Steering Torque Estimation via Yaw Rate and Lateral Acceleration
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Solution Overview
Problem
Current Motor Driven Power Steering (MDPS) systems face challenges in estimating steering torque accurately when the torque detector fails, leading to unstable steering assistance and potential safety risks during vehicle operation.
Innovation Solution
A system and method that estimate steering torque by using a controller to receive yaw rate and lateral acceleration data, calculate rack force using a model formula, and generate an estimated steering torque value, incorporating friction compensation and weighting factors based on vehicle conditions, allowing for precise torque estimation even without a torque detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a torque detector is removed or fails, then system cost and complexity are reduced, but steering torque estimation accuracy deteriorates
Solution Approach 1:
The patent introduces intermediate parameters (steering angle, steering angular velocity, vehicle velocity, yaw rate, lateral acceleration) as mediators to indirectly estimate steering torque. Instead of directly measuring torque with a failed detector, the system uses these intermediary measurements combined with friction torque models and dynamic equations to calculate the steering torque, thereby resolving the contradiction between removing the torque detector and maintaining estimation accuracy
Solution Approach 2:
The patent replaces the mechanical torque detection system with a computational estimation system. By substituting the physical torque detector with an algorithm that processes data from other sensors (steering angle detector, vehicle velocity detector, yaw rate sensor, lateral acceleration sensor) and applies mechanical models (friction torque, dynamic equations), the system achieves torque estimation without the original mechanical detection device
2Device complexity
If traditional estimation methods using only steering angle and motor rotation angle are used, then system simplicity is maintained, but estimation accuracy during dynamic conditions deteriorates
Solution Approach 1:
The patent applies preliminary friction compensation based on steering angular velocity and motor angular velocity before calculating the final steering torque. By pre-calculating and compensating for friction torque using established models, the system prepares corrected data in advance, improving accuracy during dynamic steering operations without adding complex real-time computation during the main estimation process
Solution Approach 2:
The patent introduces dynamic parameters (yaw rate, lateral acceleration, vehicle velocity) that capture the dynamic state of the vehicle. By incorporating these time-varying parameters into the estimation model, the system adapts to changing driving conditions, making the estimation accurate during both static and dynamic steering operations rather than relying solely on steady-state assumptions
Data Source
AI summary
A system and a method for estimating a steering torque, may include receiving, in a controller, information including a value of a yaw rate and a value of a lateral acceleration of a vehicle collected in the vehicle in real time; determining and estimating, in the controller, a value of a rack force from the received information and a setting information using a predetermined model formula of estimating the rack force; and generating, in the controller, an estimated value of the steering torque according to an operation of a steering wheel of a driver from the estimated value of the rack force using a predetermined value of a gain.