步进电机运动控制系统外文文献翻译中英文

步进电机运动控制系统外文文献翻译中英文外文文献翻译

(含:英文原文及中文译文)

文献出处:YH Lee. Stepper motor motion control system design [J]. Equipment Manufacturing Technology, 2015，2(6):31-41.

英文原文

Stepper motor motion control system design

YH Lee

Abstract

Stepper motors are open-loop control elements that convert

electrical pulse signals to angular or linear displacements. In the case of non-overload, the rotation speed and stop position of the motor depend only on the frequency and pulse number of the pulse signal, and is not affected by the load change, that is, a pulse signal is applied to the motor, and the motor rotates through a step angle. The existence of this linear relationship, coupled with the fact that the stepper motor has only periodic errors and no cumulative errors, is a feature. It is very simple to use a stepper motor to control the speed and position. Stepper motor speed control is generally to change the frequency of the input stepper motor pulse to achieve stepper motor speed control, because the stepper motor for each pulse to rotate a

fixed angle, so that you can control the stepper motor The time interval

from one pulse to the next pulse changes the frequency of the pulse. The length of the delay controls the step angle

specifically to change the rotation speed of the motor, thereby realizing the stepping motor speed control. In this design scheme, the internal timer of the AT89C51 microcontroller is used to change the frequency of the CP pulse to realize the control of the rotation speed

of the stepper motor to realize the functions of the motor speed adjustment and forward and reverse rotation. The design takes into consideration that the CPU may be disturbed when executing instructions, causing the program to "run away" or enter the "endless loop". Therefore, the watchdog circuit is designed using a microprocessing system monitoring integrated chip manufactured by MAXIM. MAXI813. This article also gives the related hardware block diagram and software flow chart in detail, and has compiled the assembly language program.

Keywords: stepper motor single chip microcomputer speed control system

Introduction

Stepper motors were first developed by the British in 1920. The invention of the transistor in the late 1950s was also gradually applied to a stepping motor, which made it easier to control the digitization. After continuous improvement, today's stepper motors have been widely used in mechanical systems with high controllability such as high positioning accuracy, high decomposition performance, high

responsiveness, and reliability. In the production process, where automation, labor saving, and

high efficiency are required, we can easily find traces of stepper motors, especially those that emphasize speed, position control, and flexible control applications that require precise command operation. The most. As an actuator, a stepper motor is one of the key products of electromechanical integration and is widely used in various automation control systems. With the development of microelectronics and computer technology, the demand for stepper motors is increasing day by day, and there are applications in various national economic fields. A stepper motor is an actuator that converts an electrical pulse signal into an angular or linear displacement. Stepper motors can be driven directly with digital signals and are very easy to use. The general motor is continuous rotation, while the stepper motor has two basic states of positioning and operation. When there is a pulse input, the stepping motor rotates step by step, and when it is given a pulse signal, it turns a certain angle. The angular displacement of the stepping motor is strictly proportional to the number of input pulses and is synchronized in time with the input pulse. Therefore, as long as the number of input pulses, the frequency, and the phase sequence of the motor windings are controlled, the desired rotation angle can be obtained. Speed and direction of rotation. When there is no pulse input, the air gap magnetic field can keep the rotor in the original position under the

excitation of the winding power supply. So it is very suitable for

single chip microcomputer control. Stepper motors also have features such as fast start, precise stepping and positioning, and are thus widely used in CNC machine tools, plotters, printers, and optical instruments. Stepping motors have become the third category of motors except for DC motors and AC motors. Traditional electric motors, as electromechanical energy conversion devices, play a key role in human production and life into the electrification process. The stepper motor can be used as a special motor for control, and it is widely used in various open-loop control because it has no accumulated error (accuracy is 100%). Now more commonly used stepper motors include reactive stepper motors (VR), permanent magnet stepper motors (PM), hybrid stepper motors (HB), and single-phase stepper motors. Permanent-magnet type stepping motor is generally two-phase, small torque and volume, step angle is generally 7.5 degrees or 15 degrees; Reactive stepping motor is generally three-phase, can achieve large torque output, stepping The angle is generally 1.5 degrees, but the noise and vibration are large. The rotor of the reactive stepper motor is magnetically routed from a soft magnetic material, and the stator has a multi-phase excitation winding, which generates torque using a change in the magnetic permeability. Hybrid stepping motor refers to the advantage of mixing permanent magnet type and reactive type. It is divided into two phases and five phases: the two-phase step angle is generally 1.8 degrees and

the five-phase step angle is generally 0.72 degrees. This type of stepper

motor is the most widely used and is also the stepper motor used in this subdivision drive scheme.

