Brake Caliper FBG Sensing for Accurate Braking Force Measurement

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Solution Overview

Problem

Existing brake caliper force sensors are not compact, complex, or sensitive to temperature variations, making them unsuitable for direct and accurate measurement of braking force and torque in vehicle braking systems.

Innovation Solution

Incorporation of fiber-optic strain sensors, specifically Fiber Bragg Grating (FBG) sensors, into the brake caliper to directly measure deformation and strain, combined with temperature compensation using FBG temperature sensors, to provide accurate and reliable measurements of braking force and torque.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional force sensors are incorporated in the brake caliper, then braking force measurement capability is improved, but device complexity and size increase making them unsuitable for caliper integration

Engineering Contradiction:
Improvebraking force measurementVSAvoidsensor structure
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces traditional mechanical force sensors with fiber optic sensors that use optical principles instead of mechanical components. The fiber optic sensor detects strain through optical interference patterns, eliminating complex mechanical structures while maintaining measurement capability.

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

Solution Approach 2:

The patent uses a thin flexible substrate to mount the fiber optic sensor components, allowing the sensor assembly to conform to the brake caliper geometry and enabling integration without adding significant bulk or complexity to the existing structure.

Inventive Principle:
Principle #30Flexible shells and thin films

2Measurement precision

If traditional force sensors are incorporated in the brake caliper, then braking force measurement capability is improved, but temperature sensitivity increases making them unsuitable for high-temperature environments

Engineering Contradiction:
Improvebraking force measurementVSAvoidtemperature sensitivity
Core Design Contradiction:
Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces temperature-sensitive mechanical sensors with fiber optic sensors that are inherently more resistant to temperature effects. The optical measurement principle is less susceptible to thermal expansion and material property changes that plague mechanical sensors in high-temperature brake environments.

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

Solution Approach 2:

The patent changes the measurement parameter from mechanical displacement or force to optical properties (interference patterns, light intensity) that are more stable across temperature variations. This parameter transformation reduces temperature sensitivity while maintaining measurement accuracy.

Inventive Principle:
Principle #35Parameter changes

3Ease of manufacture

If indirect measurement methods are used to estimate braking force, then ease of implementation is improved, but measurement accuracy deteriorates

Engineering Contradiction:
Improvesensor implementationVSAvoidbraking force measurement
Core Design Contradiction:
Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent extracts the measurement function directly from indirect estimation methods and places it at the source of the physical phenomenon (the brake caliper itself). By mounting sensors directly on the caliper, the system captures actual force data rather than inferring it from other measurements, improving accuracy while keeping implementation straightforward.

Inventive Principle:
Principle #2Taking out (Extraction)

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 and reliable real-time measurement of braking force and torque within the brake caliper, overcoming the limitations of existing sensors by ensuring compactness and robustness against temperature fluctuations.

Implementation Method 1

at least one fiber-optic strain sensor of the fiber Bragg grating type, configured to detect the deformation and/or strain acting locally in the respective position and to generate a respective at least one first photonic signal representative of the detected deformation and/or strain

Methodology Applied
Scientific EffectFiber Bragg Grating: Bragg Diffraction

Implementation Method 2

at least one fiber-optic temperature sensor of the fiber Bragg grating type, configured to detect a temperature value present in the respective position and to generate a respective at least one second photonic signal representative of the detected temperature

Methodology Applied
Scientific EffectFiber Bragg Grating: Bragg Diffraction

Data Source

PatentEP3983774B1Method and system for detecting and measuring a braking force of a braking system for vehicle, by means of photonic sensors incorporated in a brake caliper
Publication Date: 2025.09.03 FRENI BREMBO SPA
  • EP3983774B1 patent drawingFigure 1~3
  • EP3983774B1 patent drawingFigure 4A~4B
  • EP3983774B1 patent drawingFigure 4C

AI summary

A method is described for detecting and measuring a braking force and/or a braking torque BF/BT deriving from the actuation of a vehicle braking system 1000, by means of detection performed in at least one brake caliper 10 of the braking system. The method comprises the steps of incorporating at least one deformation and/or strain sensor 2, at a respective position, in a portion of material M of the body of the brake caliper 10, susceptible to deformation due to a reaction force which is applied onto the brake caliper at the braking force and/or torque BF/BT, so that the deformation and/or strain S acting locally in the position, in which the deformation and/or strain sensor 2 is located, is representative of the braking force and/or braking torque BF/BT. The deformation and/or strain sensor 2 is a fiber-optic strain sensor 2 of the fiber Bragg grating type. The method then comprises the step of detecting, by means of the fiber-optic strain sensor 2, the local deformation and/or strain S acting in the respective position, and generating a respective at least one first photonic signal L representative of the detected deformation and/or strain S; receiving the first photonic signal L, by an optical reading/ interrogation unit 4, optically connected to the fiber-optic strain sensor 2, and generating, by the optical reading/ interrogation unit 4, one first electrical signal E representative of the local detected deformation and/or strain S, on the basis of the first photonic signal (L) received. The method finally comprises the step of processing the aforesaid first electrical signal E representative of the deformation and/or strain S to obtain a measurement of the braking force and/or braking torque BF/BT. A sensorized brake caliper, equipped to allow the execution of the aforesaid method, and a corresponding system to detect and measure a braking force and/or braking torque are further described.