Electric Power Steering Torque Control via Lateral Acceleration
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Solution Overview
Problem
Existing electric power steering systems in motor vehicles do not consistently provide driving pleasure and appropriate steering effort across various driving conditions, as the torque at the wheel, or effort, is not adequately adjusted to account for dynamic conditions.
Innovation Solution
A method to determine the steering wheel torque setpoint based on lateral acceleration, which considers parameters such as angular position of the steering wheel, longitudinal speed, yaw rate, and wheel speed differences, using existing sensors and data from the electric power-assisted steering system, to adjust the torque assistance dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If torque assistance is provided based on basic steering parameters, then steering assistance is available, but driving pleasure and appropriate steering effort are not consistently provided across various driving conditions
Solution Approach 1:
The patent implements dynamic adjustment of steering torque by continuously adapting the assistance torque based on real-time lateral acceleration measurements and steering parameters. The control method dynamically modifies the torque assistance profile according to actual vehicle motion conditions, transforming a static assistance system into a dynamic one that responds to changing driving scenarios.
Solution Approach 2:
The patent changes the control parameters by introducing lateral acceleration as a key parameter for torque calculation. The assistance torque is recalculated based on lateral acceleration values, steering angle, and steering angle derivative, allowing the system to adapt its behavior across different driving conditions rather than relying on fixed parameter sets.
2Measurement precision
If multiple sensors are added to improve lateral acceleration measurement accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent makes the existing transverse acceleration sensor multi-functional by utilizing it not only for its primary function but also for determining lateral acceleration during cornering. This allows the same sensor to serve multiple purposes: basic vehicle motion detection and lateral acceleration measurement for torque adjustment, eliminating the need for additional dedicated sensors.
Solution Approach 2:
The system uses its own existing sensor resources and computational capabilities to generate the required lateral acceleration information. By processing data from available sensors (transverse acceleration sensor, steering angle sensor) through mathematical relationships, the system serves its own measurement needs without external additions.
3Ease of operation
If torque assistance is increased to improve steering ease, then ease of operation improves, but friction compensation and driving dynamics are compromised
Solution Approach 1:
The patent implements a feedback mechanism where the actual lateral acceleration experienced during steering is continuously measured and fed back to the control system. This feedback loop allows the system to compare expected versus actual vehicle response and adjust the torque assistance accordingly, ensuring accurate friction compensation while maintaining driving dynamics.
Solution Approach 2:
The patent applies partial torque assistance by providing only the necessary amount of torque needed to compensate for friction and support the driver, rather than maximum assistance. The assistance torque is precisely modulated based on lateral acceleration and steering parameters, providing just enough support to maintain driving dynamics while reducing unnecessary interference.
Data Source
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AI summary
The invention relates to a power steering system in which the set value for torque or force at the steering wheel is predetermined on the basis of various parameters and information so as to provide the most driving comfort in all conditions of driving the vehicle. The torque or force set value is predetermined on the basis of the sideways acceleration of the vehicle, the acceleration in turn being predetermined mainly from an estimate of the force exerted on the rack, and preferably also predetermined by other methods, with the estimate being weighted among all of the obtained values. Said method is particularly useful for vehicles provided with electrical power steering.