Comparison of open loop stepper system with close loop stepper system
One of the main advantages of stepper motor is suitable for open loop control. Under open-loop control,the stepper motor is
controlled by a pulse sequence which having a predetermined time interval,and no feedback sensor and corresponding electronic
circuit are required in the control system. This line has simple, low cost characteristics,so that stepper motor open-loop control system can be widely used.
However, the open-loop control of the stepper motor can not avoid its inherent drawbacks,namely resonance, oscillation,step lost
and difficult to achieve high speed.On the other hand,the accuracy of the open loop control stepper motor system is higher than the classification is very difficult,the positioning accuracy is relatively low.Therefore,we must use closed-loop control system when system has high requirements on accuracy and stability.
The closed-loop stepper control system uses position feedback and (or) velocity feedback to determine the phase transitions
corresponding to the rotor position,which greatly improves the performance of the stepper motor.
Under closed-loop stepper motor system,or when tracking and feedback with a given accuracy,expand operating speed range, or
at a given speed to improve tracking and positioning accuracy,or can get the limit speed index and limit precision index.
The closed-loop stepping system control performance has the following advantages compared with the open-loop control:
A.With the output torque increasing,the speed of both decreases in a non-linear style,but the closed-loop control improves
the torque-frequency characteristics.
B.Under closed-loop stepper control system,the output power / torque curve are improved,because the closed-loop,the motor
excitation conversion is based on the rotor position,the current value is determined by the motor load,so even in the low speed range,the current can fully converted to torque.
C.Under closed-loop stepper control system,the efficiency/torque curve improved.
D.Use closed-loop stepper control system,can get higher speed than open-loop stepper control, more stable and more smooth speed.
E.Use closed-loop stepper control system,the stepper motor can automatically and effectively accelerated and decelerated.
F.Closed-loop stepper control system compares with open loop stepper control system,the quantitative evaluation in terms of fastness can be obtained by comparing the time of a path interval in the step IV:n-stepping motor converted beats (N> n)
G.Application of closed-loop stepper drive,the efficiency can be increased to 7.8 times,the output power can increase to 3.3 times,the speed can increase to 3.6 times.Closed-loop driven stepper motor performance in all respects is better than open-loop driven stepper motor.Stepping motor closed-loop drive with stepper motor open-loop drive and DC brushless servo motor advantages.Therefore,in the highly reliable position control system,the closed-loop control of the stepper motor will be widely used.