Mobile Robot Sensor Calibration via Marker Posture Calculation

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Solution Overview

Problem

Existing calibration techniques for mobile robots are unable to accurately calibrate a second visual sensor without requiring it to be positioned where it can detect a common marker with the first visual sensor, limiting the flexibility and efficiency of sensor calibration.

Innovation Solution

A calibration apparatus that calculates the posture of the second sensor relative to the origin by using the known posture of the first sensor, the posture of the first marker relative to the first sensor, and the posture of the second marker relative to the first sensor, allowing calibration regardless of the second sensor's attachment position.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the second sensor is attached to a position where it can detect a common marker with the first sensor, then the calibration can be performed using existing techniques, but the attachment position is restricted and flexibility is reduced

Engineering Contradiction:

Improvecalibration accuracyVSAvoidsensor attachment position flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The calibration process is divided into two independent parts: first sensor calibration using first marker, and second sensor calibration using second marker. This segmentation allows each sensor to be calibrated independently without requiring spatial overlap in their detection fields, thereby enabling flexible attachment positions while maintaining calibration accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second marker serves as an intermediary object that enables calibration of the second sensor without requiring it to detect the first marker. By introducing this intermediate calibration target with known posture relative to the first marker, the system bridges the gap between sensors at different positions, allowing accurate calibration while maintaining attachment flexibility.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the second sensor is attached to an arbitrary position on the mobile robot, then attachment flexibility is improved, but existing calibration techniques cannot be used

Engineering Contradiction:

Improvesensor attachment position flexibilityVSAvoidcalibration process complexity

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The relative posture between the first marker and second marker is predetermined and known before calibration begins. This preliminary establishment of reference relationships simplifies the calibration process, as the system only needs to detect the markers and compute transformations based on pre-known geometric relationships, rather than requiring complex multi-step calibration procedures.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses virtual representations (posture data) of the markers and their relationships to perform calibration through computation rather than physical measurement. By copying the known relative posture information into the calibration algorithm, the system enables arbitrary sensor positioning while maintaining calibration simplicity through mathematical transformation rather than complex physical adjustment procedures.

Inventive Principle:

Principle #26Copying

3Measurement precision

If multiple sensors are calibrated using the same marker detection requirement, then calibration consistency is maintained, but the calibration time increases and productivity decreases

Engineering Contradiction:

Improvecalibration consistencyVSAvoidcalibration efficiency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The calibration process continues seamlessly across multiple sensors by maintaining the same computational framework and marker detection approach. Each sensor is calibrated in a continuous flow using its associated marker, without requiring repositioning or restarting procedures. This continuous calibration approach maintains measurement precision through consistent methodology while improving productivity by eliminating idle time between sensor calibrations.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS20240116186A1Calibration apparatus, calibration system, mobile system, calibration method, and control program

Publication Date: 2024.04.11 TOYOTA JIDOSHA KK

AI summary

A calibration apparatus calculates, from a result of detecting a first marker by a first sensor that is attached to a predetermined position on a mobile robot, a posture of the first marker relative to the first sensor; calculates, from a result of detecting a second marker by a second sensor that is attached to a position different from the predetermined position on the mobile robot, a posture of the second marker relative to the second sensor; and at least calculates the posture of the second sensor relative to the origin from the posture of the first sensor relative to the origin, the posture of the first marker relative to the first sensor, the posture of the second marker relative to the first marker, and the posture of the second marker relative to the second sensor.