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Brushless DC motor and its control technology developmentJ.S.LawlerUniversity of Tennessee Knoxville,Tennessee UDC 621.313:620.178.53Abstract: This article introduces brushless DC component and its development situation, analyses the current brushless DC motor for further in-depth research problems, and points out the development direction.Keywords: Brushless DC motor; Review; Control; Electronic commutation circuit; The rotor position detection circuit1 IntroductionWith its excellent DC torque characteristic motion control to widely, but common DC motivation to change and mechanical brush, but poor *, etc. When in the electromagnetic interference and noise, the impact of the DC motor control system in further applications. With shortcomings overcome machinery commutation, electronic commutation replace machinery commutation brushless motors. In 1955 arrison D.H America as the first application in transistors replaced machinery commutation circuit, marks the patent brush brushless motor modern. And electronic commutation brushless DC motor, is really into practical stage in 1978 MAC classic brushless DC motor and the driver. Later, the international brushless DC motor is studied, has developed square-wave brushless motor brushless DC motor and the sine wave. For more than 20 years, permanent new materials, microelectronics technology, automatic control technology and electronic technology, especially the power switch device, brushless motor development to progress. Brushless DC motor has been originally with electronic commutation DC motor, there is normally BLDCM external characteristics of electronic commutation motor.Brushless DC motor keep the traditional DC good dynamic and static characteristics, and the speed of simple structure, easy operation and control. The application of military industry, from initial to aerospace, medical appliance, information, and the rapid development in industrial automation. Translated from Izmeritelnaya Tekhnika,No.10,pp.35-37,October,1995.0543-1972/95/3810-1131512.50 9 Plenum Publishing CorporationThe structure, and have BLDCM, brushless DC motor stator windings as the armature winding consists of permanent magnetic materials and excitation replaced. Armature current waveform into different, can be divided into BLDC motor (BLDCM) torque-current DC motor (sine waves and new all-digital fuzzy), electronic BLDCM commutation replace original DC motor machinery commutation, magnetic materials, saves the brush to make the rotor, But new all-digital fuzzy is replaced by permanent magnet synchronous motor rotor windings, saves the excitation of field winding, sliping and brush. Under the same conditions, the driver circuit was easier to control, square, a simple application to extensive new all-digital fuzzy BLDCM.Brushless DC motor by electronic commutation circuit commonly, the rotor position detection circuit and motor is composed of three parts, electronic ontology commutation circuit control and driven by general part of rotor position detection, and position sensors usually use to finish. When the work place, the controller of motor rotor position sensors in each driver circuit orderly trigger power tube, orderly, to drive in DC motor. From the three parts of brushless motivation of its development were analyzed.2 Each component of development2.1 Motor ontologyBrushless dc motor electromagnetic structure and a BLDCM are basic and same, but it is the armature winding put on weight of the stator, rotor adoptted, simplify the structure and improve the performance, so that it can be * * to enhance sexual. Brushless permanent magnet motor development and development is inseparable, magnetic materials development process basically has the following several development stages experience: aluminum nickel-cobalt, ferrite materials, NdFeB (NdFeB). With high energy and nd-fe-b magnetic materials appear caused a revolution. The third generation of nd-fe-b materials, further reducing the motor with copper, prompted brushless motors to efficiency, miniaturization, energy development direction.At present, to improve the motor power density, transverse magnetic field, its permanent magnet motor stator tooth and armature coils space position, the main motor are perpendicular to the motor axial magnetic flux, the structure to improve the circulation of air-gap flux density, can provide more than most traditional motor output torque. This type of motor is in research and development stage.2.2 Electronic commutation circuitControl circuit, brushless dc motor control power switching device driver circuit to control motor speed, steering, and protect the torque motor, including over-current, over-voltage, overheating protection, etc. Control circuit, control circuit of initial analogue simpler. Digital circuit, many hardware work can be directly by software, can reduce the hardware circuit and improve its, also can improve the control circuit and control circuit of anti-jamming ability by analog circuits to digital circuits.At present, control circuit commonly application-specific integrated circuit, microprocessor and digital signal processor, three form. For motor control requirements of high places, by professional IC component control circuit is simple and practical method, Digital signal processor arithmetic faster, peripheral circuit, system composition is simple, less, can * brushless dc motor composition, performance greatly improved greatly simplified and motor miniaturization and intelligent, and digital signal processor is the development direction of control circuit.Driving circuit, drive circuit output power: the armature winding motor drive, and controlled in control circuit. By the power switch device driver circuit. It appears, thyristor motor from a brush to brush leap. But the thyristor is only have control