Motor Driving Device Noise Filtering for Vacuum Pump Stability
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Solution Overview
Problem
Conventional motor driving devices for vacuum pumps, such as turbo-molecular pumps, face challenges in accurately estimating the magnetic pole position and rotational speed due to harmonic noises in detection signals, leading to fluctuations in the calculated electrical angle and steady-state errors, which affect driving stability and efficiency.
Innovation Solution
A motor driving device with an inverter, arithmetic sections for calculating rotational speed and magnetic pole electrical angle, and a PWM signal generating section to control switching elements, utilizing counter electromotive voltage calculations in both fixed and rotating coordinate systems to improve accuracy and stability, and a delay correcting section to address phase delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional arc tangent operation is used to calculate estimated electrical angle, then calculation is simple, but waveform fluctuation is great and steady-state error occurs
Solution Approach 1:
The patent introduces an intermediary low-pass filter between the detection signals and the arc tangent operation. This filter removes harmonic components (PWM carrier components and other noises) from the two-phase ac signals Eα and Eβ before they are used to calculate the electrical angle, thereby reducing waveform fluctuation and steady-state error while maintaining the simplicity of the arc tangent calculation method
Solution Approach 2:
The patent extracts and removes the harmful harmonic components from the detection signals using a low-pass filter. By separating the fundamental rotational component from the harmonic noises, the system achieves more accurate electrical angle estimation without complicating the overall calculation structure
2Device complexity
If rotational speed is calculated directly from two-phase ac signals, then calculation is straightforward, but noise affects accuracy and steady-state error occurs
Solution Approach 1:
The patent introduces a low-pass filter as an intermediary component to process the two-phase ac signals before rotational speed calculation. This filter eliminates noise and harmonic components, allowing the direct calculation method to maintain its simplicity while achieving accurate rotational speed measurement by filtering the input signals
3Measurement precision
If electrical angle calculation utilizes periodicity, then accuracy is improved, but harmonic noises still cause fluctuations
Solution Approach 1:
The patent places a low-pass filter as an intermediary between the periodic detection signals and the electrical angle calculation process. This filter preserves the periodicity needed for accurate angle estimation while removing harmonic noises that cause waveform fluctuations, thereby achieving both accuracy and noise rejection
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 enhances the accuracy of magnetic pole position estimation and rotational speed calculation, reducing steady-state errors and improving driving stability and efficiency by effectively filtering noise and correcting phase delays.
Implementation Method 1
a counter electromotive voltage arithmetic section for calculating a first counter electromotive voltage in a fixed coordinate αβ system based on the information about the motor phase voltage and the information about the motor phase current
Implementation Method 2
a converting section for receiving the magnetic pole electrical angle through feedback and converting the first counter electromotive voltage into a second counter electromotive voltage in a rotating coordinate dq system based on the magnetic pole electrical angle
Implementation Method 3
a PWM signal generating section for generating a PWM control signal for controlling an ON/OFF state of the plurality of switching elements based on the sinusoidal wave driving command
Data Source
AI summary
A motor driving device comprises an inverter, a first arithmetic section, a driving command generating section and a PWM signal generating section. The first arithmetic section calculates a rotational speed and a magnetic pole electrical angle of a motor rotor based on information about a motor phase voltage and information about a motor phase current. The first arithmetic section includes a counter electromotive voltage arithmetic section, a converting section, a second arithmetic section, a third arithmetic section, and a fourth arithmetic section. The first arithmetic section outputs a sum of the magnetic pole phase error and the integrated value as the magnetic pole electrical angle.