Autonomous Vehicle Steering Redundancy via Segmented Actuators
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Solution Overview
Problem
Existing steer-by-wire systems in autonomous vehicles lack the necessary redundancy and integrity to meet the stringent safety requirements of mass-transit vehicles, which can lead to inadequate availability and safety in critical situations.
Innovation Solution
The implementation of a four-steering-system configuration for autonomous vehicles, each with two actuators and a controller, powered by separate sources, providing high redundancy and integrity. This setup allows for independent control of each wheel, ensuring continued operation even if one actuator or controller fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a separate steering actuator is assigned to each steerable wheel, then independent control of steering angle is achieved, but the number of sensors and actuators increases beyond acceptable minimum
Solution Approach 1:
The steering system is divided into four independent steering systems, each controlling one steerable wheel. Each steering system includes its own actuator and controller, enabling independent control of each wheel's steering angle. This segmentation allows the system to achieve full adaptability for different driving modes (Ackermann steering, crabbing, etc.) while maintaining modular architecture that simplifies control logic.
Solution Approach 2:
The patent introduces redundancy as an additional dimension to the steering system design. Each steerable wheel is equipped with two actuators instead of one, creating a redundant control path. This dimensional addition ensures that if one actuator fails, the other can take over, thereby maintaining system functionality without requiring excessive sensors and actuators in normal operation.
2Ease of manufacture
If automotive safety levels are used, then cost is reduced, but safety requirements for mass-transit vehicles are not met
Solution Approach 1:
The steering system incorporates redundant actuators and controllers that serve as pre-prepared backup components. In the event of a failure in the primary actuator or controller, the redundant components are already in place and can immediately take over, cushioning against safety failures. This prior cushioning approach ensures that the system meets stringent mass-transit safety requirements without requiring excessive components during normal operation.
Solution Approach 2:
The patent changes the safety parameter from automotive level to mass-transit level by implementing a redundant architecture. Each steering system has two actuators and the controllers are cross-connected, fundamentally changing the safety parameter. This parameter change ensures that the system can tolerate component failures while maintaining safe operation, thereby meeting the higher reliability requirements for mass-transit vehicles.
3Reliability
If redundancy is increased to meet safety requirements, then safety and availability are improved, but device complexity increases
Solution Approach 1:
The steering system is segmented into four independent modules, each controlling one steerable wheel. Each module contains its own actuator and controller, creating modular redundancy. This segmentation allows the system to achieve high reliability through redundancy while keeping each module's complexity manageable. The modular architecture simplifies the overall system management compared to a fully integrated redundant system.
Solution Approach 2:
Each controller is designed with multi-functionality, serving both as the primary controller for its associated steering system and as a backup controller for adjacent steering systems. This universal design reduces the need for separate dedicated backup controllers, thereby reducing device complexity while maintaining high redundancy levels. The cross-connectivity of controllers enables them to perform multiple functions, simplifying the overall system configuration.
Data Source
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AI summary
An autonomous vehicle (10) for passengers comprises four steerable wheels (18) where each steerable wheel (18) is steered by a steering system (16) having a set of two actuators (20). One actuator (20) of each set of actuators is powered by a first power source (26) while the other actuator (20) of the set of powered by a second power source (26). Four controllers (24) each control one actuator (20) of each set of actuators (20) and one actuator (20) from another set of actuators (20).