Robot Joint Angle Calibration Using Distance Reference Measurement
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Solution Overview
Problem
Existing methods for calibrating the angle of a robot, such as using a laser tracker, are expensive and difficult to implement when only a part of the robot, like an electric motor, needs replacement.
Innovation Solution
An angle calibration method that involves measuring the distance between two measurement object portions on a robot's members and calculating the angular difference based on past reference measurements, allowing for accurate adjustment of the actuator command value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser tracker is used for angle calibration, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses a simple scale as a copy or substitute for the complex laser tracker system. Instead of using expensive laser tracking technology, the invention creates a simplified measurement system using basic scaling tools and geometric relationships to achieve the same calibration function with much simpler equipment.
Solution Approach 2:
The patent replaces expensive, complex calibration equipment with inexpensive, simple tools like scales and markers. These simple objects can be easily manufactured and discarded if needed, eliminating the need for investing in and maintaining expensive laser tracker systems while achieving sufficient calibration accuracy.
2Measurement precision
If a laser tracker is used for angle calibration, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The patent simplifies the calibration operation by replacing complex laser tracker procedures with simple visual and manual measurement steps using scales and markers. The complex optical alignment and data processing of laser trackers are copied into simple geometric measurements that can be performed with basic tools.
Solution Approach 2:
The calibration system uses the robot's own structure and components (links, joints, and existing features) as the measurement references, eliminating the need for external complex calibration equipment. The robot essentially calibrates itself using simple tools attached to or integrated with its own structure.
3Measurement precision
If traditional calibration methods are used, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent copies the essential measurement function from complex laser tracker systems into simple scale-based measurements. This allows calibration to be performed quickly during actuator replacement without requiring time-consuming setup and operation of sophisticated laser tracking equipment.
Solution Approach 2:
The patent incorporates measurement markers and scaling features into the robot's structure during manufacturing, so that when calibration is needed, the measurements can be taken immediately without requiring preliminary setup of complex measurement equipment. The measurement infrastructure is prepared in advance as part of the robot's design.
Data Source
AI summary
A robot includes an actuator that changes an angle of a second member relative to a first member in accordance with a command value. In a first step of an angle calibration method, a measurement object distance is obtained by measuring a distance between wall surfaces of the two measurement object portions, the measurement being made while the actuator is given an arbitrary command value. In a second step, an angular difference is obtained by calculation, the angular difference corresponding to a difference in distance between two measurement object portions, the calculation being made based on a reference measurement object distance obtained in the past and the measurement object distance obtained in the first step, the reference measurement object distance having been obtained by measuring the measurement object distance while the actuator was given an arbitrary command value.