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1、基于TB6560的步进电机驱动电路设计作者：王党利 宁生科 马宝吉 整理转载：PPC888引言步进电机是一种将电脉冲转化为角位移的执行机构。驱动器接收到一个脉冲信号后，驱动步进电机按设定的方向转动一个固定的角度。首先，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；其次，通过控制脉冲顿率来控制电机转动的速度和加速度，从而达到涮速的目的。目前，步进电机具有惯量低、定位精度高、无累积误差、控制简单等特点，在机电一体化产品中应用广泛，常用作定位控制和定速控制。步进电机驱动电路常用的芯片有L297和 L298组合应用、3977、8435等，这些芯片一般单相驱动电流在2 A左右，无法驱动更大功率
2、电机，限制了其应用范围。本文基于东芝公司2008年推出的步进电机驱动芯片TB6560提出了一种步进电机驱动电路的设计方案。1步进电机驱动电路设计1.1 TB6560简介TB6560是东芝公司推出的低功耗、高集成两相混合式步进电机驱动芯片。其主要特点有：内部集成双全桥MOSFET驱动；最高耐压40 V，单相输出最大电流3.5 A(峰值)；具有整步、12、18、116细分方式；内置温度保护芯片，温度大于150时自动断开所有输出；具有过流保护；采用HZIP25封装。TB6560步进电机驱动电路主要包括3部分电路：控制信号隔离电路、主电路和自动半流电路。1.2步进电机控制信号隔离电路步进电机控制信号隔
3、离电路如图1所示，步进电机控制信号有3个(CLK、CW、ENABLE)，分别控制电机的转角和速度、电机正反方向以及使能，均须用光耦隔离后与芯片连接。光耦的作用有两个：首先，防止电机干扰和损坏接口板电路；其次，对控制信号进行整形。对CLK、CW信号，要选择中速或高速光耦，保证信号耦合后不会发生滞后和畸变而影响电机驱动，且驱动板能满足更高脉冲频率驱动要求。本设计中选择2片6N137高速光耦隔离CLK、CW，其信号传输速率可达到10 MHz，1片TLP521普通光耦隔离ENABLE信号。应用时注意：光耦的同向和反向输出接法；光耦的前向和后向电源应该是单独隔离电源，否则不能起到隔离干扰的作用。1.3步
4、进电机主电路如图2所示，步进电机主电路主要包括驱动电路和逻辑控制电路两大部分。驱动电路电源采用28 V，电压范嗣为4.540 V，提高驱动电压可增大电机在高频范围转矩的输出，电压选择要根据使用情况而定。VMB、VMA为步进电机驱动电源引脚，应接入瓷片去耦电容和电解电容稳压。OUT_AP、OUT_AM、OUT_BP、OUT_BM引脚分别为电机2相输出接口，由于内部集成了续流二极管，这4个输出口不用像东芝公司的 8435驱动芯片那样外接二极管，从而极大地减小电路板的布线空间。NFA、NFB分别为电机A、B相最大驱动电流定义引脚，最大电流计算公式为IOUT(A)=0.5(V)RNF()，若预先定义电
5、机每相的最大驱动电流为2.5 A，取RNF=0.2 ，则PGNDA、PGNDB、SGND分别为电机A、B相驱动引脚地和逻辑电源地。逻辑控制电路电源为5 V，VDD为逻辑电源引脚，应接入去耦电容和旁路电容减小干扰噪声；M0、PROTECT为工作状态和过流保护指示灯；RESET为芯片复位脚，低电平有效；OSC所接电容的大小决定了斩波器频率，推荐1001 000 pF，斩波频率为40044 kHz；M2、M1为细分设置引脚，外接拨码开关可设定不同的细分值，如整步、半步、18细分、116细分。由于步进电机在低频工作时，有振动大、噪声大的缺点，需要细分解决。步进电机的细分控制，从本质上讲是通过对步进电机
6、励磁绕组中电流的控制，使步进电机内部的合成磁场为均匀的圆形旋转磁场，从而实现步进电机步距角的细分。一般情况下，合成磁场矢量的幅值决定了步进电机旋转力矩的大小，相邻两合成磁场矢量之间的夹角大小决定了步距角的大小。DCY2、DCY1外接拨码开关设置电流衰减模式(0、25、50、100)，用于满足不同的步进电机需要。由于电机本身状况、供电电源状况及脉冲频率等其他因素的影响，步进电机可能会产生高频噪声，通过电流衰减模式的设置可减小甚至消除这种噪声。图3显示了衰减模式为0和50时线圈电流的变化，可看出波形具有明显的改善。1.4步进电机自动半流电路步进电机要减少发热，就要减少铜损和铁损。减少铜损就是减小电
7、阻和电流，要求在选型时尽量选择电阻小和额定电流小的电机，但是这往往与力矩和高速的要求相抵触。对于已选定的电机，首先，应充分利用驱动器的自动半流控制功能和脱机功能，自动半流在电机处于静态时自动减小电流，脱机功能是将输出电机电流切断；其次，细分驱动器由于电流波形接近正弦，谐波少，电机发热也会较少。减少铁损与电机驱动电压有关，高压驱动的电机虽然会带来高速特性的提升，但也带来发热的增加。所以应当选择合适的驱动电压等级，兼顾高速性、平稳性和发热、噪声等指标。为尽可能减小电机发熟，需要TB6560的TQ2和 TQ1引脚电平在电机工作时设置为电流输出最大，在电机不工作时电流减半甚至更小，故称为“自动半流电路
8、”。用NFA、NFB定义最大输出电流后，通过 TQ2和TQ1设置电流比率输出，设为00、01、10、11时，输出的电流分别为最大电流的100、75、50、25。改变电机的驱动电流，也就改变了电机输出扭矩的大小。自动半流电路设计选用可重复触发的单稳态电路芯片74CH123，用电机的驱动脉冲CLK作为单稳态电路的触发脉冲。单稳态电路的反向输出接TQ2引脚，电机驱动脉冲持续时TQ2一直保持低电平，无驱动脉冲时保持高电平。在图2电路中，TQ1连接3个跳线帽。接跳线 1，TQ2、TQ1始终同为高或低电平，驱动电流在25100切换；接跳线2，TQ2始终为低，电流在50100切换；接跳线3，电流在 2575
