Stepping motor application and control

stepper motor is an electrical pulse will be converted into angular displacement of the implementing agencies. Put it in simple language-speaking: When the stepper drive pulse signal to a receiver, it drives stepper motor rotation direction by setting a fixed point of view (and the step angle). You can control the number of pulses to control the amount of angular displacement, so as to achieve the purpose of accurate positioning; At the same time, you can by controlling the pulse frequency to control the motor rotation speed and acceleration, so as to achieve the purpose of speed.

Stepper motor directly from the AC-DC power supply, and must use special equipment - stepper motor drive. Stepper motor drive system performance, in addition to their own performance with the motor on the outside, but also to a large extent depend on the drive is good or bad. A typical stepper motor drive system is operated by the stepper motor controller, stepper motor drives and stepper motor body is composed of three parts. Stepper motor controller stepper pulse and direction signal, each made of a pulse, stepper motor-driven stepper motor drives a rotor rotating step angle, that is, step-by-step further. High or low speed stepper motor, or speed, or deceleration, start or stop pulses are entirely dependent on whether the level or frequency. Decide the direction of the signal controller stepper motor clockwise or counterclockwise rotation. Typically, the stepper motor drive circuit from the logic control, power driver circuit, protection circuit and power components. Stepper motor drive controller, once received from the direction of the signal and step pulse, the control circuit on a pre-determined way of the electrical power-phase stepper motor excitation windings of the conduction or cut-off signal. Control circuit output signal power is low, can not provide the necessary stepping motor output power, the need for power amplifier, which is stepper motor driven power drive part. Power stepper motor drive circuit to control the input current winding to form a space for rotating magnetic field excitation, the rotor-driven movement. Protection circuit in the event of short circuit, overload, overheating, such as failure to stop the rapid drive and motor.

Motor is usually for the permanent magnet rotor, when the current flows through the stator windings, the stator windings produce a magnetic field vector. The magnetic field will lead to a rotor angle of rotation, making a pair of rotor and stator magnetic field direction of the magnetic field direction. When the stator rotating magnetic field vector from a different angle. Also as the rotor magnetic field to a point of view. An electrical pulse for each input, the motor rotation angle step. Its output and input of the angular displacement is proportional to the pulses, with pulse frequency proportional to speed. Power to change the order of winding, the electrical will be reversed. We can, therefore, control the pulse number, frequency and electrical power windings of each phase to control the order of rotation of stepper motor. Stepper motor types:

Permanent magnet (PM). Magnetic generally two-phase stepper, torque and are smaller and generally stepping angle of 7.5 degrees or 15 degrees; put more wind for air-conditioning.

Reactive (VR), the domestic general called BF, have a common three-phase reaction, step angle of 1.5 degrees; also have five-phase reaction. Noise, no torque has been set at a large number of out.

Hybrid (HB), common two-phase hybrid, five-phase hybrid, three-phase hybrid, four-phase hybrid, two-phase can be common with the four-phase drive, five-phase three-phase must be used with their drives;

Two-phase, four-phase hybrid step angle is 1.8 degrees more than a small size, great distance, and low noise; Five-phase hybrid stepping motor is generally 0.72, the motor step angle small, high resolution, but the complexity of drive circuits, wiring problems, such as the 5-phase system of 10 lines.

Three-phase hybrid stepping motor step angle of 1.2 degrees, but according to the use of 1.8 degrees, the three-phase hybrid stepping motor has a two-phase mixed than the five-phase hybrid more pole will help electric folder symmetric angle, it can be more than two-phase, five-phase high accuracy, the error even smaller, run more smoothly.

Stepper motor to maintain torque: stepper motor power means no rotation, the stator locked rotor torque. It is a stepper motor, one of the most important parameters, usually in the low-speed stepper motor torque at the time of close to maintain the torque. As the stepper motor output torque increases with the speed of constant attenuation, the output power also increases with the speed of change, so as to maintain torque on the stepper motor to measure the parameters of one of the most important. For example, when people say that the stepper motor 2N.m, in the absence of special circumstances that means for maintaining the torque of the stepper motor 2N.m.

