Steering Torque Control With Inertia and Friction Compensation
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Solution Overview
Problem
Existing electromechanically assisted steering systems face challenges in accurately tuning the steering feel due to mechanical properties like mass inertias, rigidities, and friction, limiting the ability to provide a pleasant torque perception at the steering wheel in various driving conditions.
Innovation Solution
A model-based control approach is employed to modify the mechanical behavior of the steering system by using a modification controller, which includes a Kalman filter, inertia, damping, and friction compensation modules to adjust the torque perception, reducing the reliance on direct measurement of mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the steering feel controller is tuned based on mechanical properties (mass inertias, rigidities, friction), then the torque perception at the steering wheel can be adjusted, but the tuning freedom is limited and the mechanical properties constrain the achievable steering feel
Solution Approach 1:
The patent introduces a modification controller as an intermediary between the steering feel controller and the controlled system. This modification controller generates compensation torques (inertia compensation torque, damping torque, friction compensation torque) that mediate the interaction between the steering feel controller and the mechanical system, thereby decoupling the tuning process from direct mechanical property constraints while maintaining system stability
Solution Approach 2:
The patent replaces direct mechanical property-based tuning with a model-based control approach. Instead of relying on physical mechanical properties (mass inertias, rigidities, friction) to determine steering feel characteristics, the system uses a mathematical model to calculate compensation torques that simulate the desired mechanical behavior, thereby substituting mechanical constraints with computational control
2Reliability
If the controlled system has inherent mechanical properties (mass inertias, rigidities, friction), then the system structure is simple, but these properties limit the ability to provide pleasant torque perception in all driving situations
Solution Approach 1:
The patent makes the steering feel characteristics dynamic and adjustable by introducing a model-based control approach. The modification controller dynamically calculates compensation torques based on the current operating conditions and desired steering feel characteristics, allowing the system to adapt to different driving situations rather than being constrained by fixed mechanical properties
Solution Approach 2:
The patent changes the effective mechanical parameters of the steering system through computational compensation. By calculating and applying inertia compensation torque, damping torque, and friction compensation torque, the system effectively modifies the perceived mass inertia, damping, and friction characteristics without physically altering the mechanical components, thereby achieving versatile torque perception across different driving situations
Data Source
AI summary
A method for torque control for an electromechanically assisted steering system of a motor vehicle is described. The method includes a modified controlled system, detecting at least one measured variable of the controlled system by a sensor, and superimposing a torque demand of the steering feel controller with the inertia compensation torque and/or the damping torque and/or the friction compensation torque.