電動線性執(zhí)行器的類型介紹及選型指南（連載二）
需要了解的術(shù)語
Terms to Know About
這里介紹了一些描述電動線性執(zhí)行器的的術(shù)語。
Here we define some of the most prevalent terms describing electric linear actuators.
靜態(tài)負(fù)載能力
Static Load Capacity
電動線性執(zhí)行器的靜態(tài)負(fù)載是指當(dāng)所連接的電機(jī)處于滑行模式時，移動執(zhí)行器活塞所需的最小外力。在滑行模式下，電機(jī)處于空轉(zhuǎn)狀態(tài)，沒有驅(qū)動電壓，電機(jī)端子處于開路狀態(tài)（未短接）。
最大靜態(tài)負(fù)載規(guī)格對于大多數(shù)應(yīng)用至關(guān)重要，因?yàn)樗鼪Q定了電動線性執(zhí)行器在驅(qū)動電源關(guān)閉或斷開時的保持力。如果應(yīng)用需要將負(fù)載保持在適當(dāng)位置，例如打開的艙口或升起的面板，則執(zhí)行器的靜態(tài)負(fù)載必須大于艙口或面板施加在活塞上的力。
當(dāng)外部負(fù)載推動或拉動電動線性執(zhí)行器活塞時，它還必須移動整個執(zhí)行器組件，包括活塞、絲杠、齒輪系和電機(jī)軸。絲杠和齒輪系的特性會顯著影響靜態(tài)負(fù)載額定值。
大多數(shù)執(zhí)行器的絲杠類型為 ACME 或滾珠絲杠。一般而言，ACME 螺紋的效率低于滾珠絲杠，但其抗反向驅(qū)動能力更強(qiáng)。因此，ACME 螺紋具有更高的靜態(tài)負(fù)載能力。此外，特定的螺母材料（例如金屬或聚合物）以及任何添加劑潤滑劑的粘度也會影響絲杠設(shè)計(jì)的反向驅(qū)動阻力。
如上文線性執(zhí)行器配置部分所述，電機(jī)相對于活塞和絲杠的不同方向會影響齒輪系的選擇。直角配置通常利用蝸輪將扭矩從電機(jī)軸以 90 度角傳遞到絲杠。蝸輪往往具有自鎖功能，反向驅(qū)動效率非常低。因此，垂直電動線性執(zhí)行器往往能夠承受更高的靜態(tài)負(fù)載。
齒輪比等因素也會影響線性執(zhí)行器的靜態(tài)負(fù)載。高齒輪比會通過降低速度來放大扭矩，并具有較高的反向驅(qū)動阻力，最終導(dǎo)致更高的靜態(tài)負(fù)載。
The static load of an electric linear actuator is the minimum external force required to move the actuator piston when the attached electric motor is in coast mode. In coast mode, the motor is idle with no drive voltage, and the motor terminals are in an open circuit (not shorted together).
The maximum static load specification is essential for most applications because it determines the electric linear actuator’s holding strength when the drive power is off or disconnected. If an application includes keeping a load in position, such as an open hatch or raised panel, then the static load of the actuator must be greater than the force placed upon the piston by the hatch or panel.
When an external load pushes or pulls an electric linear actuator piston, it must also move the entire actuator assembly, including the piston, lead screw, gear train, and motor shaft. The lead screw and gear train properties significantly affect the static load rating.
Most actuator’s lead screws are either an ACME or Ball screw type. In general, ACME threads are lower efficiency than Ball screws but offer much higher resistance to back driving. Thus, ACME threads offer a higher static load capacity. Further, the specific nut material, for example, metal or polymer, and the viscosity of any additive lubrication will also influence the back-driving resistance of the lead screw design.
As described above in the linear actuator configuration section, different orientations of the motor relative to the piston and lead screw influence the selection of the gear train. Right angle configurations generally utilize a worm gear to transfer torque 90 degrees from the motor shaft to the lead screw. Worm gears tend to be self-locking with a very low reverse drive efficiency. Thus, perpendicular electric linear actuators tend to support a higher static load.
Factors such as the gear ratio will also affect linear actuators’ static load. High gear ratios amplify torque by reducing speed and will have high resistance to back driving and contribute to a higher static load.