through, without the ability to shut off the controllability of switching devices, and the lower frequency switch, cannot satisfy the brushless dc motor performance further improved. Power electronic technology rapid development, appeared all-controlling power switching device, which can be shut off the transistor (GTO), electric field effect transistors MOSFET), metal bar (bipolar transistors IGBT module, integrated the thyristor (in) and new development in recent years IGCT enhanced grid transistors into electronic IEGT. These devices, the corresponding improving performance brushless motor driving circuit is also obtained a rapid development. At present, all-controlling switching device is substituting route complex function indexes, huge volume, low ordinary thyristor and drive circuit from linear amplification convert pulse width modulation circuit switch state, from power tube division circuit to integrated circuits, modular driving circuit for intelligent, high-frequency, miniaturization, created conditions.2.3 Rotor position detection circuitBrushless motor is a closed loop mechatronics system, it is the rotor position as a signal switch poles of electronic circuit, the accurate detection of rotor position, and the rotor position of power switching devices in brushless dc motor, is the normal operation of the key.Use a position sensor to the rotor position detection device is as the most direct and efficient method. General will position sensor installed on the rotor shaft, realize real-time detection of rotor position. Magnetoelectric sensor is the earliest position, heavy and complicated, have been eliminated, Currently magnetic susceptibility type hall position sensor is widely applied in brushless dc motor, another photoelectric position sensor. Position sensor, increase weight of brushless dc motor and the structure size is smaller, Rotation sensors are worn, and not easy maintenance, At the same time, the sensor sensitivity and installation accuracy directly affect motor operating performance, Another, transmission, easy to introduce interference signals too much, Is the collection signal, hardware more reduced system. In order to adapt to the further development of brushless motors, sensorless arises at the historic moment, it generally use the armature winding back emf induction by magnetic rotor position indirectly, and direct method, saves the position sensor, simplify the structure of ontology, the motor to good effect, and a wide range of applications. But back emf for detecting position sensorless brushless motors, resting not back emf, how is the motor start smoothly to solve the problem.In recent years, people put forward a new kind of sensorless brushless motor, it is used to detect the rotor position back emf, stick on the rotor surface of conductive materials, the use of magnetic stator winding high-frequency switch when working on the magnetic materials, eddy current open phase voltage size varies with the rotor position, can open testing phase voltage to judge the rotor position, the sensorless brush motor overcome the brushless motor position usually start and low operation problem, but the methods of motor, need special motor manufacturing high requirements proposed.3 Resarch problems3.1 Torque rippleAt present, brushless dc motor with the main problem is saved torque ripple. Torque pulsation of the deposit, brushless dc motor servo system is restricted, especially the application of direct drive applications, torque motor speed control characteristics to worsen. Especially for audio-visual equipment, film machine, computer of brushless dc motor, smooth operation, no more requirements. Inhibit or eliminate torque servo system to improve performance as the key.Torque ripple reason mainly has: the cogging effect and flux distortion caused by torque ripple, Harmonic cause torque ripple, The armature equivalent inductance, caused by change current torque ripple. At present, universities and research institutions simulating torque ripple in-depth study of the problems, according to different causes various inhibit or weaken the torque ripple method, from different extent brushless motor to improve performance. These are the original structure, and puts forward some solutions and not weaken or compensation method from the principle of eliminating the torque ripple. Torque ripple remains to further study.3.2 Sensorless rotor position detectionSensorless rotor position detection methods are mainly: back emf, free-wheeling diode, inductive method and the state observation method. Among the most common method of back emf is the most widely used and methods. But this method is based on the principle of armature reaction on deposit, brushless motor, power error, the armature reaction for air-gap flux density effect more apparent, the error is bigger. Another, motor start-up and low back emf, zero or small, hard to detect the rotor position back emf, sensorless brushless motor save the startup problem 9. How the brushless motor, power back emf method to compensate the rotor position error caused by signal, and how to overcome the problem of motor startup method of emf is urgent. The startup problem, commonly used in other ways to start again after switch to run position sensor.4 Brushless DC motor of development1831, Faraday discovered electricity induction phenomenon, laid the foundation of modern basic theory. In the nineteen forties has successfully developed the first direct motivation, experience about 17 years time, dc motor technology to mature. With the application of dc motor, the demand is higher and higher, the mechanical commutation devices limit the contact a BLDCM on many occasions. In order to replace a BLDCM brush - commutator structure of machinery, people have to do long-term exploration. In 1915, americans Langnall invented with the grid control mercury arc