A stepper motor is an open-loop control element that converts electrical pulse signals into angular or linear displacement. By controlling the sequence, frequency, and number of electrical pulses applied to the motor coils, the direction, speed, and rotation angle of the stepper motor can be controlled. Combined with a linear motion actuator or gearbox, it can achieve more complex and precise linear motion control requirements. A stepper motor generally consists of front and rear end covers, bearings, a central shaft, a rotor core, a stator core, a stator assembly, corrugated washers, screws, etc. Also called a stepper motor, it utilizes electromagnetic principles to convert electrical energy into mechanical energy, driven by coils wound around the stator teeth. Normally, a coiled metal wire is called a solenoid, while in a motor, the metal wire wound around the stator teeth is called a winding, coil, or phase.
• Basic Structure
• Working principle
The stepper motor driver, based on external control pulses and direction signals, uses its internal logic circuitry to control the stepper motor windings to be energized in a specific timing sequence in the forward or reverse direction, causing the motor to rotate in the forward / reverse direction or lock.
Taking a 1.8-degree two-phase stepper motor as an example: When both phase windings are energized, the motor output shaft will remain stationary and locked in position. The maximum torque required to keep the motor locked under rated current is the holding torque. If the current in one phase winding changes direction, the motor will rotate one step ( 1.8 degrees) in a predetermined direction. Similarly, if the current in the other phase winding changes direction, the motor will rotate one step ( 1.8 degrees) in the opposite direction. When the current through the coil windings is energized in sequence with changing directions, the motor will achieve continuous stepping rotation in a predetermined direction with very high operating accuracy. A 1.8- degree two-phase stepper motor requires 200 steps to complete one revolution.
Two-phase stepper motors have two winding configurations: bipolar and unipolar. A bipolar motor has only one winding coil per phase. As the motor rotates continuously, the current must sequentially change direction within the same coil for excitation. The drive circuit design requires eight electronic switches for sequential switching.
A unipolar motor has two winding coils with opposite polarities on each phase. When the motor rotates continuously, it only requires alternating energization of the two winding coils on the same phase. The drive circuit design only requires four electronic switches. In bipolar drive mode, because the winding coils of each phase are 100% energized, the output torque of the motor in bipolar drive mode is increased by approximately 40% compared to unipolar drive mode .
• Precise position control
A stepper motor rotates at a fixed step angle, much like the second hand of a clock. This angle is called the basic step angle. Mingzhi offers two basic step angles as standard motors: a two-phase stepper motor with a basic step angle of 1.8° and a three-phase stepper motor with a basic step angle of 1.2° .
In addition to standard motors, Mingzhi also offers stepper motors with other basic step angles of 0.72° , 0.9° , 1.5° , 3.6° , and 3.75° . These motors are not listed in this catalog; please contact Mingzhi for details.
• Simple pulse signal control
The system requiring high-precision positioning is shown below. The pulse signals emitted by the controller can accurately control the rotation angle and speed of the stepper motor.
What is a pulse signal?
A pulse signal is an electrical signal whose voltage repeatedly changes between ON and OFF .
Each ON/OFF cycle is recorded as one pulse. A single pulse signal command causes the motor output shaft to rotate one step.
The signal levels corresponding to the ON and OFF voltage conditions are referred to as "H" and "L" respectively .
• The rotation distance is proportional to the number of pulses.
The rotation distance of a stepper motor is proportional to the number of pulse signals applied to the driver.
The relationship between stepper motor rotation (rotation angle of the motor output shaft) and pulse count is shown below:
• Rotational speed is proportional to pulse frequency
The speed of a stepper motor is proportional to the frequency of the pulse signal applied to the driver.
The relationship between the motor speed [r/min] and the pulse frequency [Hz] is as follows (in full-step mode).
High torque, small size
One of the key characteristics of stepper motors is their high torque and small size.
These characteristics give the motors excellent acceleration and response, making them ideal for applications that require frequent starts and stops.
Mingzhi also offers motors with gearboxes to meet the need for higher torque at low speeds.
• Capable of frequent start / stop
• Comparison of speed and torque characteristics of servo motors and stepper motors of the same size
• The motor self-holds the stop position.
When the windings are energized, the stepper motor has its full holding torque. This means that the stepper motor can remain in a stopped position without the use of mechanical brakes.
• Motor equipped with electromagnetic brake
Once the power is cut off, the motor loses its holding torque and cannot remain in a stopped position during vertical operation or under the application of external force. Motors with electromagnetic brakes are required in lifting and other similar applications.
• Closed-loop servo control stepper motor
Mingzhi has innovatively integrated servo control technology into stepper motors, creating a motion control terminal with superior performance — the stepper servo. The stepper servo driver significantly improves the operating performance of stepper motors, offering features such as smarter control, higher efficiency, more compact structure, more accurate positioning, and faster and smoother operation.