1 stepper motor overview

1. 1 stepper motor features:

1) The accuracy of a typical stepper motor is 3-5% of the step angle and does not accumulate. 2) The allowable temperature of the stepper motor is high. Excessively high temperature of the stepping motor first demagnetizes the magnetic material of the motor, resulting in a drop in torque and even loss of synchronism. Therefore, the maximum temperature allowed for the appearance of the motor should depend on the demagnetization point of the magnetic material of different motors; generally, the demagnetization of the magnetic material. The points are all above 130 degrees Celsius, and some are even up to 200 degrees Celsius. Therefore, the external temperature of the stepper motor is completely normal at 80-90 degrees Celsius. 3) The torque of the stepper motor will decrease as the rotation speed increases. When the stepper motor rotates, the inductance of each phase winding of the motor will form a counter electromotive force; the higher the frequency, the greater the counter electromotive force. Under its effect, the motor's phase current decreases as the frequency (or speed) increases, causing the torque to drop. 4) The stepping motor can run normally at low speed,

but it cannot start if it is higher than a certain speed, accompanied by howling. The stepper motor

has a technical parameter: No-load starting frequency, that is the pulse frequency that the stepping motor can start normally under no-load conditions. If the pulse frequency is higher than this value, the motor cannot start normally, and step loss or stall may occur. In the case of load, the starting frequency should be lower. If the motor is to be rotated at a high speed, the pulse frequency should have an acceleration process, that is, the starting frequency is low, and then it is increased to a desired high frequency (motor speed is raised from low speed to high speed) at a certain acceleration. TC \* MERGEFORMAT

1. 2 working principle of stepping motor

A stepper motor is a type of motor that is controlled by an

electrical pulse and converts the electrical pulse signal into a phase-shifted motor whose mechanical displacement and rotational speed are proportional to the number of pulses and the pulse frequency of the input motor winding. Each pulse signal can be stepped The feed motor rotates at a fixed angle. The number of pulses determines the total angle of rotation. The frequency of the pulse determines the speed of the motor. When the stepper receives a pulse signal, it drives the stepper motor to rotate in the set direction. At a fixed angle (called "step angle"), its rotation is performed step by step at a fixed angle. By controlling the number of pulses to control the angular displacement,

so as to achieve the purpose of accurate positioning; At the same time, by controlling the pulse frequency

to control the speed and acceleration of the motor rotation, so as

to achieve the purpose of speed control.

2 Basic requirements for design

Study the characteristics, working principle, and specific speed regulation principle of stepper motor. TC \* MERGEFORMAT

Basic requirements The stepper motor uses a three-phase stepper

motor with a power of 1W. When the speed is in the range of 0 to

1000r/min, the maximum accuracy is 2%. To basically complete the graduation design, the stepper motor can perform precise speed control, positive and negative rotation, and it can not lose step when starting. Basically, there is no Oscillation, can complete the complete hardware circuit diagram, software design.

3 Argumentation of the plan

3.1 Determination of control methods

Although the stepper motor control is a relatively accurate, open-

loop stepper motor control system has the advantages of low cost, simple, convenient control, etc., in the open-loop system of the stepper motor using the microcontroller, the frequency of the CP pulse of the control system or change The cycle is actually controlling the speed of the stepper motor. There are two ways the system can achieve stepper motor speed control. One is delay, the other is timing. The delay method is to call a delay subroutine after each commutation. After the delay is

