Active Steering Compensation for Road Disturbances
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Solution Overview
Problem
Active steering systems face challenges in effectively mitigating the transmission of road disturbances to the driver's hands, which can lead to discomfort and reduced control during maneuvers over uneven road surfaces.
Innovation Solution
The system employs a combination of existing vehicle sensors and a controller to detect road disturbances and introduce compliance by adjusting the superimposition angle and torque provided by an electric motor, reducing the transmission of disturbances to the steering wheel through methods such as altering the target angle, adjusting current, or reducing gain, thereby damping road disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If active steering systems are used to improve steering responsiveness and stability, then steering control performance is improved, but road disturbances are transmitted to the driver's hands causing discomfort
Solution Approach 1:
The patent introduces a compliance mechanism as an intermediary between the road wheels and steering wheel. This compliance element (electric motor acting as a compliant element) decouples the direct mechanical connection, allowing the system to maintain steering control performance while filtering out road disturbances before they reach the driver's hands.
Solution Approach 2:
The system dynamically adjusts the compliance characteristics of the steering system by controlling the electric motor's torque and stiffness in real-time. Based on detected road conditions and steering state, the controller modulates the motor's mechanical impedance to provide optimal disturbance rejection while maintaining responsive steering control.
2Object-affected harmful factors
If the steering system is made compliant to reduce disturbance transmission, then driver comfort is improved, but steering precision and responsiveness may be reduced
Solution Approach 1:
The electric motor's compliance characteristics are dynamically adjusted based on steering state and road conditions. During normal steering maneuvers, the motor maintains high stiffness for precise control. When road disturbances are detected, the motor increases compliance to filter disturbances, then returns to high stiffness mode to restore steering precision.
Solution Approach 2:
The system proactively compensates for anticipated disturbance effects by using the compliance mechanism to preemptively counteract disturbance torques before they significantly affect steering wheel position, thereby maintaining steering precision while still providing disturbance rejection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces the transmission of road disturbances to the steering wheel, enhancing driver comfort and control by decoupling the steering wheel from road wheel movements, allowing the vehicle to maintain stability and follow the desired trajectory.
Implementation Method 1
an electric motor, the output shaft of which is in a mechanical drive relationship with the steered road wheels
Implementation Method 2
introducing compliance into the steering system... thereby damping road disturbances
Data Source
AI summary
A vehicle includes an adaptive front steering system including an assist motor that provides an overlay angle superimposed on a steering wheel angle. External torque to the assist motor is estimated by a controller and evaluated to determine whether it is the result of an external disturbance. If so, the controller evaluates whether the external disturbance is a road disturbance, such as by determining that road wheel speed varied from the vehicle speed or that an impact site is present in outputs of external sensors of the vehicle. If a road disturbance is determined to have occurred, compliance may be introduced in order to reduce the transmission of torque to the steering wheel. Compliance may be introduced by adjusting current to the assist motor, a target angle to the assist motor, reducing gain in the control system for the assist motor, or shorting leads of the assist motor.