Here, we discuss two main categories: Rotary motor and linear motor.
Torque motor is a kind of rotary motor. Sometimes, rotary direct drive motors are also referred to as torque motors because they can deliver high torque at low speeds even when stalling. Regarding its design, torque motors are usually brushless and permanent magnet synchronous motors. Their usually frameless design means that they do not have housing and bearing configuration.
Pancake motor is also a kind of rotary motor. But differences to torque motor described above is that pancake motor usually has brushed DC format and whose armature windings are printed on a set of insulating and non-magnetic materials.
Linear motor converts input electric energy into linear motion instead of torsion and rotation. Linear motor is also a type that produces linear motion without a transmission system. This is the key difference from the rotary motor. The conventional transmission system includes many components, such as rack and pinion, ball screw, screw, cam, etc, for building a rotary motor.
The armature group is located between two stator groups. The stator group contains permanent magnets arranged alternately in north and south. At the same time, the magnetic flux runs along the length of the motor and the current runs along the radial direction. This arrangement leads to the fact that the torque generated around the motor axis.
The other type is the linear direct drive motor, usually referred to as linear motor in the field of machine tools. This category includes coreless and core types, depending on the windings in the frame assembly. In coreless type, there is a primary tendency that is made of windings embedded in an epoxy resin. On the other hand, the iron core subcategory has windings that are installed on an iron-laminated stack.
Within the linear category, there is another unique feature: flat or tubular structures. The coreless flat linear motor has a forged flat magnet composed of a coil mounted on an aluminum plate. This type of motor has excellent speed control, but produces less force than other motor designs.
Another configuration of the coreless motor is to use two magnetic tracks facing each other to achieve a better magnetic effect, thereby achieving the disc effect. The second main component runs between the tracks. Therefore, these motors have no cogging and can achieve very agile acceleration and deceleration ratios.
The iron core flat linear motor has two kinds of slotted or slotless design, and the slotted iron core design is more common in the market because of its practicality and reasonable cost. The second part of the slotted iron core linear motor is composed of the back iron plate and the iron tooth group, and the coil is tightly wound on the iron tooth group to prevent the magnetic reverse effect. They have the greatest strength ability, but they may encounter a huge cogging effect.
On the other hand, the slotless design of the linear DD motor is considered to be an integrated structure that combines the ironless core and the traditional slotted iron core structure. Their coils are not wound with iron pieces, but are installed on the iron plate on the back. The second part is usually put in aluminum housing. Compared to slotted core type, the slotless linear DD motor has lower cogging and inertia.
In tubular structure, it contains the magnet in a cylindrical tube that houses the winding in a thrust block around the tube. Similar to the linear flat motor, the second part of the tubular linear motor can be made with or without iron core. The main advantage of the tubular linear motor is its precise symmetrical design, which allows all magnetic flux to be used to generate a thrust force. These characteristics make the tubular linear DD motor very suitable for servo machinery installed in the assembly line, so as to achieve the best assembly and disassembly performance.
The design advantage of the DD motor is to avoid mechanical components that can cause backlash problems and reduce positioning accuracy, while providing high repeatability.
Whether DD motors are linear or rotary type, they are widely used in industrial fields, such as robot components, machine tools, and defense industries.
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