Current Sensor Failure Diagnosis in 3-Phase BLAC Motors
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Solution Overview
Problem
Current technologies lack a method to effectively diagnose failures in current sensors of 3-phase brushless AC motors, which are crucial for accurate operation and stability in systems like motor-driven power steering systems.
Innovation Solution
A failure diagnostic apparatus and method that uses a control unit to calculate phase current errors and accumulate error counts based on rotor angle positions, allowing for the detection of failures in current sensors by comparing expected and measured currents, thereby diagnosing sensor failures when error counts reach preset values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If three current sensors are used to measure three phase currents, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses two current sensors to measure two phase currents, and the third phase current is calculated based on the relationship that the sum of three phase currents is zero. This copying approach replaces one physical sensor with a computational method, reducing device complexity while maintaining measurement capability
Solution Approach 2:
The control unit acts as an intermediary that calculates the third phase current based on the measured two phase currents and the current sum vector. This computational intermediary enables indirect measurement of the third phase without requiring a dedicated sensor
2Device complexity
If two current sensors are used to reduce cost, then device complexity is reduced, but the ability to detect sensor failures is worsened
Solution Approach 1:
The patent implements a feedback mechanism where the control unit continuously monitors the measured phase currents, calculates current sum vectors, and compares them against expected values. When discrepancies exceed a threshold, error counts are accumulated and trigger failure diagnostics, enabling the system to detect sensor failures despite using fewer sensors
Solution Approach 2:
The control unit performs preliminary calculations of current sum vectors and phase current errors at preset time intervals based on rotor angle positions. This preliminary monitoring action enables early detection of sensor failures before they cause system malfunction
Data Source
AI summary
A failure diagnostic apparatus for current sensors of a 3-phase brushless AC (BLAC) motor may include: a 3-phase BLAC motor; current sensors each configured to measure a phase current of the 3-phase BLAC motor; a motor driving unit configured to drive the 3-phase BLAC motor; and a control unit configured to drive the 3-phase BLAC motor through the motor driving unit, periodically calculate a phase current error using the phase current fed back through each of the current sensors, and diagnose that a failure occurred in the current sensor of the corresponding phase, when an error count accumulated during a preset time reaches a preset value, based on the phase current error.