Robot End Effector Alignment Using Object Coordinate Axes
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Solution Overview
Problem
Existing robot teaching methods face challenges in accurately aligning the direction of the robot's fingers with the desired direction, especially for tasks like inserting an object into a hole, due to difficulties in aligning the robot's coordinate system with the object's coordinate system.
Innovation Solution
A control apparatus for a robot that includes a movable unit and a force detection unit, with control modes that allow the robot to adjust its position and orientation based on detected forces and angles, enabling precise alignment of the robot's end effector with the object's coordinate system by setting angle and distance thresholds, and automatically aligning axes to minimize relative angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the robot is taught by applying external force to fingers to move and rotate them according to force detection, then the robot can perform force control tasks, but it is not easy to accurately align the direction of the fingers with the desired direction
Solution Approach 1:
The patent introduces an object coordinate system as an intermediary reference frame that mediates between the robot's moving coordinate system and the desired alignment target. By defining a second axis in the object coordinate system and comparing it with the first axis of the moving coordinate system, the system provides a clear reference for alignment that simplifies the teaching process and improves accuracy.
Solution Approach 2:
The patent replaces pure mechanical force-based alignment with a computational approach using coordinate system transformation and angle calculation. Instead of relying solely on manual mechanical adjustment through force application, the system uses mathematical computation to determine the relative angle between coordinate axes and automatically calculates the rotation needed for alignment.
2Manufacturing precision
If the robot manually aligns the fingers direction with the hole depth direction, then accurate insertion is achieved, but the teaching process becomes complex and time-consuming
Solution Approach 1:
The patent performs preliminary coordinate system setup and axis definition before the actual alignment task. By pre-defining the object coordinate system and its second axis, and establishing the moving coordinate system with its first axis, the system prepares all necessary reference frames in advance, eliminating the need for time-consuming manual alignment adjustments during the teaching process.
Solution Approach 2:
The patent implements a feedback mechanism that continuously monitors the relative angle between the first axis of the moving coordinate system and the second axis of the object coordinate system. This feedback allows the system to automatically determine when alignment has been achieved and makes real-time adjustments if necessary, reducing teaching time while maintaining high precision.
3Adaptability or versatility
If the robot uses force control mode for teaching, then natural interaction is achieved, but automatic alignment with desired direction is difficult
Solution Approach 1:
The patent implements a dynamic control system that can switch between different control modes (first control mode for force-based natural interaction and second control mode for automated alignment). The system dynamically adjusts the control strategy based on the task requirements, allowing it to leverage the strengths of both approaches: natural interaction when needed and precise automated alignment when coordinate system comparison indicates misalignment.
Data Source
AI summary
A control apparatus includes a processor that is configured to control a robot, and receive an object coordinate system set for an object not an end effector and not moving or rotating with the end effector. The processor is configured to execute a first control mode in which the end effector is moved and rotated according to a detected force while the force is detected by a force detector, and execute a second control mode in which, when a relative angle between a predetermined first axis of a moving coordinate system moving and rotating with the end effector and a predetermined second axis of the object coordinate system is smaller than an angle threshold value, the end effector is rotated to make magnitude of the relative angle closer to zero.