Steering System Position Control via Frequency Response
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Solution Overview
Problem
Existing electromechanically assisted steering systems for motor vehicles face challenges in maintaining high control quality due to reactions from the road and non-linear effects, limiting their effectiveness in various driving situations.
Innovation Solution
A method for position control that involves determining the frequency response of the controlled system using a mathematical model or measurement, adjusting controller parameters based on this response, and incorporating an observer to estimate and compensate for disturbance torques and frictional torques, ensuring robust control behavior across different driving conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional position control methods are used in electromechanically assisted steering systems, then the system structure remains simple, but control quality deteriorates due to road reactions and non-linear effects
Solution Approach 1:
The patent applies parameter changes by determining the frequency response of the controlled system and using it to optimize controller parameters. The transfer function of the controlled system is calculated based on a mathematical model, and controller parameters are adjusted according to this frequency response to achieve optimal control quality while accounting for road reactions and non-linear effects.
2Reliability
If controller parameters are optimized based on frequency response, then control quality improves, but the complexity of system setup and calibration increases
Solution Approach 1:
The patent applies preliminary action by determining the frequency response and optimizing controller parameters during the system setup phase before actual operation. The transfer function is calculated and controller parameters are pre-adjusted based on the frequency response, so that optimal control performance is achieved without requiring complex real-time adjustments during vehicle operation.
3Device complexity
If the controlled system includes only the lower part of the steering system, then the model complexity is reduced, but the accuracy of control deteriorates due to unmodeled upper part effects
Solution Approach 1:
The patent applies the taking out principle by separating the controlled system into the lower part (containing the electric motor) and the upper part (steering column and steering wheel). The mathematical model focuses only on the lower part, which simplifies the model complexity, while the controller is designed to compensate for the effects of the upper part through frequency response-based parameter optimization.
Data Source
AI summary
A method is described for position control for an electromechanically assisted steering system of a motor vehicle, which has electromechanical steering assistance with an electric motor and at least one controller, wherein a torque to be applied by the electric motor is the controlled variable of the at least one controller, and wherein the controlled system for the design of the at least one controller comprises at least a lower part of the steering system containing the electric motor. A frequency response of the controlled system is determined based on a mathematical model of the controlled system and/or by measuring the controlled system. Controller parameters of the at least one controller are adjusted based on the frequency response of the controlled system.