rectifier, made by direct exchange of inverter unit change. In the 1930s, someone with ion of the motor stator windings device realized according to the rotor position of so-called motor commutator, but due to the motor of poor reliability and low efficiency, the device bulky and complex and no use value.Rapid development of science and technology, electronic semiconductor technology. Switch the successful development of transistors, to create a new dc motor - brushless dc motor with life. In 1955, the americans first put forward by Harrison thyristor commutation replace motor brush contact line of thought, this is the rudiment of brushless dc motor. It consists of power amplifier, signal detection, and the magnetic circuit components, such as transistors switch, its principle of work is as the rotor spinning, winding in signal of periodic signal emf induction emf respectively, and signal transistor turns to achieve through commutation. Problem is, first of all, when rotor spinning, winding signal not do not produce induction emf, transistors, unbiased power cannot feed, so the windings of the brushless dc motor not start torque, Secondly, due to the frontier steepness signal emf, the power transistor.In order to overcome the drawback of above, people used centrifuge device, or using the commutator during the stator is placed on surface-mounted auxiliary method to ensure the reliable starter motor. But the former structure is complex, which requires additional start pulse. After repeated experiments, and constantly practice, people found the use of electronic commutation circuit position sensor and instead of BLDCM are mechanical commutation device, thus for dc and a new way of development.In the 20th century to the early 1930s, switch position sensor, electromagnetic resonant position sensor and high-frequency coupling position sensor field, then appeared magnetoelectricity coupling and photoelectric position sensor. The rapid development of semiconductor technology, make people in 1879 americans found hall hall effect happened again, after years of hard work, and finally in 1962 has successfully trial-produced using hall element to realize the commutation of brushless dc motor. In the early 1970s, has successfully trial-produced using more than a thousand times hall componets of high sensitivity of magnetic susceptibility diode realize around the commutation of brushless dc motor. In various position sensor, people try to seek a position sensor structure without attachment of brushless dc motor. In 1968, the German W.M ieslinger proposed move to realize the capacitance of a new method. On this basis, the germans R.H anitsch successfully trial-produced using digital annular splitter and zero discriminators combinations to realize sensorless phase to the brushless dc motor.In recent years, Chinas small and medium-sized motor and micro &special motor industry development is rapid, table 1 is 2002-2006 in motor industry sales and earnings of incomplete statistics. Among them, because of brushless dc motor with high efficiency, long life and low noise and has better torque - speed characteristics, advantages in automotive, aerospace, household appliances, industrial manufacturing areas such as well.Tab.3 2002-2006 sales and sales income and motor statisticsTab.3 2002-2006 sales and sales income and motor statisticsvintage20022003200420052006Product sales /104kW356263197847970210950Product income / million69873110858471560933218228126861471) Cars with brushless DC motorAs a kind of quick and convenient traffic tools already and peoples life. A car usually includes dozens of internal to hundreds of motor car, as to energy saving and environment protection, including the development direction of brushless dc motor, efficient permanent magnet motor car in good application prospects. Table 1-3 is the motive power of electric vehicle performance, we can see that belongs to the permanent magnet motor brushless dc motor in the electric car driver has very good technical advantages.Tab.4 EV compared with motor performanceTab.4 EV compared with motor performancemotorperformanceDc motorInduction motorPermanent magnet motorSwitched reluctance motorPower densitylowmiddlehigherhighPeak efficiency /%909095959790Loading efficiency /%8087909285977886Controllablesimple controlmore complexweak magneticmore complexReliabilitygeneralgoodoptimalgoodBut you need to be aware that position sensor installation and use, can increase the cost of general motors, and the influence of brushless dc motor control system reliability and the working life, additional sensor in motor, still can increase internal motor cars, and the volume of motor volume has strict requirements and restrictions. Therefore, the sensorless brushless dc motor control of the study is very necessary.2) Aerospace use brushless dc motorDue to its aviation motor applications particularity, the general requirements of small size, use simple structure. Brushless dc motor of special structure characteristics and sensorless control mode in the aerospace field widely applied for.Space of brushless dc motor with variable load operation conditions for running, general requirement is high control accuracy and the dynamic response ability, the typical applications are gyro and mechanical arms control, etc. They closed or by half speed closed-loop feedback control, corresponding systems commonly used advanced control algorithm.3) Brushless dc motor in the application of household appliancesIn recent years, the electrical appliances electronic motor with every year about 30% of growth development, modern appliances in energy saving, low noise and high reliability, intelligent direction. With the improvement of peoples living standard and the countrys growing importance of energy conservation and emission reduction, many household appliances motor but choose brushless d