外文翻譯--巴雷特機(jī)械手爪-可編程式可彎曲部分的搬運(yùn)和組裝

1、<p>　　MCB – Industrial Robot Feature Article</p><p>　　The BarrettHand grasper – programmable flexible part handling and assembly</p><p><b>　　Abstract </b></p><p>　　

2、This paper details the design and operation of the BarrettHand BH8-250, an intelligent, highly flexible eight-axis gripper that reconfigures itself in real time to conform securely to a wide variety of part shapes withou

3、t tool-change interruptions. The grasper brings enormous value to factory automation because it: reduces the required number and size of robotic work cells (which average US$90,000 each – not including the high cost of f

4、ootprint) while boosting factory throughput; consolidates th</p><p>　　Introduction</p><p>　　This paper introduces a new approach to material handling, part sorting, and component assembly called

5、 “grasping”, in which a single reconfigurable grasper with embedded intelligence replaces an entire bank of unique, fixed-shape grippers and tool changers. To appreciate the motivations that guided the design of Barrett’

6、s grasper, we must explore what is wrong with robotics today, the enormous potential for robotics in the future, and the dead-end legacy of gripper solutions.</p><p>　　For the benefits of a robotic solution

7、to be realized, programmable flexibility is required along the entire length of the robot, from its base, all the way to the target work piece. A robot arm enables programmable flexibility from the base only up to the to

8、ol plate, a few centimeters short of the target work piece. But these last few centimeters of a robot must adapt to the complexities of securing a new object on each robot cycle, capabilities where embedded intelligence

9、and software excel. L</p><p>　　Grippers have individually-customized, but fixed jaw shapes. The trial-and-error customization process is design intensive, generally drives cost and schedule, and is difficult

10、 to scope in advance. In general, each anticipated variation in shape, orientation, and robot approach angle requires another custom-but-fixed gripper, a place to store the additional gripper, and a mechanism to exchange

11、 grippers. An unanticipated variation or incremental improvement is simply not allowable.</p><p>　　By contrast, the mechanical structure of Barrett’s patented grasper, illustrated in Figure 1, is automatical

12、ly reconfigurable and highly programmable, matching the functionality of virtually any gripper shape or fixture function in less than a second without pausing the work cell throughput to exchange grippers.</p><

13、;p>　　For tasks requiring a high degree of flexibility such as handling variably shaped payloads presented in multiple orientations, a grasper is more secure, quicker to install, and more cost effective than an entire

14、bank of custom-machined grippers with tool changers and storage racks. </p><p>　　For uninterrupted operation, just one or two spare graspers can serve as emergency backups for several work cells, whereas on

15、e or two spare grippers are required for each gripper variation – potentially dozens per work cell. And, it’s catastrophic if both gripper backups fail in a gripper system, since it may be days before replacements can be

16、 identified, custom shaped from scratch, shipped, and physically replaced to bring the affected line back into operation. By contrast, since graspers are p</p><p>　　Gripper legacy </p><p>　　Most

17、 of today’s robotic part handling and assembling is done with grippers. If surface conditions allow, vacuum suction and electromagnets can also be used, for example in handling automobile windshields and body panels. As

18、part sizes begin to exceed the order of 100gms, a gripper’s jaws are custom shaped to ensure a secure hold. As the durable mainstay of handling and assembly, these tools have changed little since the beginning of robotic

19、s three decades ago.</p><p>　　Grippers, which act as simple pincers, have two or three unarticulated fingers, called “jaws”, which either pivot or remain parallel during open/close motions as illustrated in

20、Figure 2. Well organized catalogs are available from manufacturers that guide the integrator or customer in matching various gripper components (except naturally for the custom jaw shape) to the task and part parameters.

