Position Sensor Signal Injection for Zero-Crossing Fault Detection
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Solution Overview
Problem
Conventional position sensors suffer from blind angle ranges due to zero crossings in measurement signals, limiting reliable position determination and failing to meet functional safety standards, especially in applications requiring continuous and accurate position detection.
Innovation Solution
Applying an electrical interference signal to secondary windings via a voltage divider circuit, allowing for the generation and evaluation of reaction signals to detect faults and ensure reliable position determination across the entire range of motion without modifying the sensor hardware, using additional circuitry and software extensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional measurement signal evaluation is used, then the position sensor structure remains simple, but blind angle ranges occur due to zero crossings limiting reliable position determination
Solution Approach 1:
An interference signal is introduced as an intermediary element to enable fault detection. This external signal is superimposed on the measurement signal, allowing the system to detect changes in the position sensor's transfer ratio without modifying the sensor hardware itself. The interference signal acts as a mediator that carries diagnostic information through the existing signal path.
Solution Approach 2:
The system changes the parameter being measured by superimposing an interference signal with a known frequency and amplitude onto the measurement signal. By monitoring changes in the reaction signal's parameters (amplitude, phase) rather than the original measurement signal parameters, the system can detect faults in the position sensor's transfer ratio while maintaining simple hardware.
2Reliability
If interference signal is applied to detect faults, then functional safety is improved, but device complexity increases due to additional circuitry
Solution Approach 1:
The evaluation unit is designed to perform multiple functions: it processes both the original measurement signal for position determination and the interference signal for fault detection. By making the evaluation unit multi-functional, the system achieves functional safety without adding separate dedicated fault detection hardware, thus limiting the increase in device complexity.
Solution Approach 2:
The fault detection function is merged with the existing position evaluation unit rather than being implemented as a separate system. The same evaluation unit that processes measurement signals also analyzes the reaction signals generated by the interference signal, combining diagnostic and measurement functions in a single integrated circuit.
3Measurement precision
If measurement signals are evaluated for position, then position information is obtained, but error detection is not possible in zero crossing regions
Solution Approach 1:
The interference signal is continuously applied to the position sensor before any fault occurs, establishing a baseline reaction signal. This preliminary action enables the system to detect changes in the transfer ratio at any position, including zero crossing regions, because the interference signal provides a continuous reference that is independent of the measurement signal's amplitude.
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
Enables reliable fault detection and continuous position determination, eliminating dead zones and ensuring functional safety by comparing reaction signals from multiple windings, compensating for external influences.
Implementation Method 1
A position encoder contains a magnetic excitation unit, such as a permanent magnet or an excitation winding, which moves along with a moving component, and at least two secondary windings that are stationary relative to the excitation unit. The excitation unit generates an (electro)magnetic field that induces electrical voltages in the secondary windings, which serve as measurement signals.
Implementation Method 2
Applying an electrical interference signal to secondary windings via a voltage divider circuit
Data Source
Figure 1~3
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Figure 6~7
AI summary
In order to enable reliable position determination for a position sensor over the entire range of motion, it is provided that a defined electrical disturbance signal (SS) is applied to at least one secondary winding (A, B) of the position sensor (1), which causes an electrical reaction signal (RSA, RSB) that is superimposed on the measurement signal (MA, MB), and the reaction signal (RSA, RSB) is evaluated in an evaluation unit (2) for fault detection.