Yaw Rate Control Activation for Earlier Vehicle Stabilization
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Solution Overview
Problem
Current yaw rate control systems face challenges in efficiently activating interventions to prevent vehicle instability, leading to high development efforts due to stringent ASIL D requirements, and existing use case detection methods result in late or weak interventions, necessitating a method to reduce ASIL classification to ASIL B.
Innovation Solution
A yaw rate control method that includes a deactivation function activating the yaw rate control system based on specific activation requirements, such as longitudinal deceleration, lateral acceleration, and yaw rate deviations, using separate memory tasks to ensure safe and timely interventions, allowing for early activation and reducing the frequency of interventions to less than 1% of operating time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If use case detection is defined to include all situations except unbraked stable straight-ahead driving, then intervention timing is improved (earlier activation), but ASIL classification increases to ASIL D (higher safety requirements and development effort)
Solution Approach 1:
The system segments the control function into two independent parts: a deactivation function running in a safety task with ASIL D requirements that detects use cases and manages activation, and a yaw rate control function running in a normal task with reduced ASIL B requirements that executes the actual control interventions. This segmentation allows the safety-critical detection logic to be isolated from the control execution logic.
Solution Approach 2:
The deactivation function acts as an intermediary between the sensor inputs and the yaw rate control function. It receives sensor data, determines whether a use case is present based on activation requirements, and controls the activation state of the yaw rate control function accordingly. This intermediary structure protects the control function from directly processing all sensor data, reducing its safety burden.
2Reliability
If the entire yaw rate control function is designed according to ASIL D requirements, then safety barrier requirements are met, but development effort increases significantly
Solution Approach 1:
The system divides the yaw rate control functionality into a deactivation function (ASIL D) and a yaw rate control function (ASIL B). The deactivation function handles all safety-critical decisions about when to activate control, while the yaw rate control function handles the actual control execution with reduced safety requirements. This segmentation reduces overall development effort while maintaining safety barriers.
Solution Approach 2:
The safety-critical use case detection and activation control logic is extracted from the main yaw rate control function and placed into a separate deactivation function. This extraction removes the safety burden from the control function, allowing it to be developed with ASIL B requirements instead of ASIL D, significantly reducing development effort while maintaining safety through the separate deactivation function.
3Measurement precision
If a complex vehicle model is used for yaw rate control, then control precision is improved, but ASIL classification increases to ASIL D due to additional input signals and complexity
Solution Approach 1:
The system uses different levels of model complexity in different functional segments. The deactivation function uses a simple stationary Ackermann model sufficient for ASIL D classification, while the yaw rate control function uses a more complex dynamic vehicle model for improved control precision. The segmentation allows each segment to use the appropriate level of complexity for its specific purpose without requiring the entire system to meet the highest ASIL requirements.
Solution Approach 2:
Different parts of the system use different levels of model complexity appropriate to their function. The deactivation function uses a simpler model suitable for its safety monitoring role, while the yaw rate control function uses a more complex model optimized for precise vehicle stabilization. This local quality approach allows each component to have the complexity it needs without unnecessarily increasing the ASIL classification of the entire system.
Data Source
AI summary
A yaw rate control method comprises a yaw rate control function for stabilizing a vehicle carries out wheel-specific braking interventions based on a first reference yaw rate. A deactivation function is provided and activates the yaw rate control function as soon as at least one activation requirement is met. The activation requirement checks whethera longitudinal deceleration is greater than a longitudinal deceleration limit value, in particular by a sensor tolerance,a lateral acceleration is greater than a lateral acceleration limit value, in particular by a sensor tolerance, anda deviation between a second reference yaw rate and a measured yaw rate is greater than a yaw rate deviation limit value, in particular by a sensor tolerance.