Steer-by-Wire Feedback Arrangement With Mechanical Self-Centering
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Solution Overview
Problem
Existing steer-by-wire (SbW) steering systems face challenges such as high energy consumption, reliance on rare earth metals, environmental impact, complexity, and safety issues due to reliance on electric motors for feedback, which can lead to loss of self-centering and steering feel in case of failure.
Innovation Solution
A steering system incorporating both an electric feedback motor and a mechanical feedback arrangement, such as a passive force feedback element (PFFE) like springs or cam profiles, to provide additional feedback torque and ensure self-centering, reducing the reliance on the electric motor and enhancing safety and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a high performance electric motor is used to provide feedback torque, then the steering feedback force is sufficient, but the cost, weight, volume and use of raw materials like copper and rare earth metals increase significantly
Solution Approach 1:
The feedback torque provision is segmented into two independent sources: an electric motor for active feedback and a mechanical feedback arrangement with passive force feedback elements (springs, dampers) for passive feedback. This segmentation allows the electric motor to be smaller and lighter while still achieving sufficient total feedback torque when combined with the mechanical arrangement.
Solution Approach 2:
The patent combines an electric motor with a mechanical feedback arrangement into a unified feedback system. The electric motor and mechanical feedback elements work together to provide the required feedback torque, merging active and passive feedback mechanisms to reduce the burden on the electric motor alone.
2Force
If a high performance electric motor is used to provide feedback torque, then the steering feedback force is sufficient, but the energy consumption increases significantly
Solution Approach 1:
The mechanical feedback arrangement with passive force feedback elements provides feedback torque without requiring external energy input. The springs and dampers automatically generate the necessary forces based on their mechanical properties, making the system self-sufficient for part of the feedback requirement and reducing overall energy consumption.
Solution Approach 2:
By segmenting the feedback torque provision between an energy-consuming electric motor and an energy-free mechanical arrangement, the patent reduces the energy burden on the electric motor while maintaining sufficient total feedback torque.
3Device complexity
If the feedback force is generated solely by an electric motor, then the steering system is simple, but the self-centering effect is lost if the motor fails
Solution Approach 1:
The mechanical feedback arrangement with passive force feedback elements serves as a pre-prepared backup system that automatically takes over or supplements the electric motor's function in case of failure. This beforehand cushioning ensures that the self-centering effect is maintained even when the electric motor fails, improving reliability without significantly increasing complexity.
Solution Approach 2:
The patent changes the operational parameters of the feedback system by introducing a dual-source architecture. The mechanical feedback arrangement operates with different parameters (passive, energy-free, fail-safe) compared to the electric motor (active, energy-consuming, controllable), providing redundancy and improved reliability.
4Ease of operation
If an electric motor is used for feedback, then steering control is precise, but friction feel especially for slow, zero and reversing angular speed is not optimal
Solution Approach 1:
The patent merges the precision control capability of the electric motor with the natural friction characteristics of mechanical feedback elements. The mechanical arrangement with springs and dampers provides authentic friction feel during slow, zero, and reversing movements, complementing the electric motor's precise control to eliminate steering feel defects.
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
The combined system reduces energy consumption, minimizes the need for rare earth metals, enhances steering safety and feel, and ensures self-centering even in failure scenarios, while being compact and cost-effective.
Implementation Method 1
The mechanical feedback arrangement (PFFE) may comprise any kind of spring, i.e. an element that builds up force in a direction which is opposite to the direction of movement, without any input of energy than the energy provided by the movement itself
Data Source
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AI summary
The present invention relates to power assisted Steer by Wire steering system (100) for a vehicle or similar comprising a steering arrangement (1), a steering shaft (2) connected to the steering arrangement (1), steerable elements (13,13), an electrically controllable actuator (8) arranged on or connected to a link arrangement (9) connected to the steerable elements (13,13), an Electronic Control Unit, ECU, (5) controlling the electrically controllable actuator (8) and a feedback arrangement (10) connected to the ECU (5). The feedback arrangement (10) comprises an electric feedback motor (3) and a mechanical feedback arrangement (4). The mechanical feedback arrangement (4) comprises a deformation reactive, elastic arrangement arranged to react on a force produced by the steering arrangement (1) by generation of a reaction force counteracting the force produced by the steering arrangement (1) to provide a mechanical feedback force. The feedback force applied to the steering arrangement (1) comprises a combination of, or the sum of, the mechanical feedback force and an electric feedback force provided by the electric feedback motor (4).