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With the development of artificial intelligence and Internet of Things, traditional home appliances transform toward intelligence gradually, among which the smart upgrade of washing machine has greatly improved the quality of life. At present, washing machine manufacturers integrates smart washing, high efficiency and energy saving, large capacity, ultra-thin embedding process, extremely silent experience and clothing care functions into the core competitiveness to cope with the energy efficiency requirements, which undoubtedly brings higher challenges to the motor control technology.

As the core of motor control system, microcontrollers are in charge of diverse control requirements and high performance. With excellent performance and perfect motor development ecology, Artery’s AT32 MCU family provides motor control solutions for washing machine, scooters, electric motorcycles and other motor-driven products, and such microcontrollers have been put into mass production.

Efficient drive capability and accurate control

The AT32F421 series aims to replace and promote traditional Cortex®-M0/M3-based solutions, and it imports high-speed mainstream platform based on Cortex®-M4 architecture, which integrates rich peripherals, fast and efficient algorithm and high cost performance to cater to smart household appliances, motor control and industrial automation, such as meeting accuracy, efficiency and safety requirements of washing machine motor control.

The AT32F421 series operates at a frequency of up to 120 MHz and features 64 KB Flash memory and 16 KB SRAM to complete FOC algorithm and current regulating rapidly. Its high PWM frequency and resolution guarantee efficient and stable motor running, which further improves washing and energy-saving performance. The AT32F421 series also expands one high-speed rail-to-rail input/output analog voltage comparator to reduce BOM and achieve overcurrent protection so that the washing machine can respond to abnormal situations rapidly and protect the product and users.

In addition, the AT32F421 series embeds one high-speed 2 Msps 12-bit ADC to achieve the minimum sampling time of 54ns and total conversion time of 0.5 us at 28 MHz. It is suitable for one-shunt sensing drivers, and it samples within a very short sampling time window, which make it competent for washing machine control loop computing. It provides high frequency sampling rates in current, speed and position control loops, thus to ensure stable and accurate operation of the washing machine.

High efficiency motor upgrades laundry performance and user experience

Direct drive control

The washing machine drive control solution based on AT32F421 MCU uses DD (direct drive) technology to connects the motor directly to the wash basket or drum, instead of traditional belt or gear driving, thus to realize efficient and accurate power transmission. This kind of technology reduces energy loss and running noise, and improves response speed and washing efficiency. Direct drive motor is excellent in washing cycle control to ensure that clothes are properly cleaned and extend the service life of washing machine.

Thanks to the compact design of direct drive motor, the washing machine size can be minimized while the drum capacity is not affected. Without belt and wheel system, the direct drive washing machine reserves more space for the drum and internal structure to guarantee the maximum washing capacity in the same machine size, making it the best choice for small-sized houses.

Deep field weakening control algorithm

Since the low/medium spin speed options are dominant during the washing cycles, the motor design usually focuses on optimizing low-speed performance to balance torque and efficiency. However, the dehydration speed is generally between 800 to 1600 rmp, far below the requirement for high-speed performance. Different from regular control strategy, the deep field weakening control algorithm used by AT32F421 MCU-based solution for washing machine tunes Id and Iq according to the real-time speed and load to guarantee smooth increase of motor running speed and eliminate step changes in speed regulation. This innovation not only meets the requirements of dehydration mode for high-speed, efficient and stable operation of motor, but also improves the user experience, making the washing machine quieter and smoother when dewatering at high speed.

Automatic weighing and detection

Users always require that the washing machine can automatically give the appropriate water level according to the weight of clothes to avoid unclean washing or water/electricity costs. To improve weighing accuracy and reduce costs, the AT32F421 MCU-based solution for washing machine provides high-performance CPU computing capability to automatically detect and calculate the weight of clothes with the algorithm far more accurate than the industry requirements, reducing waste of water and ensuring that clothes are well cleaned without damages to the fabric. In addition, intelligent weighing is easy to operate, that is, just put clothes into the drum and select the desired washing program.

Off-balance detection

Off-balance due to an unequal load of washing is a common problem during spin cycle. The AT32F421 MCU can detect unbalanced load in real-time manner through sensors and algorithm, and selects a control solution according to the detection result. The washing machine can automatically adjust the washing program, for example, re-balance before dewatering or change the water flow direction to reduce vibration to ensure stable washing operation. In addition, the AT32F421 MCU supports diagonal eccentricity detection as a supplement to eccentricity detection for real-time monitoring and adjusting eccentricity changes due to movement of clothes during washing.

Motor ecosystem

Artery provides motor control algorithm library BSP package to build its motor control development ecosystem, which includes encoder, sensored/sensorless FOC sine-wave control mode, and six-step BLDC control, supporting Hall state self-learning, automatic identification of motor winding parameters, and current PI controller parameter auto tuning. Its motor monitoring PC software provides a user-friendly UI debugging interface to allow users to monitor real-time motor running parameters, status and dynamic waveforms to help online tuning and debugging of control parameters. Such powerful development toolkit and easy-to-use motor control algorithm library BSP package help developers to work out high efficient motor control solutions, involving square-wave drive, FOC sine-wave drive, Hall sensor feedback and sensorless feedback. Artery’s motor control development ecosystem improves development efficiency of smart home appliance manufacturers, fastens product mass production and speeds the time to market.

Furthermore, AT32 MCU guarantees safety of household appliances. Artery has obtained IEC 60730 certification for functional safety, and provides Class B software library to assist customers in product certification and cost effectiveness, which significantly enhances the stability and security of the product from the hardware underlying architecture level, and lays a solid foundation for market access and consumer trust.