Steering Control System Torque Detection Threshold Switching
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Solution Overview
Problem
The existing vehicle steering control systems with steer-by-wire technology face limitations in detecting steering torque beyond the range of the steering torque sensor, which affects the accuracy and resolution of steering control, especially when large steering torques are applied.
Innovation Solution
The system compares the absolute value of the detected steering torque with a predetermined threshold, using the steering reaction force for control when the torque is below the threshold and utilizing the reaction motor current as a reference when it exceeds, allowing for enhanced detection and control of steering torque across a broader range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a torsion bar having a large spring constant is employed to broaden the detection range of the steering torque sensor, then the detection range is improved, but the detection resolution within a range in which a steering torque is small is reduced
Solution Approach 1:
The patent applies dynamics by switching between two different control methods based on the detected steering torque magnitude. When steering torque is small, feedback control using the steering torque sensor is applied. When steering torque exceeds the threshold, direct control using reaction motor current is applied. This dynamic switching allows the system to adapt to different operating conditions and maintain both detection range and resolution.
Solution Approach 2:
The patent changes the control parameter approach based on the operating condition. The control method transitions from using steering torque feedback to using reaction motor current directly, depending on whether the steering torque exceeds the predetermined threshold. This parameter change enables the system to handle both small and large steering torques effectively.
2Measurement precision
If feedback control is used to control the reaction motor based on steering torque detection, then control accuracy is improved, but the system cannot handle steering torque beyond the sensor's detection range
Solution Approach 1:
The system dynamically switches control strategies based on the magnitude of steering torque. For small steering torques within the sensor's detection range, feedback control is used to maintain high accuracy. For large steering torques exceeding the detection range, the system switches to direct control using reaction motor current, thereby extending the handling range while maintaining accuracy through the appropriate control method for each condition.
Solution Approach 2:
The patent uses the reaction motor current as an intermediary parameter to bridge the gap between the sensor's detection limit and the actual steering torque. When the steering torque exceeds the sensor's range, the reaction motor current serves as a proxy measurement that correlates with the steering torque, enabling the system to infer and control large torque values that the sensor cannot directly detect.
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 enables accurate control of steering torque beyond the sensor's detection limit, maintaining high detection resolution and providing a smooth steering feel by reducing torque fluctuations and compensating for mechanical friction, thus addressing the limitations of existing systems.
Implementation Method 1
a reaction motor coupled to a steering shaft, simulates reaction force that is transmitted from a road surface, or the like, to the steered wheels with the use of the reaction motor, and applies the simulated reaction force to the steering member as steering reaction force
Implementation Method 2
a torsion bar having a large spring constant may be employed as a torsion bar that is a component of the steering torque sensor
Data Source
AI summary
The absolute value of a steering torque detected by a steering torque sensor is compared with a predetermined threshold. When the absolute value of the detected steering torque is smaller than the threshold, a steering reaction force is controlled on the basis of the steering torque; whereas, when the absolute value of the detected steering torque is larger than or equal to the threshold, the steering reaction force is controlled using a detected reaction motor current value as a reference value.