Forklift Mast Strain Sensing for Accurate Load Center Detection

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Solution Overview

Problem

Existing load determination systems in forklift trucks, particularly counterbalance forklifts and reach trucks, struggle to accurately measure load weight and center of gravity, especially when dealing with complex loads, and do not account for lateral offset, leading to potential accidents and transport damage.

Innovation Solution

A method using strain gauges to detect elastic deformation of the mast profile, combined with a vehicle-specific computational model, allows for precise determination of load mass and center of gravity by measuring strains and torsions in three-dimensional space, processing deformation data to determine load parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If pressure measurement in the hydraulic circuit is used to determine load weight, then the measurement system can be integrated into existing forklift systems, but internal disturbances such as pressure pulsations and slipstick effects distort the load determination

Engineering Contradiction:
Improveintegration into existing forklift systemsVSAvoidload determination accuracy
Core Design Contradiction:
Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The invention extracts the measurement function from the hydraulic circuit by placing strain gauges directly on the mast profile. This separates the measurement system from the hydraulic system, eliminating the distortion caused by pressure pulsations and slipstick effects while maintaining integration with the forklift's structural components

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The strain gauges act as an intermediary measurement element that directly senses the mechanical load on the mast profile without being influenced by hydraulic circuit disturbances. This intermediary approach provides a clean measurement signal that accurately reflects the actual load weight

Inventive Principle:
Principle #24Intermediary (Mediator)

2Measurement precision

If strain gauges are used to measure elastic deformation of the mast profile, then load weight and center of gravity can be determined accurately, but the device complexity increases

Engineering Contradiction:
Improveload weight and center of gravity determination accuracyVSAvoidsensor device and computational model complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The strain gauge measurement system serves multiple functions simultaneously: it measures both load weight and center of gravity position, and provides data for both static and dynamic stability assessment. This multi-functionality justifies the added complexity by delivering comprehensive load information from a single measurement system

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

Solution Approach 2:

The invention replaces complex mechanical load measurement mechanisms with electrical strain gauge sensors combined with computational modeling. This substitution simplifies the physical measurement system while enabling precise determination of multiple load parameters through signal processing and mathematical models

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

3Duration of action of moving object

If existing load-measuring devices are utilized, then the system can provide continuous load monitoring, but lateral offset of the load center of gravity is not accounted for

Engineering Contradiction:
Improvecontinuous load monitoring capabilityVSAvoidlateral offset information
Core Design Contradiction:
Duration of action of moving objectVSLoss of information

Solution Approach 1:

The strain gauge arrangement on the mast profile measures deformations in multiple dimensions, enabling determination of both vertical load weight and lateral center of gravity position. This multi-dimensional measurement capability captures complete load information including the previously missing lateral offset

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 accurate, real-time measurement of load mass and center of gravity, reducing the risk of accidents by providing operators with precise load information and enabling automated interventions to maintain stability.

Implementation Method 1

an elastic deformation of the mast profile is detected by means of a sensor device, wherein the elastic deformation of the mast profile is detected by measuring strains and torsions by means of at least one strain gauge

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Implementation Method 2

measuring strains and torsions by means of at least one strain gauge as a sensor device

Methodology Applied
Scientific EffectStrain measurement: Piezoresistive Effect

Data Source

PatentEP3670428B1Industrial truck and method for determining load in an industrial truck
Publication Date: 2026.01.28 STILL GMBH
  • EP3670428B1 patent drawingFigure 1
  • EP3670428B1 patent drawingFigure 2
  • EP3670428B1 patent drawingFigure 3

AI summary

The invention relates to a method for determining the load on a material handling vehicle, in particular a counterbalance forklift or reach truck, comprising a load handling device (1) with a lifting mast (1a) and at least one mast profile (1d), and a corresponding material handling vehicle. It is proposed that elastic deformation of the mast profile (1d) is detected by means of a sensor (4) and that the resulting deformation data is processed with a physical computational model (D) of the material handling vehicle, stored in a control unit (SE) of the material handling vehicle and based on vehicle-specific information, and that the load mass (L) and load center of gravity (LS) are determined from this.