Steering Assist Torque Limiting via Transient Control
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Solution Overview
Problem
Conventional vehicle steering assistance systems face challenges in quickly and effectively limiting faulty torque demands without compromising performance or controllability, leading to potential instability and unsatisfactory compromises between assistance and steerability.
Innovation Solution
A method that involves providing a sensor to obtain vehicle operating parameters, establishing a limit criterion, and implementing a transient assistance-torque limit to dynamically adjust and limit excessive torque demands, ensuring stable steerability and rapid fault compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If torque demands are limited based on amplitude and change in amplitude, then faulty torque demands are restricted, but the assistance function performance is compromised
Solution Approach 1:
The patent implements dynamic limiting by introducing a transient assistance-torque limit that adapts based on the violation state of limit criteria. The system transitions between different limiting states (normal operation, transient limitation, and stationary limitation) depending on whether torque demands violate established criteria, allowing full performance during normal operation while providing rapid limitation when faults are detected
Solution Approach 2:
The system changes the torque limit parameter dynamically based on system state. During normal operation, the full assistance torque is allowed. When a limit criterion violation occurs, the system switches to a transient assistance-torque limit that is lower than the normal limit, and can further transition to a stationary assistance-torque limit for sustained faults, thereby adjusting the parameter to balance reliability and performance
2Reliability
If conventional systems limit torque demands, then faulty torque demands are restricted, but the response time is too slow
Solution Approach 1:
The system performs preliminary action by establishing limit criteria for torque demands before faults occur. The monitoring mechanism continuously checks whether torque demands violate these pre-established criteria, enabling immediate detection and response to faulty conditions without waiting for fault symptoms to manifest, thereby reducing response time significantly
Solution Approach 2:
The system implements continuous feedback monitoring of torque demands against established limit criteria. When a violation is detected, the feedback loop immediately triggers the transient assistance-torque limit, creating a rapid closed-loop control system that responds to faulty torque demands in real-time rather than with delayed conventional limiting
3Reliability
If assistance torques are limited individually and/or in combination, then faulty torque demands are restricted, but the steerability and controllability are compromised
Solution Approach 1:
The patent segments the torque limiting into different levels: normal operation torque, transient assistance-torque limit, and stationary assistance-torque limit. Each segment applies to specific fault conditions, allowing the system to maintain full steerability during normal operation while providing graduated limitation only when and where faults occur, preserving ease of operation during normal use
Data Source
AI summary
A method and apparatus for limiting an assistance-torque demand on an actuator, for example a servomotor, of a power steering system. An assistance-torque demand is received and examined based on a predetermined limit criterion. If a violation of the limit criterion is ascertained, a transient assistance-torque limit is adopted and progressively reduced so long as the violation of the limit criterion is ascertained. The assistance-torque demand is limited based on the transient assistance-torque limit. The limited assistance-torque demand is sent to an interface of the actuator of the power steering system.