Steering Torque Assist Without a Torque Sensor Using Yaw Modeling
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Solution Overview
Problem
Existing vehicle steering systems that rely on torque sensors for assist functionality face challenges when the sensor's functionality is diminished, leading to a loss of assist, and the use of redundant sensors increases costs and resource requirements.
Innovation Solution
A method and system that estimate the road friction coefficient without a torque sensor, using vehicle speed, steering angle, and yaw rate values to generate torque assist, and adjust steering system maneuvers based on updated friction coefficient values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a torque sensor is used for steering assist, then steering system performance is improved, but system cost and complexity increase
Solution Approach 1:
The patent extracts the torque sensing function from a dedicated torque sensor and relocates it to the steering angle sensor by utilizing the relationship between steering angle and torque through vehicle dynamics modeling. This eliminates the need for a separate torque sensor while maintaining the steering assist functionality.
Solution Approach 2:
The patent replaces the mechanical torque sensing system with an electronic estimation system that uses vehicle dynamics models, steering angle data, and road friction coefficients to calculate torque values, thereby eliminating the need for physical torque sensors.
2Reliability
If redundant torque sensors are added, then reliability is improved, but cost and resource requirements increase
Solution Approach 1:
The patent makes the steering angle sensor multi-functional by enabling it to perform both steering angle measurement and torque sensing functions through electronic estimation, thereby eliminating the need for redundant torque sensors and reducing overall sensor quantity.
Solution Approach 2:
The system uses existing vehicle signals (steering angle, vehicle speed, yaw rate) and road friction coefficient data to self-generate torque information without requiring additional sensors, allowing the system to serve itself rather than relying on redundant components.
3Reliability
If torque sensor functionality is diminished, then system reliability deteriorates, but adding redundant sensors increases cost
Solution Approach 1:
The patent implements beforehand cushioning by continuously monitoring the health and functionality of the torque sensing system through model-based estimation, allowing the system to detect and compensate for potential failures before they occur, ensuring continuous steering assist functionality without requiring redundant sensors.
Solution Approach 2:
The system uses feedback from vehicle dynamics models and road friction coefficient updates to continuously adjust and maintain accurate torque estimation, ensuring reliable steering assist even when the original torque sensor functionality is diminished or fails.
Data Source
AI summary
A method for generating torque assist includes determining a model yaw rate value based on a vehicle speed, a steering angle, and a road-friction coefficient value and determining a differential yaw rate value using a difference between the model yaw rate value and a vehicle yaw rate value. The method also includes determining an updated road-friction coefficient value using at least the differential yaw rate value and generating a torque assist value based on the updated road-friction coefficient value and a model rack force value.