Steer by Wire Control System Using Velocity-Adaptive Error Correction
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Solution Overview
Problem
Steering systems in vehicles and machines face safety and reliability issues due to sensor malfunctions, leading to potential incorrect movements, and are costly to maintain with high-quality or multiple sensors for accurate positioning.
Innovation Solution
A control system that uses a first signal processor to generate an error signal from handle and steering element position signals, a second processor to create a correction signal based on handle velocity, and a third processor to adjust the velocity reference, reducing the need for high-quality sensors and minimizing the risk of overcorrection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple high-quality sensors with fault diagnosis features are used to increase safety, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The system uses the existing sensor's output signal to diagnose its own fault status through the driver's operational patterns. The control unit monitors whether the sensor signal correlates with expected driver behavior, allowing the system to self-diagnose sensor failures without additional diagnostic sensors or complex redundancy systems.
Solution Approach 2:
The driver's operational patterns serve as an intermediary to indirectly assess sensor health. Instead of directly monitoring sensor quality with additional sensors, the system uses the driver's expected behavior as a reference to detect when sensor readings deviate from normal operational patterns, indicating potential sensor failure.
2Reliability
If correction signal is applied at any speed and any error to improve reliability, then reliability is improved, but the driver may feel overruled and ease of operation deteriorates
Solution Approach 1:
The correction signal application is made dynamic rather than static. The system adaptively applies correction based on real-time conditions: it activates only when the vehicle is moving (velocity threshold) and only when the steering angle error exceeds a predetermined threshold. This dynamic approach ensures reliability correction is applied only when necessary, avoiding unnecessary interference with normal driver operation.
3Manufacturing precision
If correction signal is applied at low velocities to improve manufacturing precision, then manufacturing precision is improved, but reliability deteriorates due to increased risk of dangerous situations if sensor fails
Solution Approach 1:
The system dynamically adjusts correction application based on vehicle velocity. A velocity threshold is established where correction signals are only applied when the vehicle is moving above this threshold. This dynamic velocity-based control prevents dangerous overcorrection at low speeds (such as during parking maneuvers) while maintaining steering accuracy at normal operating speeds.
Solution Approach 2:
The correction system changes its operational parameters based on vehicle velocity. The predetermined velocity threshold acts as a parameter that switches the correction function on or off. When velocity exceeds the threshold, correction is applied; when it falls below, correction is withheld. This parameter change approach safely balances steering precision with operational safety across different driving conditions.
Data Source
AI summary
The invention provides a steering system for a vehicle, a ship etc. The steering system has a steering handle for the operator of the vehicle, a set of signal processors, a sensor which determines a position of the steered element of the vehicle, and a controller which moves the steered element. The steered element could e.g. be the front wheels of a car. The signal processors are adapted to determine an error between the desired position of the steered element and an actual position of the steered element. In order to make the steering system more fault tolerant, the error signal is amplified based on the speed by which the steering handle is moved, and an error in the sensor therefore becomes less critical. The invention further provides a steering method, a steering control unit and a vehicle provided with a steering system of the mentioned kind.