動態(tài)負(fù)載能力
Dynamic Load Capacity
電動線性執(zhí)行器的動態(tài)負(fù)載是指電動機(jī)在最大電壓和峰值電流驅(qū)動下，執(zhí)行器活塞產(chǎn)生的峰值力（推力或拉力）。與上述靜態(tài)負(fù)載類似，活塞產(chǎn)生的力必須從電動機(jī)開始，經(jīng)齒輪系傳遞至絲杠，最終通過連接在活塞上的驅(qū)動螺母，穿過整個執(zhí)行器組件。該傳遞鏈中的每個環(huán)節(jié)都會影響傳遞到活塞的力的大小。
電動機(jī)驅(qū)動軸產(chǎn)生的扭矩等于通過電動機(jī)電樞驅(qū)動的電流乘以電動機(jī)常數(shù)。電流越大，扭矩越大。電源輸送到電動機(jī)的電流量與驅(qū)動電壓成正比，電壓越高，電流也就越大。因此，電壓越高，電流也就越大，扭矩也就越大。
對于任何給定的驅(qū)動電壓，產(chǎn)生的電流（以及扭矩）是電動機(jī)繞組內(nèi)阻和電動機(jī)旋轉(zhuǎn)時產(chǎn)生的反電動勢電壓的函數(shù)。內(nèi)阻是一個固定值，反電動勢會隨著電動機(jī)轉(zhuǎn)速的增加而增大。隨著電機(jī)每分鐘轉(zhuǎn)速 (RPM) 和反電動勢 (EMF) 的增加，輸送到電機(jī)的電流會減小。因此，對于任何給定的驅(qū)動電壓，在電機(jī)剛開始旋轉(zhuǎn)時產(chǎn)生的電流和扭矩最大。隨著電機(jī)轉(zhuǎn)速的增加，電流和扭矩會減小，直到電機(jī)達(dá)到平衡狀態(tài)，此時扭矩剛好足以驅(qū)動負(fù)載并保持恒定速度。
直流電機(jī)的驅(qū)動軸直接連接到大多數(shù)執(zhí)行器的齒輪系輸入軸。齒輪系是由兩個或多個串聯(lián)的齒輪組成，齒輪系的齒輪比是從動齒輪與驅(qū)動齒輪齒數(shù)之比。根據(jù)齒輪傳動定律，輸出扭矩與輸入扭矩之比等于齒輪比，輸出速度與輸入速度之比是齒輪比的倒數(shù)。例如，當(dāng)齒輪比為 2 時，齒輪系的輸出主軸將以輸入主軸一半的速度運(yùn)轉(zhuǎn)，產(chǎn)生的扭矩是輸入主軸的兩倍。大多數(shù)電動線性執(zhí)行器的齒輪比大于 1，以有效降低高速直流電機(jī)的速度，從而為絲杠提供更大的扭矩。因此，經(jīng)驗(yàn)法則是，必須在速度和強(qiáng)度之間做出取舍。高速線性執(zhí)行器通常比低速線性執(zhí)行器輸出的扭矩更小。
最后，絲杠的螺紋在驅(qū)動螺母內(nèi)旋轉(zhuǎn)，迫使其伸縮連接的執(zhí)行器活塞，從而將旋轉(zhuǎn)扭矩轉(zhuǎn)換為線性力。在這種情況下，螺母的類型（ACME 或滾珠絲杠）、螺母材料以及潤滑劑將決定傳輸?shù)交钊膭恿π?，而不會因摩擦而損失。
The dynamic load of an electric linear actuator is the peak force (push or pull) delivered by the actuator piston when the electric motor is driven at maximum voltage and peak current. Like the static load above, the force produced at the piston must traverse the entire actuator assembly from the electric motor, through the gear train to the lead screw, and finally through the drive nut attached to the piston. Each interface in this chain affects the magnitude of the force delivered to the piston.
The torque developed at the motor drive shaft is a product of the electric current driven through the motor armature times the motor constant. Higher currents generate greater torque. The amount of current delivered to the motor from the power supply is proportional to the drive voltage, where higher voltages will have higher currents. Thus, higher voltages drive higher currents and develop greater torques.
For any given drive voltage, the current (and thus torque) produced is a function of the internal resistance of the motor windings and the back-EMF voltage developed by the motor as it rotates. The internal resistance is a fixed value and the back-EMF increases with motor velocity. As the motor’s revolutions per min (RPM) and back-EMF increase, the current delivered to the motor decreases. Thus, for any given drive voltage, the greatest current and torque are produced when the motor first begins to rotate. As the motor velocity increases, the current and torque reduce until the motor reaches equilibrium, and the torque is just sufficient to drive the load and maintain a constant velocity.
The DC motor drive shaft connects directly to most actuators’ gear train input shaft. A gear train is two or more gears connected in series, and the train’s gear ratio is the ratio of the number of teeth in the driven gear versus the driving gear. According to the law of gears, the ratio of output torque to input torque is equal to the gear ratio, and the ratio of output velocity to input velocity is the inverse of the gear ratio. So, for example, the output spindle of a gear train with a ratio of 2 will run at half the velocity of the input spindle and generate twice the torque as the input spindle. Most electric linear actuators have a gear ratio greater than one to effectively reduce the velocity of the high-speed DC motor in exchange for greater torque delivered to the lead screw. Thus, the rule of thumb is you must trade speed or strength. Fast linear actuators will generally deliver less torque than slow linear actuators.
Finally, the lead screw converts from rotational torque to linear force as its threads rotate within the drive nut forcing it to extend or retract the attached actuator piston. In this case, the type of nut (ACME or ball screw), the nut material, and any lubricants will determine the efficiency of power transmitted to the piston and not lost to friction.
占空比
Duty Cycle
電動線性執(zhí)行器的額定占空比是指為避免加速磨損和損壞而設(shè)定的最大驅(qū)動頻率。制造商將占空比定義為工作時間與關(guān)斷時間之比的百分比。例如，運(yùn)行 30 秒，停止 90 秒，則占空比為 25%。采用耐用性較差的材料制成的廉價線性執(zhí)行器通常會指定較低的占空比，以避免損壞電機(jī)繞組或齒輪。
在建議的占空比范圍內(nèi)運(yùn)行有助于避免內(nèi)部組件過熱，過熱會導(dǎo)致內(nèi)部組件過早磨損。尤其是齒輪、軸承、襯套和電機(jī)繞組最容易過熱。
由于占空比規(guī)格限制了累積的熱量和磨損，因此應(yīng)將其視為設(shè)計(jì)指南，而非硬性限制。外部環(huán)境因素也是管理線性執(zhí)行器熱量的重要因素。例如，在炎熱的室外環(huán)境中以峰值動態(tài)負(fù)載運(yùn)行，可能需要使用低于制造商規(guī)格的最大占空比。另一方面，在低溫室內(nèi)環(huán)境中峰值動態(tài)負(fù)載下運(yùn)行良好可能允許在制造商的占空比規(guī)格內(nèi)運(yùn)行。
An electric linear actuator’s rated duty cycle is the maximum frequency of drive time to avoid accelerated wear and damage. Manufacturers specify duty cycle as a percentage of the ratio of on-time to off-time. For example, running for 30 seconds and resting for 90 seconds is a 25% duty cycle. Cheap linear actuators built from less durable materials will often specify a low duty cycle to avoid damage to the motor windings or gears.
Operating within the recommended duty cycle will help avoid overheating the internal components, which can lead to premature wear of internal components. In particular, gears, bearings, bushing, and motor windings are the most vulnerable to overheating.
