Steer-by-Wire Model Following Controller for Steering Feel
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Solution Overview
Problem
Steer-by-wire steering devices face challenges in enhancing steering performance by accurately replicating the mechanical connection between the steering assembly and turning assembly, leading to suboptimal steering feel and responsiveness.
Innovation Solution
A control device with a model following controller that generates correction torque based on a nominal model, ensuring the transfer function of the control target matches the nominal model in a specific frequency band, thereby improving steering performance by simulating mechanical connection and enhancing steering feel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a steer-by-wire steering device is used to improve steering performance, then steering responsiveness is enhanced, but steering feel and mechanical connection accuracy deteriorate
Solution Approach 1:
The patent implements a feedback control mechanism where the control device continuously monitors the actual output of the turning assembly and compares it with the nominal model prediction. The difference (modeling error) is fed back to generate correction torque that adjusts the motor output, ensuring the actual transfer function matches the nominal model in the frequency band where complementary sensitivity gain is approximately one, thereby restoring accurate steering feel while maintaining responsiveness
Solution Approach 2:
The patent dynamically adjusts control parameters including the correction torque magnitude and frequency band characteristics based on the complementary sensitivity function gain. By changing the control parameters adaptively, the system maintains optimal steering feel accuracy across different operating conditions while preserving the responsiveness benefits of steer-by-wire architecture
2Measurement precision
If mechanical connection between steering assembly and turning assembly is simulated, then steering feel is improved, but device complexity increases
Solution Approach 1:
The patent replaces the complex mechanical connection simulation with an electrical/control-based solution. Instead of using complex mechanical linkages to replicate physical connection, the system uses a control algorithm that calculates and applies correction torque to electrically simulate the mechanical connection characteristics, thereby improving steering feel while avoiding the complexity of mechanical implementations
Solution Approach 2:
The patent creates a nominal model that copies the essential dynamic characteristics of the mechanical connection between steering assembly and turning assembly. This virtual model captures the transfer function behavior without requiring physical replication, allowing the control system to simulate mechanical connection effects through software-based correction rather than hardware complexity
Data Source
AI summary
A control device mounted on a steer-by-wire steering device mounted on a vehicle includes a steering assembly including a steering wheel to be steered by a steering operator, a turning assembly including a first turning wheel and a second turning wheel, a turning side motor to drive the turning assembly, and a turning side controller configured or programmed to control a control target including the turning side motor. The turning side controller is configured or programmed to include a model following controller configured or programmed to generate a correction torque to correct an input torque input to the control target based on output of the control target and a nominal model based on a configuration of the control target. The model following controller is configured or programmed such that a transfer function of the control target is restricted to a transfer function of the nominal model.