/ Asahi/May 30, 2022Guangzhou -- Under the global trend of environmental protection and industrial automation, the fields of home appliances, commerce, industry and medical have begun to "technological change", and the high-efficiency motor drive technology has gradually renovated the traditional drive applications.
High efficiency motor drive system is equipped with high performance drivers, replacing the low efficiency and low efficiency of the traditional motor, including many internal combustion drive products have been electrified, using the form of motor drive. In the performance optimization of motor drive system, in addition to the characteristics of the motor itself, the driver has a decisive impact on the overall system. MCU, as the control core of the driver, has become the key to the design of high performance driver.
AT32 industrial MCU uses high performance ARM® Cortex®-M4F kernel with floating point operation instructions, Operating frequency up to 288MHz, 512 bytes Zero wait-state Flash, three 12-bit 5.33Msps ADCs, 32-bit resolution count/capture timer, proprietary chip code protection mechanism, and competitive pricing. Especially suitable for motor drive applications, the following will be detailed introduction of AT32 MCU excellent performance characteristics and advantages in motor control applications.
A floating point operation instruction ARM® Cortex®-M4F kernel
In the application of motor vector control, fast and accurate computing power is required, such as coordinate conversion of voltage/current vector, position velocity current control, rotor pole position estimation in sensorless control and so on. AT32 MCU Cortex-M4F core floating-point arithmetic can easily achieve these algorithms, and has the ability to high-speed arithmetic and improve arithmetic accuracy.
Ii. 288MHz high-speed main frequency
The world's martial arts, only fast not broken. AT32 MCU working frequency up to 288MHz, leading other equivalent MCU in the industry, with Cortex-M4F core operation, with fast and efficient algorithm capabilities. Especially in servo control applications, the need for high frequency sampling rate of fast current/speed/position and other control loop calculation, AT32 MCU can easily competent, and can retain MCU executive margin to provide other auxiliary function program operation, such as communication functions and so on.
The high speed clock frequency also allows the pulse width modulation PWM to reflect the advantages of high resolution. Because the driver adjusts the output pulse voltage by the pulse width to change the motor current, the PWM resolution determines the ability to control the voltage amplitude of the motor. The higher the PWM frequency, the better the control analysis of the voltage phase and the reduction of the motor current ripple. The diagram in Figure 2 illustrates how the resolution and frequency of the PWM signal affect the current. But at the same frequency, the higher the PWM resolution, the lower the PWM frequency, because the product of the two is compared with the system frequency, so the high clock frequency can take into account the PWM resolution and frequency at the same time, especially in the application of hundreds of thousands of revolutions of motor drive, because the motor speed is fast, the current frequency is high, the inductance of the motor coil is small, need to provide high frequency, high analytic PWM voltage, Can make the motor efficient and stable operation.
Three, zero wait Flash
High frequency MCU is fast, but without high speed memory, the overall execution efficiency will be limited by the Flash instruction capture speed. Although the critical program segment can be moved to SRAM, it will reduce the available SRAM space and increase the program complexity. AT32 MCU has built-in Flash elastic mapping function. As shown in Figure 3, when MCU is started, the Flash data in the mapped area will be automatically moved to ZW(zero wait-state) memory block, and the maximum zero-wait Flash can be used is 512k byte. With the perfect cooperation of Cortex-M4F core, 288MHz high master frequency and zero-wait Flash, MCU can achieve the ultimate performance. In addition, although zero-wait Flash is not designed for cost-effective MCU series, Yatli Technology specially optimizes its pre-fetch and catch buffer architecture and operation mechanism to ensure that the execution efficiency is equivalent to zero-wait Flash in most execution situations.
Four, high-speed 12-bit ADC
In the motor control application, the current state of the motor must be sensed in real time to carry out high-speed current loop control operation. Especially in the single resistance current sampling, the current return credit number must be read in a very short time (<1us) to avoid noise, as shown in FIG. 4. Real-time sensing of DC BUS voltage or motor terminal voltage is also required, so high-speed ADC peripheral support is required. In addition, 12-bit ADC is a reasonable choice for both analysis and cost in order to accurately obtain highly analytic current and voltage information. AT32 MCU has a 12-bit ADC with a sampling rate up to 5.33MHz, and has 24 external channels designed to provide sufficient signal sampling requirements related to motor control.
5. Count/capture timer with 32-bit resolution
In the application of servo controller, in order to meet a wide proportion of high and low speed control, as well as accurate speed and positioning control, it is common to use more than 20-bit high resolution encoder, so MCU needs a 32-bit timer with 4 times the frequency of the encoder signal. In addition, in the low-cost application of sensing rotor position using Hall element, under the consideration of low speed operation conditions, limited by the count range of 16-bit capture timer, the timer timing frequency must be properly de-frequency, but this will sacrifice the speed resolution of the motor at high speed. In view of this, AT32 MCU designed two sets of 32-bit resolution count/capture timers, which can meet the needs of high level servo controller and low cost driver applications.
Six and three sets of advanced timers
Advanced timer used to output three-phase complementary PWM signal is an indispensable unit of MCU in motor control applications. Three groups of 16-bit resolution advanced timers are designed. Combined with the fast computing power of MCU and the fast sampling of ADC, the three-axis motor control system can be easily realized.
7. Communication peripheral support
As the motor drive is widely used in various professional and life fields, in order to meet the communication needs of different products, its communication interface is also very diverse. AT32 MCU built in multiple groups of UART, CAN, I2C, SPI and USB interface, can meet most of the product communication needs. Among them, AT32WB415 series adopts low power (BLE) Bluetooth 5.0, integrates Bluetooth radio frequency (RF) transceiver and baseband function, which is composed of wireless communication MCU, providing the best solution for various iot applications.
Viii. Elastic DMA channel mapping
There are many MCU peripherals used by motor drivers, which often need real-time processing. It is a common method to use DMA channel for real-time update of specific location data. However, due to the large use of MCU peripherals, it is inevitable to encounter the dilemma of DMA channel conflict. The DMA channel configuration is more flexible, you can assign a peripheral DMA request channel to any of the 22 channels in the three DMA controllers, greatly improving the flexibility and convenience of application.
Nine, patent chip code protection mechanism
AT32 MCU has multiple chip security protection measures, including absolute read protection (RDP), random number Flash burning, and Attrix's self-developed sLib(security library) function, can specify the scope to password protect a specific program area, such as upstream vars to protect the core algorithm, Can be provided to downstream customers to do secondary program development. When external extended SPI NOR Flash is burned and expanded through MCU, the program and data in this section will be scrambled numerically encrypted by the chip's internal hardware, which provides comprehensive protection for MCU code.
In addition to the consideration of MCU performance and function, the price is also an important factor in the selection of MCU. AT32 MCU has a strong price competitiveness. The whole series adopts Cortex®-M4 and M0+ cores, among which some M4 kernel products are comparable in price to M0+ MCU. For customers to design cost-effective and high quality motor drive products to provide the possibility.