9、切换。可根据工作驱动电流需要选择不同跳线。2步进电机失步和越步问题及解决方法步进电机中产生的同步力矩无法使转子速度跟随定子磁场的旋转速度，从而引起失步。失步产生的主要原因及解决方法：步进电机的转矩不足，拖动能力不够，当驱动脉冲频率达到某临界值开始失步。由于步进电机的动态输出转矩随着连续运行频率的上升而降低，因而凡是比该频率高的工作频率都将产生失步。有3种解决方法：可使步进电机产生的电磁转矩增大，为此可在额定电流范围内适当加大驱动电流；在高频范围转矩不足时，适当提高驱动电路的驱动电压；改用转矩大的步进电动机等，也可使步进电机需要克服的转矩减小，为此可适当降低电机运行频率，以便提高电机的输出转矩。
10、步进电机起动失步。由于步进电机自身及所带负载存在惯性，当加速时间过短时会出现这一现象。应该设置合理的加速时间，使电机从低速度平稳上升到某个速度。 步进电机产生共振也是引起失步的一个原因。步进电机处于连续运行状态时，如果控制脉冲的频率等于步进电机的固有频率，将产生共振。在一个控制脉冲周期内，振动尚未得到充分衰减，下一个脉冲就已来到，因而在共振频率附近动态误差最大并导致步进电机失步。解决方法：减小步进电机的驱动电流；采用细分驱动方法和阻尼方法。转子在步进过程中获得过多的能量时，转子的平均速度会高于定子磁场的平均旋转速度，使得步进电动机产生的输出转矩增大，从而使步进电机产生越步。当步进电机存在越步时
11、，可减小步进电动机的驱动电流，以便降低步进电机的输出转矩或使减速时间加长。3试验结果设计时应该保证芯片逻辑电压低于驱动电压，否则芯片不能正常工作；在选取NFA、NFB检流电阻时应选功率不小于2 W的无感电阻；对电机驱动电源及驱动输出连线和地的印制板布线，应保证能稳定通过3 A电流；电源入口加熔断器保护驱动电路，以免电机的电流过大烧毁电路板。设计的驱动器应用于雕刻机X、Y、Z三轴步进电机的驱动，经过试验，雕刻的样品如图4所示。从最终结果看，精度满足目标要求。结语本文提出了基于TB6500的步进电机驱动电路设计方案，并给出了步进电机失步和越步问题的解决方法。试验证明，效果良好，达到预期目标。Edi
12、tors note: Judson Jones is a meteorologist, journalist and photographer. He has freelanced with CNN for four years, covering severe weather from tornadoes to typhoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder what it was like to huddle around a shortwave radio and through the cr
13、ackling static from space hear the faint beeps of the worlds first satellite - Sputnik. I also missed watching Neil Armstrong step foot on the moon and the first space shuttle take off for the stars. Those events were way before my time.As a kid, I was fascinated with what goes on in the sky, and wh
14、en NASA pulled the plug on the shuttle program I was heartbroken. Yet the privatized space race has renewed my childhood dreams to reach for the stars.As a meteorologist, Ive still seen many important weather and space events, but right now, if you were sitting next to me, youd hear my foot tapping
15、rapidly under my desk. Im anxious for the next one: a space capsule hanging from a crane in the New Mexico desert.Its like the set for a George Lucas movie floating to the edge of space.You and I will have the chance to watch a man take a leap into an unimaginable free fall from the edge of space -
16、live.待添加的隐藏文字内容1The (lack of) air up there Watch man jump from 96,000 feet Tuesday, I sat at work glued to the live stream of the Red Bull Stratos Mission. I watched the balloons positioned at different altitudes in the sky to test the winds, knowing that if they would just line up in a vertical str
17、aight line we would be go for launch.I feel this mission was created for me because I am also a journalist and a photographer, but above all I live for taking a leap of faith - the feeling of pushing the envelope into uncharted territory.The guy who is going to do this, Felix Baumgartner, must have
