Instrument Head Pose Calibration With On-Board Distance Sensing

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Solution Overview

Problem

Construction sites present complex, changing environments that require precision in the millimeter range for assembly tasks, which existing on-board sensor devices like LiDAR cannot achieve, and external sensors are cumbersome due to the need for pre-referencing and limited to determining position rather than orientation.

Innovation Solution

A method using a sequence of steps involving on-board sensor devices and distance measuring devices to determine the position and orientation of a device head connected to a robot arm, where pose data is collected, distance measurements are taken, error values are calculated, and the device head is moved until sufficient error values allow for error minimization and accurate positioning.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If external sensor units (total stations) are used to achieve millimeter-level accuracy, then measurement precision is improved, but device complexity and ease of operation worsen due to pre-referencing requirements and separate positioning

Engineering Contradiction:
Improvemillimeter-level accuracyVSAvoidexternal sensor units
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines multiple sensor types (LiDAR, cameras, distance measuring devices) into an integrated on-board sensor system mounted directly on the device head. This merging eliminates the need for external total stations and pre-referencing procedures, achieving millimeter-level accuracy through the synergistic combination of sensors while reducing system complexity and improving ease of operation.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent introduces a coordinate system transformation mechanism as an intermediary that maps measurements from different sensor coordinate systems to a unified reference frame. This intermediary layer enables the integrated sensor system to achieve accurate positioning and orientation by reconciling data from multiple sensors with different coordinate references, resolving the complexity of integrating diverse sensor types.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Measurement precision

If external sensor units are used to determine position, then measurement capability is improved, but adaptability worsens because they cannot determine orientation

Engineering Contradiction:
Improveposition determinationVSAvoidorientation determination
Core Design Contradiction:
Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent implements a universal on-board sensor system that performs both position and orientation determination functions. The integrated system includes LiDAR for spatial mapping, cameras for visual recognition and angle measurement, and distance measuring devices for range data. This multi-functional sensor suite enables the device head to simultaneously determine its position, orientation, and pose relative to the construction environment, eliminating the limitation of external total stations.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Device complexity

If on-board sensor devices like LiDAR are used, then device complexity is reduced, but measurement precision deteriorates as they cannot achieve millimeter-level accuracy

Engineering Contradiction:
Improveon-board sensor integrationVSAvoidmillimeter-level accuracy
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The patent employs a composite sensor system that combines multiple sensor technologies (LiDAR, cameras, distance measuring devices) rather than relying on a single sensor type. Each sensor contributes its strengths: LiDAR provides spatial structure and range data, cameras provide visual recognition and angular information, and distance measuring devices provide precise range measurements. The fusion of these complementary sensor data streams achieves millimeter-level accuracy while maintaining on-board integration.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent implements a feedback mechanism where the control device continuously processes sensor data, compares measured positions and orientations with expected values from construction models, and adjusts device head positioning accordingly. This closed-loop feedback system enables the on-board sensor suite to achieve and maintain millimeter-level accuracy through iterative correction, compensating for individual sensor limitations.

Inventive Principle:
Principle #23Feedback

4Measurement precision

If target objects are positioned in the measurement environment, then measurement precision is improved, but ease of operation worsens due to the need for pre-positioning and referencing

Engineering Contradiction:
Improveposition and orientation determinationVSAvoidpre-positioning requirements
Core Design Contradiction:
Measurement precisionVSEase of operation

Solution Approach 1:

The patent enables the device head to perform self-positioning and self-orientation using its own on-board sensor system. The LiDAR, cameras, and distance measuring devices mounted on the device head autonomously scan and map the construction environment, determining the device's own position and orientation without requiring external target objects or pre-positioning procedures. This self-service capability eliminates the need for manual target placement and referencing, significantly improving ease of operation.

Inventive Principle:
Principle #25Self-service

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

Enables precise determination of the device head's position and orientation in the millimeter range, improving the accuracy and flexibility of robotic assembly tasks on construction sites by integrating on-board sensors with geometry models and compensation calculations.

Implementation Method 1

In the second step of the sequence, the distance sensors perform a distance measurement to surfaces within the measurement environment and transmit their measured distance values to the control device

Methodology Applied
Scientific EffectTime of Flight: Time of Flight

Data Source

PatentEP4034348B1Method for determining a position and/or the orientation of a device top
Publication Date: 2024.11.20 HILTI AG
  • EP4034348B1 patent drawingFigure 1
  • EP4034348B1 patent drawingFigure 2
  • EP4034348B1 patent drawingFigure 3A~3C

AI summary

The invention relates to a method for specifying a position and/or orientation of an instrument head (10) in a measuring environment (11) by means of a distance measuring device (16) which comprises a number of M, M ≥ 1 distance measuring sensors (18) and which is connected to the instrument head (10). Also comprising a control device (17) which is communicatively connected to the distance measuring device (16) and an on-board sensor device (14), wherein the position and/or orientation of the instrument head (10) has been determined by means of the on-board sensor device (14) and transmitted to the control device (17).