# Subdivision drive is an innovation of stepping motor drive technology

by：V&T Technologies     2020-01-03
Subdivision drive refers to changing only a part of the current in the corresponding winding instead of passing in or cutting off all the current in the winding during each pulse switching, the synthetic magnetic potential of the motor is only part of the rotation step angle. When driving in Subdivision, the winding current is not a square wave but a stepped wave, and the rated current is a stepped input or cut-off. For example, if the current is divided into n steps, the rotor needs n times to turn through a step angle, I . e. n subdivision. The main advantages of subdivision drive are that the step angle becomes smaller, the resolution is improved, and the positioning accuracy, starting performance and high frequency output torque of the motor are improved; Secondly, the low-frequency vibration of the stepping motor is weakened or eliminated, and the probability of the stepping motor working in the resonance region is reduced. It can be said that Subdivision drive technology is a leap in stepper motor drive and control technology. The general subdivision method only changes the current of one phase and the current of the other phase remains unchanged. At O~ 45 ° , Ia remains unchanged, Ib increases step by step from O; At 45~ 90 ° , Ib remains unchanged, and Ia changes from rating to 0 step by step. The advantages of this method are simple control and easy realization in hardware; However, the amplitude of the synthesized vector is constantly changing, and the output torque is also constantly changing, thus causing the constant change of the hysteresis angle. This is the defect of the current commonly used subdivision method, so is there a method to keep the amplitude unchanged when the vector angle changes? From the above analysis, it is impossible to change only the single phase current, so what about changing the two-phase current at the same time? Next, the mathematical model of the amplitude of the synthesized vector will be introduced by the vibrating motor that supplies the micro stepping motor and the motor driver motor products: when Ia = Im · cosx, Ib = Im ·Sinx ( Where Im is the current rating, Ia and Ib are the actual phase current, and x is determined by the subdivision number) The synthetic vector is always the radius of the circle, that is, the constant force distance. That is, Ia and Ib change simultaneously with a certain mathematical relationship to ensure that the amplitude of the synthesized vector remains unchanged during the change process. Based on this, when the subdivision is very large and the micro-step angle is very small, the difference of the change of the lag angle is greater than the micro-step angle required for subdivision, which makes subdivision actually meaningless. The equal angle means that the angle of each rotation of the synthetic force arm is the same. Adjustable rated current refers to meeting the requirements of various series of motors. For example, the rated current of 86 series motors is 6 ~ 8 A, while 57 series motors generally do not exceed 6 A, stepping motor drivers have various gear currents to choose from. Subdivided into subdivision of rated current. In order to achieve' Equal angle constant force distance with adjustable rated current' In theory, as long as the phase current can meet the above mathematical model. This requires very high current control accuracy, otherwise the vector angles synthesized by Ia and Ib will deviate, I . e. the distance angles of each step are different, and subdivision will lose its meaning. This article establishes a' Constant Torque subdivision with adjustable rated current' Driving method to eliminate the problem of hysteresis angle caused by changing force distance. TAG subdivision driver
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