LOGO

Stepper motor is a kind of motor that converts the electrical pulse signal into the corresponding angular displacement or linear displacement. Each input pulse signal,
the rotor rotates an Angle or further forward, the output angular displacement or linear displacement is proportional to the number of input pulses, and the speed is
proportional to the pulse frequency. Therefore, stepping motor is also called pulse motor.

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There are many structure forms and classification methods of stepper motor, which are generally divided into three kinds according to the excitation mode: magnetoresistive
type, permanent magnet type and mixed magnetic type. According to the number of phases, it can be divided into single phase, two phase, three phase and multiple equal forms.

In the stepper motor used in our country, the reactive stepper motor is the main one. The operation performance of the stepper motor is closely related to the
control mode, and the stepper motor control system can be divided into the following three categories from its control mode: open loop control system,
closed loop control system, semi-closed loop control system. Semi-closed loop control system is generally classified as open loop or closed loop system in practical application.

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Stepper motor acceleration and deceleration process control technology

Because of the wide application of the stepper motor, more and more research on the control of the stepper motor, if the stepping pulse changes too fast when
starting or accelerating, the rotor does not follow the change of the electrical signal due to inertia, resulting in gridlock or loss of step when stopping or decelerating
for the same reason may produce super step. In order to prevent gridlock, out-of-step and overstep, and improve the working frequency, it is necessary to
control the speed up and down of the stepper motor.

The speed of the stepper motor depends on the pulse frequency, the number of rotor teeth and the number of beats. Its angular velocity is proportional to the
pulse frequency and synchronizes with the pulse in time. Therefore, when the number of rotor teeth and the number of running beats is certain, the required
speed can be obtained as long as the pulse frequency is controlled. Since the stepper motor is started by virtue of its synchronization torque, in order not
to lose step, the starting frequency is not high. Especially with the increase of power, the rotor diameter increases, the inertia increases, and the starting
frequency and the highest operating frequency may be ten times as much.

The starting frequency characteristics of the stepper motor make it impossible to directly reach the running frequency when the stepper motor starts, but
there must be a starting process, that is, from a low speed to the running speed. When stopped, the operating frequency cannot be immediately reduced to
zero, but there must be a high-speed gradual deceleration process to zero.

The output torque of the stepper motor decreases with the rise of the pulse frequency, the higher the starting frequency, the smaller the starting torque, the
worse the ability to drive the load, the out-of-step will be caused when starting, and overshooting will occur when stopping. In order to make the stepper motor
quickly reach the required speed without losing step or overshoot, the key is to make the acceleration process, the torque required by the acceleration can
make full use of the torque provided by the stepper motor at each operating frequency, and can not exceed this torque. Therefore, the operation of the
stepper motor generally goes through three stages of acceleration, uniform speed and deceleration, requiring the acceleration and deceleration
process time to be as short as possible, and the constant speed time to be as long as possible. Especially in the work requiring rapid response, the
time required to run from the starting point to the end point is the shortest, which must require the shortest process of acceleration and deceleration,
and the highest speed at constant speed.

Scientific and technological workers at home and abroad have conducted a lot of research on the speed control technology of stepper motor,
established a variety of acceleration and deceleration control mathematical models, such as exponential model, linear model, etc., and designed and
developed a variety of control circuits on this basis to improve the motion characteristics of stepper motor. The exponential acceleration and
deceleration takes into account the inherent torque frequency characteristics of the stepper motor, which not only ensures that the stepper motor does
not lose a step in motion, but also gives full play to the inherent characteristics of the motor, shortening the speed up and down time, but because of
the change of the motor load, it is difficult to achieve linear acceleration and deceleration only considers the angular speed of the motor in the
range of load capacity is proportional to the pulse. The acceleration of this acceleration method is constant, and its disadvantage is that it does
not fully consider the characteristics of the stepper motor output torque changing with the speed, and the stepper motor will lose step at high speed.

Stepper motor subdivision drive control

Due to the limitations of its own manufacturing process, such as the size of the step Angle is determined by the number of rotor teeth and the number of
running beats, but the number of rotor teeth and the number of running beats is limited, so the step Angle of the stepper motor is generally large and
fixed, the resolution of the step is low, the lack of flexibility, and the vibration in the low frequency operation. The noise is higher than other micromotors,
making the physical device easy to fatigue or damage. These shortcomings make the stepper motor can only be applied in some occasions with lower
requirements, for the occasions with higher requirements, only closed-loop control can be taken, increasing the complexity of the system, and
these shortcomings seriously limit the effective use of the stepper motor as an excellent open-loop control component. Subdivision drive technology
to some extent effectively overcome these shortcomings.

Stepper motor subdivision drive technology is a kind of drive technology developed in the middle of the decade that can significantly improve the comprehensive
performance of stepper motor. The control method of step Angle subdivision of stepper motor was proposed for the first time at the Annual meeting of Incremental
Motion Control Systems and Devices in the United States. In the following two decades, the stepper motor subdivision drive has been greatly developed.
Gradually developed to full maturity in the 1990s. The research on subdivision driving technology in China starts at the same time as abroad.

In the mid-1990s to a greater development. Mainly used in industry, aerospace, robotics, precision measurement and other fields, such as tracking satellite
photoelectric theodolite, military instruments, communications and radar and other equipment, the wide application of subdivision drive technology, so that
the phase number of the motor is not limited by the step Angle, which brings convenience to product design. At present, in the subdivision drive technology of
the stepper motor, the chopper constant current drive, the meter pulse width modulation drive, the current vector constant amplitude uniform rotation drive
control stop, greatly improve the running accuracy of the stepper motor, so that the stepper motor in the field of medium and small power applications to
high speed and precision direction.