Sensorless Motor Controller for Turbo-Molecular Pump
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Solution Overview
Problem
Existing sensorless motor control methods struggle to accurately estimate rotation angle and rotational speed, especially in low-speed ranges due to instability in coil resistance and inductance values, leading to inaccurate motor control.
Innovation Solution
A motor controller system that includes a rotation angle estimation unit, speed calculation unit, drive signal generating unit, and switching circuit, which uses binarization, d-axis/q-axis voltage calculation, and two-phase to three-phase conversion to generate drive signals for accurate motor control without sensors, and incorporates a low-pass filter and differentiator for stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless control method is used to reduce device complexity, then device complexity is reduced, but measurement precision of rotation angle and rotational speed deteriorates
Solution Approach 1:
The patent introduces an intermediary calculation process that uses easily measurable quantities (coil voltage and current) combined with binarization of rotation angle signals to derive rotational speed. This intermediary approach avoids direct sensor measurement while maintaining precision through mathematical transformation of the estimation data.
Solution Approach 2:
The patent transforms the rotation angle estimation into a binarized signal and uses this transformed parameter to calculate rotational speed. By changing the parameter representation from continuous angle estimation to binary signal processing, the system achieves higher precision in speed measurement without additional sensors.
2Device complexity
If conventional speed calculation method is used to simplify the control system, then device complexity is reduced, but measurement precision of rotational speed deteriorates in low-speed range
Solution Approach 1:
The patent performs preliminary binarization of the rotation angle estimation signal before speed calculation. This preliminary processing step prepares the data in an optimized form that enables accurate speed measurement even at low speeds, where conventional methods fail.
Solution Approach 2:
The patent replaces conventional mechanical speed sensing with an electronic signal processing approach. By substituting physical sensors with electronic binarization and period calculation based on voltage and current measurements, the system achieves precise speed measurement without mechanical components.
3Device complexity
If coil resistance and inductance values are treated as constants to simplify calculation, then calculation complexity is reduced, but measurement precision of rotation angle and rotational speed deteriorates
Solution Approach 1:
The patent extracts and eliminates the problematic dependency on coil resistance and inductance constants from the speed calculation process. By removing these unstable parameters from the calculation chain and relying instead on direct voltage and current measurements with binarization, the system achieves precision without needing accurate constant values.
Data Source
AI summary
A motor controller comprises: a rotation angle estimation unit for estimating and computing a rotation angle of a motor repeatedly based on the current and voltage of the motor without using a motor rotation angle detector; a speed calculation unit for calculating the period of the signal waveform of the rotation angle that is repeatedly estimated and calculated by the rotation angle estimation unit and for calculating an actual rotational speed of the motor based on the period; a drive signal generating unit for generating a drive signal to drive and control the motor based on at least a deviation between the actual rotational speed and a target rotational speed and the rotation angle; and a switching circuit that is switched based on the drive signal to provide drive power to the motor.