Motor Control Device Power Feeding Abnormality Detection
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Solution Overview
Problem
Existing electric power steering devices face challenges in determining power feeding abnormality without using battery current detection values, leading to potential erroneous voltage drop identification due to high current consumption, which complicates device design and operation.
Innovation Solution
A motor control device that determines power feeding abnormality based on inverter input voltage and motor current, setting thresholds to differentiate between voltage drops caused by current increases and actual power feeding issues, thereby simplifying the device configuration and preventing erroneous abnormality determinations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a battery sensor is provided outside the ECU to detect battery current for power feeding abnormality determination, then the abnormality determination accuracy is improved, but the device complexity and size are increased due to additional terminals and reception circuits
Solution Approach 1:
The patent merges the battery current detection function into the existing motor current detection system. The same current detector that measures motor current is used to detect battery current by measuring the current flowing through the inverter circuit input. This eliminates the need for separate battery sensors, terminals, and reception circuits, thereby reducing device complexity while maintaining abnormality determination accuracy.
Solution Approach 2:
The current detector is designed to serve multiple functions: it detects both motor current for motor control purposes and battery current for power feeding abnormality determination. This multi-functionality approach allows the system to achieve accurate abnormality detection without adding dedicated battery current detection hardware, thus reducing overall device complexity.
2Measurement precision
If the inverter input voltage threshold is set low to detect power feeding abnormality, then the sensitivity of abnormality detection is improved, but voltage drops due to high current consumption are erroneously identified as abnormalities
Solution Approach 1:
The system uses feedback from motor current detection to dynamically adjust the voltage threshold for abnormality determination. When motor current (and thus battery current) is high, the system recognizes that voltage drop is expected and adjusts the threshold accordingly. This feedback mechanism allows the system to maintain high detection sensitivity while avoiding false positives caused by normal voltage drops under high load conditions.
Solution Approach 2:
The abnormality determination threshold is made dynamic rather than fixed. The threshold varies based on the detected battery current level - when current is high, the threshold is adjusted to account for expected voltage drops. This dynamic approach enables the system to maintain accurate abnormality detection across varying operating conditions without generating false alarms.
3Reliability
If battery current detection is implemented to prevent erroneous abnormality determination, then the reliability of power feeding abnormality determination is improved, but the device complexity is increased due to additional detection circuits
Solution Approach 1:
The system uses its existing motor current detection capability to also detect battery current, making the system self-sufficient for both motor control and power feeding abnormality determination. No external or additional detection circuits are needed - the existing infrastructure serves dual purposes, thereby improving reliability without increasing device complexity.
Data Source
AI summary
A motor control device for a motor includes: an inverter circuit supplying power of a battery to the motor; an inverter input voltage detector detecting an inverter input voltage; and a controller including a drive controller for the motor and an abnormality determination unit for determining power feeding abnormality. The abnormality determination unit determines the power feeding abnormality when the inverter input voltage is lower than a voltage threshold and a current from the battery to the inverter circuit is in a determinable range. The abnormality determination unit determines, based on a motor current electrically conducted to the motor or a rotational speed of the motor, whether the current is in the determinable range. A determination threshold in accordance with the determinable range is set that the inverter input voltage is equal to or higher than the voltage threshold when the power feeding region is normal.