Steer-By-Wire Torque Control With Continuous Gain Scheduling
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Solution Overview
Problem
Existing steer-by-wire steering systems face challenges in simultaneously achieving multiple conflicting targets such as effective guidance behavior, sufficient interference suppression, and haptic stability due to non-independent specifications, making it difficult to optimize controller calibration.
Innovation Solution
A method and device that adjust controller properties based on operational variables using Youla parameterization and coprime factorization to ensure stability while optimizing target variables like guidance and robustness, allowing continuous adaptation to steering and driving situations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a controller is designed to satisfy multiple target variables (guidance behavior, interference suppression, robustness, haptic stability) simultaneously, then the system should achieve comprehensive performance, but the non-independent specifications make it very difficult to meet all targets at the same time requiring compromises
Solution Approach 1:
The patent applies parameter changes by introducing a gain scheduling parameter that continuously adjusts controller properties based on operational variables. This allows the controller to adapt its characteristics (such as gain values) according to different operating conditions, thereby satisfying multiple target variables across different scenarios without requiring complex manual calibration for each case. The monotonic relationship between the gain scheduling parameter and target variables enables systematic parameter optimization.
2Reliability
If a gain scheduler is used to improve robustness by increasing gain, then robustness is improved, but further increase causes robustness to deteriorate, making it difficult to determine the optimal direction for parameter adjustment
Solution Approach 1:
The patent implements feedback by establishing a monotonic relationship between the gain scheduling parameter and target variables through Youla parameterization. This creates a predictable feedback mechanism where the controller can systematically determine the direction of parameter adjustment based on the desired target variable changes. The coprime factorization provides a structured framework for this feedback, allowing the system to automatically adjust parameters in the correct direction without trial-and-error.
3Adaptability or versatility
If controller properties are continuously adjusted based on operational situations, then the controller becomes adaptable to different conditions, but discontinuities may be created that are perceivable by the driver
Solution Approach 1:
The patent applies dynamics by making the controller properties continuously adjustable based on operational variables such as steering angle and vehicle speed. The gain scheduling parameter dynamically modifies controller characteristics in real-time according to the operating situation. This dynamic adaptation allows the controller to optimize performance for different conditions while maintaining smooth transitions that prevent perceivable discontinuities for the driver.
4Ease of operation
If Youla parameterization with coprime factorization is used to linearize closed control circuit behavior, then the relationship between target variable and gain scheduling parameter becomes monotonic, but the controller design becomes more complex
Solution Approach 1:
The patent applies segmentation by decomposing the controller design into distinct modular components: coprime factorization of the plant transfer function, Youla parameterization for stability assurance, and gain scheduling for performance optimization. This segmentation allows each component to be designed and analyzed separately, making the overall complex system manageable while achieving the desired monotonic relationship between parameters.
Data Source
AI summary
A method is for determining a controller output variable of a control unit having a controller for a controlled system, more particularly for manual torque control of a steer-by-wire steering system for a vehicle. The method includes adjusting a specified controller property of the controller using a specified adjustment portion, and continuously changing an influence of the specified adjustment portion on the controller property based on a parameter. The parameter is determined based on an operating situation of the controlled system, more particularly a steering and/or driving situation of the vehicle. The controller output variable is determined using the controller.