21、</p><p>　　Payload sizes range from grams for tiny pneumatic grippers to 100+ kilograms for massive hydraulic grippers. The power source is typically pneumatic or hydraulic with simple on/off valve control sw

22、itching between full-open and full-close states. The jaws typically move 1cm from full-open to full-close. These hands have two or three fingers, called “jaws”. The part of the jaw that contacts the target part is made o

23、f a removable and machine ably soft steel or aluminum, called a “soft jaw”.</p><p>　　Based on the unique circumstances, an expert tool designer determines the custom shapes to be machined into the rectangula

24、r soft-jaw pieces. Once machined to shape, the soft-jaw sets are attached to their respective gripper bodies and tested. This process can take any number of iterations and adjustments until the system works properly. Too

25、l designers repeat the entire process each time a new shape is introduced.</p><p>　　As consumers demand a wider variety of product choices and ever more frequent product introductions, the need for flexible

26、automation has never been greater. However, rather than make grippers more versatile, the robotics industry over the past few years has followed the example of the automatic tool exchange technique used to exchange CNC-m

27、ill cutting tools.</p><p>　　But applying the tool-changer model to serial-link robots is proving expensive and ineffective. Unlike the standardized off-the-shelf cutting tools used by milling machines, a rob

28、ot tool designer must customize the shape of every set of gripper jaws — a time-consuming, expensive, and difficult-to-scope task. Although grippers may seem cheap at only US$500 each, the labor-intensive effort to shape

29、 the soft jaws may cost several times that. If you multiply that cost times a dozen grippers as in th</p><p>　　To aggravate matters, unknowns in the customization process confound accurate cost projections.

30、So the customer must commit a purchase order to the initial installation fee on a time and materials basis without guarantee of success or a cost ceiling. While priced at US$30,000, intelligent graspers are not cheap. Ho

31、wever, one can “customize” and validate the process in software in a matter of hours at the factory in a single day. If the system does not meet performance targets, then only a day’s </p><p>　　Beyond cost,

32、the physical weight of tool changer mechanisms, located at the extreme outer end of a serial-link robotic arm, limits the useful payload and dynamic response of </p><p>　　the entire system. The additional le

33、ngth of the tool changer increases the critical distance between the wrist center and payload center, degrading kinematic flexibility, dynamic response, and safety.</p><p>　　Description of the BarrettHand &l

34、t;/p><p>　　Flexibility and durability in a compact package </p><p>　　The flexibility of the BarrettHand is based on the articulation of the eight joint axes identified in Figure 3. Only four brush

35、less DC servomotors, shown in Figure 4, are needed to control all eight joints, augmented by intelligent mechanical coupling. The resulting 1.18kg grasper is completely self-contained with only an 8mm diameter umbilical

36、cable supplying DC power and establishing a two-way serial communication link to the main robot controller of the work cell. The grasper’s communication</p><p>　　The BarrettHand has three articulated fingers

37、 and a palm as illustrated in Figure 5 which act in concert to trap the target object firmly and securely within a grasp consisting of seven coordinated contact vectors — one from the palm plate and one from each link of

38、 each finger.</p><p>　　Each of the BarrettHand’s three fingers is independently controlled by one of three servomotors as shown in Figure 6. Except for the spread action of fingers Fl and F2, which is driven

39、 by the fourth and last servomotor, the three fingers, Fl, F2, and F3, have inner and outer articulated links with identical mechanical structure.</p><p>　　Each of the three finger motors must drive two join

40、t axes. The torque is channeled to these joints through a patented, TorqueSwitch mechanism (Figure 7), whose function is optimized for maximum grasp security. When a fingertip, not the inner link, makes first contact wit

41、h an object as illustrated in Figure 8, it simply reaches its required torque, locks both joints, switches off motor currents, and awaits further instructions from the microprocessors inside the hand or a command arrivin

42、g across </p><p>　　But when the inner link, as illustrated in Figure 9, makes first contact with an object for a secure grasp, the TorqueSwitch, reaches a preset threshold torque, locks that joint against th

43、e object with a shallow-pitch worm, and redirects all torque to the fingertip to make a second, enclosing contact against the object within milliseconds of the first contact. The sequence of contacts is so rapid that you

44、 cannot visualize the process without the aid of high-speed photography. After the grasper r</p><p>　　The finger articulations, not available on conventional grippers, allow each digit to conform uniquely an

45、d securely to the shape of the object surface with two independent contact points per finger. The position, velocity, acceleration, and even torque can all be processor controlled over the full range of 17,500 encoder po

46、sitions. At maximum velocity and acceleration settings, each finger can travel full range in either direction in less than one second. The maximum force that can be actively p</p><p>　　power until commanded

47、to readjust or release their grasp.</p><p>　　While the inner and outer finger-link motions curl anthropomorphically, the spread motion of Figure 10 is distinctly non-anthropomorphic. The spread motion is clo

