Technical Data

When the operating frequency point of the motor is within the continuous operating area of the speed-torque curve, it is crucial to shorten the acceleration or deceleration time during motor startup or stop, allowing the motor to run longer in the optimal speed state, thereby improving the effective operating time of the motor.

As shown in the figure on the right, the dynamic torque characteristic curve of the stepper motor is a horizontal straight line at low speeds; at high speeds, due to the influence of inductance, the curve exhibits an exponential decline.

A. Linear acceleration operation at low speed, given that the motor load is TL, assuming we want to accelerate from F0 to F1 in the shortest time (tr)

How to calculate the shortest time tr?

(1) Generally, TJ = 70%Tm

(2) tr = 1.8 * 10

-5 * J * q * (F1-F0)/(TJ-TL)

(3) F (t) = (F1-F0) * t/tr + F0, 0<t<tr

B. Exponential acceleration operation at high speed

(1) Generally,

TJ0 = 70%Tm0,

TJ1 = 70%Tm1,

TL = 60%Tm1

(2) tr = F4 * In [(TJ0-TL)/(TJ1-TL)]

(3) F (t) = F2 * [1 – e^(-t/F4)] + F0, 0<t<tr

F2 = (TL-TJ0) * (F1-F0)/(FJ1-TJ0)

F4 = 1.8 * 10 -5 * J * q * F2/(TJ0-TL)

Note:

J represents the moment of inertia of the motor rotor when loaded.

q represents the rotation angle per step, which refers to the step angle of the motor during the entire drive.

During deceleration, simply reverse the acceleration pulse frequency calculation.

• Vibration and Noise

Generally, when the stepper motor operates under no load, resonance occurs when the operating frequency approaches or equals the inherent frequency of the motor rotor, which can lead to severe loss of steps.

Several solutions to resonance:

A. Avoid the vibration zone

Ensure that the motor's operating frequency does not fall within the vibration range.

B. Use a microstepping drive mode

Using microstepping drive mode, the original step is subdivided into multiple steps, increasing the resolution of each step of the motor, thereby reducing vibration. This can be achieved by adjusting the phase current ratio of the motor. Microstepping does not increase the accuracy of the step angle but allows the motor to run more smoothly and with less noise. Generally, when the motor runs in half-step mode, the torque will be 15% lower than in full-step mode, and when using sine wave current control, the torque will decrease.