Welding Force Control Using a Sensorless Spring Model

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Solution Overview

Problem

Existing welding control systems face challenges in maintaining consistent weld quality due to difficulties in setting and maintaining force sensors, leading to incorrect force measurements, which can result in poor weld quality, tool damage, and increased maintenance costs.

Innovation Solution

A device and method for generating force values without a force sensor, using a determination module to calculate welding tool parameters and a force value generation module that models the welding tool as a spring, allowing for accurate force regulation and reducing the need for force sensors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a force sensor is used to measure actual force for force control, then force measurement accuracy is improved, but device complexity and maintenance requirements increase

Engineering Contradiction:
Improveforce measurement accuracyVSAvoidforce sensor setup complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical force sensor system with a mathematical model-based calculation system. The force value is computed using a model that incorporates welding tool parameters, drive characteristics, and component properties, eliminating the need for physical force sensors and their associated complexity.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent creates a virtual copy or model of the welding tool system that replicates force behavior through mathematical relationships. This model includes spring constants, drive characteristics, and geometric parameters that together reproduce the force characteristics without requiring physical measurement devices.

Inventive Principle:
Principle #26Copying

2Reliability

If a force sensor is installed for force control, then force measurement capability is improved, but installation and maintenance costs increase

Engineering Contradiction:
Improveforce control reliabilityVSAvoidinstallation and maintenance cost
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The system uses readily available data from existing sensors and system parameters to compute force values without requiring separate force measurement infrastructure. The control system serves its own measurement needs by calculating force from drive current, position data, and pre-determined model parameters.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The mathematical model serves multiple functions: it provides force values for control, predicts weld quality, and adapts to different welding tools and components. This single model-based approach replaces multiple specialized measurement and control functions that would otherwise require separate hardware systems.

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

3Manufacturing precision

If incorrect actual force values are used for force control, then force control precision deteriorates, but tool damage risk increases

Engineering Contradiction:
Improveweld spot qualityVSAvoidtool damage risk
Core Design Contradiction:
Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The system continuously monitors welding parameters and adjusts the force calculation in real-time based on actual drive behavior and component response. This feedback mechanism ensures that the calculated force values accurately reflect actual conditions, preventing both poor weld quality and tool damage from incorrect force control.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent implements protective measures by calculating maximum allowable forces based on tool specifications and component properties before welding begins. The control system uses these pre-determined limits to prevent excessive force application that could damage the tool or produce defective welds.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

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

This solution enables consistent weld quality with reduced installation and maintenance efforts, lowers costs by eliminating the need for force sensors, and extends the service life of welding tools by preventing damage, thereby minimizing system failures and increasing industrial plant output.

Implementation Method 1

a force value generation module for generating, from a welding tool parameter determined by the determination module, an actual force which occurs during the welding process with the welding tool, wherein the force value generation module is designed to generate the actual force using a model of the welding tool

Methodology Applied
Scientific EffectSpring model: Spring

Data Source

PatentEP3854509B1Welding control device and method for generating force values in the control of a welding tool
Publication Date: 2024.02.07 ROBERT BOSCH GMBH
  • EP3854509B1 patent drawingFigure 1
  • EP3854509B1 patent drawingFigure 2~3
  • EP3854509B1 patent drawingFigure 4~5

AI summary

A device (50; 50A) for a welding control system (10) and a method for verifying the plausibility of force values ​​during the control of a welding tool (21) are provided. The device (50; 50A) has a determination module (51) for determining at least one welding tool parameter (AB, M_B) that depends on a drive of the welding tool (21) relative to the at least one component (5, 6) during a welding process with the welding tool (21), and a force value generation module (52) for generating, from a welding tool parameter (AB, M_B) determined by the determination module (51), an actual force (FS(t); FS_ACT) that occurs during the welding process with the welding tool (21), wherein the force value generation module (52) is configured to generate the actual force (FS(t); FS_ACT) with a model (511) of the welding tool (21).