The closed-loop control methods of NEMA 23 closed loop stepper motor are roughly divided into two types:
1. Keep the phase relationship between the exciting magnetic flux and the current consistent, so that it can generate electromagnetic torque that can drive the load torque. This method of controlling the motor current is the same as the brushless DC motor control method, which is called the brushless drive method or the current closed-loop control method.
2. The motor current is kept constant and the method of controlling the phase angle of the exciting magnetic flux and the current is called the power angle closed-loop control method. The power angle is the phase angle formed by the mutual attraction between the rotor magnetic poles and the stator excitation phase (or the axis of the stator rotating magnetic field of a synchronous motor). This power angle is smaller at low speed or light load, and larger at high speed or high load. As shown in the following figure in the principle of open-loop control in the previous article, the "bar A" phase attracts the rotor pole, and the angle of the "bar B" phase is π/2 when the phase is excited, and the rotor pole is located at the leading edge of the "bar A" phase ( When the S pole of the rotor in the picture is on the left side of phase A), the magnetic pole "bar B" phase starts to be excited.
Why? Because at high speed, affected by the coil inductance, the turn-off time of the A-phase current is prolonged, and the rise time of the B-phase current is also prolonged. Therefore, the angle that produces the maximum torque acceleration increases with the speed.
Nema 23 closed loop stepper motor working principle diagram
This control method directly or indirectly detects the position or speed of the transfer (or load), and then through feedback and appropriate processing, the drive pulse sequence of the stepper motor is automatically given. This drive pulse sequence is based on the load or There are many ways to realize this control method that the position of the rotor changes at any time. In the occasions that require high precision, the combination of micro-step drive technology and microcomputer control technology can achieve high position accuracy requirements.
The advantages of nema 23 closed loop stepper motor
A. As the output torque increases, the speeds of both decrease in a non-linear form, but the closed-loop control improves the torque-frequency characteristics.
B. Under closed-loop control, the output power/torque curve can be improved. The reason is that under closed-loop, the motor excitation conversion is based on the rotor position information, and the current value is determined by the motor load. Therefore, even in the low speed range, the current It can also be fully converted into torque.
C. closed-loop control, the efficiency-torque curve is improved.
D. Using closed-loop control, higher operating speed, more stable and smoother speed can be obtained than open-loop control.
E. Using closed-loop control, stepping motors can be automatically and effectively accelerated and decelerated.
F. The quantitative evaluation of the improvement in the rapidity of closed-loop control relative to open-loop control can be obtained by comparing the time between a certain path interval in step IV:
G. Using 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 the closed-loop driven stepper motor is better than the open-loop driven stepper motor in all aspects. Stepper motor closed-loop drive has the advantages of stepper motor open-loop drive and DC brushless servo motor. Therefore, in a position control system with high reliability requirements, closed-loop control stepping motors will be widely used.