over, the commutation is executed again. In this way, CP pulses or commutation cycles with a certain frequency can be issued. The delay time of the delay subroutine and the time used by the commutation program are the cycles of the CP pulse. This method is simple, uses less resources, and is implemented by software. Different subroutines can be called to achieve different speeds. However, it takes a long time to process the CPU and cannot handle other tasks at runtime. Therefore, it is only suitable for a simpler control process. The timing method is to use the timer timing function in the microcontroller system to generate an arbitrary period of the timing signal, so that the period of the system output CP pulse can be conveniently controlled. When the timer is started, the timer counts up the system and its cycle starting from the loaded initial value. When the timer overflows, the timer generates an interrupt and the system transfers to execute the timer interrupt subroutine. The motor commutation subroutine is placed in the timer interrupt service routine. The timer interrupt is once and the motor is reversed once to achieve motor speed control. Since there is a certain time interval from the start of restarting the timer to the timer application interruption, the timing time is increased. In order to reduce this timing error and achieve accurate timing, it is necessary to make appropriate adjustments to the initial value of reloading counts. . The initial value of adjusted reloading mainly considers two factors and one is the time required to interrupt the

response. The second is the time occupied by reloading the initial value instruction, including other instructions that interrupt the service program before reloading the initial value. After these two factors are combined, the correction amount of the reload count initial value takes 8 machine cycles, that is, the timing time is shortened by 8 machine cycles. When using the timer interrupt to control the motor shift, it is actually changing the size of the timer load value. In the control process, a discrete approach is used to approximate the ideal speed curve. In order to reduce the time for calculating the load value in each step, the load value required for the speed of each discrete point is fixed in the ROM of the system when the system is designed. The system uses the table look-up method to find the required load value in the system. Significantly reduce the time spent on CPU and improve the response speed of the system. Most stepper motor motion control systems are designed to run in an open-loop state, because the cost is low, and the position control inherent in the motion control technology can be provided without feedback. However, in some applications, more reliability, security, or product quality assurance is required. Therefore, closed-loop control is also an option. Here are some methods for achieving closed-loop control of stepper motors: 1) Step-by-step confirmation, This is the simplest displacement control, using a low-value optical encoder to calculate the amount of step movement. A simple loop compares the stepper motor with the command

verification and verifies that the stepper motor moves to the expected position; 2) Back-EMF, a sensorless detection method, uses a stepper motor's back EMF (eleCtromotiveCe, emf) signal , Measure and control speed. When the back-EMF voltage drops to the monitoring detection level, the closed-loop control is changed to the standard open-loop to complete the final displacement movement; 3) Full-servo control refers to the full-time use of feedback devices for stepper motors - encoders, decoding , or other feedback sensors to more accurately control the stepper motor displacement and torque. Other methods include a variety of different back-EMF control motor parameter measurements and software techniques that some manufacturers use. Here, the stepper drive monitors and measures the motor coils and uses voltage current information to increase the stepper motor control. Positive damping uses this information to block the speed of vibration, producing more usable torque output and reducing torque-induced mechanical vibration losses. No encoder installation monitoring uses information to detect the loss of synchronous speed. Conventional stepper motor control usually employs feedback devices and non-sensing methods, and is an effective method to implement a sports application with safety requirements, dangerous conditions or high accuracy requirements. Most stepper motor-based systems typically operate in an open-loop state, which provides a low-cost solution. In fact, stepper systems can improve the performance

of displacement control without feedback. However, when the stepper motor is running in open loop, there may be a simultaneous loss between the command pace and the actual step. Closed-loop control, which is part of traditional step control, can effectively provide higher reliability, safety, or product quality. In these stepper systems, the closed loop of the feedback device or indirect parametric sensing method can correct or control out-of-step, monitor motor stagnation, and ensure greater available torque output. Recently, closed-loop control (CLC) of stepper motors can also help implement smart distributed motion architectures. However, there is a risk of out-of-step operation in open-loop operation, which will result in positioning errors. However, compared to encoders used in servo systems, closed-loop stepper motors use encoders that are less costly. Therefore, closed-loop control is selected.

