Current Sensor State Determination for In-Vehicle Rotating Electric Machines
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Solution Overview
Problem
Current sensor state determination in in-vehicle rotating electric machines faces challenges in reliably detecting normal operation and abnormalities, particularly due to the difficulty in distinguishing between zero current and abnormal conditions, which affects the system's ability to switch between normal and automated control modes effectively.
Innovation Solution
A current sensor state determination device that includes a power converter and an abnormality determiner, which calculates the sum of phase currents and uses a second determination value based on an electric current in a rotating coordinate system to assess the normality of the current sensor, allowing for more frequent and accurate normality determinations with a smaller amplitude of phase current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sum of phase currents is used to determine current sensor abnormality, then abnormality detection capability is improved, but the ability to reliably determine normal operation deteriorates due to difficulty in distinguishing zero current from abnormal conditions
Solution Approach 1:
The patent transforms the determination parameter from the sum of phase currents (which cannot distinguish zero from abnormality) to the electric current value in the rotating coordinate system (which provides distinct values for normal and abnormal states). This parameter transformation enables reliable normality determination by comparing against a second determination value threshold.
Solution Approach 2:
The patent introduces a new dimension of analysis by converting stationary coordinate system currents to rotating coordinate system currents. This dimensional transformation allows the system to evaluate current sensor state from a different perspective where normal operation produces clearly distinguishable values from abnormal conditions.
2Measurement precision
If a larger amplitude of phase current is used for normality determination, then the accuracy of distinguishing normal from abnormal conditions is improved, but the frequency of determination opportunities deteriorates
Solution Approach 1:
The patent changes the evaluation parameter to electric current in the rotating coordinate system, which maintains sufficient discrimination capability between normal and abnormal states even at smaller current amplitudes. This allows normality determination to be performed more frequently without sacrificing accuracy.
3Reliability
If the system requires high confidence in current sensor normality before switching to automated control, then safety is improved, but the responsiveness to switch to automated control deteriorates
Solution Approach 1:
The patent implements continuous feedback monitoring of the electric current value in the rotating coordinate system, comparing it against the second determination value. This ongoing feedback mechanism allows the system to build confidence in sensor normality progressively, enabling timely transitions to automated control when confidence thresholds are met.
Solution Approach 2:
The patent performs preliminary assessment of current sensor normality by evaluating the electric current value in the rotating coordinate system before initiating control mode transitions. This preliminary verification ensures safety requirements are met while enabling responsive switching when conditions are favorable.
Data Source
AI summary
A current sensor state determination device determines that an abnormality is caused in a current sensor when a sum of phase currents based on current detection values from each of the current sensors in three phases is greater than a first determination value, and determines that no abnormality is caused in the current sensor when the sum of phase currents is equal to or less than the first determination value. The state determination device determines that the current sensor is normal when it is determined that (i) no abnormality is caused in a preset electric angle range equal to or less than one electric-angle cycle of the rotating electric machine and (ii) a value of an electric current flowing in the rotating electric machine in a rotating coordinates system calculated based on the current detection value is equal to or greater than a second determination value.