Sensorless BLDC Motor Drive for Stand Mixer Speed Control
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Solution Overview
Problem
Stand mixers using brushed direct current (DC) motors face reduced motor life and increased maintenance costs due to brush degradation, and existing motor drive technologies struggle with high efficiency and reliable speed control, especially at low speeds.
Innovation Solution
A stand mixer with a synchronous-type motor drive operating in a sensorless field-oriented control (FOC) scheme, utilizing a brushless DC (BLDC) or permanent magnet synchronous motor (PMSM) and a sensorless feedback system with a back electromotive force (EMF) observer to provide accurate position and speed data for efficient control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If brushed DC motors are used in stand mixers, then the motor can provide both low speed high torque and high speed low torque operation, but the brushes break down over time resulting in decreased motor life and increased maintenance costs
Solution Approach 1:
The patent replaces the mechanical brush-commutator system with an electronic commutation system using Hall effect sensors and a microcontroller. The brushless DC motor uses electronic switching of stator windings to achieve commutation without physical contact, thereby eliminating brush wear while maintaining the ability to provide both low speed high torque and high speed low torque operation through electronic control of the motor phases
Solution Approach 2:
The patent changes the operational parameters by using variable frequency drive technology to control the motor speed. By varying the frequency and duty cycle of the PWM signals applied to the motor phases, the system can operate across a wide speed range while maintaining optimal torque characteristics at each speed level, replacing the need for mechanical brush contact
2Device complexity
If sensorless feedback system with observer is used, then speed sensors are eliminated reducing cost and complexity, but accurate position and speed data must be obtained through electrical characteristics processing
Solution Approach 1:
The patent implements a sensorless feedback system using Hall effect sensors to monitor the rotor position and a microcontroller to process electrical characteristics such as back EMF and current measurements. The observer algorithm continuously estimates rotor position and speed by analyzing the electrical characteristics of the motor phases, providing accurate feedback without requiring additional speed sensors
Solution Approach 2:
The patent uses Hall effect sensors as intermediaries to detect rotor position indirectly through magnetic field changes. These sensors provide position information that the microcontroller uses to calculate rotor speed and control the commutation timing, serving as a mediator between the motor's electrical characteristics and the control system's decision-making process
3Ease of operation
If field-oriented control is implemented, then precise torque and speed control is achieved, but complex control algorithms and processing are required
Solution Approach 1:
The patent pre-calculates and stores lookup tables for motor parameters such as back EMF constants, winding resistances, and inductances. The microcontroller uses these pre-computed values to rapidly execute the field-oriented control algorithm without requiring complex real-time calculations, thereby achieving precise torque and speed control while reducing the computational burden during operation
Solution Approach 2:
The patent implements dynamic adjustment of control parameters based on operating conditions. The field-oriented control algorithm dynamically adjusts the d-axis and q-axis current references according to the desired torque and speed commands, allowing precise control across the entire operating range while adapting the control strategy to match the motor's instantaneous state
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 offers a highly reliable and efficient motor drive with reversible three-phase operation, enabling field weakening at high speeds and reducing maintenance costs by eliminating the need for speed sensors, thus enhancing control flexibility and precision.
Implementation Method 1
utilizing a brushless DC (BLDC) or permanent magnet synchronous motor (PMSM) and a sensorless feedback system with a back electromotive force (EMF) observer to provide accurate position and speed data for efficient control
Data Source
AI summary
A stand mixer appliance is provided. In one example implementation, the stand mixer can include a base, a housing, a mixer shaft rotatably mounted on the housing, and a motor assembly. The motor assembly can include a motor drive and a motor operably coupled to the mixer shaft. A controller can be operably coupled to the motor drive. The motor assembly can further include a sensorless feedback system configured to obtain feedback measurements of one or more electrical characteristics from the motor. The feedback system can include an observer configured to process the one or more electrical characteristics and provide data indicative of a position or a speed of the motor. In turn, the controller can operate the motor drive based at least in part on the data indicative of the position or the speed of the motor.