Motor Controller A/D Conversion Accuracy Under Low Voltage
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Solution Overview
Problem
Existing motor controllers face inaccuracies in Analog-to-Digital (A/D) conversion when the reference voltage falls below normal levels, leading to poor Signal-to-Noise (S/N) ratios and reduced control accuracy of rotating electric machines, particularly in electric power steering devices during engine restarts after idle stop.
Innovation Solution
A motor controller design incorporating a first regulator to convert the external power source voltage to a higher preset voltage, a second regulator to convert it to an even lower voltage, and a microcomputer with an A/D converter that uses the higher voltage as a reference for accurate conversion, along with a corrector to adjust conversion values based on the second voltage's A/D conversion results, ensuring high accuracy even when the reference voltage is lower than normal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a lower reference voltage (2.5V) is used for A/D conversion when battery voltage falls below 5V, then the A/D conversion can still be performed, but the Signal-to-Noise ratio deteriorates and conversion accuracy decreases
Solution Approach 1:
The patent introduces a first regulator that generates a stable 5V reference voltage as an intermediary, which is then used by the A/D converter regardless of the actual battery voltage level. This mediator reference voltage isolates the A/D conversion process from the fluctuations in battery voltage, allowing accurate conversion even when battery voltage is low.
Solution Approach 2:
The system dynamically changes the reference voltage parameter used for A/D conversion based on battery voltage conditions. When battery voltage is sufficient, the system uses the battery voltage directly; when it falls below a threshold, the system switches to using the regulated 5V reference voltage, thereby optimizing conversion accuracy under varying voltage conditions.
2Use of energy by moving object
If the battery voltage falls below the predetermined voltage value, then the system can continue operation with lower power, but the A/D conversion accuracy deteriorates
Solution Approach 1:
The first regulator acts as an intermediary power conversion stage that takes the fluctuating battery voltage and produces a stable 5V reference voltage for the A/D converter. This allows the A/D conversion to maintain high accuracy even when the battery voltage is low, decoupling the conversion accuracy from the battery voltage level.
3Device complexity
If a single regulator is used to convert battery voltage, then the device complexity is reduced, but the control accuracy under varying voltage conditions cannot be maintained
Solution Approach 1:
The patent segments the voltage regulation function into two distinct stages: a first regulator that converts battery voltage to a stable 5V reference voltage, and a second regulator that generates a lower voltage for the microcomputer core. This segmentation allows each regulator to be optimized for its specific function, with the first regulator dedicated to providing a stable reference for accurate A/D conversion.
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 ensures high accuracy and reliability of motor control by maintaining a high S/N ratio and correcting for errors in A/D conversion, allowing precise control of rotating electric machines regardless of the reference voltage level, thus enhancing the performance of electric power steering devices.
Implementation Method 1
a first regulator which converts an external power source voltage of an external power source to a first voltage that is a preset voltage lower than the external power source voltage and outputs the first voltage
Implementation Method 2
a second regulator which converts the external power source voltage of the external power source to a second voltage that is a preset voltage lower than the first voltage and outputs the second voltage
Implementation Method 3
performs an A/D conversion for the input voltage and the second voltage with reference to the first voltage that serves as a reference voltage
Data Source
AI summary
A motor controller includes, in a microcomputer, a voltage fall determiner determining whether a reference voltage falls from a normal value based on an Analog-to-Digital (A/D) conversion value of a second voltage from an A/D converter, and a corrector (i) calculating a correction coefficient based on the A/D conversion value of the second voltage from the A/D converter and (ii) correcting an A/D conversion value of an input voltage that is output from the A/D converter. A core of the microcomputer generates a control signal based on an input voltage A/D conversion value, when the voltage fall determiner determines that the reference voltage is equal to or higher than a normal reference value. The motor controller keeps its motor control accuracy in such manner, even when a fall of an A/D conversion reference voltage is observed.