Electric Vehicle Motor Malfunction Detection and Safety Control
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Solution Overview
Problem
Electric vehicle motor controllers are vulnerable to electromagnetic and electrostatic noise, which can cause malfunctions such as rotational direction and speed abnormalities, compromising vehicle safety by potentially leading to unintended travel directions or accelerations.
Innovation Solution
The implementation of a malfunction detection system within the inverter unit, comprising rotational direction and frequency estimators and abnormality determiners, which continuously monitor torque commands and motor signals to detect abnormalities and trigger shut-off of motor drive current or mechanical braking, ensuring safety by preventing unsafe vehicle operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If motor control is implemented with a microcomputer, then the electric vehicle can operate the motor, but the system becomes vulnerable to electromagnetic noise and electrostatic noise causing malfunctions
Solution Approach 1:
The patent implements preliminary detection of motor abnormalities by continuously monitoring rotational direction and frequency before malfunctions can occur. The abnormality determiners compare actual motor behavior against expected values derived from torque commands, enabling early detection of noise-induced deviations and preventing unsafe operations.
Solution Approach 2:
The system establishes a feedback loop where the malfunction detector continuously monitors motor rotational characteristics and feeds this information back to the controller. When abnormalities are detected, the system responds by shutting off drive current or activating mechanical brakes, creating a closed-loop safety mechanism that counteracts the effects of electromagnetic or electrostatic noise.
2Power
If a reducer with significant reduction ratio is used to transmit torque, then the motor can effectively drive the wheel, but torque generated by unstable motor control is amplified and transmitted to the wheel
Solution Approach 1:
The patent applies preliminary detection of motor instability before the reducer amplifies it. By monitoring rotational frequency and direction at the motor level and comparing against torque command expectations, the system identifies unstable motor behavior before it reaches the reducer, enabling preventive shutdown or braking action.
Solution Approach 2:
The system prepares safety measures in advance by continuously monitoring motor characteristics and having ready the ability to shut off drive current or activate mechanical brakes. This beforehand cushioning prevents unstable torque from being amplified by the reducer and transmitted to the wheel, protecting against the harmful effects of motor instability.
3Reliability
If malfunction detection and safety measures are implemented, then vehicle safety is improved, but the device complexity increases
Solution Approach 1:
The patent integrates multiple functions into the existing motor control system. The malfunction detector utilizes the same torque command signals already present in the control system, and the abnormality determiners leverage existing rotational frequency and direction sensors. This multi-functional approach enables comprehensive safety monitoring without requiring entirely separate detection systems.
Solution Approach 2:
The system performs self-diagnosis by comparing its own operational parameters (rotational frequency, direction) against expected values derived from its control inputs (torque commands). This self-service capability enables the motor control system to detect its own abnormalities without requiring external monitoring equipment, reducing overall system complexity.
Data Source
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AI summary
An electric vehicle includes a malfunction detector (37) configured to continuously monitor a torque command from an ECU (21) as well as one of the followings: signals indicating a rotational frequency of a motor unit (6); signals indicating a rotational frequency of a wheel (2, 3) driven by the motor unit (6); signals indicating a rotational direction of the motor unit (6); signals indicating a rotational direction of the wheel (2, 3) driven by the motor unit (6); and a motor current, and detect, according to a predefined rule, a malfunction of the motor unit (6), based on the monitoring information. The electric vehicle also includes a malfunction-responsive controller (38) configured to cause at least one of shut-off of a drive current to the motor unit (6) and braking with a mechanical brake (9, 10), if the malfunction detector (37) detects a malfunction.