3.2 Determination of Drive Mode

There are generally two methods for driving a stepping motor. One is directly driven by the CPU. This method is generally not suitable because the output current pulse of the CPU is extremely small and it cannot sufficiently rotate the stepping motor. One is indirect driving

by the CPU, which is to amplify the signal output from the CPU, and then directly drive or indirectly drive the stepper motor through

photoelectric isolation. This method is relatively safe and reliable. The solid design should use a CPU to drive the stepper motor indirectly. The

tachogenerator of the encoder is also used as the speed measurement tool. Because the closed-loop control is selected, there must be feedback components. There are generally two types of feedback components. One is the coaxial tachometer generator, and the speed of the stepping motor is fed back. Back, and then through the display and stepper motor adjustment; Another is through the optical coaxial encoder to the stepper motor speed feedback back to the stepper motor to adjust; compared to the latter, the latter The design is relatively simple, inexpensive, safe and reliable, and less polluting. The latter is generally used for solids, and photoelectric crumblers are used as feedback components.

3. 3 Selection of Drive Circuit

There are many kinds of driving motors for stepping motors, but the most common ones are single voltage driving, dual voltage driving, chopper driving, subdivision control driving and so on. Single-voltage driving is the simplest driving circuit in stepper motor control. It is essentially a single-phase inverter. Its greatest feature is its simple structure, because of its low work efficiency, especially its prominent features at high frequencies. Its external resistor R consumes a considerable amount of heat, which affects the stability of the circuit. This type of drive is generally used only in the drive circuit of a low-power stepper motor. Dual-voltage driving is generally driven by two power supply voltages. Since these two power supplies are one high

voltage and one low voltage, they are also called high and low voltage driving circuits. The disadvantage of the dual-voltage driving circuit is that the valley point appears in the current at the high-low voltage connection, which inevitably causes the torque to drop at the valley point. Not suitable for normal operation of the motor. For the chopper circuit drive, this disadvantage can be overcome and the efficiency of the stepper motor can also be improved. Therefore, it is a good driver circuit from the standpoint of improving efficiency. It can use a higher power supply voltage and does not require an external resistor to limit the rated current and reduce the time constant. However, due to the sawtooth fluctuations at the top of the waveform, large electromagnetic noise is generated. The subdivision drive is powered by a pulse voltage. For a voltage pulse, the rotor can rotate one step. Generally, according to the voltage pulse distribution method, each phase winding of the stepping motor will alternately switch, and the rotor of the stepping motor can be fixed. Rotate. The subdivided control circuit is generally divided into two types. One is to use a linear analog power amplifier to obtain a staircase current. This method is simple but inefficient. The other method is to use a single-chip microcomputer to obtain the step current by using the method of pulse width modulation. This method requires complex calculations to make the substepped step angles uniform. However, due to the fact that the design of the stepper motor requires a relatively wide range of

high-speed adjustments, the drive chip 8713 should be used to drive the

motor and the speed of the stepper motor must be controlled by software.

中文译文

步进电机运动控制系统设计

作者:YH Lee

摘要

步进电机是将电脉冲信号转变为角位移或线位移的开环控制元件。在非超载的情况下，电机的转速、停止的位置只取决于脉冲信号的频率和脉冲数，而不受负载变化的影响，即给电机加一个脉冲信号，电机则转过一个步距角。这一线性关系的存在，加上步进电机只有周期性的误差而无累积误差等特点。使得在速度、位置等控制领域用步进电机来控制变的非常的简单。步进电机的调速一般是改变输入步进电机的脉冲的频率来实现步进电机的调速，因为步进电机每给一个脉冲就转动一个固定的角度，这样就可以通过控制步进电机的一个脉冲到下一个脉冲的时间间隔来改变脉冲的频率，延时的长短来具体控制步进角来改变电机的转速，从而实现步进电机的调速。在本设计方案中采用 AT89C51 型单片机内部的定时器改变CP 脉冲的频率从而实现对步进电机的转速进行控制，实现电机调速与正反转的功能。设计时考虑到 CPU 在执行指令时可能受到干扰的冲击, 导致程序” 跑飞” 或者进入” 死循环” , 因此,设计了看门狗电路, 使用的是MAXIM 公司生产的微处理系统监控集

