Electric Power Steering Torque Estimation and Control
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Solution Overview
Problem
Current electric power steering systems often experience undesirable phenomena such as over-assistance, under-assistance, and counter-assistance, leading to self-steering or inadequate steering control.
Innovation Solution
A method that estimates the effort on the steering system's rack by combining the driver's torque on the steering wheel with the assistance torque, and compares it to predefined zones to correct and potentially interrupt the electric assistance, ensuring the assistance torque remains within authorized limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the electric assistance motor provides high assistance torque to facilitate driver steering actions, then the steering effort is reduced, but the system risks over-assistance leading to self-steering or under-assistance causing inadequate control
Solution Approach 1:
The system continuously estimates rack effort from torque sensor data and motor parameters, compares it against target values, and adjusts assistance torque in real-time to maintain optimal steering assistance while preventing over-assistance or under-assistance conditions
Solution Approach 2:
The system dynamically adjusts the assistance torque parameter based on estimated rack effort, vehicle speed, and steering angle, changing the assistance level to match driving conditions and prevent abnormal operating zones
2Power
If the assistance torque is increased to improve steering facilitation, then driver effort is reduced, but the system may enter abnormal operating zones causing self-steering or counter-assistance
Solution Approach 1:
The system proactively estimates rack effort and compares it with target values before abnormal conditions develop, taking corrective action by adjusting assistance torque to prevent entry into over-assistance or under-assistance zones that could cause self-steering
Solution Approach 2:
Continuous monitoring of rack effort estimation provides real-time feedback to adjust assistance torque, preventing the system from entering abnormal operating zones that generate harmful self-steering effects
3Reliability
If the assistance torque is decreased to prevent over-assistance, then self-steering is avoided, but the system may provide insufficient assistance causing under-assistance or counter-assistance
Solution Approach 1:
The system dynamically adjusts assistance torque parameters based on real-time estimation of rack effort, ensuring optimal assistance level is maintained without entering under-assistance or counter-assistance zones that would reduce steering facilitation
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a method for securing the assistance torque (15) supplied by an electric assistance motor (8) in a motor vehicle power steering system, the securing method being characterized in that it includes the steps of: estimating the force on the steering system rack from the torque exerted by the driver on the steering wheel (2), from the assistance torque (15), and optionally from other parameters such as the speed of the electric assistance motor; comparing a target assistance torque with an authorized assistance range, defined with respect to the estimated rack force (17) at any moment, and in the event the target assistance torque is maintained above predefined limits for a predefined duration, correcting and optionally interrupting the power steering.