48、sest in function to a primate’s opposable (thumb) finger, but instead of one opposable finger, the BarrettHand has twin, symmetrically opposable fingers centered on parallel joint axes rotating 180 degrees around the ent

49、ire palm to form a limitless variety of gripper-shapes and fixture functions. </p><p>　　The spread can be controlled to any of [3,000] positions over its full range in either direction within 1/2 second. Un

50、like the mechanically lockable finger-curl motions, the spread motion is fully back drivable, allowing its servos to provide active stiffness control in addition to control over position, velocity, acceleration, and torq

51、ue. By allowing the spread motion to be compliant while the fingers close around an object, the grasper seeks maximum grasp stability as the spread accommodates i</p><p>　　Electronic and mechanical optimizat

52、ion </p><p>　　Intelligent, dexterous control is key to the success of any programmable robot, whether it is an arm, automatically guided vehicle, or dexterous hand. While robotic intelligence is usually ass

53、ociated with processor-driven motor control, many biological systems, including human hands, integrate some degree of specialized reflex control independent of explicit motor-control signals from the brain. In fact, the

54、 BarrettHand combines reflexive mechanical intelligence and programmable microprocessor</p><p>　　By strict mathematical definition, dexterity requires independent, intelligent </p><p>　　motor co

55、ntrol over each and every articulated joint axis. For a robot to be dexterous, at least n independent servomotors, and sometimes as many as n + 1 or 2n, are required to drive n joint axes. Unfortunately, servomotors cons

56、titute the bulkiest, costliest, and most complex components of any dexterous robotic hand. So, while the strict definition of dexterity may be mathematically elegant, it leads to impractical designs for any real applicat

57、ion.</p><p>　　According to the definition, neither your hand nor the BarrettHand is dexterous. Naturally, their superior versatility challenges the definition itself. If the BarrettHand followed the strict d

58、efinition for dexterity, it would require between eight and 16 motors, making it far too bulky, complex, and unreliable for any practical application outside the mathematical analysis of hand dexterity. But, by exploitin

59、g four intelligent, joint-coupling mechanisms, the almost-dexterous BarrettHand require</p><p>　　In some instances reflex control is even better than deliberate control. Two examples based on your own body i

60、llustrate this point. Suppose your hand accidentally touches a dangerously hot surface. It begins retracting itself instantly, relying on local reflex to override any ongoing cognitive commands. Without this reflex beha

61、vior, your hand would burn while waiting for the sensations of pain to travel from your hand to your brain via relatively slow nerve fibers and then for your brain, throu</p><p>　　As the second example, try

62、to move the outer joint of your index finger without moving the adjacent joint on the same finger. If you are like most people, you cannot move these joints independently because the design of your hand is optimized for

63、grasping. Your muscles and tendons are as streamlined and lightweight as possible without forfeiting functionality.</p><p>　　The design of the BarrettHand recognizes that intelligent control of functional de

64、xterity requires the integration of microprocessor and mechanical intelligence.</p><p>　　Control electronics </p><p>　　Inside its compact palm, the BarrettHand contains its central supervisory m

65、icroprocessor that coordinates four dedicated motion-control microprocessors and controls I/O via the RS232 line. The control electronics, partially visible in Figure 4 are built on a parallel 70-pin backplane bus. Assoc

66、iated with each motion-control microprocessor are the related sensor electronics, motor commutation electronics, and motor-power current-amplifier electronics for that finger or spread action.</p><p>　　The s

67、upervisory microprocessor directs I/O communication via a high-speed, industry-standard RS232 serial communications link to the work cell PC or controller. RS232 allows compatibility with any robot controller while limit

68、ing umbilical cable diameter for all power and communications to only 8mm. The openly published grasper communications language (GSL) optimizes communications speed, exploiting the difference between bandwidth and time-o

69、f-flight latency for the special case of graspers. It i</p><p>　　While the robotic arm requires high control bandwidth during the entire cycle, the grasper has plenty of time to receive a large amount of set

70、up information as it approaches its target. Then, with precision timing, the work cell controller releases a “trigger”command, such as the ASCII character “C” for close, which begins grasp execution within a couple milli

71、seconds.</p><p>　　Grasper control language (GCL) </p><p>　　The grasper can communicate and accept commands from any robot-work cell controller, PC, Mac, UNIX box, or even a Palm pilot via standa

