Washing Machine Motor Startup Using Sensorless Rotor Rest Position
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Solution Overview
Problem
Existing methods for operating electric motors in washing machines, such as those used in drum drives, often result in jerky startup due to the lack of precise rotor position detection when the motor is re-energized, especially during sensorless operation, leading to inefficient energy use and potential mechanical stress.
Innovation Solution
A method that detects and stores the rotor's rest position when the motor is de-energized using magnetic properties, allowing for sensorless position detection and smooth startup by utilizing the electromagnetic force (EMF) to induce voltage signals, which are processed by a microprocessor control to align the motor correctly at the start of subsequent rotation cycles, eliminating the need for position sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless energizing methods are used to operate the motor, then the device complexity is reduced by eliminating position sensors, but the measurement precision of rotor position deteriorates, causing jerky startup movements
Solution Approach 1:
The patent replaces mechanical position sensors with a sensorless detection method that uses electrical measurements (current profiles) to estimate rotor position. The microprocessor analyzes the current response during voltage application to mathematically determine rotor position without physical sensors, thereby eliminating mechanical components while maintaining position detection capability.
Solution Approach 2:
The patent introduces an intermediary estimation process where the microprocessor uses the current profile as an intermediate measurement to infer rotor position. By applying test voltages and analyzing the resulting current response, the system creates an indirect measurement path that bridges the gap between electrical inputs and mechanical position without requiring direct sensor contact.
2Ease of operation
If the rotor position is not detected when the motor is switched off, then the ease of operation is maintained, but the stability of the motor startup deteriorates due to jerky movements and inability to control startup direction
Solution Approach 1:
The patent performs preliminary detection of the rotor rest position by applying test voltages and analyzing current profiles immediately when the motor is switched off or at standstill. This preliminary action captures the rotor position information before the next startup cycle begins, enabling the control system to prepare the correct energization sequence in advance and ensure smooth, jerk-free startup without requiring continuous monitoring during operation.
3Measurement precision
If the motor is braked or held in a stopped state to prevent coasting, then the position control is improved, but the energy consumption increases
Solution Approach 1:
The patent enables the motor to serve itself by detecting its own rest position through electrical measurements during the natural coasting period after shutdown. Instead of requiring external braking systems or holding forces to maintain position, the motor's own electrical characteristics (current response to applied voltage) provide the necessary information for position detection, eliminating the need for additional energy-consuming control 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
This approach ensures the motor starts in the correct direction without jerking, optimizing rotational movements, reducing energy consumption, and minimizing mechanical stress, while avoiding the need for complex circuitry or additional components.
Implementation Method 1
The magnetic properties of the motor are used for sensing, so that no sensors such as position sensors are required. This is a sensorless position detection of the rotor.
Data Source
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AI summary
The method involves recording rotary speed and position of a rotor (13) that runs in a pre-determined direction using a detection device (15) for controlling individual stator-windings (16u-16w). A resting position (RP) of the rotor in a power-less electrical motor (3) is detected and stored in a continuous manner using the detection device so that the stored position value is utilized for flow of current in the motor, during starting of a succeeding rotary cycle. Voltage that is produced by the stator-windings is utilized as a signal for detection of rotary speed/position of the rotor. Independent claims are also included for the following: (1) a frequency converter that comprises a voltage divider for operating the two-phase or multi-phase electrical motor for driving the drum in the washing machine (2) a washing machine that comprises a brine container.