The development of new technologies has brought new opportunities for development in the motor control industry, from the development of control theory


The development of new technologies has brought new opportunities for development in the motor control industry. From the aspects of the development of control theory, the development of power electronics technology, and the application of computer technology in the field of control, combined with the current status, the introduction of domestic and foreign industries latest progress. In particular, ASICs, DSP digital signal processing, and FPGAs have made remarkable progress in recent years, bringing new opportunities to motor control systems.
Keywords motor control vector control digital signal processor programmable gate display xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

The rapid development of electronic technology (including large-scale integrated circuit technology, power electronics technology and computer technology) in the late 20th century and the perfection of modern motor control theory and the maturing of the simulation industry have greatly promoted the basic unit motor that is used as an electromechanical energy conversion. With the development of control technology, the impact of this development on all walks of life is enormous. After entering the 11th century, the combination of electronic technology, computer technology, and motor control technology has become even more obvious, and the promotion of motor technology has grown at a faster rate. This article summarizes the new opportunities brought about by the development of these new technologies for motor control. From the application of control theory, controllers, power electronics and microcomputer technology, combined with the current state of motor control, the latest technological advances in these fields at home and abroad are introduced. Looking ahead, we hope to help you understand and track the latest technology and information in the field of motor control and grasp the direction of the industry.

First, the motor control theory

Since the seventies induction motor vector transformation control method has been proposed, it has obtained rapid development so far. The main idea of ​​this theory is to simulate the asynchronous motor into a direct current machine and control the excitation current component and the torque current component of the motor through the coordinate transformation method, so as to obtain the same good dynamic speed regulation characteristics as the direct current motor. This control method is now more mature, has been productized, and the product quality is relatively stable. Because this method adopts coordinate transformation and requires fast and complex mathematical operations, it has high requirements on the operation speed and processing capability of the controller. The development of microcomputer technology provides good external conditions for vector transformation control. . In recent years, around the defects of vector transformation control, such as the complexity of the system structure, nonlinearity and the influence of changes in motor parameters on the performance of the system, domestic and foreign scholars have conducted a lot of research.

In 1985, Professor Depenbrock of Germany proposed a new control method, namely asynchronous motor direct torque control system. It is the result of the above study. It does not require coordinate transformation, nor does it need to rely on a rotor mathematical model, which is theoretically very attractive. A prototype with a very high performance index has also been made under laboratory conditions. However, there are still some problems that have not been resolved, such as low-speed torque observers and rotational speed fluctuations, which have not been productized. Nowadays, in the market, the system that claims to have implemented direct torque control mostly uses a method that combines flux linkage with direct torque control. At low speeds, it adopts flux-oriented vector control and direct torque control at high speeds. . Or observe the rotor flux at the same time as a correction of the direct torque control system. It is difficult to determine the timing for this kind of method to switch smoothly. At present, scholars at German universities are studying this issue; secondly, if the flux-oriented vector control is used at low speeds, or the method of observing the rotor flux is used, it still depends on the rotor parameters. In other words, as long as the components of the rotor flux are inside, it is still more sensitive to the rotor parameters. Can not reflect the advantages of direct torque control. It seems that full torque direct control is still some distance away from productization.

In addition, the sliding mode variable structure control technology based on modern control theory, nonlinear decoupling control using differential geometry theory, and model reference adaptive control method were introduced, which improved the system performance. However, these theories are still based on the precise mathematical model of the object, and some require a large number of sensors and observers. Therefore, the structure is complex, and some still cannot get rid of the effects of nonlinearity and changes in the motor parameters. Therefore, it is necessary to further explore and solve the above problems. way.

