Steering Axial Force Computation Circuit for Road Surface Feedback
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Solution Overview
Problem
Steer-by-wire vehicle control systems struggle to accurately transmit road surface information to drivers due to unwanted components like inertia, viscosity, noise, and friction, which affect the steering reaction force, making it difficult for drivers to feel the road surface status.
Innovation Solution
A vehicle control device with computation circuits that compensate for dynamic and static characteristics of the steering mechanism, using an estimated axial force computation circuit to refine the axial force, ensuring the steering reaction force accurately reflects the road surface state, thereby improving the driver's feel of the road surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the steering reaction force is generated based on the estimated axial force, then the road surface information can be transmitted to the driver, but unwanted components (inertia, viscosity, noise, friction) degrade the accuracy of road surface information transmission
Solution Approach 1:
The patent extracts and removes unwanted components (inertia component, viscosity component, noise, and friction effects) from the estimated axial force through separate computation circuits. The dynamic characteristic computation circuit specifically extracts and compensates for inertia and viscosity effects, while the static characteristic computation circuit handles friction and other static unwanted components, thereby purifying the road surface information transmission.
Solution Approach 2:
The patent employs feedback control mechanisms where the computed unwanted components are fed back to adjust and compensate the estimated axial force. The dynamic characteristic computation circuit uses feedback to compensate for inertia and viscosity effects in real-time, and the static characteristic computation circuit provides feedback compensation for friction and other static characteristics, improving the overall accuracy of road surface information transmission.
2Ease of operation
If the steering mechanism includes mechanical elements (motors, gears), then steering control functionality is achieved, but dynamic characteristics (inertia, viscosity) and static characteristics (friction) degrade the axial force estimation accuracy
Solution Approach 1:
The patent segments the unwanted components into distinct categories: dynamic characteristics (inertia and viscosity) handled by the dynamic characteristic computation circuit, and static characteristics (friction and mechanical play) handled by the static characteristic computation circuit. This segmentation allows for targeted compensation of each type of unwanted component, improving overall measurement precision while maintaining steering control functionality.
Solution Approach 2:
The patent introduces computation circuits as intermediary elements between the mechanical steering mechanism and the control system. These intermediaries (dynamic characteristic computation circuit and static characteristic computation circuit) process and compensate for the unwanted effects of mechanical elements, thereby improving axial force estimation accuracy without eliminating the necessary mechanical components for steering control.
3Ease of operation
If the reaction force motor generates steering reaction force, then the driver can feel steering feedback, but the mechanical separation in steer-by-wire system prevents direct transmission of road surface reaction force
Solution Approach 1:
The patent replaces the direct mechanical transmission system with an electronic computation and control system. Instead of mechanically transmitting road surface reaction forces through the steering mechanism, the system uses the reaction force motor to generate synthetic feedback forces based on computed estimated axial forces that reflect road surface conditions. This substitution enables feedback transmission despite mechanical separation.
Solution Approach 2:
The patent creates a copied representation of the road surface reaction force through the estimated axial force computation. The system computes what the axial force should be based on sensor data and vehicle state, then uses the reaction force motor to generate a copied feedback force that mimics the sensation of direct mechanical connection, allowing the driver to feel road surface information without direct mechanical coupling.
Data Source
AI summary
An estimated axial force computation circuit of a control device has an axial force computation circuit that computes an axial force that acts on a steered shaft on the basis of a current value of a steering motor. The estimated axial force computation circuit has a friction compensation circuit, an efficiency compensation circuit, and a gradient compensation circuit as static characteristic computation circuits that compensate for an effect of the static characteristics of a steering mechanism on the axial force computed. The estimated axial force computation circuit has a filter as a dynamic characteristic computation circuit that compensates for an effect of the dynamic characteristics of the steering mechanism. The filter removes, from the axial force, an effect of the viscosity and the inertia of the steering motor. The axial force after compensation is used to control a reaction force motor.