18、that same feeling, at a level I will never reach. However, it did not stop me from feeling his pain when a gust of swirling wind kicked up and twisted the partially filled balloon that would take him to the upper end of our atmosphere. As soon as the 40-acre balloon, with skin no thicker than a dry
19、cleaning bag, scraped the ground I knew it was over.How claustrophobia almost grounded supersonic skydiverWith each twist, you could see the wrinkles of disappointment on the face of the current record holder and capcom (capsule communications), Col. Joe Kittinger. He hung his head low in mission co
20、ntrol as he told Baumgartner the disappointing news: Mission aborted.The supersonic descent could happen as early as Sunday.The weather plays an important role in this mission. Starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limi
21、ted cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial
22、 airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause), he can expect a lot of turbulence.The balloon will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.53 kilometers). Here, Fearless Felix will unclip. He will ro
23、ll back the door.Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform.Below, the Earth becomes the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, hell be traveling fast, so despite the distance, it will not be like
24、diving into the deep end of a pool. It will be like he is diving into the shallow end.Skydiver preps for the big jumpWhen he jumps, he is expected to reach the speed of sound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the top of the water, he will begin to slow as he approaches th
25、e more dense air closer to Earth. But this will not be enough to stop him completely.If he goes too fast or spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes its not needed. Instead, he plans to deploy his 270-square-foot (25-square-meter) m
26、ain chute at an altitude of around 5,000 feet (1,524 meters).In order to deploy this chute successfully, he will have to slow to 172 mph (277 kph). He will have a reserve parachute that will open automatically if he loses consciousness at mach speeds.Even if everything goes as planned, it wont. Baum
27、gartner still will free fall at a speed that would cause you and me to pass out, and no parachute is guaranteed to work higher than 25,000 feet (7,620 meters).It might not be the moon, but Kittinger free fell from 102,800 feet in 1960 - at the dawn of an infamous space race that captured the hearts of many. Baumgartner will attempt to break that record, a feat that boggles the mind. This is one of those monumental moments I will always remember, because there is no way Id miss this.
