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The subsequent development of the permanent UAV

         Recently, the CCTV report US aircraft carriers and nuclear submarines underwater drones have successfully launched. EU Member States and Israel are tight with tension developed UAVs. Because in the future the national airspace will be dominated by UAVs.

         Here under the rare earth permanent magnet used in the UAV:
         With rare earth permanent magnet materials, progressive power electronics, microelectronics, computer, new control theory and electrical theory, technology development of rare earth permanent magnet motor is very fast, in the aviation sector showed a broad prospect and strong vitality.
         Rare earth permanent magnet motor application on aviation has the following characteristics:

        1, due to the high energy product rare earth permanent magnet materials, so the motor can significantly reduce weight, reduce the volume. Aviation motors have very strict requirements for its size, weight. Modern aviation aircraft, each 1 kg weight of the device takes about 15 ~ 30 kg of additional weight to support.

        2, the coercive force Hc of the rare earth permanent magnet material is high, a large remanence Br, which can produce a large air gap flux, the outer diameter of the permanent magnet rotor is greatly reduced, thereby reducing the moment of inertia of the rotor, to reduce the time constant, improve the dynamic characteristics of the motor.
        3, the gap width can choose a larger value, which can reduce the torque ripple caused due to the cogging, torque ripple can be suppressed influence of armature reaction. Armature reaction demagnetization of rare earth permanent magnet for smaller, more suitable for a sudden reversal, blocking drive and other special performance requirements.
        4, using a brushless DC motor also has the following salient features:
        long lasting. Currently widely used on aircraft Brush DC motor, life is only a few hundred hours. With the continuous development of aviation technology, various aviation motor production plant are facing pressure to extend the life of the product technology. When life requirements increase to 1000-2000 hours, brush DC motors its own characteristics has been unable to meet the requirements. Brushless DC motor brushless and commutator, can greatly improve the life indicators.
        Suitable for high-speed operation. The higher the speed, the motor can be made smaller volume weight. But brushed DC motor due to limitations of mechanical commutation, speed is difficult to further improve on the existing basis. Brushless DC motor bearing allowed under the conditions of speed can be doubled.
        High reliability. Increasing altitude commutation cremation, affect the reliability is not conducive to electromagnetic compatibility; altitude increased brush wear, toner affect insulation performance, reduce motor life. These problems do not exist brushless DC motors.
        Heat easily. The main heat source brushless DC motor in the stator, natural heat dissipation good condition. At the same time can be easily cooled oil cooler or in the stator housing, especially through oil or fuel injection cooling can greatly increase the power density of the motor. This brush DC motors are very dangerous.
        Redundant convenient control. Reliability weaknesses brushless DC motor on the controller and the motor winding, the excess of the control method is flexible. Brush DC motor commutation weaknesses, difficult to achieve the degree of control over the output of uniaxial.
        Intrinsic coercivity rare earth permanent magnet material is high, the magnetic field orientation is good, and therefore easy to achieve the establishment of a magnetic field similar to a rectangular wave in the air gap, achieve square wave drive, increase motor output.
        Since the rare earth permanent magnet motor having the above series of advantages, which makes it very suitable for performance, size, weight require special aviation; especially rare earth permanent magnet brushless DC motor, it is considered the most promising aviation motors.


        Second, the rare earth permanent magnet motor application status on aviation

        In developed countries, the rare earth permanent magnet motor applications in aviation has been more widely, domestic lagging behind, so far only a small number of new aircraft models are applied.
        Rare earth permanent magnet motor in the aircraft's main application object for a variety of power for the system. Power actuating system is based on the implementation of elements of the motor drive system, widely used in aircraft flight control systems, environmental control systems, brake systems, fuel oil and starting systems.
        On aircraft using hydraulic actuation system, electricity, air pressure and mechanical four kinds. Wherein the hydraulic actuator system most widely used; however, currently is developing and most promising actuation system is the power for the system. With the development of rare earth permanent magnet materials, high-power semiconductor devices and microprocessors, power actuating system has been developed to the hydraulic actuator system competitive level.
        (1) Flight Control System
        Flight control systems of power actuation system called Power telex actuators, mainly for the airfoil and rudder operation. Divided into electro-hydraulic actuators and electromechanical actuators.
        The mid-1970s, the hydraulic system in the United States helicopter important international events frequently fails, prompting them to rare earth permanent magnet electric steering research and development. US General Electric Company, Vickers company and HR was Alex Bertrand company for the next generation of flight control surfaces developed electro-hydraulic actuators using NdFeB permanent magnet brushless DC motor technology. Developed electromechanical actuator uses a high-voltage DC rare earth permanent magnet brushless DC motor technology and pulse width modulation power converter technology.