成芯片 MAXI813。本文还详细地给出了相关的硬件框图和软件流程图，并编制了该汇编语言程序。

关键词: 步进电机单片机调速系统

引言

步进电机最早是在 1920 年由英国人所开发。 1950 年后期晶体管的发明也逐渐应用在步进电机上，这对于数字化的控制变得更为容易。以后经过不断改良，使得今日步进电机已广泛运用在需要高定位精度、高分解性能、高响应性、信赖性等灵活控制性高的机械系统中。在生产过程中要求自动化、省人力、效率高的机器中，我们很容易发现步进电机的踪迹，尤其以重视速度、位置控制、需要精确操作各项指令动作的灵活控制性场合步进电机用得最多。步进电机作为执行元件，是机电一体化的关键产品之一, 广泛应用在各种自动化控制系统中。随着微电子和计算机技术的发展，步进电机的需求量与日俱增，在各个国民经济领域都有应用。步进电机是将电脉冲信号变换成角位移或直线位移的执行部件。步进电机可以直接用数字信号驱动，使用非常方便。一般电动机都是连续转动的，而步进电动机则有定位和运转两种基本状态，当有脉冲输入时步进电动机一步一步地转动，每给它一个脉冲信号，它就转过一定的角度。步进电动机的角位移量和输入脉冲的个数严格成正比，在时间上与输入脉冲同步，因此只要控制输入脉冲的数量、频率及电动机绕组通电的相序，便可获得所需的转角、转速及转动方向。在没有脉冲输入时，在绕组电源的激励下气隙磁场能使转子保持原有位置处于定位状态。因此非常适合于单片机控制。步进电机还具有快速启动、精确步进和定位等特点，因而在数控机床，绘图仪，打印机以及光学仪器中得到广泛的应用。步进电动机已成为除直流电动机和交流电动机以外的第三类电动机。传统电动机作为机电能量转换装置，在人类的生产和生活进入电气化过程中起着关键的作用。步进电机可以作为一种控制用的特种电机，利用其没有积累误差(精度为 100%) 的特点，广泛应用于各种开环控制。现在比较常用的步进电机包括反应式步进电机(VR) 、永磁式步进电机(PM) 、混合式步进电机(HB)和单相式步进电机等。永磁式步进电机一般为两相，转矩和体积较小，步进角一般为

7. 5 度或 15 度; 反应式步进电机一般为三相，可实现大转矩输出，步进角一般为 1. 5 度，但噪声和振动都很大。反应式步进电机的转子磁路由软磁材料制成，定子上有多相励磁绕组，利用磁导的变化产生转矩。混合式步进电机是指混合了永磁式和反应式的优点。它又分为两相和五相: 两相步进角一般为 1. 8 度而五相步进角一般为 0. 72 度。这种步进电机的应用最为广泛，也是本次细分驱动方案所选用的步进电机。 1步进电机概述

1. 1 步进电机的特点:

1) 一般步进电机的精度为步进角的 3-5%，且不累积。 2) 步进电机外表允许的温度高。步进电机温度过高首先会使电机的磁性材料退磁，从而导致力矩下降乃至于失步，因此电机外表允许的最高温度应取决于不同电机磁性材料的退磁点; 一般来讲，磁性材料

的退磁点都在摄氏 130 度以上，有的甚至高达摄氏 200 度以上，所以步进电机外表温度在摄氏 80-90 度完全正常。 3) 步进电机的力矩会随转速的升高而下降。当步进电机转动时，电机各相绕组的电感将形成一个反向电动势; 频率越高，反向电动势越大。在它的作用下，电机随频率(或速度) 的增大而相电流减小，从而导致力矩下降。 4) 步进电机低速时可以正常运转, 但若高于一定速度就无法启动, 并伴有啸叫声。步进电机有一个技术参数: 空载启动频率，即步进电机在空载情况下能够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，可能发生丢步或堵转。在有负载的情况下，启动频率应更低。如果要使电机达到高速转动，脉冲频率应该有加速过程，即启动频率较低，然后按一定加速度升到所希望的高频(电机转速从低速升到高速) 。 TC \* MERGEFORMAT

