Electric Pump PWM Frequency Signaling for Motor Failure Detection
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Solution Overview
Problem
Existing electric pumps face challenges in efficiently monitoring motor states during abnormal stopping, as current methods burden the processing capacity of the ECU by requiring recognition of both frequency and duty ratio changes in PWM signals.
Innovation Solution
The electric pump employs a control unit that sets the frequency and duty ratio of PWM signals outside normal ranges when the motor stops abnormally, allowing for detailed monitoring without increasing processing load by using distinct frequencies and duty ratios for normal and abnormal states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If both frequency and duty ratio of PWM signal are changed to indicate motor state, then measurement precision of motor state is improved, but device complexity increases due to burden on ECU processing
Solution Approach 1:
The patent segments the PWM signal parameters into two distinct functions: duty ratio indicates motor rotational speed (normal operation), while frequency indicates motor state (normal/abnormal/stop). This segmentation allows the ECU to process only one parameter (duty ratio) during normal operation, reducing processing burden while maintaining detailed state detection capability through frequency changes when abnormalities occur.
Solution Approach 2:
The patent utilizes parameter changes by assigning different meanings to PWM signal parameters under different operating conditions. During normal operation, only duty ratio varies with rotational speed. When abnormality or stop occurs, frequency changes to indicate the specific state. This dynamic parameter assignment enables detailed state monitoring without continuously burdening the ECU with dual-parameter processing.
2Reliability
If frequency band for abnormal state is distinct from normal state, then reliability of failure detection is improved, but loss of time increases due to frequency recognition requirement
Solution Approach 1:
The patent implements dynamics by making the PWM signal characteristics adaptive to motor operating conditions. During normal operation, the signal maintains a standard frequency with duty ratio varying according to rotational speed, enabling fast recognition. When abnormality or stop occurs, the frequency dynamically changes to a distinct band, providing reliable failure detection. This dynamic adaptation ensures both fast normal operation recognition and reliable abnormal state detection.
Data Source
AI summary
An electric pump includes a pump, a motor configured to drive the pump, a motor drive unit having a switching element and configured to drive the motor with electric power output from the switching element, and a control unit configured to output a pulse width modulation (PWM) signal for driving the switching element to the motor drive unit. The PWM signal output from the control unit, is used for monitoring a state of the motor. When the motor stops abnormally, the control unit sets a frequency of the PWM signal for use in monitoring the state of the motor to a frequency outside of a frequency band which is used when the motor is normal.