Precision stepper motors: stepper motor step angle accuracy of 3-5%, not cumulative.

Stepper motor to allow the minimum amount of surface temperature：Stepper motor causes the motor temperature is too high the first magnetic demagnetization, resulting in loss of torque down even further, so the motor surface temperature should be the maximum allowed depending on the motor demagnetization of magnetic material points; Generally speaking, the magnetic demagnetization points are above 130 degrees Celsius, and some even as high as 200 degrees Celsius, so the stepper motor surface temperature of 80-90 degrees Celsius is normal.

Start frequency of no-load: the stepper motor in case of no-load to the normal start of the pulse frequency, if the pulse frequency is higher than the value of motor does not start, possible

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步进电机应用和控制

步进电机是将电脉冲转换成角位移的执行机构。通俗的讲：当步进电机驱动器接收到脉冲信号，它就驱动步进电机按设定的方向转动一个固定的角即步进角。你可以控制脉冲的个数来控制角位移量，从而能准确定位；同时你可以通过控制脉冲频率来控制电机转动的速度和加速度，从而达到改变速度的目的。

步进电机不能直接用交直流电源供电，而必须使用专用设备即步进电机驱动器。步进电机驱动系统的性能，除与电机自身性能有关外，在很大程度上取决于驱动器的好坏。一个典型的步进电机驱动系统是由步进电机控制器，步进电机驱动器和步进电机三部分组成。步进电机控制器发出步进脉冲和方向信号，每一个脉冲，步进电机驱动器驱动步进电机转子旋转一个步距角，就是一步。步进电机转速的高低，加速和减速，启动或停止完全取决脉冲的有无和频率的高低。控制器的方向信号决定步进电机的正转或者反转。通常，步进电机驱动器由逻辑控制电路、保护电路、功率驱动电路和电源组成。当步进电机驱动器接收到来自控制器的方向信号和步进脉冲，控制电路就按照预先设定的电机通电方式产生步进电机各相励磁绕组导通或截止信号。由于控制电路输出的信号功率很低，不能提供步进电机所需的输出功率，所以必须进行功率放大，这就是步进电机驱动器的功率驱动部分。功率驱动电路向步进电机控制绕组输入电流，使其励磁形成空间旋转磁场，驱动转子运动。保护电路在出现短路、过载、等故障时迅速停止驱动器和电机的运行。

电机转子通常是永磁转子，通过定子绕组的电流流时，定子绕组产生的磁场矢量。会使转子的旋转一定角度，使一对转子的磁场方向和定子的磁场方向一致。当定子旋转磁场矢量旋转一个角度，转子也随着这个磁场旋转一个角度。每个输入一个电脉冲，电机的旋转一个角度前进一步。它的输出角位移和输入脉冲数是成正比的，速度与脉冲频率成正比。改变绕组通电的顺序，电机就会反转。因此，我们可以用控制脉冲数，脉冲频率和电机绕组的通电顺序来控制步进电机旋转。

步进电机类型：

永磁式（PM）。永磁式步进电机一般两相步进电机，转矩和体积较小，一般步进角度为7.5度或15度，多用于空调风摆上。

反应式（VR），国内一般称为BF，常见的是三相反应式，步进角度为1.5度，也有五相反应式。

混合式（HB），普通的两相混合式，五相混合式，三相混合，四相混合式，两相和四相可以通用驱动器。五相和三相只能用自己的驱动器。两相，四相混合式步进角为1.8度，具有小体积，大力距，低噪的特点。

五相混合式步进电机一般为0.72度，电机步距角小，分辨率高，但驱动电路复杂，接线麻烦。

三相混合式步进电机步距角为1.2度，但使用中要按1.8度计算，三相混合式步进电机拥有比两相混合，五相混合式更多的磁极。有利于电动机夹角的对称，因此可以比两相，五相精度更高，误差更小，运行更平稳。

