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How much do you know about stepper motor?

Views: 31     Author: Site Editor     Publish Time: 2023-05-06      Origin: Site

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Introduction of stepper motor

1. About the stepper motor

As a special motor for precise displacement control and large-scale speed regulation, the stepper motor rotates step by step with its own inherent step angle (determined by the mechanical structure of the rotor and stator). Its characteristic is that each step of rotation, The step angle is always constant, which can keep the precise and accurate position. So no matter how many times you rotate, there is always no quadrature error. Due to the simple control method and low cost, it is widely used in various open-loop controls. The operation of the stepper motor needs to be driven by a power electronic device with pulse distribution, which is the stepper motor driver. It receives the pulse signal sent by the control system, according to the structural characteristics of the stepping motor, distributes the pulse sequentially, and realizes the control of angular displacement, rotation speed, rotation direction, brake loading state, and free state. Every time the control system sends a pulse signal, the driver can drive the stepper motor to rotate a step angle. The speed of the stepper motor is proportional to the frequency of the pulse signal. The angular displacement is related to the number of pulses. When the stepper motor stops rotating, two states can be produced: brake loading can produce maximum or partial holding torque (usually called brake holding, without electromagnetic brake or mechanical brake) and the rotor is in a free state (can be driven by external thrust drive with easy rotation). The stepping motor driver must match the type of the stepping motor. Otherwise, the stepper motor and driver will be damaged.

2. Step angle and subdivision

The step angle of the stepping motor is the angle at which the control system sends a step pulse signal. The step angle of each motor is confirmed when it leaves the factory. It can be called "the inherent step angle of the motor". There are 0.9/1.2/1.8 etc.

The subdivision number of the driver refers to the real step angle when the motor is running, which is a fraction of the inherent step angle (full step). For example, when the driver is working in 10 subdivisions, the actual step angle is only one-tenth of the "motor's natural step angle". The subdivision function is completely generated by the stepper driver by precisely controlling the phase current of the motor, and has nothing to do with the motor.

Under the condition of constant controller pulse, the greater the subdivision, the lower the speed. For example, the controller sends out pulses of 200 pulses per second. When the subdivision is not set, it makes one revolution per second; when the subdivision is set to 4, it takes 800 pulses to make one revolution, so sending 200 pulses per second can only make a quarter of a revolution. Yes, the speed is 1/4 of the original!




3. Driver

As we know before, due to the unique structure of the stepping motor, the inherent step angle of the motor is like 0.9/1.8°, which means that the angle turned by each step is 0.9 for half-step work, and 1.8 for a full step. However, in many precision control and occasions, the angle of the whole step is too large, which affects the control accuracy, and the vibration is too large, so it is required to complete the inherent step angle of the motor in many steps. This is the so-called subdivision drive, which can realize this function. The electronic device is called a subdivision driver.

The stepper motor adopts a subdivision driver, which can eliminate the low-frequency resonance phenomenon of the stepper motor, reduce vibration, reduce working noise, and increase the output torque of the stepper motor. At the same time, the current provided to the stepper motor is "continuous and strong", which greatly reduces the back electromotive force when the stepper motor rotates, and improves the rotational displacement resolution of the stepper motor.

stepper motor drivers

 4. Motor pulse

The pulse refers to a cycle of the motor coil level from high to low, or from low to high. The conversion of several cycles is a few pulses, and the frequency is the number of conversions in one second, not the number of energizations in one second. If the frequency of the pulse signal sent by the PLC is 50HZ, it means that the speed at which the stepper motor executes the number of pulses is 50 cycles in one second.

The pulse signal is the power supply of the stepping motor, which is characterized by discontinuity. Every time the stepping motor receives a pulse signal, it rotates at a certain angle, and the controller sends out a certain number of pulse signals, and the motor rotates at a certain angle. The pulse frequency is high. The motor spins fast. One is the total amount and the other is the amount per second, that's the difference.




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Stepper Motor FAQ


What is a stepper motor, and how does it work?

A stepper motor is an electromagnetic device that converts digital pulses into mechanical movement. It moves in discrete steps, with each step representing a fixed angle of rotation. The motor's rotor aligns with the magnetic field generated by the stator, causing controlled rotation.


What are the advantages of using stepper motors?

Stepper motors offer precise control of movement, high torque at low speeds, simplicity of control, and open-loop operation (no feedback required). They are ideal for applications requiring accurate position control.


How is the step resolution of a stepper motor determined?

Step resolution is the smallest angle the motor can move in response to a single input pulse. It is determined by the motor's construction, the number of poles, and the drive electronics. Higher pole counts and microstepping can enhance resolution.


What is microstepping, and why is it important?

Microstepping is a technique that divides each full step of a stepper motor into smaller increments. This provides smoother motion, reduces vibration, and improves accuracy. Microstepping is essential for applications demanding precision.


Can stepper motors operate in an open-loop configuration?

Yes, stepper motors can operate in an open-loop system, where position control is achieved without external feedback devices. However, for critical applications, closed-loop systems with feedback may be preferred to enhance accuracy and correct errors.


What is a stepper motor, and how does it differ from other types of motors?

A stepper motor is an electromechanical device that converts electrical pulses into precise mechanical movements. Unlike other motors, it moves in discrete steps, allowing for accurate control of position and speed.


What are the key components of a stepper motor system?

A stepper motor system consists of the stepper motor itself, a driver to control the motor, and a controller or microcontroller that generates the sequence of pulses to drive the motor.


How do I determine the appropriate stepper motor for my application?

Factors such as torque requirements, speed, step resolution, and physical size are crucial considerations. Understanding the specific needs of your application will guide you in selecting the right stepper motor.


What is the significance of step angle in stepper motors?

Step angle is the angle through which the motor rotates for each input pulse. It is a critical parameter that determines the motor's resolution and accuracy. Smaller step angles result in finer control but may require more complex drive electronics.


Can stepper motors operate in both directions?

Yes, stepper motors can rotate in both clockwise and counterclockwise directions by changing the sequence of input pulses. The direction of rotation is controlled by the order in which the motor windings are energized.


What is microstepping, and how does it improve stepper motor performance?

Microstepping is a technique that divides each full step of a stepper motor into smaller sub-steps. This allows for smoother motion, reduced vibration, and improved positioning accuracy, especially at low speeds.


Do stepper motors require feedback for position control?

While stepper motors can operate in an open-loop system without feedback, closed-loop systems with feedback devices like encoders or sensors are used in applications where precise position control and error correction are essential.


How do I troubleshoot common issues with stepper motors?

Check for loose connections, verify power supply compatibility, inspect wiring for correct polarity, and ensure there are no mechanical obstructions. Reviewing controller settings and testing with an alternate controller or driver can help identify and resolve issues.


What is the difference between bipolar and unipolar stepper motors?

The main difference lies in the winding configuration. Bipolar motors have two coils per phase, while unipolar motors have a center-tapped winding. Bipolar motors generally provide higher torque, but unipolar motors are easier to control.


Can I run a stepper motor without a dedicated driver?

While it is possible to run a stepper motor directly from a microcontroller, using a dedicated stepper motor driver is recommended for better performance and protection against overcurrent and overheating. Stepper motor drivers provide the necessary current control and waveform shaping for optimal motor operation.








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