Electric Motor Control Device for Faulty Current Sensor Isolation
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Solution Overview
Problem
Existing control systems for three-phase electric motors fail to accurately identify and isolate faulty current sensor readings, leading to incorrect current regulation.
Innovation Solution
A control device and method that uses phase-shifted PWM voltage control and ADC sampling, along with a space vector controller, to compare current sensor readings across multiple sub-motors, allowing for the identification and correction of faulty sensors by comparing sinusoidal current values and accounting for time differences in ADC sampling points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current sensor readings are used for current regulation without fault detection, then the control system operates simply, but faulty sensors cause incorrect current regulation
Solution Approach 1:
The system performs preliminary fault detection by checking Kirchhoff's current law (sum of currents at star point equals zero) before current regulation. This preliminary check identifies faulty sensors in advance, allowing the system to flag and handle bad readings before they affect motor control, thus improving reliability without significantly increasing complexity
Solution Approach 2:
The system implements feedback by continuously monitoring current sensor readings and comparing them against Kirchhoff's current law. When a discrepancy is detected (non-zero sum at star point), the system feeds back this fault information to identify and isolate the faulty sensor, enabling corrective action to maintain accurate current regulation
2Measurement precision
If multiple current sensors are used for each phase to improve measurement accuracy, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The system uses itself to detect faults by applying Kirchhoff's current law to the existing current sensor readings. Instead of adding redundant sensors, the system leverages the mathematical relationship between phase currents (Iu + Iv + Iw = 0 at star point) to self-diagnose sensor faults, maintaining measurement precision without increasing sensor quantity or system complexity
3Measurement precision
If ADC sampling points are not synchronized across sub-motors, then sampling timing is simpler, but time differences cause errors in current value comparison
Solution Approach 1:
The system performs preliminary identification of ADC sampling time differences between sub-motors. By calculating and storing the time offset between sampling points of different sub-motors in advance, the system can compensate for these differences when comparing current values, ensuring accurate fault detection without requiring complex real-time synchronization
Solution Approach 2:
The system cushions against timing errors by pre-calculating and storing the time difference between ADC sampling points of different sub-motors. This beforehand preparation allows the system to compensate for sampling time offsets when comparing current readings, preventing timing-related false fault detections without adding real-time complexity
Data Source
AI summary
A control device for an electric motor having a first set of coil windings arranged to form a first sub motor and a second set of coil windings arranged to form a second sub motor, wherein current flow in the first set of coil windings is controlled using a first pulse width modulation, PWM, having a first switching sequence and current flow in the second set of coil windings is controlled using a second PWM having a second switching sequence, the control device comprising means arranged to measure the current flow in each of the first set of coil windings, wherein upon determining that the sum of the current flow in the first set of coil windings is substantially non zero, deriving the first PWM values from voltage values used to generate the second PWM.