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FMI计量泵STH系列:如何解决步进电机震动问题

  • 更新时间2018-06-19 15:42:23

详细描述

How To Take Vibration Out of Step Motors如何解决步进电机震动问题

The best way to handle resonance in stepmotors usually involves moving troublesome areas out of harm's way.解决步进电机共振问题最好的方法就是将引起破坏的麻烦部分去除。

 

By Machine Design

Stepmotors are one of the most robust yet intricate motion-control products available. Although these motors are an engineering marvel, there are times when their performance just can nott cut it.

步进电机是其中一种可运用的最强大且复杂的动力控制产品,尽管电机是一个工程奇迹但有时他们的表现也不会降低他们的性能。

Take Vibration Out of Step MotorsFortunately, for those times, innovation and evolving problem-solving techniques can provide many options. Gearboxes can boost speed or torque. Special motors rated for IP65 or IPX7 handle applications needing protection from dust or liquids. But what if the stepper motor suffers from resonance? Again, several different techniques are available to damp stepper-motor resonance. But before exploring those methods and how they cut resonance, it helps to understand how resonance originates.

拿步进电机的震动来说,很幸运的是,在这种情况下,由于技术更新,相关问题的解决技巧为这个问题提供了多种方案。变速箱可提升速度或扭矩。IP65IPX7专属的电机可以解决需要防尘或防水的情况(案子)。但如果步进电机发生共振,那应该如何处理呢?目前已有几种可使用的方案可帮助减少或抑制步进电机共振问题,在列举如何减少共振的方法前,我们需要先了解共振是如何产生的。

Every stepmotor has a resonance spot. For each step that the motor takes, the rotating part, or rotor, oscillates around the new position before coming to a stop. The amount of time the motor oscillates is called its settling time. The rate of oscillation matches the resonant frequency with every step that the motor takes. The result is a motor that vibrates and has jitter. Its resonant frequency comes from the relationship between torque stiffness and inertia; changing either parameter changes the resonant frequency. For smooth operation, engineers try to design motors with resonant frequencies higher or lower than the operational envelope.

每个步进电机都有一个共振点,步进电机每走的一步,转子或者旋转体在停止之前都会摆动着(旋转着)去寻找一个新的位置,这个旋转时间称为它的稳定时间(校正时间),当步进电机每走一步的旋转的频率与共振频率相匹配(一致)时,就会导致电机震动和抖动。共振频率取决于扭矩的刚度与惯性的关系,改变任意一个参数均可改变共振频率。为了顺畅的操作或使用,工程师普遍会将共振频率设计得高于或者低于操作极限。

Most troubleshooting guides recommend modifying several factors to fit the application. For example, raising or lowering operating voltage or current, adding inertial load, or using a higher step resolution shifts the resonant frequency of the motor.

主流的故障解决指南推荐改变几种影响因素以便适应相应的运用从而达到解决目的。例如,增加或减低供应电压或电流,增加惯性的负载,或使用更高的步进细分来改变电机的共振频率。

resonance.jpg

However, it may not be possible to change operating parameters enough to improve performance without jeopardizing the overall design. In such situations it might be best to go with an inertial dampening device or damper. Each damper type has its own pros and cons, but most effectively improve stepmotor performance in certain situations. The most common dampers are the rear-mounted inertial damper and the internal design damper.

然而,这样的方式并不能达到改变相应的参数从而实现不破坏电机原有设计的情况下提升工作性能。这样的情形,最好的方式可能是在内部或者外部增加一个减震设备或阻尼器,虽然每款阻尼器都有它的利弊,但在这种情形,这个是最有效的提升电机性能的方式。最常见的增加阻尼器的方式是在电机的后背安装一个外置阻尼器或内置一个阻尼器。

Rear-mounted dampers essentially add an extra inertial load to the motor shaft which, in turn, changes the resonant frequency. As resonant frequency changes, the resonance spot shifts to a lower speed range. This effectively reduces vibration or jittery movement at mid to high speeds. Furthermore, it appears that rear-mounted dampers also decrease resonant spikes throughout the operational speed range of a motor.

电机尾端增加一个阻尼器,明显地电机的转轴增加一个额外的惯性复杂,从而实现改变共振频率,随着共振频率的改变,电机的共振点就会降至一个较低的速度范围。这个方式可以有效解决中高度出现的电机共振问题。并且,后置阻尼器也能在电机的整个极限操作速度范围内降低共振极点(触发点)。

A rear-mounted damper can significantly reduce the amount of resonance. Although these dampers are designed to be sleek and small, some systems lack the space for this type of damper. But even in designs with adequate space they tend to be an unattractive option because of the larger size and added cost of the dmper. Those situations might call for an internal damper.

