How Adaptive Observer Technology Enables Highly Robust Vacuum Cleaner Control Schemes
“The traditional brushed motor control uses a mechanical commutator and a brush to realize the motor control. The control is simple, but it is easy to generate sparks, and has high noise, short life and poor reliability. Compared with the brushless DC motor control technology, because it often uses the back EMF zero-crossing to detect the rotor position, it is easy to realize commutation, but it will cause problems such as large noise, large torque fluctuation, poor efficiency, and difficult detection of low-speed back EMF. .
Adaptive observer technology: a breakthrough to solve the difficult problems of brushed and brushless?
The traditional brushed motor control uses a mechanical commutator and a brush to realize the motor control. The control is simple, but it is easy to generate sparks, and has high noise, short life and poor reliability. Compared with the brushless DC motor control technology, because it often uses the back EMF zero-crossing to detect the rotor position, it is easy to realize commutation, but it will cause problems such as large noise, large torque fluctuation, poor efficiency, and difficult detection of low-speed back EMF. ;
At present, it is a common solution to use the brushless DC motor FOC control scheme instead of the traditional brushed control scheme, but there will be corresponding control difficulties. When the observer debugs the driving motor, it is difficult to achieve a better driving effect without detailed and complex software and hardware matching and debugging. In order to solve this difficult control problem, FengG Technology has independently developed an AO adaptive observer. Using this observer, the same program can not only start compatible with various types of motors, but also achieve ultra-low speed without losing synchronization.
Chips embedded in AO adaptive observer, such as: Peak GFU6861Q2, is a high-performance motor drive dedicated chip integrating motor control engine (ME) and 8051 core. The 8051 core handles routine transactions, and the ME handles motor real-time transactions. High performance motor control. Most of the 8051 core instruction cycles are 1T or 2T, and the chip integrates high-speed operational amplifiers, comparators, high-speed ADCs, multipliers/dividers, CRC, SPI, I2C, UART, various TIMER, PWM and other functions, built-in high-voltage LDO , suitable for square wave, SVPWM/SPWM, FOC drive control of BLDC/PMSM motors.
Figure 1 FU6861Q2 package pin diagram
Figure 2 Functional block diagram of FU6861Q2
What are the advantages of a vacuum cleaner control scheme using an adaptive observer?
A. Strong compatibility and high robustness
Traditional household vacuum cleaners are gradually being replaced by more convenient hand-held vacuum cleaners. The power supply method of lithium batteries and battery life have become the performance points that everyone is very concerned about. High-efficiency motor design is critical to the battery life of the vacuum cleaner. In order to design a vacuum cleaner in the best state, vacuum cleaner manufacturers will often adjust the number of turns or structure of the motor. If the traditional sliding film FOC scheme is used, since the angle is observed based on the motor model, the adjustment of the motor parameters will lead to the entire startup and operation. and efficiency need to be rematched.
Peak G Technology AO Adaptive Observer has strong compatibility. We tested 8 different vacuum cleaner motors, including V45, V55, V65, 3 common vacuum cleaner motors of different sizes, using the same product board + a set of fixed , each motor can start smoothly, and the estimator will not lose step at zero speed.
Figure 3 Several of the vacuum cleaners tested
B. Higher efficiency and lower noise
The drive angle is adaptively corrected by the built-in adaptive observer to realize the optimal angle drive. The maximum efficiency of the V45 model vacuum cleaner can reach 56% (as shown in Figure 4), while the efficiency of traditional vacuum cleaners is generally around 42%~52%. Therefore, the adaptive observer makes the solution more efficient, and brings a significant improvement to the battery life of the lithium battery-powered handheld vacuum cleaner.
Figure 4 Vacuum cleaner PQ test
The measured noise spectrum of a 1-pole, 200W, 7-blade vacuum cleaner shows that the harmonic component of FOC noise is significantly smaller than that of the square-wave driving method (as shown in Figures 5 and 6), which is better than the traditional brush and square-wave controlled vacuum cleaner solutions. Note: The two noise peaks in the figure are derived from the 7-fold wind noise and the double-frequency wind noise brought by the fan blades.
Fig.5 Noise spectrum diagram of vacuum cleaner driven by FOC
Figure 6. Noise spectrum of vacuum cleaner driven by square wave
C, dual-core drive to achieve ultra-high speed
It takes only 5.6us for a single ME core to complete a FOC operation. For the ultra-high-speed application of a 2-pole vacuum cleaner, the maximum speed will reach 150KRPM, 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 FOC estimation speed. For the pure software FOC of ordinary single-chip microcomputers, it is difficult to meet the needs of high-speed motors. However, the dual-core driver chip of FengG Technology can achieve ultra-high speed, which is used in the practical application of vacuum cleaners. In the scheme, the measured electrical speed is close to 300KPM, and it can run stably (as shown in Figure 7).
Figure 7 2-pole vacuum cleaner, the electrical speed is close to the waveform of 290KRPM
D. The cost of the solution is low, the peripheral devices are few, and the circuit is simple
The vacuum cleaner solution using FU6861Q2, due to the high integration of the chip, reduces the number of peripheral components, saves the layout area, helps customers achieve a smaller and more compact product structure, reduces the cost of the solution BOM, and the product will have a more competitive advantage
Figure 8 Scheme comparison diagram
Figure 9 Application PCB
E. Configure rich development tools
In addition, in order to better support customers in developing vacuum cleaner products, FengG provides complete product development tools, such as:
SPI debugging simulator: You can observe the estimator angle, sampling current and other information in real time to determine whether the estimation and sampling are abnormal. As shown in Figure 10, when the sampling is abnormal, the red part is the current waveform displayed by the SPI, and the blue part is the actual phase current. waveform, it can be seen that there are obvious signal sampling errors. (The reason for the sampling current error here is that the minimum sampling window is too small); as shown in Figure 11, when the sampling is normal, the SPI and the actual phase current waveform can be seen to be in complete agreement.
Develop and test DEMO board: Feng G also designed a DEMO for vacuum cleaner customers to simulate the product board. Customers can drive their own motors in the fastest way, and can roughly understand the performance of the product at the beginning of product development, greatly shortening the time development cycle.
Figure 10 SPI waveform when sampling is abnormal (red is the SPI Display sampling waveform, blue is the actual phase current waveform)
Figure 11 When the sampling signal is normal, the sampling current fed back by the SPI and the actual phase current will exactly match
In the field of high-speed vacuum cleaner applications, FengG Technology has rich experience and a high market share, and has sustainable iterative optimization strategies in terms of efficiency, noise, robustness, compatibility, temperature rise and other issues. Committed to helping customers improve quality performance, reducing the design and development cycle of the program, and enhancing the overall competitive advantage, we will make unremitting efforts.