Because duty cycle specifications limit accumulated heat and wear, they should be considered a design guideline, not a hard limit. External environmental factors are also a significant factor in managing linear actuator heat. For instance, operating at peak dynamic load in a hot outdoor environment may dictate a maximum duty cycle below the manufacturer’s specification. While on the other hand, running well under peak dynamic load in a low-temperature indoor environment may allow you to operate over the manufacturer’s duty cycle specification.
IP 防護(hù)等級系統(tǒng)
IP rating system
IEC 605529 定義的侵入防護(hù) (IP) 等級系統(tǒng)根據(jù)機(jī)械和電氣外殼是否符合標(biāo)準(zhǔn)防護(hù)等級，對人身意外接觸和灰塵、水等有害物質(zhì)的侵入進(jìn)行分類。IP 等級使消費(fèi)者能夠以標(biāo)準(zhǔn)格式了解產(chǎn)品提供的具體防護(hù)等級，并選擇能夠適應(yīng)其預(yù)期工作條件的產(chǎn)品。
IP 代碼格式以前綴 IP 開頭，后跟兩位數(shù)字，最多可添加兩位字母，用于指定防護(hù)等級。IP 等級的第一位數(shù)字始終表示對固體顆粒侵入的防護(hù)。數(shù)值越大，表示對較小顆粒的防護(hù)等級從 1 級（定義為對較大身體部位的防護(hù)）到 6 級（定義為防塵外殼）。
環(huán)境中的灰塵和其他顆?？赡芎艿停ɡ缭谵k公室環(huán)境中），也可能很密集（例如在機(jī)械加工或農(nóng)業(yè)環(huán)境中）。對于低塵環(huán)境，選擇 IP 固體防護(hù)等級 5（IP5x）即可；對于高塵環(huán)境，請選擇等級 6（IP6x）的執(zhí)行器。
第二位數(shù)字表示產(chǎn)品的防液體侵入防護(hù)等級。與第一位數(shù)字類似，第二位數(shù)字越高，表示在溫度和壓力升高的情況下，防護(hù)等級也越高。防護(hù)等級范圍從1級（定義為防垂直滴落）到9K級（定義為防強(qiáng)力高溫水射流）。
與防塵一樣，所需的液體侵入防護(hù)等級也因預(yù)期工作環(huán)境而異。例如，在室內(nèi)辦公環(huán)境中操作時，可能只需要4級（IPx4）防護(hù)等級即可保護(hù)執(zhí)行器免受偶爾的意外溢漏。在工業(yè)工廠環(huán)境中操作時，可能需要5級（IPx5）防護(hù)等級，以防清潔噴射。同時，在食品加工廠操作時，可能需要9K級（IPx9K）防護(hù)等級，以防強(qiáng)力消毒噴霧。
最常見的兩種電動線性執(zhí)行器IP等級是IP54和IP66。IP54等級的電動線性執(zhí)行器適用于低塵、干燥的環(huán)境，在這些環(huán)境中，執(zhí)行器可能會被濺到，但不會經(jīng)常被淋濕。帶有 IP66 的執(zhí)行器非常適合高塵戶外潮濕環(huán)境，包括雨水和噴射水，但不包括浸沒。
The Ingress Protection (IP) rating system, defined in IEC 605529, classifies mechanical and electrical enclosures by their conformance to standard protection categories against accidental human contact and intrusion of harmful material such as dust and water. IP ratings allow consumers to understand the specific levels of protection a product provides in a standard format and to select products that will survive their intended operating conditions.
The IP codes format begins with the prefix IP followed by two digits and optionally up to two letters to specify the levels of protection. The first digit of an IP rating always specifies protection against solid particle intrusion. Greater values indicate protection against smaller particles from level 1, defined as protection from large body parts to level 6, defined as a dust-tight enclosure.
Dust and other particles in the environment may be low such as in an office environment, or dense such as in a machining or agricultural setting. For low dust environments, selecting an IP solid protection rating of 5 (IP5x) is sufficient; for dense dust environments, select an actuator with a rating of 6 (IP6x).
The second digit specifies the product’s protection against liquid ingress. Similar to the first digit, higher values of the second digit indicate increasing levels of protection at increasing temperature and pressure. Protection ranges from level 1, defined as protection from verticle drips to level 9K, defined as protection from powerful high-temperature water jets.
Like dust, the required liquid ingress protection varies with the intended operating environment. Operation in an indoor office environment, for example, may only require level 4 (IPx4) to protect the actuator from occasional accidental spills. Operation in an industrial factory environment may call for level 5 (IPx5) protection from cleaning jets. At the same time, operations in a food processing plant may require a level 9K (IPx9K) to protect from powerful sanitizing sprays.
Two of the most common electric linear actuator IP ratings are IP54 and IP66. Electric linear actuators rated IP54 are suitable for low dust, dry environments where the actuator may be splashed but not routinely wet. Actuators carrying an IP66 are ideal for high dust outdoor wet environments, including rain and jets but not submersion.
電動線性執(zhí)行器的優(yōu)缺點(diǎn)
Pros and cons of Electric Linear Actuators
與所有技術(shù)一樣，與氣動和液壓等其他執(zhí)行器技術(shù)相比，電動線性執(zhí)行器也有其優(yōu)缺點(diǎn)。
As with all technologies, there are pros and cons to the use of electric linear actuators when compared with other actuator technologies such as pneumatic and hydraulic.
優(yōu)點(diǎn)
? 電動線性執(zhí)行器易于部署且自成一體。它們只需極少的支撐系統(tǒng)，例如壓縮空氣或液壓油處理。
? 許多電動線性執(zhí)行器具有較高的靜態(tài)力，即使在沒有動力的情況下也能將負(fù)載固定到位。
? 電動線性執(zhí)行器比液壓執(zhí)行器更清潔，防護(hù)等級達(dá)到 IP66 或更高，適用于潮濕、消毒的環(huán)境。
? 電動線性執(zhí)行器與功能強(qiáng)大的控制器搭配使用時，靈活性極佳，可實(shí)現(xiàn)精確的位置、速度和力控制。
? 電動線性執(zhí)行器使用壽命長，幾乎無需維護(hù)。
Pros
? Electric linear actuators are easy to deploy and self-contained. They require minimal supporting systems such as pressurized air or hydraulic fluid handling.
