Motor Drive Device Failure Detection via Impedance Observer
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Solution Overview
Problem
The complexity and cost of failure detection in motor drive devices, such as electric pumps in vehicles, are increased due to the need for various sensors, which complicates the system and raises costs, especially in redundant systems required for reliable operation.
Innovation Solution
A motor drive device with a control device that includes an impedance observer, a comparator, and a failure detection unit, which estimates impedance variation and calculates differences between command and actual currents to output a failure flag when thresholds are exceeded, allowing for efficient detection of failures in motor drive devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If various sensors are used for failure detection, then detection accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The motor drive device uses its own existing components (inverter, motor, control device) to perform failure detection through impedance observation and current comparison. The control device leverages data already being processed for motor control, eliminating the need for separate detection sensors and making the system self-diagnostic.
Solution Approach 2:
The control device performs multiple functions: it controls the inverter for motor operation and simultaneously detects failures through impedance observation and current comparison. This multi-functionality eliminates the need for dedicated failure detection hardware, reducing system complexity while maintaining detection capability.
2Measurement precision
If various sensors are used for failure detection, then detection accuracy is improved, but cost increases
Solution Approach 1:
The motor drive device uses its own existing components (inverter, motor, control device) to perform failure detection through impedance observation and current comparison. The control device leverages data already being processed for motor control, eliminating the need for separate detection sensors and making the system self-diagnostic.
Solution Approach 2:
Instead of using physical sensors to measure impedance and current, the system creates virtual copies of these measurements through mathematical calculations based on existing electrical parameters. The impedance observer calculates impedance values and the comparator generates current difference signals, providing detection capability without additional physical components.
3Device complexity
If impedance observation and current comparison are used, then device complexity is reduced, but detection precision must be maintained
Solution Approach 1:
The patent replaces physical measurement sensors with mathematical calculation methods. Impedance is calculated from voltage and current waveforms through impedance observation algorithms, and failures are detected by comparing commanded versus actual current values, substituting computational methods for physical sensing.
Solution Approach 2:
The impedance observer acts as an intermediary that processes raw electrical signals (voltage and current waveforms) to extract meaningful impedance information. The comparator then uses this processed information along with command signals to detect failures, creating a layered information processing structure that maintains precision while reducing hardware complexity.
Data Source
AI summary
Provided is a motor drive device including a motor having a rotor and a stator, an inverter electrically connected to the motor, and a control device for controlling the inverter. The control device includes: an impedance observer that estimates at least an amount of variation in impedance of the motor on the basis of a voltage command value, a current command value, and an actual current flowing between the inverter and the motor; a comparator that calculates a difference between the current command value and the actual current flowing between the inverter and the motor; and a failure detection unit that outputs a failure flag when the amount of variation in impedance exceeds or falls below a predetermined threshold, or when the difference calculated by the comparator exceeds or falls below a predetermined threshold.