后置阻尼器虽然可以明显的减少共振的次数,且有些阻尼器的设计也很小巧简洁,但某些产品的设计还是没有足够的空间安装阻尼器,即使有足够的空间,安装阻尼器的方式并不那么吸引人,因为这样会增加占用的空间且阻尼器也会额外增加了成本,这样的情况可考虑内置阻尼器。

Nema-17-damper.jpg

One internal technique developed by Lin Engineering is to let the motor act as its own damper. This is done by placing an electromagnetic drag on the rotor through a special winding and hookup design called an R-winding and T-connection. Stepmotors rotate whenever the motor control receives a step pulse. However, the pulse that steps the motor never actually reaches the motor. Instead it controls power applied to two phase windings in the motor called Phase 1 and Phase 2. If both phases are powered, then the direction of rotation is controlled by which phase is turned off. Each step corresponds to a motor rotation of 0.45°, 0.9°, or 1.8°. The off phase is powered with opposite polarity for the third step, while the other phase is deenergized for the fourth step. The sequence the motor steps through is such that half of the motor is energized for one step, then both halves of the motor energize for the next. The one-on, two-on sequence sets up an imbalance in the motor that creates noise, vibration, and resonance.

Lin Engineering开发了一种内置的让电机本身就成为阻尼器的技术(产品),通过在转轴(旋转器)上安装一个电磁阻力器,这种电磁阻力器是一种称为R绕转和T连接的特殊绕组和连接设计。不管任何时候,一旦电机的控制接收到步进脉冲时,转轴(旋转器)就会转动,然而,实际上让电机转动的脉冲没有达到电机,相反,它控制供应给电机相位1和相位2绕组的供电,如果两组相位都激活,那么转轴(旋转器)的旋转方向则取决于哪个相位断电了。每一步,电机相应的旋转0.45°,0.9°或1.8°,关闭的相位通上相反极向的电并进入第三步,同时另外一个相位则被断电(断开)而进去第四步。电机的步数次序是单个相位的电机被激活发生第一步,然后两个单相位的电机被激活进入下一步,这种一个通电,两个激活的次序接连着在一种不平衡的方式下运作,就会导致电机发出噪音,震动和共振。

Settling times for the one-phase-on period are shorter than the times with two phases powered. A motor with only one phase does not rotate. However, by keeping both phases powered, settling times for both parts of the sequence remain the same and are easily damped. The Tconnection and R-winding were created to eliminate the one-phase on position.

单相位开的稳定时间(校正时间)比两相位同时激活所需的时间短,只有单相位的电机不会运转。然后,同时保持双相位激活,每个相位所需的时间一样且更容易被阻尼的(减弱的)。T连接和R绕组的设计就是为了消除单相位的接通位置。

Step_Motor_Settling_time.jpgSettling_Time_vs_power.jpg

The T-connection forces the motor to always energize both phases. It uses a ratio of the two phases so the system needs no extra energy nor creates additional heat, yet the motor remains in a two-phases-on state at all times.

T连接促使电机一直激活两个相位,它利用两个相位的频率使两个相位一直保持激活状态,所以系统无需额外的能量或制造额外的热。

Furthermore, the T-connection changes the motor’s electrical characteristics such that the inductance level falls between a series and parallel connection. This connection uses less current and produces more torque at midrange speeds. Under normal wiring, series connections work best at low speeds and parallel connections at high speeds. However, the midrange speeds were always poorly served by both connection types. The T-connection fills that gap.

T连接改变了电机的电力特性,例如电感系数落在串联和并联之间。这种连接方式在中等速度范围使用更小的电流但产生更大的扭矩。常规的电线,在串联的低速时性能最好,并联时则高度性能最好,所以就会出现中速时,两种连接方式的工作性能都较差,T连接正好弥补了这个空缺。

The R-winding also forces the motor to always step in a two-phase-on state. This is an internal design built into the windings rather than made at the outer connections as with the T-connection. Specific ratios of both phases are turned on as well, but still result in a two-phase-on state during each step. Internally, both phases are wound and connected such that electrically, there is a 22.5° shift.

R绕组也迫使电机一直保持进入两相位同时被激活的状态,这种是内置在绕组上而不像T连接在设计在外部连接上。即使激活两个相位的特定比率,也会使在每一步时两个相位处于同时激活的状态。在内部,两个相位相互绕组和连接,有一个22.5°的位移。

Electric_Phase_Diagram.jpg

All in all, stepmotors will always have resonance. The key to eliminate its effects lies in either controlling where the resonant point falls or in reducing its severity.

综上所述,步进电机总是避不开共振,解决共振的影响在关键在于控制共振的点和减少它的强度或严重性。

Figure A – Series connections work well at low speeds, while parallel connections provide good high-speed operation. However, neither provides proper operation at midrange speeds. The T-connection with R-winding by Lin Engineering optimizes midrange operations while reducing noise and jitter by maintaining current thourgh both phase windings at all times.

图片A,串联在低速时运作良好,并联则出现在高速,但中速时两种连接方式的表现均不令人满意。Lin开发的T连接和R绕组则弥补了中速的空缺并使得电机在整个工作过程中减少了噪音和颤动。

Series_Connection.jpg