Adaptive Steering Accuracy Control for Latency and Comfort
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Solution Overview
Problem
Railborne driver assistance systems face challenges with high signal latency and comfort issues due to the interaction of EPS controller integral components with steering system friction, leading to twitchy steering wheel behavior and uncomfortable oversteering, which complicates achieving both high control dynamics and comfort.
Innovation Solution
A railborne driver assistance device with a first processing unit controlling steering torque and a second unit adjusting the stationary control accuracy via an accuracy request signal, allowing adaptive scaling of control accuracy between threshold values, thereby attenuating control accuracy and reducing integrator charging, implemented through a cascading control structure and feedforward control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If simple PI(D) controller structures are used in the EPS steering angle controller, then the controller provides adequate reference variable control, but the steering wheel behavior becomes twitchy and the steering feel becomes uncomfortable during oversteering
Solution Approach 1:
The control system is divided into two independent processing units: a first processing unit that executes the steering angle control with integral components, and a second processing unit that separately handles the attenuation of stationary control accuracy. This segmentation allows each unit to be optimized independently - the first unit maintains reliable reference variable control while the second unit prevents twitchy steering wheel behavior by attenuating the integral component's effect on stationary control accuracy.
2Manufacturing precision
If the controller integral components are used to correct steering angle deviations, then the target angle and actual angle are harmonized, but the driver feels increasing counter-torque during constant steering wheel deflection which is uncomfortable and incomprehensible
Solution Approach 1:
The second processing unit acts as an intermediary between the first processing unit's steering angle control and the driver's steering wheel input. It receives the control accuracy signal from the first unit and selectively attenuates the stationary control accuracy based on driver input detection, thereby mediating the conflict between maintaining precise steering angle control and providing comfortable, comprehensible steering torque feedback to the driver.
Solution Approach 2:
The system dynamically adjusts the stationary control accuracy attenuation based on real-time detection of driver steering input. When the driver steers with or against the assistance system, the second processing unit detects this and modifies the attenuation level accordingly, allowing the control accuracy to be reduced when needed for comfort while maintaining precision when the driver is not intervening.
3Measurement precision
If the EPS controller uses integral components to eliminate steady-state error, then the control accuracy improves, but the interaction with steering system friction creates limit cycles and twitchy steering wheel behavior
Solution Approach 1:
The second processing unit extracts and separately handles the stationary control accuracy attenuation function from the main steering angle control loop. By taking out the attenuation of stationary control accuracy as a separate function, the system can maintain the integral components necessary for eliminating steady-state error while simultaneously preventing them from causing twitchy steering wheel behavior through friction-induced limit cycles.
4Manufacturing precision
If the driver assistance system continuously corrects steering angle deviations, then the lane keeping accuracy improves, but the driver experiences uncomfortable and implausible oversteering torque during constant steering wheel deflection
Solution Approach 1:
The system changes the parameter of stationary control accuracy dynamically based on driving conditions and driver input. The second processing unit adjusts the attenuation level of stationary control accuracy in response to detected driver steering actions, thereby modifying the control behavior to balance lane keeping accuracy with driver comfort and steering torque plausibility during constant deflection scenarios.
Data Source
AI summary
A railborne driver assistance device for supporting or automating the lateral control of a vehicle includes a first processing unit configured to control a steering torque intervention by establishing a steering angle with a stationary control accuracy of an electrically supported steering system. A second processing unit is configured to adjust the stationary control accuracy of the steering angle via the output of an accuracy request signal to the first processing unit in such a way that there is a scaling of the control accuracy between a lower and an upper threshold value. The second processing unit includes a control unit having an integrator with an input and an output, wherein the output of the integrator is connected to the input in a closed-loop manner with a weighting dependent on the accuracy request signal.