Power Steering Securing Function for ASIL Safety

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Solution Overview

Problem

Current power steering systems with driving assistance functions face challenges in achieving high safety standards while maintaining rapid response times, as they require complex and resource-intensive algorithms and redundant sensors, leading to increased costs and weight.

Innovation Solution

A method that separates the path control function from a securing function, where the securing function monitors vehicle behavior and intervenes to neutralize the path control function in dangerous situations, allowing for a simpler and less resource-intensive path control system while ensuring high safety standards.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If complex processing algorithms and redundant sensors are implemented to meet high safety standards, then the reliability of the path control function is improved, but the device complexity and cost increase

Engineering Contradiction:

Improvesafety levelVSAvoidalgorithm complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system is divided into two independent functional segments: a path control function (which may be less reliable) and a securing function (which ensures safety). The securing function monitors the path control function and can intervene to neutralize it when safety risks are detected. This segmentation allows each function to be optimized independently, with the securing function bearing the safety burden rather than the path control function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The securing function acts as an intermediary between the path control function and the steering system. It monitors the behavior of the path control function and intervenes when necessary to ensure safety. This intermediary approach allows the path control function to operate with simpler algorithms while the securing function provides the necessary safety oversight.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If complex processing algorithms and redundant sensors are implemented to meet high safety standards, then the reliability of the path control function is improved, but the weight of the system increases

Engineering Contradiction:

Improvesafety levelVSAvoidsystem weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The system separates the safety-critical functions from the path control functions. The securing function can be implemented with minimal additional sensors by monitoring existing control parameters (steering wheel position, driver torque, rotational speed) rather than requiring redundant high-definition cameras and complex sensor arrays. This segmentation reduces the weight penalty while maintaining safety.

Inventive Principle:

Principle #1Segmentation

3Reliability

If complex processing algorithms are implemented to meet high safety standards, then the reliability is improved, but the response time decreases

Engineering Contradiction:

Improvesafety levelVSAvoidresponse time

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The securing function continuously monitors control parameters in advance and pre-establishes safety thresholds. When a dangerous situation is detected (e.g., steering wheel position exceeding thresholds, abnormal rotational speed), the securing function can immediately neutralize the path control function without requiring complex real-time calculations. This preliminary monitoring approach enables rapid response while maintaining simplicity.

Inventive Principle:

Principle #10Preliminary action

4Reliability

If redundant sensors and complex algorithms are implemented, then the safety level is improved, but the energy consumption increases

Engineering Contradiction:

Improvesafety levelVSAvoidcalculation energy

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The system segments energy-intensive path control algorithms from the securing function. The securing function relies on monitoring existing control parameters (steering wheel position, driver torque, rotational speed) that are already being measured by the power steering system, rather than requiring additional high-energy sensors like high-definition cameras. This segmentation significantly reduces the energy burden of safety functions.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS10407096B2Securing of a driving assistance function within a power steering

Publication Date: 2019.09.10 JTEKT EUROPE SAS

AI summary

A method of controlling a power steering system including at least one course control function, whereby a position setpoint is determined automatically according to a reference course that a vehicle is to be made to follow, then a motor setpoint applied to an assistance motor is adjusted accordingly, the method including a safety function which is distinct from the course control function and meets a higher ASIL safety level according to ISO-26262 standard, said safety function including a diagnostics subfunction according to which a control parameter such as the angular position of the steering wheel, the driver torque applied to the steering wheel, or the rate at which the steering wheel is turned is monitored in order to detect the onset of an alert situation considered to be hazardous, then an intervention subfunction according to which, if an alert situation is detected, the course control function is neutralized.