1. 2 步进电机的工作原理

步进电机是一种用电脉冲进行控制 , 将电脉冲信号转换成相位移的电机 , 其机械位移和转速分别与输入电机绕组的脉冲个数和脉冲频率成正比 , 每一个脉冲

信号可使步进电机旋转一个固定的角度. 脉冲的数量决定了旋转的总角度 , 脉冲的频率决定了电机运转的速度. 当步进驱动器接收到一个脉冲信号，它就驱动步进电机按设定的方向转动一个固定的角度(称为“步距角”) ，它的旋转是以固定的角度一步一步运行的。可以通过控制脉冲个数来控制角位移量，从而达到准确定位的目的; 同时可以通过控制脉冲频率来控制电机转动的速度和加速度，从而达到调速的目的。

2 设计的基本要求

研究步进电机的特性、工作原理、及其具体的调速原理。 TC \* MERGEFORMAT

基本要求步进电机采用三相步进电机，功率为 1W。调速范围为 0 到

1000r/min 最高转速时，精度 2% 要基本上完成毕业设计，作到步进电机能精确的调速，正反转、并能在起动时不失步，基本上没有振荡，能完成完整的硬件电路图，软件设计。 3 方案的论证

3. 1 控制方式的确定

步进电机控制虽然是一个比较精确的，步进电机开环控制系统具有成本低、简单、控制方便等优点，在采用单片机的步进电机开环系统中，控制系统的 CP 脉冲的频率或者换向周期实际上就是控制步进电机的运行速度。系统可用两种办法实现步进电机的速度控制。一种是延时，一种是定时。延时方法是在每次换向之后调用一个延时子程序，待延时结束后再次执行换向，这样周而复始就可发出一定频率的 CP 脉冲或换向周期。延时子程序的延时时间与换向程序所用的时间和，就是 CP 脉冲的周期，该方法简单，占用资源少，全部由软件实现，调用不同的子程序可以实现不同速度的运行。但占用 CPU 时间长，不能在运行时处理其他工作。因此只适合较简单的控制过程。定时方法是利用单片机系统中的

定时器定时功能产生任意周期的定时信号，从而可方便的控制系统输出 CP 脉冲的周期。当定时器启动后，定时器从装载的初值开始对系

统及其周期进行加计数，当定时器溢出时，定时器产生中断，系统转去执行定时中断子程序。将电机换向子程序放在定时中断服务程序中，定时中断一次，电机换向一次，从而实现电机的速度控制。由于从定时器装载完重新启动开始至定时器申请中断止，有一定的时间间隔，造成定时时间增加，为了减少这种定时误差，实现精确定时，要对重装的计数初值作适当的调整。调整的重装初值主要考虑两个因素一是中断响应所需的时间。二是重装初值指令所占用的时间，包括在重装初值前中断服务程序重的其他指令因。综合这两个因素后，重装计数初值的修正量取 8 个机器周期，即要使定时时间缩短 8 个机器周期。用定时中断方式来控制电动机变速时，实际上是不断改变定时器装载值的大小。在控制过程中，采用离散办法来逼近理想的升降速曲线。为了减少每步计算装载值的时间，系统设计时就把各离散点的速度所需的装载值固化在系统的 ROM 中，系统在运行中用查表法查出所需的装载值，这样可大幅度减少占用 CPU 的时间，提高系统的响应速度愿大多数步进电机运动控制系统都运行在开环状态下，因为成本较低，并可提供运动控制技术固有的位置控制，无须反馈。但是，在某些应用中，需要更多的可靠性、安全性或产品质量的保证，因此，闭环控制也是一种选择. 以下是一些实现步进电机闭环控制的方法: 1) 步进确认，这是最简单的位移控制，使用一个低值的光学编码器计算步进移动的数量。一个简单的回路与指令校验的步进电机比较，验证步进电机移动到预计的位置; 2) 反电动势, 一种无传感器的检测方法，使用

步进电机的反电动势(eleCtromotiveforCe， emf) 信号，测量和控制速度。当反电动势电压降至监测探测水平时，闭环控制转为标准开环，完成最终的位移移动; 3) 全伺服控制，指全时间的使用反馈设备，用于步进电机--编码器、解

