Rare Earth Permanent Magnet Motors (REPMs) are mainly used in various electric systems on aircraft. An electric braking system is a drive system having an electric motor as its actuator. Widely used in aircraft flight control systems, environmental control systems, braking systems, fuel and starting systems.
Due to the excellent magnetic properties of rare earth permanent magnets, a strong permanent magnetic field can be established without additional energy after magnetization. The rare earth permanent magnet motor made by replacing the electric field of the traditional motor is not only high in efficiency, but also simple in structure, reliable in operation, small in size and light in weight. It can not only achieve high performance (such as ultra-high efficiency, ultra-high speed, ultra-high response speed) that cannot be achieved by traditional excitation motors, but also can manufacture special motors that meet specific operating requirements, such as elevator traction motors, special motors for automobiles, etc.
Aircraft use four braking systems: hydraulic, electric, pneumatic and mechanical. The hydraulic actuation system is the most widely used one, but the most promising is the electric actuation system. With the development of permanent magnets, high power semiconductors and microprocessors, electric braking systems have evolved to compete with hydraulic braking systems.
Flight control system
The electric actuation system used in the flight control system is also called electric fly-by-wire actuator, which is mainly used for the operation of wings and rudders. It is mainly divided into electrohydraulic actuators and electromechanical actuators. In the mid-1970s, the hydraulic system of American helicopters frequently failed during important international events, prompting them to research and develop rare earth permanent magnet electric actuators. An electrohydraulic actuator developed by General Electric, Vickers and HR Dextran incorporates neodymium-iron-boron permanent magnet brushless DC motor (NdFeB PMBLDCM) technology for use in the next generation of flight control rudders. The electromechanical actuator developed uses high voltage permanent magnet brushless DC motor technology and pulse width modulation power converter technology.
The motor controller receives control instructions from the flight control computer on the aircraft, and processes, synthesizes and amplifies the signals through the servo amplifier of the three-channel rudder loop system, and then drives the output angle of the corresponding rudder to control the rudder angle. The rudder and ailerons of the aircraft change the attitude and direction of the aircraft and realize the automatic control of the flight control system of the aircraft.
Electric environmental control system
The electric environmental control system uses electromechanical drive technology, which is characterized by high-power, high-speed variable-speed drive motors. Since 1982, the United States has developed an electric steam cycle environmental control system and tested it on the P-3 anti-submarine aircraft. The system uses a 30000-70000 r/min variable speed high voltage rare earth permanent magnet brushless DC motor to drive the compressor. The samarium cobalt permanent magnet motor can output a power of 34.3 kilowatts at a speed of 45000 r/min.
Air oxygen generation system
Oxygen concentrators are critical onboard equipment for advanced aircraft, providing life support to pilots. Currently, only four countries, such as the United States, have the technology. Our country has been among the internationally advanced ranks of this technology, and has successfully developed an oxygen generator. The motor used is a speed stabilization system of a low-speed high-precision brushless DC motor. Samarium cobalt permanent magnet excitation is used to drive the valve to rotate 6r/min.
Electric braking system
The electric braking system was successfully developed in the United States in 1982 and tested on the A-10 attack aircraft. In 1990, the third-generation electric braking system was completed. It adopts a strong moment cobalt permanent magnet brushless DC motor and pulley worm actuator. In 1998, the F-16 fighter jet adopted a new electronic braking system. Four rare earth permanent magnet brushless DC motors are used in the system's electric actuators. Thanks to the use of brushless motors and low inertia components, the electromechanical actuator has a response frequency of 2030 Hz, while the hydraulic actuator has a response frequency of only 10 Hz. With the help of this electronic braking system, the fighter can lose 22.5-45 kg.
Fuel system
In the past, most hydraulic pumps and valves were previously driven by brushed DC motors. Brushless DC motors are now used. The electric motor works with the pump immersed in fuel, and the controller and electromagnetic rotor body are installed in the same housing, completely sealed. The motor is made of high temperature resistant NdFeB magnets or SmCo magnets and 1J22 high permeability stator core material. It has the function of speed closed loop and digital control soft start.
