Autonomous Steering Actuator Blocked Detection and Mitigation
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Solution Overview
Problem
Autonomous vehicles operating in cold conditions can encounter latent fault situations due to a blocked steering actuator, such as frozen water in the steering gear housing, leading to degraded or complete loss of steering function, which may not be detected until a significant steering command is sent, causing deviations from the planned trajectory.
Innovation Solution
The autonomous driving system detects insufficient steering movement and applies a specific movement profile with sufficient amplitude and frequency to diagnose latent faults without disturbing the vehicle's position, and optionally activates a heating element to prevent high friction conditions, ensuring continuous operation by determining the likelihood of a blocked actuator based on environmental and steering system data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the autonomous driving system sends a large steering command to correct trajectory deviation, then the vehicle trajectory can be adjusted, but the blocked steering actuator may not respond appropriately leading to complete loss of steering function
Solution Approach 1:
The system performs preliminary diagnostic actions by monitoring steering actuator response to normal commands and detecting latent faults before they cause complete failure. The autonomous driving system tracks the relationship between steering commands and actual steering responses, identifying blocked actuator conditions early when only partial blockage is present, allowing for preventive mitigation before total steering loss occurs.
2Measurement precision
If the system applies excitation profiles to diagnose latent faults, then detection accuracy improves, but vehicle position disturbance and occupant discomfort increase
Solution Approach 1:
The system applies partial excitation profiles - small amplitude steering inputs designed to provoke diagnostic responses without causing noticeable vehicle position changes or occupant discomfort. These partial actions are sufficient to detect latent faults by monitoring actuator response characteristics, while remaining below the threshold of what would be perceived as vehicle disturbance by passengers.
Solution Approach 2:
The system implements periodic diagnostic monitoring by continuously analyzing steering actuator responses during normal operation. Rather than applying large test commands intermittently, the system performs ongoing subtle assessments of actuator health by examining the relationship between commanded and actual steering positions, enabling fault detection without disrupting normal vehicle operation.
3Reliability
If the system monitors steering actuator response continuously, then latent fault detection capability improves, but computational resources and system complexity increase
Solution Approach 1:
The system employs feedback monitoring by continuously comparing the commanded steering position with the actual steering position returned from the actuator. This closed-loop monitoring detects latent faults by identifying discrepancies or abnormal response patterns in the actuator feedback signal, enabling reliable fault detection through simple comparative analysis rather than complex diagnostic routines.
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 effectively mitigates the risk of steering failures by detecting and addressing potential blockages before they cause significant deviations, ensuring stable vehicle trajectory and occupant comfort, even in cold conditions.
Implementation Method 1
a heating element in the steering system (e.g., within or along the steering column or steering gear housing) may be activated by the autonomous driving system to reduce the likelihood of a high friction condition such as a blocked steering actuator
Data Source
AI summary
Aspects of the technology involve controlling a vehicle configured to operate in an autonomous driving mode. This includes receiving a set of environmental inputs including temperature information from different temperature sources, receiving initial steering information from a steering system of the vehicle, and obtaining an initial rack position command by a motion control module of the vehicle. The system determines, based on the environmental inputs, the initial steering information and an initial rack position, a likelihood that a steering actuator of the steering system of the vehicle is blocked or likely to become blocked. The system determines whether a threshold excitation amount has been applied to the steering system within a selected amount of time or a selected driving distance. When the threshold amount of excitation is not met, an excitation profile is applied to the steering system in order to modify the initial rack position.