码器、或其它反馈传感器上，从而更为精确地控制步进电机位移和转矩。其它的方法包括各种不同的反电动势控制电机参数测量和软件技术，一些制造企业都会使用这些方法。这里，步进驱动监控和测量电机线圈，使用电压额电流信息提高步进电机控制。正阻尼使用这一信息阻挡振动的速度，产生更多的可用的转矩输出，降低转矩的机械振动损耗。无编码器安装监测采用信息检测同步速度的损耗。传统步进电机控制通常采用反馈设备和非传感方法，是有效的实现带有安全需求、危险状况或高精确度要求的运动应用的方法。大多数基于步进电机的系统，一般都运行在开环状态下，这样可提供一个低成本的方案。事实上，步进系统可提高位移控制的的性能，且不需要反馈。但是，当步进电机在开环时运行，在命令步幅和实际步幅之间会有同步损耗的可能。闭环控制，是传统步进控制的一个部分，能有效地提供更高地可靠性、安全性或产品质量。在这些步进系统中，反馈设备或间接参数传感方法的闭环能进行校正或控制失步、监测电机停滞，以及确保更大的可用转矩输出。近期，步进电机的闭环控制(CLC) 还能帮助执行智能分布运动架构。然而，开环操作会有失步的风险，这将产生定位失误。但与伺服系统中使用的编码器相比，闭环步进电机采用的编码器成本更低。故选择闭环控制。

3.2 驱动方式的确定

并于步进电机的驱动一般有两种方法，一种是通过 CPU 直接来驱动，这种方法一般不宜采用，因为 CPU的输出电流脉冲是特别小的它不能足以让步进电机的转动; 别一种是通过 CPU 来间接驱动，就是把从 CPU输出的信号进行放大，然后直接驱动或是再通过光电隔离间接来驱动步进电机，这种方法比较安全可靠。固本次设计应采用 CPU 间接驱动步进电机。用编码器还的测速发电机作为转速测量工具, 因为选择了闭环控制，就必须有反馈元件，反馈元件一般有两种，一种是采用同轴的测速发电机，把步进电机的转速反馈回来，然后通过显示器显

示出来并对步进电机进行调节; 别一种是通过光同轴的电编码器把步进电机的转速反馈回来对步进电机进行调节; 两者相比，后者的设计比较简单，价格便宜，安全可靠，污染少。固一般采用后者，用光电骗码器作为反馈元件。 3. 3 驱动电路的选择

步进电机的驱动电机有多种，但最为常用的就是单电压驱动、双电压驱动、斩波驱动、细分控制驱动等。单电压驱动是步进电机控制中最为简单的一种驱动电路，它在本质上是一个单间的反相器。它的最大特点是结构简单，因它的工作效率低，特别是在高频下更显的突出。它的外接电阻 R 要消耗相当一部分的热量，这样就会影响电路的稳定性所以此种驱动方式一般只用在小功率的步进电机的驱动电路中。双电压驱动是电路一般采用两种电源电压来驱动，因这两个电源分别是一个为高压一个为低压，因此也称为高低

压驱动电路。双电压驱动电路的缺点是在高低压连接处电流出现谷点，这样必然引起力矩在谷点处下降。不宜于电机的正常运行。对于斩波电路驱动则可以克服这种缺点，并且还可以提高步进电机的效率。所以从提高效率来看这是一种很好的驱动电路，它可以用较高的电源电压，同时无需外接电阻来限定期额定电流和减少时间常数。但由于其波形顶部呈现锯齿形波动，所以会产生较大的电磁噪声。细分驱动是用脉冲电压来供电的，对于一个电压脉冲，转子就可以转动一步，一般会根据电压脉冲的分配方式，步进电机各相绕阻会轮流切换，固可以使步进电机的转子旋转。细分控制的电路一般分为两类，一类是采用线性模拟功率放大器的方法获得阶梯形电流，这种方法简单，但效率低。别一种是用单片机采用数子脉宽调制的方法获得阶梯电流，这种方法需要复杂的计算可使细分后的步距角一致。但因本次设计对步进电机的精度要求比较高转速的调节范围比较广，固应选用驱动芯片 8713 来驱动，并通过软件来实现步进电机的调速。