Steering System Interference Suppression via Vertical Acceleration
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Solution Overview
Problem
Existing steering systems in motor vehicles fail to effectively suppress disturbance variables caused by changes in vehicle weight and road conditions, leading to unwanted steering torques and potential vehicle instability, especially during fast driving on curved roads or when the driver has an asymmetric hand position on the steering wheel.
Innovation Solution
A method utilizing a servomotor, sensors for detecting steering angle and torque, and an evaluation and control unit that applies a modified mapping function to adjust the support torque and steering damping, based on vertical acceleration and hand position, to counteract interference steering impulses and maintain stable steering behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional electric power steering system is used, then the basic steering function is provided, but disturbance variables from drive train and asymmetric wheel friction are not effectively suppressed, causing unwanted steering torques and potential instability
Solution Approach 1:
The system performs preliminary detection of vertical acceleration and asymmetric wheel friction conditions, then preemptively adjusts steering damping and support torque before disturbance variables can significantly affect steering stability. This prevents rather than reacts to steering disturbances.
Solution Approach 2:
The system continuously monitors steering angle, steering torque, wheel speeds, and vertical acceleration, then feeds this information back to dynamically adjust the steering damping and support torque. This closed-loop feedback mechanism suppresses disturbance variables by constantly adapting to current steering conditions.
2Reliability
If steering damping is increased to suppress disturbance variables, then steering stability improves, but the steering system becomes less responsive to driver inputs
Solution Approach 1:
The steering damping is made dynamically adjustable rather than fixed. The system increases damping only when disturbance variables are detected (through vertical acceleration and asymmetric friction detection), and reduces damping when conditions are normal, thus maintaining both stability and responsiveness as needed.
Solution Approach 2:
The system changes the damping parameter based on detected conditions, switching between different damping levels. This allows the steering system to optimize between stability and responsiveness by adjusting the damping parameter according to actual operating conditions.
3Productivity
If a simplified simulation model is used for predicting disturbance variables, then the calculation is computationally efficient, but prediction reliability deteriorates when speed difference of driven front wheels moves with small amplitudes around zero point
Solution Approach 1:
The system applies different processing qualities to different operating conditions. For most conditions, a simplified model suffices, but for the specific condition where speed difference moves with small amplitudes around zero, the system detects this local condition and applies enhanced processing (increased damping, modified mapping function) to ensure adequate prediction accuracy.
Solution Approach 2:
The system introduces an intermediary detection mechanism (vertical acceleration sensor and asymmetric friction detection) that mediates between the simplified simulation model and the actual disturbance conditions. This intermediary provides additional information that compensates for the simplified model's limitations in critical operating regions.
4Reliability
If correction torque is applied to compensate for disturbance variables, then steering stability improves, but the system complexity increases due to additional control algorithms and sensors
Solution Approach 1:
The system uses existing sensors (steering angle sensor, steering torque sensor, wheel speed sensors) and makes them serve multiple functions: basic steering control, disturbance detection, and stability correction. This multi-functionality reduces the need for additional dedicated sensors and control algorithms.
Solution Approach 2:
The disturbance variable compensation function is merged with the existing electric power steering control system. The correction torque calculation is integrated into the existing support torque generation, and the damping adjustment is combined with the existing steering control logic, rather than being implemented as a separate system.
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 impact of disturbance variables, preventing unwanted steering movements and ensuring stable vehicle direction, even during rapid changes in weight distribution or asymmetric steering inputs, thereby enhancing driving safety and comfort.
Implementation Method 1
calculates, in dependence on data from at least one sensor, a support torque which is applied by the servomotor
Implementation Method 2
changes which occur after detection of a vertical acceleration greater than a threshold value for a subsequent observation time are evaluated
Implementation Method 3
steering damping is changed
Data Source
Figure 1
Figure 2
AI summary
The method involves calculating mapping function as function of data of a torque sensor (3) by a control unit (6). Vertical acceleration (az) of a motor car is detected based on the data of the torque sensor. Set steering angle (phi) or set steering torque or set steering force is determined. Changes in the steering angle and/or the steering torque and/or the force is evaluated after detecting the vertical acceleration that is greater than a threshold value for subsequent observation period by modified mapping function for support moment and/or steering attenuation by using the control unit. An independent claim is also included for a steering system.