Steer-by-Wire Reaction Force Control via Vehicle Motion Model
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Solution Overview
Problem
Conventional steer-by-wire steering devices experience impaired steering feeling due to high frequency components from sensors, leading to unstable control systems and discomfort, as they lack mechanical connection between the steering unit and turning mechanism, affecting the generation of steering reaction forces.
Innovation Solution
A steer-by-wire steering reaction force control device that combines steering angle data with vehicle state detection signals to estimate and generate steering reaction forces using a vehicle motion model, selectively choosing between estimated and detected values based on vehicle speed and threshold conditions to filter out high frequency components, ensuring stable and comfortable steering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensor values (yaw rate, lateral acceleration, turning reaction force) are used directly to generate steering reaction force, then the steering reaction force reflects actual vehicle behavior, but high frequency components from vibration and alignment differences impair steering feeling
Solution Approach 1:
The steering reaction force is segmented into multiple components: high-frequency component (from direct sensor measurement), low-frequency component (from vehicle motion model), and intermediate-frequency component. Each component is processed separately through different filtering and estimation methods, then synthesized to achieve both accuracy and comfort.
Solution Approach 2:
Different frequency ranges of the steering reaction force are treated with different quality characteristics. High-frequency components are filtered for comfort, while low-frequency components are preserved for accuracy. The vehicle motion model provides locally optimized estimation for specific frequency ranges affected by vibration and alignment issues.
2Ease of operation
If a lowpass filter is applied to attenuate high frequency components, then steering feeling is improved, but a time lag occurs and control system stability is compromised
Solution Approach 1:
The filtering characteristics are made dynamic rather than static. The vehicle motion model adapts its estimation based on current vehicle state (speed, steering angle, acceleration), automatically adjusting the effective filter characteristics to maintain stability while improving steering feeling under varying operating conditions.
Solution Approach 2:
The vehicle motion model acts as an intermediary between the raw sensor data and the steering reaction force generation. It processes the sensor inputs through physics-based equations that inherently provide frequency-selective filtering without introducing the time lag problems of traditional lowpass filters, maintaining control stability while improving steering feel.
3Adaptability or versatility
If steer-by-wire system is implemented without mechanical connection, then steering system flexibility and control precision are improved, but the natural steering reaction force feedback is lost
Solution Approach 1:
The natural steering reaction force feedback is copied and reconstructed using the vehicle motion model. Instead of relying on mechanical transmission, the system creates an artificial feedback signal that replicates the characteristics of natural feedback by estimating vehicle behavior from sensor data and processing it through the motion model to generate appropriate reaction forces.
Solution Approach 2:
The mechanical connection for force transmission is replaced with an electronic control system. The steering reaction force actuator, controlled by processed sensor signals through the vehicle motion model, substitutes for the mechanical force feedback that would naturally occur in a mechanically connected steering system, providing flexibility while restoring feedback.
Data Source
AI summary
In this steer-by-wire steering reaction force control device, a steering controller is provided with: a turning reaction force estimation unit configured to calculate an estimated value of a turning reaction force or a parameter representing vehicle behavior from a vehicle motion model; and a comparison unit configured to compare the estimated value calculated by the turning reaction force estimation unit with a value detected by a turning reaction force sensor, and configured to select either one of the estimated value and the detected value in accordance with a predetermined condition. Further, a steering reaction force generation unit is provided that is configured to use the estimated value or the detected value selected by the comparison unit for generation of a steering reaction force.