EMB Clamping Force Estimation Using Motor Torque Hysteresis

Solution Overview

Problem

Conventional electromechanical braking (EMB) systems require a force sensor to measure clamping force, increasing system cost and complexity while compromising accuracy due to sensor calibration challenges.

Innovation Solution

A method to estimate clamping force based on motor torque hysteresis without using a force sensor, by generating a displacement-torque curve from displacement and motor torque data, determining high and low torque values, calculating a friction coefficient, and estimating clamping force using these coefficients.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a force sensor is used to measure clamping force, then measurement accuracy is improved, but device complexity and cost increase

Engineering Contradiction:

Improveclamping force measurement accuracyVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical force sensor measurement system with an electrical measurement system. It uses the electric motor's torque data and displacement data to calculate clamping force through a mathematical model, substituting direct mechanical sensing with indirect electrical measurement and computation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces motor torque and displacement as intermediary parameters to indirectly determine clamping force. Instead of directly measuring clamping force with a sensor, the system uses the relationship between motor torque, piston displacement, and friction coefficients to calculate the clamping force applied to the brake disc.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If a force sensor is used to measure clamping force, then measurement accuracy is improved, but system cost increases

Engineering Contradiction:

Improveclamping force measurement accuracyVSAvoidsystem cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent replaces the mechanical force sensor measurement system with an electrical measurement system. It uses the electric motor's torque data and displacement data to calculate clamping force through a mathematical model, substituting direct mechanical sensing with indirect electrical measurement and computation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses existing, inexpensive data (motor torque and displacement data already collected by the EMB system) instead of expensive force sensors. The calculation model uses readily available electrical parameters to derive clamping force information that would otherwise require costly hardware.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Measurement precision

If a force sensor is used to measure clamping force, then measurement accuracy is improved, but calibration difficulty increases

Engineering Contradiction:

Improveclamping force measurement accuracyVSAvoidsensor calibration difficulty

Core Design Contradiction:

Measurement precisionVSEase of repair

Solution Approach 1:

The patent replaces the mechanical force sensor measurement system with an electrical measurement system. It uses the electric motor's torque data and displacement data to calculate clamping force through a mathematical model, substituting direct mechanical sensing with indirect electrical measurement and computation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system uses its own existing data (motor torque and displacement data) to calculate clamping force, making the system self-sufficient. The calculation model leverages parameters already measured by the EMB system's motor control, eliminating the need for separate calibration procedures for additional sensors.

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

This approach allows for real-time estimation of clamping force tailored to individual EMB system components, eliminating the need for additional sensors and reducing system complexity and cost while maintaining accuracy.

Implementation Method 1

the motor converts electrical energy into mechanical energy that causes the clamping force to be applied to the outer disc

Methodology Applied

Scientific EffectElectromagnetic conversion: Electromagnetic Induction

Implementation Method 2

When the rotating discs are forced together, friction reduces the angular speed of the rotating discs

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS20250178581A1Clamping force estimation

Publication Date: 2025.06.05 ZF ACTIVE SAFETY US INC

AI summary

Systems and methods for clamping force estimation are provided. In one example, operations include generating a displacement-torque curve based on displacement data and motor torque data of an electric motor of the EMB system for a braking episode having a switchover time. The operations also include determining a high torque value and a low torque value at the switchover time from the displacement-torque curve. The operations further include calculating a friction coefficient based on the high torque value and the low torque value. The operations yet further include determining a non-linear coefficient from the displacement-torque curve. The operations include estimating a clamping force for a constant speed based on the friction coefficient and the non-linear coefficient.