? Many electric linear actuators offer high static force, making them suitable for holding loads in place even when not powered.
? Electric actuators are much cleaner than their hydraulic counterparts and, when rated IP66 or higher, are suitable for wet, sanitized environments.
? Electric linear actuators are incredibly flexible when paired with a capable controller, delivering precision position, velocity, and force control.
? Electric linear actuators have a long operating lifetime requiring little or no maintenance.
缺點(diǎn)
? 許多電動線性執(zhí)行器需要較低的工作占空比，設(shè)計(jì)人員必須考慮工作環(huán)境條件。他們必須確保執(zhí)行器的工作頻率和負(fù)載不會導(dǎo)致其過熱和過早失效。
? 過流情況可能會在電刷、換向器或電樞中造成短路或斷路，從而損壞電動線性執(zhí)行器內(nèi)的直流電機(jī)。例如，設(shè)計(jì)人員必須注意確保失速設(shè)備不會過度驅(qū)動。直流電機(jī)突然急停也會產(chǎn)生較大的電氣瞬變，這可能會損壞直流電機(jī)。
? 雖然電動線性執(zhí)行器適用于各種環(huán)境，但只有額定功率合適的執(zhí)行器型號才能在易燃區(qū)域運(yùn)行，因?yàn)榛鸹赡軙瘘c(diǎn)火。
Cons
? Many electric linear actuators require low operating duty cycles, and the designer must consider the operating environmental conditions. They must ensure the actuator’s operating frequency and load do not cause it to overheat and fail prematurely.
? Over-current conditions may damage the DC motor within electric linear actuators by creating a short or open circuit in the brush, commutator, or armature. Designers must take care, for instance, to ensure that a stalled device is not over-driven. Exposing the DC motor to sudden hard stops will also create large electrical transients, which may damage the DC motor.
? While electric linear actuators are suited to various environments, only properly rated actuator models can be operated in flammable areas where sparks may cause ignition.
如何為項(xiàng)目選擇合適的電動線性執(zhí)行器
How to Choose the Right Electric Linear Actuator for Your Project
選擇電動線性執(zhí)行器時，必須考慮多項(xiàng)設(shè)計(jì)要求和執(zhí)行器性能規(guī)格。以下列表列出了一些最常見的設(shè)計(jì)考慮因素，可供參考。
? 確定所需的動態(tài)力：這是移動物體或目標(biāo)結(jié)構(gòu)所需的力。在預(yù)期的力需求基礎(chǔ)上增加 50% 的裕度，以指定最小動態(tài)力。
? 確定所需的靜態(tài)力：執(zhí)行器在必須支撐負(fù)載的伸展位置是否會處于閑置狀態(tài)？請考慮靜止負(fù)載將傳遞給線性執(zhí)行器活塞的力。選擇靜態(tài)力至少比預(yù)估的保持力高 50% 的執(zhí)行器。
? 確定總移動距離：測量物體在線性執(zhí)行器連接點(diǎn)處移動的總距離。同樣，在指定線性執(zhí)行器的最小伸展距離時，請?jiān)谖灰苹A(chǔ)上增加 10% 或 20% 的裕度。
? 確定所需的速度：首先確定完成移動所需的時間。然后將移動距離除以移動時間，即可計(jì)算出所需的移動速度。同樣，增加 10% 到 20% 的裕度，以設(shè)置執(zhí)行器的最小速度規(guī)格。在審查執(zhí)行器規(guī)格時，最大速度會隨動態(tài)力而變化。在確定預(yù)期執(zhí)行器速度時，請使用計(jì)劃的動態(tài)力。
? 定義占空比：確定執(zhí)行器運(yùn)動時間的百分比。此外，還要確定執(zhí)行器是在低溫至室溫還是高溫下工作。如果在室溫或更低溫度下工作，則計(jì)劃以不超過指定執(zhí)行器最大占空比的速率運(yùn)行。如果在高溫下工作，則計(jì)劃以低于執(zhí)行器最大占空比的速率運(yùn)行?？赡苄枰徺I執(zhí)行器并在預(yù)期環(huán)境中進(jìn)行評估，以確保其在計(jì)劃的占空比下不會過熱。
? 考慮可用電源：確定打算與電動線性執(zhí)行器配對的驅(qū)動器或電源的可用電壓和最大電流。確保線性執(zhí)行器的電壓規(guī)格匹配。最常見的電動線性執(zhí)行器電壓為 6 伏、12 伏和 24 伏。確保線性執(zhí)行器的峰值電流消耗（也稱為失速電流）小于最大電源電流。
? 定義可用空間：設(shè)計(jì)空間受限嗎？是否需要窄型直列式執(zhí)行器以避免在移動時撞到物體？空間是否狹窄，需要平行或垂直配置嗎？
When selecting an electric linear actuator, you must consider several design requirements and actuator performance specifications. The list below is a good starting point for the most common design considerations.
? Determine the Required Dynamic Force: This is the force required to move the object or target structure. Add a 50% margin above your anticipated force requirement to specify the minimum dynamic force.
? Determine the Required Static Force: Will the actuator sit idle in an extended position where it must support a load? Consider the force the resting load will transfer to the linear actuator piston. Select an actuator with a static force at least 50% greater than your estimated holding force.
? Define the Total Movement Distance: Measure the total distance the object will move at the point where the linear actuator will attach. Again, add a 10% or 20% margin to the displacement when specifying the minimum linear actuator extension.
? Define the Required Speed: Start with the desired time to complete the movement. Then divide the movement distance by the movement time to calculate the desired movement velocity. Again, add a margin of 10% to 20% to set your minimum actuator speed specification. When reviewing actuator specifications, the maximum speed will vary with the dynamic force. Use your planned dynamic force when determining the expected actuator speed.