72、rd ASCII RS232-C serial communication — the common denominator of communications protocols. Though robust, RS232 has a reputation for slow bandwidth compared to USB or FireWire standards, but its simplicity leads to smal

73、l latencies for short bursts of data. By streamlining the GCL, we have achieved time of flight to execute and acknowledge a command (from the wor</p><p>　　The grasper has two control modes: supervisory and

74、real time. Supervisory is the normal mode used to control the grasper. It is made up of a simple command structure, designed for optimal performance and minimized learning curve.</p><p>　　Supervisory mode ha

75、s the following grammatical structure: </p><p>　　Object (prefix) — Verb (command) — Subject (parameters) — Qualifiers (values) </p><p>　　The prefix refers to motors 1 through 4 with the ASCII va

76、lues for 1, 2, 3, and 4 corresponding to the fingers Fl, F2, F3, and the spread motion. Any number of prefixes may be used in any order. If the prefix is omitted, then the grasper applies the command to all available axe

77、s.</p><p>　　As an example, the ASCII character “C” represents the command which drives the associated motor (s) at its individual default (or user defined) velocity and acceleration profile(s) until the moto

78、r(s) stops for the default (or user defined) number of milliseconds. As each motor reaches this state its position is locked mechanically in place.</p><p>　　? 1C closes finger Fl. </p><p>　　? 2C

79、 closes finger F2. </p><p>　　? 12C closes fingers Fl and F2. </p><p>　　? C is equivalent to 1234C and closes all three fingers and the spread motion. </p><p>　　We also have defined

80、“S” (derived from “spread”) as a shortcut for “4” and “G” (from “grasp”) as a short cut for “123”, so that: </p><p>　　? GC is equivalent to 123C </p><p>　　? SC is equivalent to 4C</p><

81、;p>　　There are similar commands for opening fingers, moving any combination of the four axes to an array of positions, incremental opening and closing by default or user-defined distances, reading and setting user-def

82、ined parameter values, and reading the (optional) strain gages on the three fingers. The latest version of the BH8-250 firmware has 21 commands and 28 parameter settings, giving it almost unlimited flexibility. </p>

83、;<p>　　The real time mode is reserved for advanced uses such as real time teleportation control and is frequently accessed through Barrett’s user-friendly GUI for PCs running Windows95/98/NT. In real time mode, th

84、e user specifies a tailored packet-structure in supervisory mode. Barrett’s PC software gives the user a histogram of 20 successive time-of-flight tests so that the user can refine the packet structure by quantitatively

85、balancing information content with latency. </p><p>　　The GUI accelerates the prototyping of tasks and includes a pictorial of the grasper with sliders for position and rate control. The GUI also has a novel

86、 “Generate C++ Code” button which enables anyone to save and later recall successful algorithms without any knowledge of C or C++ programming. But, with C++ programming familiarity, you can also edit the code as desired.

87、 </p><p>　　Once real time mode is initiated, packets are exchanged in full duplex until an ASCII control character is issued to break out of real time mode and return to supervisory mode. The system has prov

88、en effective and robust in a variety of customer applications.</p><p>　　Conclusion </p><p>　　Although the BarrettHand BH8-250 was only introduced commercially in 1999, 30 units have been put int

89、o service around the globe at a price of US$30,000 each. The largest concentration of graspers is among automotive manufacturers and suppliers in Japan, including Honda, Yamaha Motorcycles, and NGK (ceramic substrates fo

90、r catalytic converters). At this time, these manufacturers are only beginning to explore the capabilities of this versatile device, while some customers, such as Fanuc Robotics an</p><p><b>　　Figure 1

91、</b></p><p><b>　　Figure 2</b></p><p><b>　　Figure 3 </b></p><p><b>　　Figure 4 </b></p><p><b>　　Figure 5 </b></p&

92、gt;<p><b>　　Figure 6 </b></p><p><b>　　Figure 7</b></p><p><b>　　Figure 8 </b></p><p><b>　　Figure 9 </b></p><p>　　F

93、igure 10 </p><p>　　MCB －工業(yè)的機(jī)械手論文</p><p>　　巴雷特機(jī)械手爪－可編程式可彎曲部分的搬運(yùn)和組裝</p><p><b>　　摘要</b></p><p>　　本文詳細(xì)介紹了巴雷特機(jī)械手爪BH8 – 250型的設(shè)計(jì)和運(yùn)行，一個智能的，靈活的八軸夾具, 一個可以隨時進(jìn)行自我完善,改變或

