Motor driving apparatus and laundry treatment machine including the same
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Solution Overview
Problem
In laundry treatment machines, the use of analog filters for high-frequency signal injection in sensorless motor control leads to measurement delays, making accurate position estimation challenging, especially at low motor speeds and high frequencies.
Innovation Solution
A motor driving apparatus with an inverter, output current detector, filter, and inverter controller that compensates for filtering delays through high-frequency signal injection, using a band pass filter and adjusting the delay compensation value based on motor speed and signal frequency to estimate the motor's position accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an analog filter is used to measure harmonic current through high-frequency signal injection, then the signal to noise ratio is improved, but the measured signal experiences delay
Solution Approach 1:
The patent applies preliminary action by calculating the filtering delay of the analog filter in advance based on its transfer function and the injection signal frequency. This pre-calculated delay value is then used to compensate for the timing error in position estimation before the final control action is taken, thereby resolving the contradiction between using the filter for SNR improvement and the delay it introduces.
2Measurement precision
If high-frequency signal injection is used for sensorless control at low speed, then position estimation accuracy is improved, but the harmonic current level decreases making measurement difficult
Solution Approach 1:
The patent introduces an analog filter as an intermediary component between the current detector and the position estimation unit. This filter amplifies the harmonic current signal caused by high-frequency injection, effectively increasing the signal level for easier measurement. The filter acts as a mediator that enables accurate detection of the weak harmonic signals at low speeds without requiring expensive high-precision analog-to-digital converters.
3Measurement precision
If the delay compensation value is increased to compensate for filtering delay, then position estimation accuracy is improved, but the system complexity increases
Solution Approach 1:
The patent replaces complex real-time delay compensation mechanisms with a simplified calculation approach. Instead of using complex adaptive filters or iterative compensation algorithms, the system substitutes the delay compensation with a straightforward calculation based on the known analog filter transfer function and injection signal frequency. This mathematical substitution simplifies the control algorithm while maintaining position estimation accuracy.
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
This solution enables accurate sensorless control of the motor by effectively compensating for filtering delays, improving position estimation accuracy as motor speed increases, thereby enhancing the performance of laundry treatment machines and other applications.
Implementation Method 1
an inverter to convert a direct current (DC) voltage into an alternating current (AC) voltage and to output the AC voltage to the motor
Implementation Method 2
The filter may pass high-frequency output current corresponding to high-frequency signal injection of the output current
Data Source
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AI summary
Disclosed herein are a motor driving apparatus (220) and a laundry treatment machine (100) including the same. The motor driving apparatus (220) includes an inverter (420) to convert a direct current (DC) voltage into an alternating current (AC) voltage and to output the AC voltage to the motor (230), an output current detector (E) to detect output current flowing in the motor (230), a filter (570) to filter the detected output current, and an inverter controller (430) to control the inverter (420). The inverter controller (430) outputs an inverter switching control signal based on high-frequency signal injection, estimates a position of a rotator of the motor (230) based on the filtered output current and a delay compensation value for compensating for filtering delay of the filter (570), and outputs the inverter switching control signal based on the estimated position, thereby compensating for a delay error due to the filter (570) upon position estimation through high-frequency signal injection in a sensorless method.