Adaptive observer Technology: a breakthrough to solve the difficult problems of brush and brushless?

The traditional brush motor control uses mechanical commutator and brush to realize motor control. The control is simple, but it is easy to produce sparks, high noise, short service life and poor reliability. Compared with brushless DC motor control technology, because it often uses back EMF to detect rotor position through zero, it is easy to realize commutation, but it will lead to problems such as high noise, large torque fluctuation, poor efficiency and difficult to detect back EMF at low speed;

At present, it is a common solution to use the FOC control scheme of Brushless DC motor instead of the traditional brush control scheme, but there will be corresponding control difficulties. For example, because the common synovial observer is very sensitive to motor parameters, it is difficult to achieve good driving effect without detailed and complex software and hardware matching debugging when debugging the driving motor with the observer. In order to solve this difficult control problem, Fengyi technology has independently developed an AO adaptive observer, which can not only start the same program and be compatible with various types of motors, but also realize the ultra-low speed without out of step of the motor.

The chip embedded with AO adaptive observer, such as Fengyi fu6861q2, is a special chip for high-performance motor drive integrating motor control engine (me) and 8051 core. 8051 core handles conventional affairs, me handles motor real-time affairs, and dual cores work together to realize various high-performance motor control. Most of the instruction cycles of the 8051 core are 1t or 2T. The chip integrates high-speed operational amplifier, comparator, high-speed ADC, multiplier / divider, CRC, SPI, I2C, UART, various timer, PWM and other functions. It has built-in high-voltage LDO, which is suitable for square wave, SVPWM / SPWM and foc drive control of BLDC / PMSM motor.


Figure 1 fu6861q2 package pin diagram


Figure 2 functional block diagram of fu6861q2

What are the advantages of vacuum cleaner control scheme using adaptive observer?

A. Strong compatibility and high robustness

Traditional household vacuum cleaners are gradually replaced by more convenient handheld vacuum cleaners. The power supply mode of lithium battery has become a performance point of great concern. High efficiency motor design is very important to the endurance of vacuum cleaner battery. In order to design the best vacuum cleaner, the vacuum cleaner manufacturer will often adjust the motor turns or structure. If the traditional synovial FOC scheme is adopted, since the angle is observed based on the motor model, the adjustment of motor parameters will lead to the need to re match the whole start, operation and efficiency.


Measured dust collection models 3

Fengyi technology Ao adaptive observer has strong compatibility. We measured 8 different vacuum cleaner motors, including V45, V55 and v65. Using the same product board and a set of fixed programs, each motor can start smoothly, and the estimator will not lose step at zero speed.

B. Higher efficiency and lower noise

The driving angle is adaptively corrected by the built-in adaptive observer to realize the optimal angle driving. According to the actual measurement, the maximum efficiency of V45 vacuum cleaner can reach 56% (as shown in Figure 4), while the efficiency of traditional vacuum cleaner is generally about 42% ~ 52%. Therefore, the adaptive observer makes the scheme more efficient and significantly improves the endurance of lithium battery powered handheld vacuum cleaner.



Figure 4 PQ test of vacuum cleaner

The measured noise spectrum of 1-pole, 200W and 7-leaf vacuum cleaner shows that the harmonic component of FOC noise is significantly less than that of square wave driving mode (as shown in Fig. 5 and 6), which is better than the traditional brush and square wave control vacuum cleaner scheme. Note: the two noise spikes in the figure come from 7-octave wind noise and 2-octave wind noise brought by fan blades.


Fig. 5 noise spectrum of vacuum cleaner driven by foc

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Fig. 6 noise spectrum of vacuum cleaner driven by square wave

C. Dual core drive for ultra-high speed

Only 5.6us for a single me core to complete a FOC operation. For the ultra-high speed application of 2-pole vacuum cleaner, the maximum speed will reach 150kHz, and the electrical frequency will exceed 5KHz. At this time, the carrier frequency should be at least about 50KHz. This brings a great test to the estimation speed of FOC. For the pure software FOC of ordinary single chip microcomputer, it is difficult to meet the demand of high-speed motor, while the dual core drive chip of Fengyi technology can realize ultra-high speed. In the practical application scheme of vacuum cleaner, the measured electrical speed is close to 300kpm and can operate stably (as shown in Figure 7).


Fig. 7 2 waveform of polar vacuum cleaner with electrical speed close to 290krpm

D. The scheme has the advantages of low cost, few peripheral devices and simple circuit

The vacuum cleaner scheme of fu6861q2 is adopted. Due to the high integration of the chip, the peripheral components are reduced, the cloth board area is saved, and the scheme helps customers realize a smaller and compact product structure. With the reduction of BOM cost, the product will have more competitive advantages

Figure 9 Application PCB

E. Configure rich development tools

In addition, in order to better support customers in developing vacuum cleaner products, Fengyi provides perfect product development tools, such as:

SPI debugging simulator: the angle of estimator, sampling current and other information can be observed in real time to judge whether the estimation and sampling are abnormal. As shown in Figure 10, when the sampling is abnormal, the red part shows the real sampled current waveform of SPI, and the blue part shows the actual phase current waveform. It can be seen that there is an obvious signal sampling error( The sampling current error here is caused by the small minimum sampling window); As shown in Figure 11, SPI and actual phase current waveforms during normal sampling can be seen that they are completely consistent.

Development and test demo board: Fengyi has also designed a demo for vacuum cleaner customers to simulate the product board. Customers can drive their own motor in the fastest way, can roughly understand the performance of the product at the beginning of product development, and greatly shorten the development cycle.


Fig. 10 SPI waveform when sampling is abnormal (red indicates SPI display sampling waveform, and blue indicates actual phase current waveform)


Fig. 11 when the sampling signal is normal, the sampling current fed back by SPI will be completely consistent with the actual phase current

In the application field of high-speed vacuum cleaners, Fengyi technology has rich experience and high market share, and has sustainable iterative optimization strategies on issues such as efficiency, noise, robustness, compatibility and temperature rise. We will make unremitting efforts to help customers improve quality and performance, reduce scheme design and development cycle and enhance overall competitive advantage.

Scan the code to watch: video of vacuum cleaner control scheme

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