Motor Control Device Sensor Malfunction Detection
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Solution Overview
Problem
Existing motor control devices for three-phase AC motors face challenges in maintaining precise control due to the reliance on current sensor detection values, which can lead to unstable motor control when sensors malfunction, particularly when judging anomalies based on equivalent phase angles.
Innovation Solution
A motor control device that computes d-axis and q-axis actual currents from two phases excluding the phase with the largest current difference, allowing for appropriate control by selecting phases with better current feedback performance and incorporating an anomaly judgment mechanism to identify malfunctioning sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If malfunction detection is performed by comparing current values from multiple current sensors based on equivalent phase angles, then sensor malfunction can be identified, but detection precision deteriorates due to variations in detection timing among sensors
Solution Approach 1:
The patent introduces an intermediary calculation process that computes equivalent phase angles and current values from two healthy sensors before comparison. This intermediary step filters out timing variations by converting raw sensor data into a common reference frame, allowing accurate malfunction detection without being affected by detection timing precision issues.
Solution Approach 2:
The system continuously monitors current values from multiple sensors, compares them against calculated equivalent values, and provides feedback to identify malfunctions. This feedback mechanism allows the system to adapt and maintain reliable detection despite timing variations by constantly adjusting based on the comparison results.
2Measurement precision
If all three phase current sensors are used for motor control, then control precision is maintained, but system reliability decreases when one sensor malfunctions
Solution Approach 1:
The patent extracts and identifies the malfunctioning sensor by comparing current values from three sensors against equivalent values calculated from two sensors. Once the faulty sensor is extracted from the system, control continues using only the two healthy sensors, maintaining reliability while accepting a reduction in measurement precision compared to using all three sensors.
Solution Approach 2:
The system dynamically changes the number of active current sensors from three to two based on malfunction detection. When a sensor is identified as faulty, the control parameters are adjusted to use only the two healthy sensors, transforming the system configuration to maintain operational reliability under degraded conditions.
3Reliability
If current sensor malfunction is detected by comparing detection values with estimation values, then malfunction can be identified, but appropriate control continuation becomes difficult due to detection timing variations
Solution Approach 1:
The patent performs preliminary calculation of equivalent phase angles and current values from two sensors before comparing with the third sensor's detection value. This preliminary action establishes a reference framework that enables reliable malfunction identification, and once a malfunction is detected, the system is already prepared to continue control using the two healthy sensors without disruption.
Data Source
AI summary
The present invention employed a motor control device including: current sensors which detect currents in each phase of a three-phase motor; a coordinate conversion device which computes a d-axis actual current and a q-axis actual current in dq-coordinates from phase currents of three phases based on detection values of the current sensors; a voltage instruction computation device which computes a d-axis voltage instruction and a q-axis voltage instruction based on a deviation between a d-axis current instruction and the d-axis actual current and on a deviation between a q-axis current instruction and the q-axis actual current; a target phase current computation device which computes target phase currents for each phase from the d-axis current instruction and the q-axis current instruction; and a current difference computation device which computes, for each phase, a current difference between the phase current and the target phase current.