendicular configuration of the z-axis. Instead of requiring the z-axis to be perfectly perpendicular (a fixed parameter constraint), the system measures and compensates for the actual deviation angle. This parameter change allows the calibration method to adapt to various configurations, transforming a rigid requirement into a measurable and correctable property.
Solution Approach 2:
Traditional calibration methods assume the z-axis is perpendicular to the workbench and fail when this assumption is violated. The patent inverts this approach by explicitly measuring the deviation from perpendicularity and using this measurement to correct the coordinate transformation. Instead of forcing the system to meet the perpendicularity assumption, the method accommodates the actual configuration by calculating and compensating for the deviation angle.
Data Source
AI summary
The invention relates to the technical field of industrial robots, and particularly relates to a coordinate system calibration method, a device, and a computer readable medium. A coordinate calibration method comprising: rotating an actuator (20) about an z″ axis of an actual actuator coordinate system (63) to reach three different positions, and controlling a camera (10) to capture an image of a target object (60) on an operation platform (40) for each of the three reached positions; merging positions of the target object (60) in images captured at the three positions into one image, and determining coordinates of a center P3 of a circumcircle of the three positions of the target object (60) in the image under a camera coordinate system (62); enabling the actuator (20) to move along the z″ axis and contact the operation platform (40) with a terminal end, and labeling a contact point as a point P2; controlling the actuator (20) to return to a first position (71) along the z″ axis, and controlling the camera (10) to capture an image; determining coordinates of P2 under the camera coordinate system (62) according to the position of P2 in the image; and determining, according to the coordinates of P2 and P3 under the camera coordinate system (62) and a moved distance of the actuator (20) from the first position (71) along the z″ axis, a deviation of the z″ axis from a theoretical z axis of an actuator coordinate system (61). The invention has an advantage of operational simplicity.