        Motor controller receives the control instruction on an airplane flight control computer issued after a three-channel signal processing circuit system rudder servo amplifier, integrated and amplified, and then the output of the servo drive system corresponding angle to manipulate the aircraft rudder and aileron rudder deflection, thereby changing the attitude and heading of the aircraft, the flight control system to achieve automatic control of the aircraft.

        (2) electric environmental control systems
        Electric environmental control system uses electromechanical actuator technology, which is characterized by high-power, high-speed variable speed drive motor. From 1982 the United States began to develop electric steam circulating climate control system, and tested on the P-3 anti-submarine aircraft. The system uses the 30000 ~ 70000 r / min variable speed HVDC rare earth permanent magnet brushless DC motor to drive the compressor. The samarium cobalt permanent magnet motor output 34.3 kW of power at 45000 r / min.
        China also has developed an electric valve electric environmental control system rare earth permanent magnet brushless DC motor, the direct use of the Hall motor rotor position sensor output signal has an indirect measurement of the motor speed, the motor to achieve high accuracy over a wide range varying load conditions stable speed, without the need for pure speed sensors, to solve the original DC brush electrical excitation time series motor-driven electric valve when the control accuracy problems.
        (3) air oxygen system
        Oxygen concentrators advanced aircraft airborne equipment is important, it provides pilots endurance life. At present, only the United States and other four countries have the technology internationally. Our country has been among the ranks of the international advanced technology, the successful development of an oxygen concentrator. The low-speed high-precision motor brushless DC motor steady speed system that uses samarium cobalt permanent magnet excitation, drive the valve to 6 r / min rotation.
        (4) electric braking system
        United States successfully developed electric braking system in 1982, and in the A-10 attack aircraft were tested. 90 years to complete the third generation of electric brake system that uses a high torque samarium cobalt permanent magnet brushless DC motor and pulley worm actuators.

        98 US F-16 fighter flight new electronic braking system. The system of electric actuator using four sets of rare earth permanent magnet brushless DC motor. As a result of low inertia brushless motors and components, electromechanical actuator frequency response up to 20 ~ 30 Hz, while the hydraulic actuator response frequency of only 10 Hz. The electric brake system allows the use of fighter alleviate 22.5 ~ 45kg.

         (5) Fuel Supply System
         Hydraulic systems, hydraulic valves are mostly used in the past brush DC motor drive. Now brushless DC motor. The motor with the pump immersed in the fuel, the controller and the motor body installed with the housing, completely sealed. NdFeB permanent magnet motor with high temperature or samarium cobalt permanent magnet, and a stator core 1J22 high permeability material, with digital closed-loop speed control and soft start function.


        Third, the development trend of aviation rare earth permanent magnet motor

        1, rare earth permanent magnet brushless DC motor
        Since the rare earth permanent magnet brushless DC motor unique advantages, its application in the aircraft speed is also accelerating. Functionality and performance in all to a higher level of development.
        In terms of reliability, redundancy increasing attention. Development redundancy design technology, fault-tolerant control technology, fault reconstruction technology. Of which more than two degrees more common forms of development: parallel and series type. Parallel features are only a fixed inlay put two separate armature windings on the rotor, stator core, each armature windings are connected to each controller, both controllers fully symmetrical fault monitor each other, forming a parallel type dual redundant structure. Tandem-type structure is characterized by two independent motor body coaxially installed with the housing, forming a tandem dual redundant structure; armature winding of each motor are connected to a respective controller, two controllers completely symmetrical with each other fault monitoring, coordination.
        In terms of reducing the size of the weight, using a variety of techniques. One is to increase insulation levels, improve high-temperature magnets against demagnetization. Second is to improve the working speed, using magnetic levitation, air suspension technology; third is to improve the cooling conditions, using circulating water, circulating cold oil, injection cooling, the stator cooling unilateral, bilateral rotor cooling technology.
        In addition, high-power and high-voltage DC is one of the important development direction.
        2, rare earth permanent magnet limited angle torque motor
        The motor can be within a certain range of angles directly drive the load to do a quick movement and precise positioning. Its characteristics are: a limited angle contribute to large, fast, high positioning accuracy, high reliability, small response, light weight. In the motor as the core can be composed of a special high-precision, high-reliability position servo system.
        The system consists of rare earth permanent magnet limited angle torque motor, position sensor and controller of three parts. Wherein the motor includes more than a single degree of permanent magnet rotor and a stator winding dual redundant controller includes a motor winding corresponding dual redundant control circuit. The system can work in dual-redundant or single condition, thereby greatly improving the reliability of the system. When running in the range of ± θ ° angle, the motor can be achieved through a specially designed at the minimum volume output maximum torque, and will receive a very wide frequency response characteristics.

