Steering Angle Sensor Self-Diagnosis via Signal Comparison
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Solution Overview
Problem
Existing rotation angle sensors for electric steering systems in industrial trucks fail to promptly detect errors caused by sensor failures or external magnetic field interference, leading to potential safety issues.
Innovation Solution
The solution involves determining ideal output signals from sensor geometric relationships, calculating redundant rotation angles using specific formulas, and comparing them to measured values to detect deviations, which trigger warning or stop signals if errors are detected, without requiring additional equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two magnetic field-sensitive sensor elements are used to determine rotation angle, then measurement precision is improved, but reliability deteriorates because errors from sensor failure or drift cannot be recognized immediately
Solution Approach 1:
The patent applies feedback by continuously monitoring the relationship between the two sensor elements' output signals. The control unit calculates expected signal relationships based on the known geometric arrangement and compares them with actual measurements. When deviations exceed a threshold, the system generates a warning signal, creating a closed-loop feedback mechanism that enables real-time detection of sensor failures or drift without additional hardware sensors.
Solution Approach 2:
The system uses its existing processor and signal processing capabilities to perform self-diagnosis. Rather than requiring external monitoring equipment, the control unit leverages the mathematical relationship between the two sensor signals (X = A cos(θ) + B and Y = A sin(θ) + B) to detect anomalies. The system essentially monitors itself by checking whether the measured signals conform to the expected trigonometric relationship, enabling autonomous fault detection.
2Reliability
If additional monitoring equipment is added to detect sensor failures, then reliability is improved, but device complexity increases
Solution Approach 1:
The control unit performs multiple functions: it calculates the rotation angle from the sensor signals, controls the steering actuator, and simultaneously monitors sensor health by verifying the mathematical relationship between signals. This multi-functionality eliminates the need for separate monitoring hardware, as the existing control unit is utilized for both operational control and diagnostic purposes, thereby avoiding increased device complexity.
Solution Approach 2:
The patent uses the mathematical relationship between the two sensor signals as an intermediary for fault detection. Rather than directly monitoring physical sensor conditions, the system checks whether the signals satisfy the expected trigonometric relationship (tan(θ) = Y/X). This mathematical intermediary enables indirect but effective monitoring of sensor health without requiring additional physical sensors or complex monitoring circuitry.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures timely intervention and safety by identifying sensor failures or drifts, allowing for corrective action or vehicle stopping, using existing processor capabilities without additional hardware.
Implementation Method 1
the first and second sensor elements (1, 2) have a known geometric relationship to one another
Implementation Method 2
The sensor elements generate sinusoidal output signals depending on the rotary movement of the magnet
Data Source
AI summary
An automatic guided vehicle angle sensor has magnetic field sensors (1, 2) orthogonally arranged around a magnet on the shaft axis and processes (10) ideal geometry dependent output signals for comparison with measured values to produce a warning or stop signal if the difference exceeds a set value. Independent claims are included for voltage sensors (26, 28) provided to monitor the magnetic sensor supply voltages.