? Define the Duty Cycle: Determine what percentage of the time the actuator will be in motion. Also, determine if the actuator will operate at a low to room temperature or an elevated temperature. If at room or lower temperature, plan to run at but not exceeding the specified actuator maximum duty cycle. If operating at a high temperature, plan to operate at less than the actuator’s maximum duty cycle. You may need to purchase and evaluate the actuator in your intended environment to ensure it does not overheat under your planned duty cycle.
? Consider the Available Power Source: Determine what voltage and maximum current are available from the driver or power supply you intend to pair with the electric linear actuator. Ensure the linear actuator voltage specification matches. The most common electric linear actuator voltages are 6, 12, and 24 volts. Be sure that the peak current consumption of the linear actuator, also known as the stall current, is less than the maximum supply current.
? Define the Available Space: How space-constrained is your design? Do you need a narrow inline actuator to avoid hitting objects while moving? Is your space short, and do you need a parallel or perpendicular configuration?
如何控制電動線性執(zhí)行器
How to Control an Electric Linear Actuator
已經(jīng)分析了設(shè)計(jì)規(guī)格，并確定了首選線性執(zhí)行器的尺寸和配置。現(xiàn)在，將如何控制它的啟動和停止？需要精確的運(yùn)動曲線還是一定程度的簡單運(yùn)動？是否需要同步兩個或多個執(zhí)行器來實(shí)現(xiàn)升降或推動？以下是一些最常見的電動線性執(zhí)行器控制方法。
So, you’ve analyzed your design specifications and have determined the size and configuration of your preferred linear actuator. Now, how are you going to control it to start and stop? Do you need a precise motion profile or simple motion to an extent? Do you need to synchronize two or more actuators to lift or push? Here are some of the most common methods of electric linear actuator control.
固定內(nèi)部限位開關(guān)
Fixed Internal Limit Switches
一些電動線性執(zhí)行器在其最小和最大伸展位置嵌入了限位開關(guān)。當(dāng)活塞完全伸展或縮回時，這些開關(guān)會切斷直流電機(jī)的電源，避免損壞內(nèi)部組件。因此，帶有內(nèi)部限位開關(guān)的線性執(zhí)行器可以直接由直流電源供電，電壓等于或低于最大額定工作電壓，并在完全打開或關(guān)閉時自動停止。仍然需要一種切換電壓極性的方法來控制執(zhí)行器的伸展或縮回。
Some electric linear actuators have embedded limit switches at their minimum and maximum extension. These switches will remove power from the DC motor and avoid damage to the internal components when the piston reaches full extension or retraction. Thus, linear actuators with internal limit switches can be powered directly from a DC supply at or below the maximum rated operating voltage and automatically stopped when fully open or closed. You will still need a means of switching the polarity of the voltage to command the actuator to extend or retract.
可調(diào)式內(nèi)部限位開關(guān)
Adjustable Internal Limit Switches
可調(diào)式內(nèi)部限位開關(guān)與固定式內(nèi)部限位開關(guān)類似，不同之處在于用戶可以更改開關(guān)的位置。限位開關(guān)的移動通常通過松開前限位開關(guān)或后限位開關(guān)上的固定螺釘，將其滑動到新位置，然后擰緊螺釘以夾緊開關(guān)來實(shí)現(xiàn)。雖然可以找到帶有可調(diào)式限位開關(guān)的線性執(zhí)行器，但它們并不普及，并且會限制在選擇力度、速度和占空比時的選項(xiàng)。
Adjustable internal limit switches are similar to fixed internal limit switches, except that the user can change the location of the switch. Limit switches typically move by loosening a set screw on the front or rear limit switch, sliding it to a new location, and tightening the screw to clamp the switch. While you can find linear actuators with adjustable limit switches, they are not widely available and will limit your options when selecting force, speed, and duty cycle.
外部限位開關(guān)
External Limit Switches
可以連接外部限位開關(guān)，以便在電機(jī)到達(dá)所需位置時斷開電機(jī)電源。例如，可以在外殼上安裝一個開關(guān)，用于檢測面板是否完全關(guān)閉。連接限位開關(guān)時，必須確保有單獨(dú)的電路來反向驅(qū)動執(zhí)行器，因?yàn)閳?zhí)行器靜止后，限位開關(guān)仍將保持?jǐn)嚅_狀態(tài)。
It is possible to wire external limit switches to disconnect motor power when reaching the desired position. For instance, you might install a switch on the casing to detect that a panel has closed fully. When wiring limit switches, you must ensure a separate circuit is available to drive the actuator in the reverse direction because the limit switch will remain open after the actuator comes to rest.
瞬時開關(guān)和搖臂開關(guān)
Momentary and Rocker Switches
無論是否決定使用限位開關(guān)，每個設(shè)計(jì)都需要一種方法來開啟和關(guān)閉線性執(zhí)行器直流電機(jī)，并通過反轉(zhuǎn)電壓極性來切換行進(jìn)方向。一種簡單的電源控制方法是在電源和線性執(zhí)行器之間連接一個開關(guān)。
選擇開關(guān)時，請確保其最大電壓和電流額定值大于線性執(zhí)行器失速時的驅(qū)動電壓和峰值驅(qū)動電流。與線性執(zhí)行器的規(guī)格一樣，選擇額定值大于預(yù)期最大工作條件的開關(guān)，以便留出足夠的余量來應(yīng)對溫度等外部變量。
為了在伸縮方向上驅(qū)動電動線性執(zhí)行器，需要一個能夠在開關(guān)切換時將電源電壓以正向和反向連接到直流電機(jī)端子的開關(guān)。為此，請選擇雙刀雙擲 (DPDT) 開關(guān)配置。DPDT 開關(guān)提供了一條將電源以正向或反向連接到直流電機(jī)的路徑。開-關(guān)-開類型在開關(guān)擲的中間提供了一個關(guān)閉位置，以斷開線性執(zhí)行器的電源并將其關(guān)閉。
Whether you decide to use limit switches or not, every design needs a means of turning the linear actuator DC motor on and off and reversing the voltage polarity to switch the direction of travel. A straightforward power control method is to wire a switch between the power supply and the linear actuator.
