Stepper motor control method
Conventional stepper motors move when they receive an instruction to push a certain number of pulses related to the interval. Steppers are considered open-loop systems, as they reduce the reaction mechanism to verify that the target orientation has been reached. The servo motor also moves when it receives a command signal from the controller. Compared to the open-loop operation of a stepper motor system, the servo motor is a closed-loop system with a built-in encoder that can communicate with the manipulator in succession and make any necessary adjustments to ensure that the target orientation is reached.
In a stepper motor system, if the available motor torque is not sufficient to overcome the load, the motor will either suspend or cross one or more pulses and then make a difference between the desired orientation and the actual arrival position. To prevent this, the stepper motor is generally oversized to ensure a large gap between the worst-case load torque and the motor's available torque. But you can choose a large motor. Then, after the encoder is added and operated in a closed-loop, the stepper motor system can achieve the same position monitoring and control as the servo motor.
The most straightforward way to operate a stepper motor in closed-loop form is to compare the theoretical orientation that should be reached according to the number of steps and the actual orientation of the arrival based on the encoder response. If there is a difference between the target orientation and the practice orientation, the manipulator initiates the proofreading movement.
Although the above method is reactive, the orientation of the motor is calibrated after the movement is completed. Still, the closed-loop stepper can also monitor the difference between the azimuth step and the encoder response in succession. After successive reactions, the compensation can be completed in real-time by increasing the pulse rate, temporarily increasing the current, or adjusting the step angle.
The third method of operating a stepper motor in closed-loop mode uses sinusoidal commutation. If the rotor and stator fields are not properly aligned, the encoder will adjust the motor current to match the torque required to move or hold the load. This form is sometimes referred to as servo steering because it is used to manipulate torque through the operation of the motor current. In the servo control mode, the stepper motor is basically like a high-pole servo motor. Still, without the noise and resonance of the traditional stepper motor, it provides smoother motion and more accurate control. In addition, since the current is dynamic rather than as stable as a conventional stepper motor, motor heating is largely prevented.
Closed-loop stepper motors eliminate many of the shortcomings of traditional open-loop stepper systems, making them similar to servo motors, however, in applications requiring high speed, high speed, high torque, or handling of varying loads, the servo motor functions even beyond the closed-loop stepper motor.
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