94、者中斷各種危險行為的工具。機(jī)械手爪帶來巨大的價值-工廠自動化,因?yàn)樗?降低所需機(jī)器人工作單元的數(shù)量和尺寸 (平均每項(xiàng)90,000美元不包括高成本的占地面積),從而提高了工廠的生產(chǎn)能力,通過一個可編程平臺控制整合了各種各樣的機(jī)械手抓;漸漸的改進(jìn)和推出新產(chǎn)品介紹，通過工廠里的軟件進(jìn)行國際聯(lián)網(wǎng)。</p><p><b>　　介紹</b></p><p>　　本文介紹了一種新

95、的方法來進(jìn)行材料處理，零件分類和構(gòu)件組裝，我們稱它為“抓”，即一個單一的嵌入式智能可重構(gòu)機(jī)械手爪，取代了獨(dú)特的，固定形狀的夾子和整個換刀庫。指導(dǎo)的目的是為了感謝巴雷特機(jī)械手爪的設(shè)計(jì)，今天我們必須探討什么是錯誤的機(jī)器人技術(shù)，機(jī)器人在未來的巨大潛力，以及以前遺留下來的行不通的手爪的解決方案。</p><p>　　為了實(shí)現(xiàn)機(jī)器人的優(yōu)秀解決方案，可編程的靈活性，需要沿著整個機(jī)器人的設(shè)計(jì)史，從它的誕生，到現(xiàn)在。機(jī)器人手臂能

96、夠從基礎(chǔ)的編程升級到靈活性的鈑金，讓機(jī)器人的外殼越來越薄。但即使要讓這些機(jī)器人的外殼變薄，也必須嵌入智能軟件Excel，以確保每個機(jī)器人能正常運(yùn)轉(zhuǎn)和適應(yīng)新的復(fù)雜的功能。就像在串行鏈中最薄弱環(huán)節(jié)，不靈活的爪子限制了整個工作單元機(jī)器人的生產(chǎn)力。</p><p>　　機(jī)械爪子已經(jīng)進(jìn)行了獨(dú)特的設(shè)計(jì)，但是固定顎板的形狀還沒有確定。在設(shè)計(jì)的過程中，一般難以預(yù)計(jì)硬盤成本和進(jìn)度的范圍。一般來說，機(jī)器人的每個形狀、方向和接近角的預(yù)

97、期的變化，需要其他自定義，但是爪子固定的位置，存放爪子的地方和更換爪子的器械，是不容許擅自改變和增加的。</p><p>　　相比之下，巴雷特的專利機(jī)械手爪如圖1所示，機(jī)械結(jié)構(gòu)，自動重新配置和高度可編程性，不到一秒鐘匹配，地工作單元不停頓的數(shù)據(jù)交換量，交換手爪的幾乎任意形狀的變換功能。</p><p>　　對于需要處理的可變等多種有效載荷的方向，提出了高度靈活性的任務(wù)，一個能讓機(jī)械手爪更安

98、全，更快捷的安裝，以及比定做加工夾具更低的成本和大容量的存儲機(jī)架。</p><p>　　不間斷運(yùn)行時，工作單元只有一個或兩個備用機(jī)械手爪可以作為應(yīng)急備份，而一個或兩個備用的手抓，是要求每個手爪都能變化 - 可能每個工作單元需要幾十人。而且，悲劇的是如果兩個手爪都系統(tǒng)備份，如果失敗，因?yàn)樗鼤鎯η皫滋斓目梢宰R別的數(shù)據(jù)，很多自定義形狀，裝運(yùn)和自身裝配，所以會影響后面的操作。與此相反，由于機(jī)械手爪是數(shù)據(jù)相同，他們總是可

99、以通過特定的軟件及時提供無限量的數(shù)據(jù)。</p><p><b>　　傳統(tǒng)夾具</b></p><p>　　今天的機(jī)器人，裝配零件的處理大部分是通過夾具。如果表面的條件允許，真空吸力和電磁鐵也可以應(yīng)用，例如：處理汽車擋風(fēng)玻璃和車身。作為部分尺寸開始超過100gms，顎板的自定義形狀，以確保安全運(yùn)行。由于處理和裝配耐用的主體，這些工具沒有什么變化，因?yàn)闄C(jī)器人是從三十年以前