Indirect Steering Torque Reconstruction in Power Steering
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Solution Overview
Problem
Existing power steering systems rely on a steering wheel torque sensor to measure flywheel torque, which can fail, leading to distorted assistance and potentially dangerous vehicle behavior, and adds weight and complexity to the system.
Innovation Solution
A method to estimate flywheel torque using external data from integrated sensors, such as steering wheel angle and assistance motor angle, eliminating the need for a dedicated flywheel torque sensor by reconstructing the torque information, thereby ensuring continuous and reliable steering assistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated flywheel torque sensor is installed to measure steering wheel torque, then measurement precision is improved, but device complexity and weight increase
Solution Approach 1:
The patent applies multi-functionality by using existing sensors (steering wheel angle sensor, motor angle sensor, vehicle speed sensor) for their primary functions while also utilizing them to reconstruct flywheel torque information. This eliminates the need for a dedicated torque sensor, reducing system complexity while maintaining measurement capability through computational reconstruction.
Solution Approach 2:
The patent creates a virtual copy of torque measurement capability through mathematical reconstruction algorithms. Instead of directly measuring torque with a physical sensor, the system reconstructs torque values by computing from angular positions and derivatives of other sensors, creating a virtual torque measurement that achieves the same functional goal without additional hardware.
2Measurement precision
If a dedicated flywheel torque sensor is installed, then measurement precision is improved, but the system becomes more vulnerable to sensor failure
Solution Approach 1:
The patent implements prior cushioning by having redundant sensing capabilities already in place through multiple existing sensors. If one sensor or the reconstruction system fails, the system can potentially use alternative sensor combinations or default to manual steering mode, providing beforehand protection against total failure and ensuring continuity of steering assistance.
Solution Approach 2:
The system uses its own existing sensors and computational resources to self-generate the torque measurement information that would otherwise require a dedicated sensor. This self-service approach reduces the number of external components that could fail and leverages the system's inherent capabilities to maintain operation.
3Device complexity
If external sensors are used to reconstruct flywheel torque, then device complexity is reduced, but measurement precision may be affected
Solution Approach 1:
The patent replaces the direct mechanical torque measurement system with a computational/mathematical system. Instead of using a mechanical torque sensor that directly measures force, the system uses mathematical reconstruction algorithms that compute torque from angular positions and their derivatives, substituting mechanical measurement with computational calculation to achieve the same functional result.
Solution Approach 2:
The patent transforms the measurement approach by changing from direct torque parameter measurement to indirect measurement through angular position parameters. By measuring angular positions, velocities, and accelerations of existing components and using these transformed parameters in reconstruction algorithms, the system achieves torque information without direct torque sensing.
Data Source
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AI summary
The invention relates to a method for managing an assisted steering device (1) for a vehicle (2) comprising a steering wheel (3) on which the driver exerts a manoeuvring effort, termed the "steering wheel torque" (T3), as well as an assistance motor (12) intended to provide an assistance effort (T12), said method comprising a steering wheel torque reconstruction step (a) in the course of which the steering wheel torque (T3) is evaluated, such as is actually exerted by the driver on the steering wheel (3), without calling upon a steering wheel torque sensor (14) specifically dedicated to the measurement of said steering wheel torque, but by reconstructing an information item representative of said steering wheel torque (T3), termed the "estimated steering wheel torque" (T3_estim), on the basis of data termed "external data" (θ3, θ12, θ'3,θ'12) that is gathered outside a specific steering wheel torque sensor (14) such as this and which include the angular position of the steering wheel (θ3), the angular position (θ12) of the shaft of the assistance motor (12), and the time derivatives (θ'3, θ'12) of these angular positions.