步进电机保持扭矩：指步进电机通电但没有转动时，定子锁住转子的力矩。它是步进电机最重要的参数之一，通常步进电机在低速的力矩接近保持转矩，由于步进电机的输出转矩随速度的增加而不断衰减，输出功率也随速度的增加而变化，从而保持扭矩成为衡量步进电机最重要的参数之一。例如，当人们说2N.m的步进电机，在没有特殊说明的情况下是指保持扭矩为2N.m.的步进电机

步进电机的精度：步进电机的精度为步距角的3-5％，且不累积。 步进电机允许的最高表面温度：步进电机温度过高首先会的磁性材料退磁，导致转矩降低甚至失步，电机表面温度允许的最大值取决于的磁性材料退磁点;一般来说，磁性材料退磁点在摄氏130度以上有些材料甚至高达摄氏200度高，所以步进电机表面温度在摄氏80-90度是正常的。

空载启动频率：步进电机在无负载时能正常启动的脉冲频率，如果脉冲频率高于该值，电机不能正常启动，可能丢步或堵转。在有负载的情况下，启动频率应更低。如果你想实现电机高速旋转，脉冲频率应该有加速过程，也就是说，在较低的频率开始，然后按一定的加速度上升到所需的频率（即电机转速从低到高）。

步距角：即发送一个脉冲，电机转动相应的角度。

扭矩定位：扭矩定位是指步进电机没有通电的情况下，定子锁住转子的力矩。 运行频率：步进电机不失步运行的最高频率。

细分驱动器： 步进电机细分驱动器的主要目的是减弱或消除步进电机的低频振动，提高电机的运转精度，减少噪音。如对于步距角为1.8°（整步）的两相混合式步进电机，如果细分驱动器的细分数为8，那么电机的运转分辨率为每个脉冲0.072°，电机的精度能否达到或接近0.225°，还取决于细分驱动器的细分电流控制精度等其他因素，细分数越大精度越难控制。

步进电机驱动器直流电源的确定:

A.电压确定：混合式步进电机驱动器的电源电压范围较广（比如IM483的供电电压12〜48VDC），电源电压通常根据电机的转速和响应要求来选择。如果要求较快的运行速度较高的响应速度就选用较高的电压，但注意电源电压的峰值不能超过驱动器的最大输入电压，否则可能会损坏驱动器。

B.电流确定：电源电流一般根据输出相电流I来确定。如果采用线性电源，电源电流一般可取I的1.1〜1.3倍;如果采用开关电源，电源电流一般可取I的1.5〜2.0倍。

步进电机的主要特性：

1. 在步进电机关机时要确保没有脉冲信号，当电机运行时如果加入适当的脉冲信号，它会转过一定的角度（称为步距角是）。转速与脉冲频率成正比。

2．永磁式式步进电机步距角7.5度，旋转360度，需要48个脉冲来完成。

3．步进电机具有快速启动和停止的优良特性。

4．只要改变脉冲，可以很容易地改变电机轴旋转的方向。

因此，目前的打印机，绘图仪，机器人设备以步进电机作为动力核心。

步进电机有以下好处：（1）成本低廉（2）坚固耐用（3）结构简单（4）高可靠性（5）无维修（6） 适用广泛（7）稳定性很高（8）无需反馈元件 相比伺服电机能适应多种工作环境使步进驱动模块正常工作。

步进电机驱动简单，并且驱动和控制在一个开放的闭环系统内。他们只需要4线。低速时，驱动器提供良好的扭矩，是有刷电机同一帧大小5 倍连续力距，或相当于无刷电机一倍扭矩。这往往不再需要变速箱。步进驱动系统迟缓，在限定的范围内，可以更好的减少动态位置误差。

步进电机有下列缺点：

1．共振效应和相对长的适应性。

2．在低速表现粗糙，除非微驱动器来驱动。 3．开环系统可能导致不可查觉的损失。

4．由于过载，他们消耗过多电流，因此趋向于过热运行。

5．亏损速度比较高，并可产生过多热量因此，他们噪音很大（尤其是在高速下）。

6．他们的滞后现象导致振荡，这是很难抑制的。

它的适用尺寸是有限制的，而他们的大小，定位精度主要取决于机器（例如，滚珠丝杠的精确度）。通过使用一个闭环控制方案这些缺点是可以克服的。

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