Sensor Fault Diagnosis in Polyphase Machines
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Solution Overview
Problem
Existing methods for diagnosing faults in angular position measurement sensors of polyphase rotary electrical machines, such as alternator-starters, are inadequate due to high harmonic levels and sensitivity to magnetic disturbances, leading to inaccurate torque control and potential semiconductor deterioration.
Innovation Solution
A method that involves direct measurement of sine and cosine signals from linear combinations of polyphase signals to determine the 'speed state' and diagnose faults using simple logic operations, without requiring precise speed measurement, and utilizing threshold values calculated through a Monte-Carlo statistical method to identify faulty sensor states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional sensor diagnosis methods are used, then the system can operate with existing hardware, but the diagnosis accuracy is insufficient due to high harmonic levels and sensitivity to magnetic disturbances
Solution Approach 1:
The patent extracts the diagnostic function from the main control system by using separate diagnostic equations that independently evaluate sensor health. The diagnostic process uses dedicated diagnostic signals and evaluation criteria that are separate from the main torque control loop, allowing accurate fault detection without being affected by the harmonic disturbances that plague the main control system.
Solution Approach 2:
The patent introduces intermediary diagnostic signals and evaluation parameters that mediate between the raw sensor outputs and the final diagnosis. These intermediary elements (diagnostic equations, threshold values, and evaluation criteria) process the sensor signals through multiple transformation stages, filtering out harmonic distortions and magnetic disturbances before reaching the final fault detection decision.
2Reliability
If complex diagnostic systems are implemented to improve fault detection, then diagnosis reliability improves, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing control system components serve multiple functions. The same hardware that performs torque control also executes diagnostic evaluations. The control unit is programmed to run both the main control algorithm and the diagnostic equations, eliminating the need for separate diagnostic hardware. This multi-functionality approach achieves reliable fault detection without increasing device complexity.
Solution Approach 2:
The system performs self-diagnosis using its own operational data. The diagnostic equations evaluate sensor health by analyzing the actual signals processed during normal torque control operation. The system uses its own control loops and sensor inputs to generate diagnostic outputs, eliminating the need for external diagnostic equipment or separate test systems.
3Measurement precision
If precise speed measurement is required for diagnosis, then diagnostic accuracy improves, but the system becomes more complex and costly
Solution Approach 1:
The patent replaces mechanical speed measurement systems with electronic signal processing. Instead of using separate speed sensors or mechanical encoders, the system derives speed information electronically from the torque control signals and diagnostic equations. The speed state is determined through mathematical evaluation of the control loop variables, eliminating the need for additional mechanical measurement devices.
Solution Approach 2:
The patent changes the parameters used for diagnosis from direct speed measurements to derived control parameters. The diagnostic equations evaluate sensor health by analyzing changes in control variables, signal amplitudes, and phase relationships that are already present in the torque control system. This parameter transformation allows accurate diagnosis without requiring separate precise speed measurement hardware.
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 allows for reliable diagnosis of sensor faults with minimal complexity and cost, effectively detecting issues like short-circuits and disconnections, and is integrated into existing systems with minimal hardware and software modifications.
Implementation Method 1
sensors (10) fixed relative to the stator and able to detect a magnetic field and provide first signals which are representative of this magnetic field
Data Source
AI summary
Disclosed is a method and device for diagnosis of functioning faults caused by the angular position measurement sensors of the rotor of a polyphase rotary electrical machine comprising a stator, in particular of the alternator-starter type. The diagnosis is obtained by carrying out direct measurements of pairs of sine and cosine signals determined on the basis of linear combinations of the polyphase signals provided by these sensors. This measurement therefore does not make it necessary to know the exact value of the speed of the machine. The diagnosis of functioning faults caused by the angular position measurement sensors requires only the execution of elementary logic operations, i.e. the determination of the “true” or “false” logic states of two inequality equations.