When selecting a switch, ensure its rating for maximum voltage and current is greater than the linear actuator drive voltage and peak drive current when stalled. As with the linear actuator specifications, select a switch with ratings greater than your anticipated maximum operating conditions to provide a margin that will cover external variables such as temperature.
To drive an electric linear actuator in the extend and retract directions, you will need a switch that can connect the power supply voltage to the DC motor terminals in both forward and reverse polarities as the switch toggles. For this purpose, select a double pole double throw (DPDT) On-Off-On configuration. The DPDT switching provides a path to connect the power supply to the DC motor in either the forward or reverse polarity. The On-Off-On style provides an off position in the middle of the switch throw to disconnect the power supply from the linear actuator and turn it off.
自動控制系統(tǒng)
Automated Control Systems
雖然基本開關(guān)提供了一種快速而直接的線性執(zhí)行器控制方法，但它們也存在一些明顯的缺點(diǎn)。首先，使用開關(guān)時，電機(jī)要么打開，要么關(guān)閉。這意味著在開啟和關(guān)閉之間的快速轉(zhuǎn)換可能會產(chǎn)生強(qiáng)大的加速度和沖擊脈沖，從而可能損壞直流電機(jī)或移動負(fù)載。其次，沒有辦法改變線性執(zhí)行器的速度來應(yīng)對可變負(fù)載或同步兩個或多個串聯(lián)工作的線性執(zhí)行器。
出于這些原因，許多設(shè)計(jì)師采用智能運(yùn)動控制器，例如 ACT-U8 DC-112。DC-112 使用實(shí)時位置和力反饋來改變高速脈寬調(diào)制 (PWM) 電機(jī)驅(qū)動，從而提供精確的執(zhí)行器軌跡控制。使用像 DC-112 這樣的電動線性執(zhí)行器控制器，可以快速創(chuàng)建包含多個路點(diǎn)和速度的詳細(xì)運(yùn)動序列的解決方案，并同步兩個或移動線性執(zhí)行器以進(jìn)行協(xié)調(diào)的多軸運(yùn)動。
While basic switches provide a quick and straightforward way to control linear actuators, they have some significant drawbacks. First, with a switch, the motor is either on or off. That means the rapid transition between on and off may generate powerful acceleration and jerk impulses that may damage the DC motor or the moving load. Second, there is no method of varying the speed of the linear actuator to account for variable loads or to synchronize two or more linear actuators working in tandem.
For these reasons, many designers employ smart motion controllers such as the ACT-U8 DC-112. The DC-112 delivers precise actuator trajectory control using real-time position and force feedback to vary a high-speed pulse-width modulated (PWM) motor drive. Using electric linear actuator controllers like the DC-112 allows you to quickly create solutions with detailed motion sequences involving multiple waypoints and velocities and synchronize two or move linear actuators to move in coordinated multi-axis motion.
常見問題解答
FAQS
以下是一些關(guān)于電動線性執(zhí)行器選型和使用的常見問題。
Here are some of the most frequently asked questions about the selection and use of electric linear actuators.
電動線性執(zhí)行器與直流電機(jī)相同嗎？
Is an Electric Linear Actuator the same as a DC motor?
電動線性執(zhí)行器與直流電機(jī)不同。直流電機(jī)利用電磁場將直流 (DC) 電能轉(zhuǎn)換為電機(jī)軸上的扭矩。扭矩的大小和方向與電流的大小和方向成正比。
電動線性執(zhí)行器包含一個直流電機(jī)。它將電機(jī)的扭矩轉(zhuǎn)換為活塞的線性運(yùn)動，活塞的伸展或收縮由電機(jī)的旋轉(zhuǎn)方向決定，而活塞的動態(tài)力則由電機(jī)扭矩和齒輪系扭矩比決定。
An electric linear actuator is not the same as a DC motor. A DC motor uses electro-magnetic fields to convert direct current (DC) electrical energy into torque at the motor shaft. The magnitude and direction of the torque are proportional to the magnitude and direction of the electrical current.
An electric linear actuator contains a DC electric motor. It converts the motor’s torque into the linear motion of a piston with piston extension or retraction determined by the direction of the motor rotation and the piston’s dynamic force determined by the amount of motor torque and gear train torque ratio.
可以在項(xiàng)目中使用電動線性執(zhí)行器嗎？
Can I use an electric linear actuator for my project?
當(dāng)然可以。電動線性執(zhí)行器比氣動或液壓執(zhí)行器設(shè)置更簡單、更快捷。它們非常適合需要長壽命和低維護(hù)成本的項(xiàng)目，例如推、拉或提升面板、橫梁、通風(fēng)口、杠桿、夾持器和關(guān)節(jié)等物體。
Absolutely. Electric linear actuators are much simpler and faster to set up than pneumatic or hydraulic actuators. They are excellent for projects requiring extended life and low maintenance pushing, pulling, or lifting objects such as panels, beams, vents, levers, grippers, and joints.
如何同步兩個或多個線性執(zhí)行器？
How do I Synchronize two or more linear Actuators?
線性執(zhí)行器活塞的速度取決于多種因素，例如附著質(zhì)量、連桿的可變方向、動摩擦力、重力以及輸送至直流電機(jī)的功率。因此，即使兩個線性執(zhí)行器接收相同的電壓，它們也幾乎肯定會根據(jù)所連接的負(fù)載以不同的速度運(yùn)行。
同步運(yùn)動控制需要一個控制回路來處理來自線性執(zhí)行器的位置反饋，并自動調(diào)整驅(qū)動功率以實(shí)現(xiàn)一致的運(yùn)動軌跡。兩個或多個在位置反饋控制下運(yùn)行且軌跡匹配的線性執(zhí)行器將同步運(yùn)行，無論負(fù)載如何變化。
“ACT-U8 DC-112 運(yùn)動控制器”是一款堅(jiān)固耐用、易于使用的電動線性執(zhí)行器控制器，可提供高速位置反饋控制、線性執(zhí)行器校準(zhǔn)和自動實(shí)時軌跡生成。
The speed of a linear actuator piston depends on factors such as the attached mass, the variable orientation of linkages, dynamic friction, the force of gravity, and the power delivered to the DC motor. Thus, even if two linear actuators receive the same voltage, they will almost certainly run at different speeds in response to their connected load.
