Robot Manipulator Calibration Using Load-Sensor Feedback

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Solution Overview

Problem

Calibration of industrial robot manipulators is tedious, expensive, and typically requires specialized equipment, making field calibration uncommon and inaccurate.

Innovation Solution

A method using a primary manipulator and a load sensor to calibrate a secondary manipulator by recording joint positions and load data, allowing for accurate calibration without expensive equipment, enabling field calibration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If field calibration is performed without load compensation, then calibration can be performed at production site, but calibration accuracy is reduced due to external loads

Engineering Contradiction:

Improvefield calibration capabilityVSAvoidcalibration accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The load sensor provides real-time feedback on external loads acting on the manipulator during calibration. The control system uses this feedback to either compensate for the loads through calculation or to adjust manipulator poses to minimize load effects, thereby maintaining calibration accuracy in field conditions

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

A load sensor is introduced as an intermediary device between the manipulator and the calibration process. This sensor measures external loads and enables the control system to account for their effects, bridging the gap between field calibration convenience and manufacturing-level accuracy

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If expensive laser tracking systems are used for calibration, then calibration accuracy is improved, but calibration cost increases

Engineering Contradiction:

Improvecalibration accuracyVSAvoidcalibration equipment cost

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces expensive, complex laser tracking systems with a relatively simple and inexpensive load sensor. While the load sensor has a limited function (measuring loads only), it provides sufficient accuracy for calibration when used in combination with load-aware control, making high-cost equipment unnecessary

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent substitutes complex optical measurement systems (laser tracking) with a simpler mechanical sensing approach (load sensor). By measuring forces and torques mechanically and using computational methods to derive position information, the system achieves comparable accuracy without the complexity of optical systems

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If manipulator is calibrated under load, then calibration can be performed in operational conditions, but measurement accuracy deteriorates due to deformation

Engineering Contradiction:

Improveoperational condition calibrationVSAvoidjoint position accuracy

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent changes the approach from measuring positions directly (which is affected by load-induced deformation) to measuring loads and using this information to calculate or adjust positions. By changing from position-based measurement to load-based measurement with computational correction, the system maintains accuracy under operational conditions

Inventive Principle:

Principle #35Parameter changes

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

Provides a cost-effective and accurate method for calibrating industrial robot manipulators using a load sensor, improving calibration accuracy by accounting for external loads and reducing deformation.

Implementation Method 1

providing a load sensor between the primary mounting interface and the secondary mounting interface, the load sensor being configured to provide load data indicative of loads between the primary mounting interface and the secondary mounting interface

Methodology Applied

Scientific EffectForce sensing: Force

Data Source

PatentUS12594673B2Method of calibrating manipulator, control system and robot system

Publication Date: 2026.04.07 ABB (SCHWEIZ) AG

AI summary

A method of calibrating a manipulator of an industrial robot, the method including providing a primary manipulator having one or more primary joints and a primary mounting interface; providing a secondary manipulator having one or more secondary joints and a secondary mounting interface, where the primary mounting interface is substantially rigidly connected to the secondary mounting interface; providing a load sensor between the primary mounting interface and the secondary mounting interface, the load sensor being configured to provide load data indicative of loads between the primary mounting interface and the secondary mounting interface; controlling the primary manipulator to adopt at least one calibration state; for each calibration state, recording a primary joint position of at least one primary joint; and calibrating the secondary manipulator based on the at least one recorded primary joint position; wherein the primary manipulator is controlled to adopt the at least one calibration state based on the load data; and/or wherein the calibration of the secondary manipulator is additionally made based on the load data.