First, the control motor is the “power core” of the robot

1.1 Introduction of motor structure and principle

A motor is a device that converts electrical energy into mechanical energy. Most motors produce torque through the interaction of a current in the wire winding with a magnetic field, which acts on the motor shaft to form a force. The motor is mainly composed of a stator and a rotor. The windings on the stator are energized to generate a magnetic field, and the rotor rotates by interacting with the magnetic field. The main components can be divided into: 1) shell: The shell is composed of a frame (or axis) and two end covers (or bearing seat). The motor’s housing not only holds the motor’s components together, but also protects the internal components from moisture and contaminants. In addition, the type of housing will also affect the cooling of the motor, and the housing can be divided into open housing and completely closed housing. 2) Stator: stator bearing magnetic field winding and pole. Together with the rotor, the stator forms the magnetic circuit or core of the machine. 3) Rotor: bearing armature winding. The armature is the part that carries the load. 4) Winding: After electrification, electromagnetic force will be generated.

There are many types of motors, which can be classified according to different ways: 1) from the operation mode, there are rotary motors (including continuous rotation, intermittent rotation and stepping rotation three categories), linear motors, flat motors, etc.; 2) From the used power supply, there are AC motor (including single-phase and three-phase, synchronous and asynchronous, power frequency and intermediate frequency and other categories) and DC motor two categories; 3) Can also be classified from the voltage level, structural form, volume or power size, use, applicable environment and other aspects.

From the application scenario, there are many motor application scenarios, which are applied in the consumer market, industry, vehicle and so on. This paper takes robot as the starting point and focuses on the control motor applied in industrial control, industrial robot and humanoid robot.

PM875-2
3BDH000606R1

1.2 Motor raw materials: Ndfeb permeability is expected to increase, encoder localization into the fast lane

The upstream of the motor is mainly magnetic materials, encoders, chips and bearings and other parts, the middle stream is motor manufacturing, and the downstream is industrial control, industrial robots and other industry applications.

Magnetic material is one of the main raw materials of motor, which has great influence on the performance of motor. Motors generally use strong magnetic materials, strong magnetic materials include permanent magnet materials, soft magnetic materials and functional magnetic materials. The characteristics of permanent magnet is that once magnetized, it is difficult to demagnetize, and soft magnetic is also easy to magnetize, but it is easy to demagnetize after magnetization: permanent magnet materials are currently divided into three categories, metal permanent magnet, ferrite permanent magnet and rare earth permanent magnet, and soft magnetic materials have ferrite soft magnetic, metal powder core, metal soft magnetic and amorphous nanocrystals. The most different feature of the two magnetic materials is the difference in coercivity. Coercive force is defined as the intensity of the external magnetic field that must be applied in the opposite direction of the original magnetization so that the magnetized magnetic material cannot provide energy to the external magnetic circuit (but there is still some energy inside the magnet), and the unit is Oe or A/m. A simple point of understanding is that the higher the coercive force, the more difficult the material is to demagnetize: 1) the goal of permanent magnet materials is to constantly pursue higher coercive force, strengthen the non-demagnetization ability, which is more used in permanent magnet motors; 2) Soft magnetic by reducing coercive force, the pursuit of higher permeability, can play a power parameter transformation, improve the efficiency of magnetic components and save space, currently as a variety of motor, transformer, relay, inductor, filter and other components of the magnetic core applied in new energy vehicles, robots, photovoltaic and many other fields.

Ndfeb performance is better, permeability is expected to increase. Ndfeb materials have excellent coercive force performance, and are also superior to other materials in magnetic energy product. Better magnetic energy product also means that the Ndfeb volume is smaller per unit magnetic field strength, which is also very conducive to saving motor space. In particular, high-performance Ndfeb magnetic materials (coercive force and magnetic energy product greater than 60) can greatly reduce the volume of the motor, reduce the motor mass, reduce the motor energy loss and improve the efficiency of the entire motor system. The only disadvantage is that the temperature stability is relatively poor, and the temperature performance needs to be improved by adding other elements such as cobalt, and the price is relatively high.