Steering System Angular Play Control for Safety
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Solution Overview
Problem
Existing steering systems, such as those described in EP 2 934 986, allow large mutual relative rotations between steering shafts, which can enhance steering feel and reduce sensitivity to road irregularities but compromise safety during power failures, as the vehicle may deviate from its intended trajectory.
Innovation Solution
A method and control unit that adjust the angular mechanical play between steering shafts based on lateral acceleration, reducing the mutual relative rotation when lateral acceleration exceeds a threshold to enhance safety by ensuring rapid engagement of steering shafts in case of power failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a large mutual relative rotation is allowed between the upper and lower steering shafts, then the steering system becomes less sensitive to road irregularities and provides better steering feel, but the safety is compromised as the vehicle may deviate from its intended trajectory during power failures
Solution Approach 1:
The patent applies the dynamics principle by making the angular mechanical play between the first and second portions of the mechanical member variable rather than fixed. The control system dynamically adjusts the mechanical play between a first angular mechanical play (larger value) and a second angular mechanical play (smaller value) based on operating conditions such as vehicle speed and steering angle. This allows the system to optimize between steering feel and safety: larger mechanical play during normal operation for better steering feel, and smaller mechanical play during critical maneuvers or low-speed conditions for enhanced safety during potential power failures.
2Stability of the object's composition
If a fixed maximum mutual relative rotation is provided between the steering shafts using a resilient material, then the steering system provides consistent steering feel, but the ability to adapt to different operating conditions is limited
Solution Approach 1:
The patent transforms the static mechanical play provided by resilient material into a dynamic, controllable parameter. Instead of relying solely on the physical properties of resilient material to provide fixed mechanical play, the system uses active control mechanisms (such as motors or actuators) to adjust the angular mechanical play between the first and second portions of the mechanical member. This allows the system to maintain stability through controlled consistency while simultaneously adapting to different operating conditions by varying the mechanical play according to vehicle speed, steering angle, and other relevant parameters.
Solution Approach 2:
The patent applies parameter changes by modifying the angular mechanical play between the first and second portions of the mechanical member based on operating conditions. The control system monitors parameters such as vehicle speed, steering angle, and acceleration, and adjusts the mechanical play accordingly. For example, at higher vehicle speeds or during steady-state cruising, a larger mechanical play may be maintained for comfort, while at lower speeds or during maneuvering, the mechanical play is reduced for safety and precision. This dynamic parameter adjustment resolves the contradiction between consistency and adaptability.
3Reliability
If the angular mechanical play is reduced to enhance safety during power failures, then the vehicle maintains better trajectory control, but the benefits of large mechanical play during straight driving are lost
Solution Approach 1:
The patent resolves this contradiction by implementing dynamic adjustment of the angular mechanical play between the first and second portions of the mechanical member. The control system continuously monitors operating conditions and adjusts the mechanical play in real-time. During straight driving at normal speeds, the system maintains a first angular mechanical play (larger value) to provide good steering feel and comfort. When detecting conditions that increase the risk of trajectory deviation (such as low-speed maneuvering, high lateral acceleration, or detected power issues), the system transitions to a second angular mechanical play (smaller value) to enhance safety and trajectory control during potential power failures. This dynamic switching allows the system to optimize both steering feel and safety across different operating conditions.
Data Source
AI summary
A method of controlling a steering system of a vehicle, the steering system comprising a first steering shaft, a second steering shaft, and a mechanical member comprising a first portion connected to the first steering shaft and a second portion connected to the second steering shaft. A mutual relative rotation between the first and second steering shafts is obtainable by an angular mechanical play between the first and second portions, the mechanical member being adapted to assume a first state in which a first angular mechanical play is provided between the first and second portions. An angular displacement between the first and second steering shafts is controlled, in response to an indication of the lateral acceleration, such that the mechanical member assumes a second state in which a second angular mechanical play is provided between the first and second portions.