Target Deceleration Determination Using Pre-Calculated Braking Time Ratios

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Solution Overview

Problem

Existing emergency braking systems face challenges in accurately selecting target decelerations, leading to undesirable changes during the braking process, which can result in safety risks and unnecessary activation of emergency braking functions.

Innovation Solution

The method determines the movement variables of a vehicle ahead to calculate the required braking time and distance to come to a standstill, allowing for the selection of a suitable target deceleration for the host vehicle based on the comparison of braking times, thereby reducing the likelihood of deceleration changes and enhancing safety.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If different target decelerations are selected based on assumed collision scenarios (moving or stationary vehicle ahead), then the emergency braking function can be adapted to different situations, but changes between setpoint decelerations during the braking process occur, leading to safety risks and driver discomfort

Engineering Contradiction:

Improveadaptation to different collision scenariosVSAvoidsafety risk due to deceleration changes

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent calculates the braking time of the vehicle ahead in advance and uses this pre-calculated value to select the appropriate target deceleration before the braking process begins. This preliminary calculation prevents the need to change setpoint decelerations during braking, as the correct deceleration is chosen from the start based on whether the vehicle ahead will be stationary or moving at the time of impact.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically calculates the braking time of the vehicle ahead based on its current deceleration and speed, and uses this dynamic information to adaptively select the appropriate target deceleration for the host vehicle. This dynamic approach ensures the most appropriate deceleration is chosen while maintaining stability throughout the braking process.

Inventive Principle:

Principle #15Dynamics

2Productivity

If different target decelerations are selected based on assumed collision scenarios, then the braking can be optimized for the suspected scenario, but unnecessary emergency braking functions may be triggered or collisions with following traffic may occur

Engineering Contradiction:

Improvebraking efficiencyVSAvoidcollision risk with following traffic

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system uses feedback from the calculated braking time of the vehicle ahead to continuously monitor and confirm the appropriateness of the selected target deceleration. By comparing the calculated braking time with the time to impact, the system can verify that the chosen deceleration is appropriate and adjust if necessary, preventing both unnecessary braking and insufficient braking responses.

Inventive Principle:

Principle #23Feedback

3Measurement precision

If the eTTC variable is used to determine collision scenarios, then the system can estimate whether the vehicle ahead will be stationary or moving at impact, but the initial assumption may be incorrect due to movement conditions during braking

Engineering Contradiction:

Improvecollision scenario estimationVSAvoidcorrectness of scenario assumption

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent performs a preliminary calculation of the braking time of the vehicle ahead using its current deceleration and speed. This pre-calculation is done before the host vehicle begins braking, allowing the system to select the appropriate target deceleration in advance based on the most accurate available information, reducing the risk of incorrect assumptions.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP3647141B1Method and arrangement for determining a target deceleration for an ego vehicle

Publication Date: 2022.08.10 VOLKSWAGEN AG

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AI summary

The invention relates to a method for determining a target deceleration for an ego vehicle (12), wherein the method comprises: - determining at least one motion parameter of a preceding vehicle (13); - determining a braking time (Object_Time_to standstill) and a braking distance (Object_Distance_to standstill) based on the motion parameter that the preceding vehicle (13) would each require to come to a standstill; - determining a braking time (Ego_Time_to standstill) for the ego vehicle (12) that would be required to come to a standstill at the same position as the preceding vehicle (13) when the latter has covered the braking distance (Object_Distance_to standstill); - Setting a target deceleration (Dreq,D, Dreq,stop) for the ego vehicle (12) based on a ratio of the braking times (Object_Time_to Standstill, Ego_Time_to Standstill) of the preceding vehicle (13) and the ego vehicle (12).Furthermore, the invention relates to an arrangement (10) for setting a target delay for an ego vehicle (12) and a vehicle comprising such an arrangement (10).