MDPS Virtual Torque Estimation via Yaw Rate and Lateral Acceleration
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Solution Overview
Problem
The Motor Driven Power Steering (MDPS) system faces instability and reliability issues when the torque sensor breaks down, leading to inappropriate assist force and potential driving hazards, as it must switch to manual mode, causing a significant difference in steering feel and potentially degrading vehicle stability.
Innovation Solution
The MDPS system estimates virtual column torque using yaw rate, lateral acceleration, and vehicle speed, enabling assist torque calculation through a dynamic model, even without a torque sensor, by employing sensors like yaw rate and lateral acceleration sensors and an MDPS controller with units for behavior estimation, tire lateral force calculation, and assist torque calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the MDPS system uses a torque sensor to measure steering torque, then steering control precision is improved, but system reliability deteriorates when the torque sensor breaks down
Solution Approach 1:
The patent introduces yaw rate sensors and lateral acceleration sensors as intermediary devices to indirectly measure steering torque when the torque sensor is unavailable. These sensors measure vehicle dynamic parameters (yaw rate and lateral acceleration) which are then used to calculate virtual column torque, serving as a mediator to maintain steering control functionality without direct torque sensing.
Solution Approach 2:
The patent replaces the mechanical torque sensor with an electronic calculation system that uses vehicle dynamic parameters. Instead of directly measuring torque mechanically, the system substitutes a computational approach using yaw rate and lateral acceleration data to estimate the required assist torque, eliminating the single point of failure represented by the torque sensor.
2Reliability
If the MDPS system switches to manual mode when torque sensor breaks down, then system safety is improved, but driving stability deteriorates due to sudden steering feel change
Solution Approach 1:
The patent prepares alternative torque estimation methods in advance by equipping the vehicle with yaw rate and lateral acceleration sensors. When torque sensor failure occurs, the system can immediately switch to using virtual column torque calculation without requiring a mode change to manual operation, maintaining steady assist torque provision and avoiding sudden steering feel changes that would affect driving stability.
3Reliability
If the MDPS system calculates assist torque using dynamic model and virtual column torque, then system reliability is improved when torque sensor is unavailable, but device complexity increases
Solution Approach 1:
The patent makes the existing yaw rate sensor and lateral acceleration sensor serve multiple functions. These sensors are already part of the vehicle's stability control system, and the patent extends their utility to also enable virtual column torque calculation for power steering assist, eliminating the need for additional dedicated sensors and reducing overall system complexity despite the enhanced functionality.
Data Source
AI summary
An MDPS (Motor Driven Power Steering) system may include: a vehicle speed sensor configured to sense vehicle speed; a yaw rate sensor configured to sense a tilted state of the vehicle, and output a yaw rate value; a lateral acceleration sensor configured to sense lateral acceleration which acts in a lateral direction of the vehicle; and an MDPS controller configured to receive the vehicle speed, the yaw rate value and the lateral acceleration from the vehicle speed sensor, the yaw rate sensor and the lateral acceleration sensor, respectively, and calculate assist torque by estimating column torque.