Motor Control Circuit Sensor Fault Detection
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Solution Overview
Problem
In electric power steering systems, motor drive systems using vector control can malfunction if any of the current or position sensors fail, leading to motor shutdown, which is inconvenient for drivers as it disrupts steering assistance.
Innovation Solution
A motor control method that acquires current values and rotor angles from multiple sensors, performs six ways of calculation to identify failed sensors, selects a normal sensor, and continues motor control using the identified normal sensor, allowing the system to operate even if one sensor fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor stops upon detection of sensor fault, then the reliability of the motor drive system is improved, but the ease of operation deteriorates due to loss of steering assistance
Solution Approach 1:
The system performs six ways of calculation using redundant sensors before a fault becomes critical, preparing alternative calculation results in advance. When a sensor fault is detected, the pre-calculated alternative results enable immediate switchover without motor shutdown, cushioning the impact on operational continuity.
Solution Approach 2:
The control circuit acts as an intermediary that mediates between faulty sensor data and motor control requirements. By introducing six different calculation methods as intermediate processing steps, the system can identify and isolate failed sensors while maintaining accurate motor control through alternative calculation paths.
2Measurement precision
If multiple sensors are used for vector control, then the measurement precision is improved, but the device complexity increases due to multiple current and position sensors
Solution Approach 1:
The control circuit is designed with multi-functionality to perform six different calculation methods using the same set of sensors. This universal approach allows the system to maintain high measurement precision through redundant sensing while avoiding additional hardware complexity by reusing existing sensors in multiple calculation configurations.
Solution Approach 2:
The system changes the parameters of calculation rather than adding more sensors. By varying the mathematical approaches (six different calculation methods) using the same sensor inputs, the system achieves enhanced measurement precision and fault tolerance without increasing the physical sensor count or system hardware complexity.
3Reliability
If six ways of calculation are performed to identify failed sensors, then the reliability is improved through fault detection, but the productivity decreases due to increased calculation time
Solution Approach 1:
The control circuit performs all six calculation methods simultaneously or in pre-planned sequences rather than sequentially after fault detection. This preliminary action approach ensures that alternative results are ready immediately when needed, maintaining fast motor control response while achieving comprehensive fault detection through multiple calculation paths.
Data Source
AI summary
A motor control method includes acquiring three current values of three-phase currents flowing through a motor, the three current values being detected by three current sensors, and two rotor angles of the motor, the two rotor angles being detected by two position sensors; performing six ways of calculation using two of the three current values and one of the two rotor angles; identifying at least one failed sensor from among the current sensors as well as the position sensors, using a table showing a relationship between a failed sensor and a pattern of a result of each of the six ways of calculation; selecting, as a normal sensor, a sensor different from the at least one failed sensor identified; and controlling the motor using the normal sensor selected.