Looking at the history of the motor industry, there are theoretical breakthroughs in almost every major development. However, as a more mature motor control theory, it is not easy to propose an epoch-making theory. Therefore, for a considerable period of time, various existing theories will be combined to complement each other, or the theories and methods of other disciplines will be introduced into motor control, taking the interdisciplinary road to solve the above problems. In recent years, smart control research has been active and has been applied in many fields. Typical examples are fuzzy control, neural network control, and expert system-based control. Because the intelligent control does not require the exact mathematical model of the object and it has strong robustness, many scholars have introduced the intelligent control method into the research of the motor control system, and predicted that the next decade will create a new era of power electronics and motion control. The more mature is the fuzzy control, which has the advantage of not relying on the exact mathematical model of the controlled object, overcoming the influence of non-linear factors, and having strong robustness to the parameter changes of the regulating object. Fuzzy control has achieved satisfactory results in AC and DC speed control systems and servo systems. Typical applications include: fuzzy controller for motor speed control; application of fuzzy logic in motor model and parameter identification; optimal control of asynchronous motor efficiency based on fuzzy logic; intelligent inverter based on fuzzy logic. In recent years, there have been some literatures discussing the introduction of neural network control or expert systems into direct torque control systems for asynchronous motors, and I believe there will be practical results soon.

Second, the motor controller

With good control methods, you also need controllers that can implement them. High reliability and good real-time performance are basic requirements for the control system. The original motor control was an analog circuit using discrete components. Later, with the advancement of electronic technology, ICs and even motor control application-specific integrated circuits were cited in motor control. Most of these circuits were analog-digital hybrid circuits, which greatly improved the The reliability and anti-jamming capability of the motor controller have also shortened the development cycle of new products and reduced the development cost. Therefore, it has developed rapidly in recent years.

As an important aspect of Application Specific Integrated Circuits (ASICs), almost all major semiconductor manufacturers in the world have provided their own special integrated circuits for motor control. Therefore, there are many kinds of specifications for motor control application specific integrated circuits, and product data and application data are very rich. But at the same time, because there is no uniform standard among manufacturers, products are extremely dispersed and new products are constantly appearing. In order to meet the needs of a design, it often takes great effort and time to collect and collate data. The current development of motor control is increasingly diversified and complicated. Existing dedicated integrated circuits may not be able to meet demanding requirements for new product development. For this reason, they may consider developing their own dedicated motor control chips. Field programmable gate arrays (FPGAs) can be used as a solution. As a development device, FPGA can be easily modified many times. In simple analogy, FPGAs are comparable to ASICs as EPROMs are to mask ROMs. Due to the very high degree of integration of FPGAs, a few FPGAs have few thousands of equivalent gates, and as many as tens or hundreds of thousands of equivalent gates. Therefore, an FPGA can realize very complicated logic, replacing the circuit composed of multiple integrated circuits and discrete components. It uses the Hardware Description Language (VHDL or Verilog HDL) to design the system. The hardware description language abandons the traditional method from the gate level up to the overall system. It uses three levels of hardware description and design style from top to bottom (starting from the system function description). It can simulate three levels of descriptions, so that digital circuit design can be easily performed. The specific level and its simple introduction are as follows: The first layer is behavior description, mainly function description, and can perform functional simulation; the second layer is RTL description, which is mainly the description of logical expression, and performs RTL level simulation; It is the gate level description, which is described with the basic gate circuit, and corresponding gate level simulation. Finally, generate the gate-level network table, and then use a special tool to generate the FPGA programming code point, and then you can program the FPGA. After successful trial production, if mass production is required, the ASIC chip can be customized according to the design of the FPGA to reduce costs. There are articles on the feasibility of this aspect. Interested readers can refer to it.

The emergence of motor control application specific integrated circuits has far-reaching impact on motor control. It has greatly promoted the development of the motor control industry. The market prospect is very broad. Unfortunately, domestic integrated circuit manufacturers have not yet been able to occupy this market. Share.

With the advancement of technology, especially with the widespread popularity of digitalization today, people will not be satisfied with staying in the era of analog-digital mixing.

Nowadays, the more common frequency converters in the market are mostly controlled by single-chip microcomputers. The 8096 series products are more commonly used. However, the processing capability of the single-chip microcomputer is limited. For the system adopting the vector transformation control, due to the large amount of data that needs to be processed, the real-time performance and accuracy requirements are high, and the single-chip microcomputer cannot meet the requirements. People naturally think of digital signal processors (DSPs). In recent years, the performance of various integrated single-chip DSPs has been greatly improved, software and development tools have become more and more, and they have become better and better; prices have been greatly reduced, and low-end products are now approaching the price level of microcontrollers. And it has a higher performance-cost ratio than the microcontroller. As a result, DSP devices and technologies are easier to use and the price can be accepted by a wide range of users. More and more microcontroller users began to use DSP devices to improve product performance. The timing of DSP devices to replace high-end microcontrollers is ripe.

