Electric Power Steering End Hitting Detection and Current Limiting
Solution Overview
Problem
Conventional electric power steering systems face durability issues and increased component size due to high stress during end hitting events, leading to potential damage and increased costs, especially in larger vehicles.
Innovation Solution
An electric power steering apparatus that detects end hitting events, counts the frequency of such occurrences, and calculates a current limit value to reduce assist torque, thereby limiting the motor's output and reducing stress on the steering mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the motor provides full assist torque during end hitting events, then the steering assist force is maximized, but the steering mechanism experiences high stress and potential damage
Solution Approach 1:
The control unit detects end hitting events in advance and counts their occurrences. When a threshold number of end hitting events is detected, the control unit proactively limits the motor current to prevent excessive stress on the steering mechanism, thereby ensuring durability before damage occurs.
Solution Approach 2:
The system continuously monitors steering torque and detects end hitting events through feedback from the torque sensor. The control unit uses this feedback to count the number of end hitting events and adjusts motor current accordingly, creating a closed-loop control system that protects the steering mechanism based on real-time operational data.
2Reliability
If the steering mechanism is designed to withstand high stress from end hitting, then durability is improved, but component size and cost increase
Solution Approach 1:
Instead of increasing the mechanical strength of the steering mechanism to withstand high stress, the patent substitutes a mechanical protection approach with an electrical control approach. The control unit limits motor current based on the count of end hitting events, replacing the need for heavier, more durable mechanical components with an intelligent control system.
3Reliability
If the motor current is limited based on end hitting count, then stress on steering mechanism is reduced, but the steering assist force decreases during frequent end hitting events
Solution Approach 1:
The motor current limit is made dynamic rather than static. The control unit adjusts the current limit based on the real-time count of end hitting events. During normal operation, full current is available for maximum assist torque. When end hitting events are detected and counted, the current limit is dynamically reduced to protect the steering mechanism, creating an adaptive control strategy that balances performance and protection.
Data Source
AI summary
[Problem]An object of the present invention is to provide an electric power steering apparatus that realizes weight saving and downsizing of component parts by counting and controlling the number of times of end hitting and simultaneously calculating a current limit value depending on the number of times of end hitting to limit assist.[Means for solving the problem]The present invention is an electric power steering apparatus that comprises an end hitting detection means that detects end hitting based on the steering torque and a differential steering torque obtained by differentiating the steering torque and outputs an end hitting detection signal, a counting means that counts a number 1 of times of end hitting detected by the end hitting detection means, a storage means that stores and keeps a total number of times of end hitting, and a current limit value calculating means that calculates a current limit value depending on a number 2 of times of end hitting obtained by adding the number 1 of times of end hitting from the counting means and the total number of times of end hitting from the storage means, wherein the current command value is limited based on the current limit value calculated by the current limit value calculating means.