Electric Power Steering Control Device for Sensor Abnormality Estimation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric power steering systems face challenges in fully reflecting driver interventions during autonomous driving, leading to feelings of strangeness and discomfort, and struggle with accurate steering angle control when angle sensor abnormalities occur.
Innovation Solution
A control device for electric power steering that estimates the steering angle using past values and motor relative angles when an abnormality is detected, allowing for seamless switching between autonomous and manual control modes without relying solely on the angle sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If steering angle control is used with gradual change gains to switch between autonomous and manual control modes, then switching smoothness is improved, but driver intervention responsiveness deteriorates
Solution Approach 1:
The system detects driver intervention in advance by monitoring steering torque variations and proactively adjusts the gradual change gain before the driver's input is fully processed. This preliminary detection and adjustment mechanism ensures that the system transitions smoothly while maintaining responsiveness to the driver's intended action.
2Measurement precision
If angle sensor data is used for steering angle control, then measurement accuracy is improved, but system reliability deteriorates when sensor abnormalities occur
Solution Approach 1:
The system introduces an intermediary mechanism that monitors the health and validity of angle sensor data. When sensor abnormalities are detected, this intermediary switches the control system to use alternative data sources or estimation methods, thereby maintaining system reliability while preserving measurement accuracy during normal operation.
Solution Approach 2:
The system dynamically changes the parameters used for steering angle control based on sensor status. When the angle sensor is functioning normally, it uses direct sensor measurements for high accuracy. When abnormalities are detected, it transitions to using alternative parameters such as motor position data or estimated steering angles, ensuring continuous reliable operation.
3Speed
If assist control command values are switched abruptly to respond to driver input, then responsiveness is improved, but steering wheel naturalness deteriorates
Solution Approach 1:
The system dynamically adjusts the switching characteristics of assist control command values based on the detected driver input state. When gradual switching is needed to maintain naturalness, it applies smoothing algorithms. When rapid response is critical for safety or driver intent, it prioritizes responsiveness. This dynamic adjustment resolves the contradiction by adapting the switching behavior to the specific operational context.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
There is provided a control device for an electric power steering device, which determines an estimate of a steering angle instead of using an angle sensor when any abnormality is detected in the angle sensor to perform steering angle control using the determined estimate of the steering angle. When it is determined that the detected steering angle is normal based on a steering angle abnormality determination signal Flg_θh, a steering angle calculating section 201 outputs a steering-wheel angle θh as an actual steering angle θr, while when it is determined that the detected steering angle is abnormal, the steering angle calculating section 201 determines and outputs an estimate θr of an actual steering angle using a past value Zθr of the actual steering angle under normal conditions, a motor relative angle Δθm, and a relative twist angle Δθ of a torsion bar.