DSP digital signal processing devices have a higher degree of integration than microcontrollers. DSP digital signal processing has a fast CPU, a larger capacity of memory, built-in baud rate generator and FIFO buffer, providing high-speed, synchronous serial port and standard asynchronous serial port. Some on-chip integrated A/D and sample/hold circuits provide PWM output. What is even more different is that DSP devices are RISC (Reduced Instruction System Computer) devices. Most of the instructions can be completed within one instruction cycle. With parallel processing technology, multiple instructions can be completed in one instruction cycle. DSP digital signal processing uses an improved Harvard architecture with independent program and data space allowing simultaneous access to programs and data. Built-in high-speed hardware multiplier, increased multi-stage water level, DSP devices have high-speed data computing capabilities. The single-chip microcomputer is a complex instruction system computer (CISC), and most instructions are completed in 2 - 3 instruction cycles. The microcontroller can adopt the Neumann structure. Programs and data are accessed in the same space, and instructions or data can only be accessed individually at the same time. ALU can only do addition. Multiplication needs to be implemented by software, so it takes up more instruction cycles, which means that the speed is slower. Therefore, the structural differences make the DSP device 8-10 times faster than a 16-bit single-chip instruction execution time and 16-30 times faster to complete a multiplication operation. Simply put, it is the DSP device that has strong computing power and the microcontroller has a strong transaction processing capability. DSP devices also provide a highly specialized instruction set that improves the speed of FFT Fast Fourier Transforms and filters. In addition, DSP devices provide JTAG (JointTsetActionGroup) interface, with more advanced development tools, batch production test more convenient.

In order to seize the share in the vast motor control market, major DSP manufacturers have introduced their own embedded DSP motor control circuit. For example, Texas Instruments Inc., which accounts for 45% of the DSP market share, has introduced DSP-TMS320C24x (TMS320F24x on-chip ROM for erasable) dedicated to motor controllers. The new TMS32024x DSP uses TI's T320C2xLP 16-bit fixed-point DSP core and integrates a motor event manager, which features electronic control of the motor steering in the best possible way. The device leverages TI's reusable DSP core technology to demonstrate TI's unique capabilities to create DSP solutions for a variety of applications by integrating a DSP core and its digital and mixed-signal peripherals on a single chip. The TMS320C24x is the first dedicated DSP series of digital motor controllers that supports motor steering, command production, control algorithm processing, data exchange, and system monitoring. The combination of an integrated DSP core, an optimized motor controller event manager, and a monolithic A/D design can provide a single-chip digital motor control solution. The TMS320C240 in the family includes a 20NIPS DSP core, an event manager, two serial ports, a pair of 10-bit A/D converters, a 32-bit digital I/O system, a monitoring calculator, a low-voltage monitor and A 16K character fast part memory, which utilizes TMS320's fixed-point DSP software development tools and JTAG emulation support, allows motor control developers to easily move from a microcontroller to a new DSP. The United States analog equipment (AD) company is not far behind, with the famous intel company to produce ADMC3xx series motor control dedicated DSP, performance and TI's products are not much difference, but also based on AD's 16-bit fixed-point DSP core ADSP2171 to design It also integrates a three-phase PWM generator (16-bit) and A/D converter. Other well-known manufacturers of DSPs are Motorola and NEC. Another benefit of using DSP-based motor control ASICs is that they can reduce the requirements for peripheral devices such as sensors. Through a complex algorithm to achieve the same control performance, reduce costs, high reliability, is conducive to the confidentiality of patented technology. Using a DSP integrated chip for motor control to implement a sensorless brushless DC motor control using a Kalman filter algorithm is a typical example.

Sometimes, the system requires more control such as human-computer interaction and printing. A DSP is not competent. At this time, a single-chip microcomputer can be used to process transactions and a DSP can handle heterogeneous multi-processor systems for operations. However, doing so not only increases the load of synchronization and communication between the two processors, but also deteriorates the real-time performance of the system and prolongs the system development time. At this point, using Tricore is a good way to solve the problem. It integrates the capabilities of microprocessors, microcontrollers, and digital signal processors on a single chip, so that it can monolithically solve most of the engineering problems encountered.