Steer-by-Wire Intermediate Shaft Assembly for Redundant Mechanical Linkage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Steer-by-wire vehicle systems lack a mechanical connection between the steering wheel and steering actuator, rendering directional control impossible during power loss, and existing redundant systems with clutches are inefficient.
Innovation Solution
An intermediate shaft assembly mechanically couples the steering shaft to a rack and pinion assembly using an outer and inner shaft with splines, providing a redundant steering mode when electrical communication is unavailable, ensuring continuous mechanical linkage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional intermediate shaft with continuous mechanical connection is used, then directional control during power loss is enabled, but the steer-by-wire system cannot achieve full electrical decoupling between steering wheel and steering actuator
Solution Approach 1:
The intermediate shaft is segmented into an outer shaft and an inner shaft that can move independently relative to each other. The outer shaft remains continuously connected to the steering wheel, while the inner shaft connects to the steering actuator. This segmentation allows the system to provide mechanical backup through the outer shaft while maintaining electrical decoupling through the inner shaft's independent operation.
Solution Approach 2:
The intermediate shaft assembly acts as an intermediary mechanism between the steering wheel and steering actuator. It provides a dual-path connection: a primary electrical path through the inner shaft and actuator, and a secondary mechanical path through the outer shaft. This intermediary structure enables the system to switch between electrical and mechanical operation modes.
2Reliability
If redundant emergency steering systems with clutches are implemented, then mechanical connection is restored during power loss, but the system complexity and response time increase
Solution Approach 1:
The outer shaft is pre-configured and continuously positioned to provide immediate mechanical connection to the steering wheel. The splines on the inner and outer shafts are pre-aligned and ready for engagement. When power loss is detected, the mechanical connection is instantly activated without requiring clutch engagement or reconfiguration, eliminating response time delays.
Solution Approach 2:
The intermediate shaft assembly incorporates dynamic elements including the inner shaft's ability to move axially within the outer shaft and the spring-loaded spline engagement mechanism. These dynamic features allow the system to automatically transition between electrical and mechanical operation modes based on real-time operational conditions, providing rapid response to power loss events.
3Strength
If the inner and outer shafts are tightly coupled, then mechanical strength is maximized, but the clearance between splines required for engagement is reduced
Solution Approach 1:
The intermediate shaft assembly applies local quality by providing different coupling characteristics in different regions. The overlapped region where the inner and outer shafts interact features a clearance between splines to enable engagement. Other regions maintain tight coupling for structural strength. This localized differentiation allows the system to achieve both strong mechanical coupling and easy spline engagement where needed.
Data Source
AI summary
A steer-by-wire steering system includes a steering wheel. Also included is a steering shaft operatively coupled to the steering wheel and rotatable therewith. Further included is a steering gear input shaft operatively coupled to an electric power assist steering gear. Yet further included is an electric actuator operatively coupled to the electric power assist steering gear. Also included is a controller in operative communication with the steering shaft and the electric actuator for steering in a primary mode. Further included is an intermediate shaft assembly mechanically coupling the steering shaft to a rack and pinion assembly to steer in a redundant mode when communication between the steering shaft and the steering gear input shaft is not available.