Rare earth permanent magnet motors (REPMs) are mainly used in various electric drive systems on aircraft. The electric actuation system is a driving system with the motor as the actuator. It is widely used in aircraft flight control system, environmental control system, brake system, fuel and start system.
Due to the excellent magnetic properties of neodym magnet, a strong permanent magnetic field can be established after magnetization without additional energy. The rare earth permanent magnet motor, which replaces the traditional electric field of the motor, not only has high efficiency, but also has simple structure, reliable operation, small size and light weight. It can not only achieve high-performance comparable to traditional electrically excited motors, such as ultra-high efficiency, ultra-high speed, and ultra-high response speed, but also can manufacture special motors that meet specific operating requirements, such as elevator traction motors and specialized motors for automobiles.
There are four types of drive systems used on airplanes: hydraulic, electric, pneumatic, and mechanical. The hydraulic drive system is the most widely used, but the most promising is the electric drive system. With the development of permanent magnets, high-power semiconductors, and microprocessors, electric drive systems have developed to the point where they can compete with hydraulic drive systems.
The electric actuation mechanism used in the flight control system is also called a power electric actuation mechanism, which is mainly used for the operation of the wings and rudder of the aircraft. It is mainly divided into electro-hydraulic actuator and electromechanical actuator.
In the mid-1970s, US helicopters frequently experienced hydraulic system failures in major international events, prompting them to develop rare earth permanent magnet electric actuators. The technology of neodymium magnet brushless DC motor (NdFeB PMBLDCM) was used for the electro-hydraulic actuator developed by General Electric, Vickers and HR Dextran companies for the next generation of aircraft. The developed electromechanical actuator adopts high-voltage permanent magnet brushless DC motor technology and pulse width modulated power converter technology.
The motor controller receives control instructions from the flight control computer on the aircraft, and through the signal processing, synthesis, and amplification of the servo amplifier of the three-channel control ring system, it drives the output angle of the corresponding servo motor to control the direction and aileron of the aircraft. Change the attitude and direction of the aircraft to achieve automatic control of the flight control system on the aircraft.
The electric environmental control system adopts electromechanical drive technology, characterized by high power and high-speed variable-speed drive motors. Since 1982, the United States has developed an electric steam cycle environmental control system and tested it on a P-3 anti-submarine aircraft. The system uses a 30,000 rpm-70,000 rpm variable-speed high-voltage rare earth permanent magnet brushless DC motor to drive the compressor. A samarium-cobalt permanent magnet motor can output 34.3 kW power at 45,000 r/min.
The oxygen production machine is an important onboard equipment for advanced aircraft, which provides the ability to maintain life for pilots. At present, only four countries, including the United States, have this technology. China has entered the forefront of international technology in this field and has successfully developed an oxygen production machine. The motor used is a low-speed, high-precision brushless DC motor steady-state system. A samarium-cobalt permanent magnet excitation drive valve rotates at 6r/min.
The electric brake system was successfully developed in the United States in 1982 and tested on the A-10 attack aircraft. In 1990, the third generation electric brake system was completed. It uses a strong torque samarium-cobalt permanent magnet brushless DC motor and a wheel and worm gear actuator.
In 1998, the F-16 fighter used a new electric brake system. The electric actuation mechanism of the system uses four rare earth permanent magnet brushless DC motors. Due to the use of brushless motors and low-inertia components, the response frequency of the electromechanical actuator is 20-30Hz, while the response frequency of the hydraulic actuator is only 10Hz. With this electric brake system, the fighter can reduce its weight by 22.5kg-45kg.
In the past, most hydraulic pumps and valves were driven by brushed DC motors. Now brushless DC motors are used. The motor works with the pump immersed in fuel, and the controller and magnetic rotor are installed in the same housing, completely sealed. The motor is made of high-temperature resistant neodym magnet or samarium-cobalt magnet and 1J22 high-permeability stator core material. It has speed closed-loop and digital control soft start function.