Synchronous motion control requires a control loop that processes position feedback from your linear actuator and automatically varies the drive power to achieve a consistent motion trajectory. Two or more linear actuators operating under position feedback control with matching trajectories will run synchronized regardless of variations in the load.
The “ACT-U8 DC-112 Motion Controller” is a robust, easy-to-use electric linear actuator control that provides high-speed position feedback control, linear actuator calibration, and automated real-time trajectory generation.
In What Direction Can I Apply Loads to a Linear Actuator?
可以在哪個方向?qū)€性執(zhí)行器施加負(fù)載？
當(dāng)活塞伸縮時，沿活塞軸線施加力時，電動線性執(zhí)行器性能最佳。它們在推動或拉動連接在活塞和主體緊固件之間的負(fù)載時同樣有效。
設(shè)計(jì)人員應(yīng)使用安裝U形夾和銷釘來安裝線性執(zhí)行器，并使負(fù)載和執(zhí)行器以低摩擦旋轉(zhuǎn)。低摩擦旋轉(zhuǎn)至關(guān)重要，例如，當(dāng)線性執(zhí)行器打開繞其鉸鏈旋轉(zhuǎn)的面板時。線性執(zhí)行器、面板和底座之間的角度會隨著面板的打開而變化。
大多數(shù)線性執(zhí)行器無法承受施加在活塞軸線外的力。這些力也稱為側(cè)向載荷，會使活塞懸臂靠在外筒上。例如，側(cè)向載荷會導(dǎo)致活塞和氣缸接口過早磨損，并降低防止碎屑侵入所需的密封性能。側(cè)向載荷還可能導(dǎo)致活塞、絲杠和驅(qū)動螺母變形或磨損。在設(shè)計(jì)系統(tǒng)時，請確保線性執(zhí)行器由外部結(jié)構(gòu)、接頭或?qū)к壷?，以免受到?cè)載。
Electric linear actuators perform best when forces are applied along the axis of the piston as the piston extends or retracts. They are equally efficient at pushing or pulling loads attached between the piston and body fasteners.
Designers should use mounting clevises and pins to mount linear actuators and allow the load and actuator to rotate with low friction. Low friction rotation is essential, for instance, when a linear actuator opens a panel that rotates about its hinge. The angles between the linear actuator, panel, and base will change as the panel opens.
Most linear actuators do not support forces applied off-axis of the piston. Also known as side-loading, these forces will cantilever the piston against the outer cylinder. Side loading can lead, for instance, to premature wear of the piston and cylinder interface and degrade any seal required for debris intrusion prevention. It may also deform or wear the piston, lead screw, and drive nut. When designing your system, ensure the linear actuator is supported by an external structure, joint, or rail so that it is not side-loaded.
線性執(zhí)行器有不同的速度嗎？
Are Linear Actuators Available in Different Speeds?
電動線性執(zhí)行器的速度范圍很廣，從每秒不到一英寸到每秒十英寸或更高。線性執(zhí)行器的最大速度取決于內(nèi)部直流電機(jī)的最高轉(zhuǎn)速和齒輪系比。根據(jù)齒輪傳動定律，電動線性執(zhí)行器的速度和扭矩（或動態(tài)力）是相互制約的。對于給定的直流電機(jī)型號，速度越快，執(zhí)行器提供的最大動態(tài)力就越小。另一方面，大推力執(zhí)行器的最高速度會較低。此外，任何電動線性執(zhí)行器的速度都會隨著活塞上的負(fù)載而變化。制造商應(yīng)該提供速度與推力的關(guān)系圖，以便查找計(jì)劃負(fù)載下的最大速度。
Electric linear actuators are available at a wide range of speeds from less than an inch per second to 10 inches or more per second. The maximum speed of a linear actuator is a function of the internal DC motor’s top speed and the gear train ratio. Due to the law of gears, an electric linear actuator’s speed and torque (or dynamic force) are a trade. For a given DC motor model, faster actuators offer lower maximum dynamic force. On the other hand, high-force actuators will run at a slower top speed. Also, the speed of any electric linear actuator will vary with the load present at the piston. Manufacturers should provide a graph of speed versus force to allow you to look up the maximum speed under your planned load.
電動線性執(zhí)行器的常見故障有哪些？
What are the common failures of Electric Linear Actuators?
電動線性執(zhí)行器是一種用途極為廣泛的工具，適用于各種行業(yè)和應(yīng)用。在設(shè)計(jì)和制作原型以了解線性執(zhí)行器的極限時，請注意以下常見故障模式。
過電流會損壞直流電機(jī)，并導(dǎo)致電刷、換向器或電樞繞組開路或短路。過電流最常見的原因之一是電機(jī)失速后未能移除驅(qū)動電壓。電機(jī)可能在達(dá)到活塞行程或負(fù)載超過最大動態(tài)力時失速。
電動線性執(zhí)行器過熱會損壞電機(jī)和齒輪系。當(dāng)運(yùn)行頻率超過其額定占空比或在高環(huán)境溫度下高負(fù)載運(yùn)行時，執(zhí)行器最常發(fā)生過熱。
Electric linear actuators are incredibly versatile tools suitable for various industries and applications. As you design and prototype to learn the limits of linear actuators, be aware of these common failure modes.
