Washing machine appliance with sensorless speed detection and temperature compensation
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Solution Overview
Problem
Washing machine appliances face challenges in accurately measuring the rotational speed of the basket without dedicated speed sensors, leading to potential inaccuracies and increased complexity or cost with existing solutions.
Innovation Solution
A method and apparatus that utilize a controller to activate and regulate the motor, measure the rotational speed of the basket, and apply an offset based on ambient temperature monitoring to ensure accurate speed measurement within a predetermined range, eliminating the need for dedicated speed sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated speed sensor is installed to measure rotational speed, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the speed measurement function from a dedicated speed sensor and relocates it to the existing motor controller. The controller measures rotational speed by monitoring motor phase currents and using back-EMF characteristics, eliminating the need for separate speed sensing hardware while maintaining measurement capability.
Solution Approach 2:
The motor controller is designed to perform multiple functions: motor control, current regulation, and speed measurement. By integrating speed measurement into the existing controller infrastructure, the system achieves multi-functionality without adding dedicated speed sensing components, thereby reducing overall device complexity.
2Device complexity
If no dedicated speed sensor is used to reduce complexity, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent replaces mechanical/electrical speed sensing mechanisms with a software-based measurement approach. The controller uses mathematical models and signal processing algorithms to calculate rotational speed from motor phase currents and back-EMF signals, substituting physical sensors with computational methods to achieve accurate measurement without additional hardware.
Solution Approach 2:
The system changes the measurement parameters by using electrical parameters (phase currents, back-EMF voltages) instead of mechanical parameters (encoder positions, tachometer signals). This parameter transformation allows the existing controller to derive speed information from electrical measurements, maintaining precision while reducing hardware complexity.
3Measurement precision
If temperature compensation is applied to correct speed measurement at high temperatures, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system performs preliminary temperature compensation by pre-calculating and storing correction factors in lookup tables during manufacturing. The controller reads appropriate compensation values from these pre-prepared tables based on measured temperature, avoiding complex real-time compensation calculations and simplifying the control algorithm while maintaining measurement accuracy.
Solution Approach 2:
The patent uses a simple temperature sensor with basic compensation algorithms rather than complex temperature monitoring systems. The compensation approach uses straightforward lookup tables and linear corrections, representing a simple, low-cost solution that adequately addresses temperature effects without requiring sophisticated thermal management infrastructure.
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 allows for accurate rotational speed measurement of the basket in washing machines, enhancing precision and reducing costs by leveraging the controller's temperature monitoring and internal oscillator adjustments, thus avoiding unnecessary deceleration and improving operational reliability.
Implementation Method 1
measuring the rotational speed of the basket with the controller
Implementation Method 2
monitoring an ambient temperature inside the cabinet of the washing machine appliance
Data Source
AI summary
A washing machine appliance includes a cabinet with a basket rotatably mounted within the cabinet and a motor configured to rotate the basket. The washing machine appliance also includes a controller in operative communication with the motor to regulate a speed of the motor. The controller may be configured for, and methods of operating the washing machine appliance may include, activating the motor to rotate the basket at a rotational speed within a predetermined speed range and measuring the rotational speed of the basket with the controller. The controller may also be configured for, and the method may also include, monitoring an ambient temperature inside the cabinet of the washing machine appliance and applying an offset to the measured rotational speed when the monitored ambient temperature exceeds a threshold.