Brushless Motor Drive AD Converter Error Diagnosis
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Solution Overview
Problem
Existing brushless motor drive devices face challenges in accurately diagnosing faults in AD converter circuits and current detection circuits, leading to errors in rotation speed and torque calculations, which affect air volume and noise control in cooling fans.
Innovation Solution
A brushless motor drive device that includes an RC filter, a pulse output circuit generating a pulse signal with changing frequency, and an AD-conversion-error calculation unit to diagnose and correct AD converter circuit errors, allowing for high-precision current value detection and reduced rotation errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pulse voltage is applied to an RC filter for diagnosing clock generation circuit faults, then clock generation circuit reliability is improved, but AD converter circuit fault diagnosis capability deteriorates because the method cannot detect AD converter errors
Solution Approach 1:
The patent divides the diagnosis process into two distinct segments: (1) applying pulse voltage to the RC filter for clock generation circuit diagnosis, and (2) applying a known voltage signal to the AD converter input for AD converter diagnosis. This segmentation allows each circuit to be diagnosed independently with appropriate test signals, resolving the contradiction between clock circuit reliability checking and AD converter fault detection capability.
Solution Approach 2:
The patent introduces an intermediary test signal - a known voltage signal applied to the AD converter input - that serves as a mediator to diagnose AD converter faults. This intermediary signal allows the system to verify AD converter functionality without interfering with the RC filter-based clock generation circuit diagnosis, enabling both diagnosis capabilities to coexist.
2Device complexity
If the AD converter circuit is not diagnosed, then device complexity is reduced, but rotation speed and torque calculation precision deteriorate due to undetected conversion errors
Solution Approach 1:
The patent implements preliminary diagnosis action by testing the AD converter with a known voltage signal before actual motor operation. This preliminary check detects potential conversion errors in advance, allowing the system to establish correction values that will improve rotation speed and torque calculation precision without adding complex ongoing diagnostic mechanisms.
Solution Approach 2:
The patent establishes a feedback mechanism where the AD converter diagnosis results are used to generate correction values that are applied to subsequent measurements. This feedback loop allows the system to continuously improve measurement precision by compensating for detected conversion errors, resolving the contradiction between simplicity and precision.
3Measurement precision
If correction values are generated for AD converter errors, then current value detection precision is improved, but device complexity increases due to additional correction mechanisms
Solution Approach 1:
The patent implements self-service by having the system automatically diagnose its own AD converter and generate correction values without external intervention. The control unit performs the diagnosis, calculates correction values, and applies them automatically, improving current value detection precision while minimizing the need for additional complex external correction mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables precise fault diagnosis and correction of AD converter circuits, reducing rotation errors and torque errors, resulting in improved air volume and noise control in cooling fans, enabling smaller and lighter fan designs.
Implementation Method 1
an RC filter including a resistor and a capacitor... the AD-conversion-error calculation unit calculates the conversion error based on the difference between the output value of the AD converter circuit produced in response to the input of a voltage of the capacitor
Data Source
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AI summary
A brushless motor drive device includes the following: an inverter circuit configured to energize and drive the winding of a brushless motor; a current detection circuit configured to detect the current value of the winding; a control unit configured to control the rotation of the motor; and an RC filter including a resistor and a capacitor. The control unit includes the following: a drive control unit configured to generate a signal to drive the inverter; a clock generation circuit configured to generate a clock pulse to be used as a reference for an operation period; a pulse output circuit configured to generate a pulse signal with a changing frequency based on the clock pulse and to apply the pulse signal to the RC filter; an AD converter circuit connected to the capacitor of the RC filter and the current detection circuit; and an AD-conversion-error calculation unit configured to calculate the conversion error of the AD converter circuit. The AD-conversion-error calculation unit calculates the conversion error based on the difference between the output value of the AD converter circuit produced in response to an input of the voltage of the capacitor and an AD-converted value calculated from the charging time of the capacitor.