Power Steering Assist Torque Map Using Vehicle Eigenvalues
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Solution Overview
Problem
Conventional motor-driven power steering systems face challenges in determining the optimal assist torque, leading to delays between driver steering input and vehicle response, resulting in an insufficient feedback sense and coincidence between steering operation and vehicle reaction.
Innovation Solution
A method is introduced to determine assist torque by setting an initial slope and maximum driver steering torque, using vehicle eigenvalue information and a torque map to calculate assist torque values, ensuring a better correlation between driver input and vehicle lateral acceleration, thereby improving feedback and coincidence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional torque map methods are used to determine assist torque, then the system structure remains simple, but the steering response delay and insufficient feedback sense occur
Solution Approach 1:
The patent pre-calculates and stores optimal assist torque values in a torque map before actual steering operations. By determining assist torque values in advance based on driver steering torque and vehicle eigenvalues, the system eliminates real-time calculation delays, achieving instantaneous steering response without compromising control accuracy
Solution Approach 2:
The patent implements a feedback mechanism where vehicle eigenvalues (mass, moment of inertia, steering axis position) are continuously considered when determining assist torque. The torque map is generated based on the relationship between driver steering torque and vehicle response characteristics, creating a closed-loop system that adapts to vehicle dynamics and improves steering feedback sense
2Reliability
If assist torque is determined using conventional methods, then implementation is straightforward, but the correlation between driver input and vehicle lateral acceleration is insufficient
Solution Approach 1:
The patent changes the parameters used for assist torque determination by incorporating vehicle eigenvalues (mass, moment of inertia, steering axis position) into the torque map generation process. This parameter transformation creates a more accurate mathematical model that directly correlates driver steering torque with vehicle lateral acceleration, significantly improving steering response reliability
Solution Approach 2:
The patent introduces a torque map as an intermediary between the driver steering torque sensor and the motor controller. This torque map serves as a lookup table that translates driver input into optimized assist torque values, mediating the relationship between steering input and vehicle response while simplifying the control algorithm implementation
Data Source
AI summary
A method for determining an assist torque of a power steering system in a vehicle: setting an initial slope indicating a correlation between a driver steering torque and a vehicle lateral acceleration, wherein the initial slope is a tangential slope at a lowest point of the vehicle lateral acceleration defined in a diagram; setting a maximum driver steering torque, which is a maximum value of a steering torque that a driver applies through a steering wheel of the vehicle; calculating an assist torque based on the driver steering torque in response to performance of a steering assist, from the set initial slope and maximum driver steering torque, and vehicle eigen value information based on a predetermined equation; generating a torque map in which an assist torque value is set based on the driver assist torque upon the performance of the steering assist using assist torque values obtained for each driver steering torque detected by a torque sensor; and determining, by an electronic control unit (ECU), the assist torque value corresponding to the driver steering torque using the generated torque map.