Electrohydraulic Steering Kalman Filter Fault Detection
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Solution Overview
Problem
Existing electrohydraulic steering systems for mobile work machines lack reliable fault detection and safe emergency steering functionality, posing risks when errors occur during vehicle operation.
Innovation Solution
A position-controlled electrohydraulic steering system incorporating a Kalman filter and error detection block within the control circuit, utilizing redundant position measuring signals to maintain steering functionality even in fault conditions, ensuring safe vehicle stoppage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a position measuring system with redundant sensors is implemented to detect faults, then the reliability of fault detection is improved, but the device complexity increases
Solution Approach 1:
The patent implements preliminary action by pre-calculating and storing steering angle values using a Kalman filter before actual faults occur. The system continuously estimates the steering angle based on the steering wheel angle sensor signals and vehicle dynamics model, so that when a fault is detected, the pre-calculated estimated values are immediately available for control, ensuring continuous and safe operation without interruption.
Solution Approach 2:
The patent uses an intermediary approach by introducing a steering angle estimator (Kalman filter) as a mediator between the steering wheel angle sensor and the steering angle sensor. This estimator processes the steering wheel angle signals and vehicle dynamics information to generate reliable steering angle estimates, acting as a bridge that maintains system functionality even when direct position measurement fails.
2Reliability
If the steering system shuts down entirely upon error detection, then safety is improved by preventing further damage, but the ability to bring the vehicle to a standstill safely deteriorates
Solution Approach 1:
The patent applies beforehand cushioning by preparing emergency steering control strategies in advance through the steering angle estimator. When a fault occurs, the system has pre-calculated alternative steering angle values ready to be deployed, cushioning the impact of the fault and enabling smooth transition to emergency mode without abrupt shutdown, thus maintaining vehicle controllability during critical failure scenarios.
3Reliability
If redundant position measuring signals are processed continuously, then fault detection capability is improved, but the use of energy increases
Solution Approach 1:
The patent implements partial action by selectively processing only the necessary signals for fault detection and estimation. The Kalman filter processes steering wheel angle sensor signals and vehicle dynamics information continuously, but only activates full fault detection and emergency control strategies when anomalies are detected, avoiding unnecessary continuous processing of all redundant signals and thereby reducing energy consumption while maintaining detection capability.
Data Source
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AI summary
The invention relates to a position-controlled, electro-hydraulic steering system for a work machine, in particular for a wheel loader, comprising at least one hydraulic steering circuit with at least one steering valve and at least one steering hydraulic cylinder, and at least one control circuit for controlling the at least one steering valve of the steering circuit, wherein the control circuit comprises at least one control unit, at least one controller, at least one control input means (22), and at least one position measuring system (21) for determining a controlled variable, wherein the position measuring system (21) comprises means for generating redundant position measurement signals, and furthermore, at least one Kalman filter (6) is provided between the position measuring system (21) and the control unit, which determines an estimated value of the controlled variable for position control, and wherein the steering system further comprises at least one fault detection block.which detects an error in the position measuring system (21) based on the redundant measurement signals.