Stepper motor overview
Stepper motor is a kind of open loop control precision driving element which converts electric pulse signal into angular displacement or line displacement, which is matched with drivers to form a set of stepper motor system.
Feed a pulse signal to the motor, the motor will accordingly turn to a step angle.
In the condition of non-overload, as long as the driver feed pulse frequency and pulse number, it can accurately control the motor speed and stop position not affected by the change of load.
Besides stepper motor has periodic position error but no accumulation error, compare with servo motor and brushless motor, it is a high-accuracy, easily-operated, low-cost program.
Stepper motor types
- Reactive stepper motor
Reactive stepper motor is usually three phase, which can achieve large output torque with 1.5 degree step angle but with loud noise and big vibration. The rotor magnetic circuit of reactive stepper motor is made of soft magnetic materials, Multi-phase exciting winding is on the stator, torque is produced by the change of magnetic conductance.
- Permanent-magnetic stepper motor
Permanent magnet stepper motors are generally two phase with small torque and volume. The step angle is generally 7.5 degree and 15 degree.
- Hybrid stepper motor
The hybrid stepper motor takes the advantages of both permanent magnet type and reaction type, it's usually divided into two phase, three phase and five phase normally correspond to step angle 1.8 degree, 1.2 degree,0.72 degree, respectively.
This kind of motor is most widely used.
1. High resolution, high accuracy positioning
Based on the working principle and high precision machining, to achieve its inherent step angle for the unit's precision operation, take the 1.8 degree motor as an example, its resolution of each rotate is up to 1/200, 1/400, the static accuracy of each step up to step*(±5%), when driven by micro step, the resolution and accuracy can be higher.
2. Simple system structure
By the control of the output of the controller pulse signal to trigger the driver, in the role of the driver (Without the speed or position monitor) the motor will be able to correctly respond to the same period of instruction.
3. Low speed and high output torque
Through the control of the pulse without the transition of the gear box, the limited speed can be obtained directly, and higher torque can be obtained. Thus, the loss of power and affection to the motion accuracy can be avoided.
4.Self-locking function When power on, the motor can hold torque(self-locking) even if it stops working, therefore, the stop position can be kept without a brake system
Stepper motor Applications
Stepper motors have variety of applications in CNC machines, embroidery machines, textile machines, printing machines, packing machines, engraving machines, winding machines, manipulator, coordinate measuring machines, dispensing machines, XYZ 3D tables, robots, medical equipment, woodworking machines, ceramic machines, welding applications etc.