Stepper motor control is generally divided into open-loop control and closed-loop control, which is the simplest way to control open-loop stepper motors is ding-loop control system, in such a control mode, the input of stepper motor control pulses does not depend on the position of the rotor, but is issued according to a fixed rule of its control pulses, stepper motors rely only on this series of established pulses and work, this This control method is more suitable for controlling stepper motors due to the unique characteristics of stepper motors.
What is NEMA 23 closed loop stepper motor:
Closed-loop control is a basic concept of control theory. It refers to a control relationship in which the output that is controlled returns in a certain way to the input that is controlled, and exerts a control influence on the input. Closed-loop control of stepper motors uses position feedback and/or velocity feedback to determine the phase transition with respect to the rotor position, which can greatly improve the performance of stepper motors.
In a closed-loop control stepper motor system, either the operating speed range can be extended when tracking and feedback with a given accuracy, or the tracking and positioning accuracy can be improved at a given speed, or limit speed indicators and limit accuracy indicators can be obtained.
NEMA 23 closed loop stepper motor control method
The closed-loop control method of stepper motor is broadly divided into two types.
1. So that the excitation flux and the phase relationship of the current to maintain the same, so that it can produce the electromagnetic torque to drive the load torque, this way of controlling the motor current is the same as the brushless DC motor control method, known as brushless drive method or current closed-loop control method.
2. Tthe motor current to maintain a certain, control the excitation flux and current phase angle way, known as the power angle closed-loop control method. Power angle for the rotor poles and stator excitation phase (or think of synchronous motor stator rotation magnetic field axis can also be) into the phase angle of mutual attraction. This power angle is smaller at low speeds or light loads and larger at high speeds or high loads.
Why? Because at high speed, the influence of the coil inductance, so that the A-phase current off time is extended, the B-phase current rise time is also extended, therefore, the angle that produces the maximum torque acceleration, its value becomes larger as the speed becomes faster.
NEMA 23 closed loop stepper motor operating principle diagram
This control method is directly or indirectly detect the position or speed of the rotor (or load), and then through feedback and appropriate processing, automatically give the stepper motor drive pulse sequence, the drive pulse sequence is based on the position of the load or rotor and change at any time this control method is implemented in many ways, in the requirements of high precision occasions, combined with micro-step drive technology and microcomputer control technology, can achieve high position accuracy requirements.
Advantages of NEMA 23 closed loop stepper motors
1. With the increase of output torque, the speed of both decreases in a non-linear form, but the closed-loop control improves the moment-frequency characteristics.
2. Under closed-loop control, the output power/torque curve is improved because, under closed-loop, the motor excitation conversion is based on rotor position information, and the current value is determined by the motor load, so the current can be fully converted to torque even in the low speed range.
3. Under closed-loop control, the efficiency a torque curve is increased.
4. With closed-loop control, higher running speed, more stable and smoother speed can be obtained than open-loop control.
5. With closed-loop control, the stepper motor can be automatically and effectively accelerated and decelerated.
6. The quantitative evaluation of the improvement of closed-loop control relative to open-loop control in terms of rapidity can be obtained by comparing the time of passing a certain path interval within IV steps with the formula
7. By applying closed-loop drive, the efficiency can be increased to 7.8 times, the output power can be increased to 3.3 times, and the speed can be increased to 3.6 times. The performance of stepper motor with closed-loop drive is better than that of stepper motor with open-loop drive in all aspects. NEMA 23 closed loop stepper motor drives have the advantages of open-loop stepper motor drives and brushless DC servo motors. Therefore, in position control systems with high reliability requirements, stepper motors with closed-loop control will be widely used.