        It is because of the unique advantages of the system, foreign in the late 1980s to carry out research in this area, and has been successfully used in the aerospace field. The system is in flight control systems and electric braking system, the actuator drive as a new direct drive system, direct drive servo actuator valve open, rather than through a gear reduction drive; thereby overcoming reduction wheel drive train system error, reducing the disadvantage of the hydraulic drive system to achieve high-precision, high torque, broadband sound driver.

        3, rare earth permanent magnet brush DC motors
        Brush DC motor is still the most widely used of a motor airplane. Although there are some inherent shortcomings of the motor, but because of its relatively low cost, mature technology, features good, thus still play an important role in some systems, and continue to seek technological progress. Using rare earth permanent magnet excitation can improve power density; the use of more than a variety of forms to improve fault tolerance; using multiple alloy precious metal brushes and commutator improve commutation performance, prolong life; the use of coreless armature structure reduces the moment of inertia.
        4, rare earth permanent magnet linear motor
        Load thrust aircraft hydraulic servo valve, oxygen valve, jettison valves, electric valves, the engine throttle lever and other linear motion occasions is not large, the use of rotary screw worm mechanism or structure just hoping rotary motion into linear motion but not suited to aircraft fast actuation valve high reliability, high frequency response and direct drive performance requirements.

        Hybrid Linear Stepping Motor (Hybrid Linear Stepping Motor, HLSM) is a pulse signal is converted into a micro-step linear movement of digital pulse motor, even under open-loop conditions, no linear displacement sensor, it is possible to achieve precise positioning control. The motor has a simple structure, long stroke, low power consumption, low temperature, easy digital control, no accumulated positioning error, small inertia, interchangeable and can directly drive other obvious advantages.

        The motor is a high torque motor, rare earth permanent magnet sheet is mounted on the stator teeth plane for the air gap, the rotor is designed to form induction. Due to the induction of rotor teeth, this motor is suitable for low speed and high torque applications. The key technologies include reduced thrust fluctuation stability control, end stroke shock and noise cancellation technology.
        5, rare earth permanent magnet generator
        At home and abroad has grown 500 ~ 2000 VA UAV rare earth permanent magnet synchronous generator series, 45 ~ 150 kVA onboard power system with a large capacity of rare earth permanent magnet generator. Air quality in order to meet the growing power needs of high standard, an adaptive complex excitation rare earth permanent magnet generator is the concern at home and abroad. The integration of the characteristics of rare earth permanent magnet generator and electric generator excitation, with high voltage and good self-tuning capabilities.
        6, rare earth permanent magnet Doubly Salient
        Rare earth permanent magnet motor is doubly salient developed on the basis of a switched reluctance motor on a new motor, the stator or implanted rare earth permanent magnet rotor, greater output torque, and has a high reliability and fault tolerance , thus demonstrating a good prospect in the field of aviation.
 
        IV Conclusion
        Although the domestic aviation rare earth permanent magnet motor aspects carried out extensive research, but the speed and scale of the practical application of technology and engineering applications developed countries there are many gaps. The need to increase development efforts in the following areas:
        1, to further improve the reliability, speed up the pace of applications. Especially in rare earth permanent magnet high temperature anti-demagnetization, the control circuit, position sensors more reliability test and exploration;
        2, the development of high-performance rare earth permanent magnet motor control system and servo systems with high precision, wide speed ratio to accommodate high-precision power actuation system needs;
        3. Research excess of (more than three degrees, more than four degrees) electric actuation technology to replace the hydraulic actuator technologies;
        4, research high performance rare earth permanent magnet motor servo system, practical control strategy.
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Hits:  UpdateTime:2015-08-27 20:24:31  【Printing】  【Close

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