Over-current will damage DC electric motors and cause an open or short circuit of brushes, commutator, or armature windings. One of the most common causes of overcurrent is the failure to remove the drive voltage after the motor stalls. It may stall upon reaching the extent of the piston or under a load that exceeds the maximum dynamic force.
Overheating an electric linear actuator will damage the electric motor and the gear train. Actuators most commonly overheat when running at a frequency exceeding their rated duty cycle or operating under high load at elevated environmental temperatures.
線性執(zhí)行器有哪四種類型？
What are the 4 types of linear actuators?
線性執(zhí)行器主要有四種類型。電動線性執(zhí)行器使用電動機(jī)產(chǎn)生運(yùn)動，這使其成為精確控制和節(jié)能的理想選擇。液壓線性執(zhí)行器利用流體壓力產(chǎn)生力，以緊湊的形式提供高功率。氣動線性執(zhí)行器依靠壓縮空氣產(chǎn)生運(yùn)動，以其高速和清潔的運(yùn)行而聞名。最后，機(jī)械線性執(zhí)行器采用機(jī)械機(jī)構(gòu)，例如絲杠或齒輪，通過手動曲柄或輪子提供簡單可靠的運(yùn)動。
There are four main types of linear actuators. Electric linear actuators use electric motors to produce motion, which makes them ideal for precise control and energy efficiency. Hydraulic linear actuators use fluid pressure to generate force, offering high power in a compact form. Pneumatic linear actuators rely on compressed air to create movement and are known for their high speed and clean operation. Lastly, mechanical linear actuators employ mechanical mechanisms, such as screws or gears, providing a simple and reliable motion through manual hand cranks or wheels.
線性執(zhí)行器有哪些優(yōu)勢？
What are the advantages of linear actuators?
線性執(zhí)行器具有諸多優(yōu)勢。它們能夠精確控制運(yùn)動和位置，這對于需要高精度的應(yīng)用至關(guān)重要。其簡潔的設(shè)計(jì)確保了可靠性和易于維護(hù)。此外，線性執(zhí)行器比其他運(yùn)動系統(tǒng)更節(jié)能，因?yàn)樗鼈儫o需任何額外機(jī)構(gòu)即可直接將能量轉(zhuǎn)換為線性運(yùn)動。線性執(zhí)行器還提供電動、液壓和氣動等多種類型，從而能夠靈活地應(yīng)用于從工業(yè)機(jī)械到機(jī)器人等各種應(yīng)用，并可根據(jù)特定的功率、速度或環(huán)境需求進(jìn)行定制。
Linear actuators offer several advantages. They provide precise control of movement and position, which is essential for applications requiring high accuracy. Their straightforward design ensures reliability and ease of maintenance. Additionally, linear actuators can be more energy-efficient than other motion systems, as they directly convert energy into linear motion without additional mechanisms. They also come in various types, like electric, hydraulic, and pneumatic, allowing for flexibility in different applications, from industrial machinery to robotics, tailored to specific power, speed, or environmental needs.
如何選擇電動線性執(zhí)行器？
How do I choose an electric linear actuator?
選擇電動線性執(zhí)行器時，務(wù)必考慮幾個關(guān)鍵因素，以確保其滿足應(yīng)用的特定要求。首先，通過評估負(fù)載能力來確定執(zhí)行器必須施加的最大力。選擇能夠承受負(fù)載且不超過其承載能力的執(zhí)行器至關(guān)重要。其次，考慮所需的運(yùn)動速度，因?yàn)閳?zhí)行器具有各種齒輪比，這些齒輪比決定了其伸縮速度。行程長度是另一個重要方面，因?yàn)閳?zhí)行器伸出的距離應(yīng)與應(yīng)用的運(yùn)動范圍需求相匹配。
考慮線性執(zhí)行器的工作環(huán)境也至關(guān)重要。評估占空比，即執(zhí)行器在不過熱或磨損的情況下可以運(yùn)行的頻率。溫度、濕度和潛在的污染物暴露等環(huán)境因素也會影響執(zhí)行器的選擇，并影響其是否配備適當(dāng)?shù)谋Ｗo(hù)措施。確保執(zhí)行器的電壓和電流要求與可用電源相匹配至關(guān)重要。最后，如果應(yīng)用需要精確控制或位置反饋，請考慮其他功能，例如內(nèi)置限位開關(guān)或反饋傳感器。
When selecting an electric linear actuator, it is crucial to consider a few key factors to make sure it meets your application’s specific requirements. First, determine the maximum force the actuator must exert by assessing the load capacity. Choosing an actuator that can handle the load without exceeding its capacity is essential. Next, consider the required movement speed, as actuators come in various gear ratios that determine the extension and retraction rates. Stroke length is another crucial aspect, as the distance the actuator extends should match your application’s range of motion needs.
It is also essential to consider the operating environment of the linear actuator. Evaluate the duty cycle, which refers to how often the actuator can operate without overheating or wearing out. Environmental factors, such as temperature, moisture, and potential exposure to contaminants, also play a role in selecting an actuator with the proper protection measures. Ensuring that the actuator’s voltage and current requirements align with your available power supply is crucial. Finally, consider additional features, such as built-in limit switches or feedback sensors, if your application requires precise control or positional feedback.
Conclusion
結(jié)論
電動線性執(zhí)行器是設(shè)計(jì)師為各種行業(yè)和應(yīng)用提供運(yùn)動解決方案的絕佳工具。它們部署快捷、操作清潔，并且?guī)缀鯚o需維護(hù)，使用壽命長。將線性執(zhí)行器與功能強(qiáng)大的運(yùn)動控制器（例如 ACT-U8 DC-112）相結(jié)合，將為高級運(yùn)動規(guī)劃和實(shí)時控制帶來無限可能。
Electric linear actuators are an exciting tool for designers to deliver motion solutions across diverse industries and applications. They are quick to deploy, clean to operate, and require little maintenance to achieve long operating life. Combine your next linear actuator with a capable motion controller such as the ACT-U8 DC-112 to open up great opportunities for advanced motion planning and real-time control.
聲明：
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