Motor Control Device Neutral Point Voltage Sensor Failure Detection
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Solution Overview
Problem
Conventional methods for determining position sensor failure in motor control devices, especially when using Hall ICs or Hall elements, suffer from low position resolution and inability to identify failures in sensors with resolution less than 60 degrees electrical angle, and lack a method for handling such failures effectively.
Innovation Solution
A control device that utilizes a neutral point voltage of a motor to determine position sensor failure by comparing rotor positions detected by a primary position sensor with those estimated from the neutral point voltage, allowing for the generation of alternate pulse width modulation signals to continue motor operation without being affected by faulty sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Hall ICs or Hall elements are used as position sensors, then the device complexity is reduced and ease of manufacture is improved, but the position resolution deteriorates to 60 degrees electrical angle and the ability to identify sensor failures is lost
Solution Approach 1:
The patent introduces neutral point voltage as an intermediary to estimate rotor position independently of the Hall sensor. By using the relationship between neutral point voltage and rotor position, the system can determine actual position with higher precision while maintaining the simple Hall sensor configuration for basic control.
Solution Approach 2:
The patent implements feedback by comparing the rotor position detected by the Hall sensor with the position estimated from neutral point voltage. This feedback mechanism enables failure detection and provides a means to correct or compensate for sensor errors, thereby improving reliability without changing the basic sensor configuration.
2Device complexity
If only two position sensor outputs are compared, then the device complexity is reduced, but the ability to identify failed sensor outputs deteriorates
Solution Approach 1:
The patent uses neutral point voltage estimation as an intermediary reference to identify failed sensor outputs. By comparing each sensor output against the independently estimated position from neutral point voltage, the system can identify which sensor has failed without requiring complex comparisons among multiple sensors.
Solution Approach 2:
The system performs self-diagnosis by using its own operational parameters (neutral point voltage) to detect and identify sensor failures. The control device monitors its own state through neutral point voltage analysis, enabling automatic failure identification without external intervention or additional complex sensor arrays.
3Reliability
If three or more position sensors are used to identify failures, then the reliability is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent uses neutral point voltage as an intermediary to enable failure identification with only two Hall sensors. The neutral point voltage provides an independent reference that allows the system to detect and identify sensor failures without requiring a third sensor, thus maintaining simplicity while achieving reliability.
Solution Approach 2:
The patent replaces the need for additional mechanical sensors with an electrical measurement approach. By using neutral point voltage analysis to estimate rotor position and compare it with Hall sensor outputs, the system achieves sensor failure identification without adding more physical sensors, reducing device complexity.
Data Source
AI summary
An applied voltage decision unit 510 performs in parallel, a process of determining three-phase AC commands V1u* to V1w* of a voltage applied to a motor by an inverter based on a position, of a rotor of a motor, detected by a position sensor with an output A, and a process of determining three-phase AC commands V2u* to V2w* of the voltage applied to the motor by the inverter based on a neutral point voltage VN of the motor. A PWM modulator 507 alternately outputs a PWM signal according to the three-phase AC commands V1u* to V1w* and a PWM signal according to the three-phase AC commands V2u* to V2w* to the inverter. A control device determines whether or not the position sensor with the output A has failed by comparing the position, of the rotor, detected by the position sensor with the output A with a position, of the rotor, estimated from a neutral point voltage VN of the motor.