縫紉機針擺動機械手的設(shè)計【縫紉機針拋光自動線上用擺動機械手設(shè)計】
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A Rapidly Deployable Manipulator System
Christiaan J.J. Paredis, H. Benjamin Brown, Pradeep K. Khosla
Abstract:
A rapidly deployable manipulator system combines the flexibility of reconfigurable modular hardware with modular programming tools, allowing the user to rapidly create a manipulator which is custom-tailored for a given task. This article describes two main aspects of such a system, namely, the Reconfigurable Modular Manipulator System (RMMS)hardware and the corresponding control software.
1 Introduction
Robot manipulators can be easily reprogrammed to perform different tasks, yet the range of tasks that can be performed by a manipulator is limited by mechanicalstructure.Forexample, a manipulator well-suited for precise movement across the top of a table would probably no be capable of lifting heavy objects in the vertical direction. Therefore, to perform a given task,one needs to choose a manipulator with an appropriate mechanical structure.
We propose the concept of a rapidly deployable manipulator system to address the above mentioned shortcomings of fixed configuration manipulators. As is illustrated in Figure 1, a rapidly deployable manipulator system consists of software and hardware that allow the user to rapidly build and program a manipulator which is customtailored for a given task.
The central building block of a rapidly deployable system is a Reconfigurable Modular Manipulator System (RMMS). The RMMS utilizes a stock of interchangeable link and joint modules of various sizes and performance specifications. One such module is shown in Figure 2. By combining these general purpose modules, a wide range of special purpose manipulators can be assembled. Recently, there has been considerable interest in the idea of modular manipulators [2, 4, 5, 7, 9, 10, 14], for research applications as well as for industrial applications. However, most of these systems lack the property of reconfigurability, which is key to the concept of rapidly deployable systems. The RMMS is particularly easy to reconfigure thanks to its integrated quick-coupling connectors described in Section 3.
Effective use of the RMMS requires, Task Based Design software. This software takes as input descriptions of the task and of the available manipulator modules; it generates as output a modular assembly configuration optimally suited to perform the given task. Several different approaches have been used successfully to solve simpli-fied instances of this complicated problem.
A third important building block of a rapidly deployable manipulator system is a framework for the generation of control software. To reduce the complexity of softwaregeneration for real-time sensor-based control systems, a software paradigm called software assembly has been proposed in the Advanced Manipulators Laboratory at CMU.This paradigm combines the concept of reusable and reconfigurable software components, as is supported by the Chimera real-time operating system [15], with a graphical user interface and a visual programming language, implemented in Onika
Although the software assembly paradigm provides thesoftware infrastructure for rapidly programming manipulator systems, it does not solve the programming problem itself. Explicit programming of sensor-based manipulator systems is cumbersome due to the extensive amount of detail which must be specified for the robot to perform the task. The software synthesis problem for sensor-based robots can be simplified dramatically, by providing robust robotic skills, that is, encapsulated strategies for accomplishing common tasks in the robots task domain [11]. Such robotic skills can then be used at the task level planning stage without having to consider any of the low-level details
As an example of the use of a rapidly deployable system,consider a manipulator in a nuclear environment where it must inspect material and space for radioactive contamination, or assemble and repair equipment. In such an environment, widely varied kinematic (e.g., workspace) and dynamic (e.g., speed, payload) performance is required, and these requirements may not be known a priori. Instead of preparing a large set of different manipulators to accomplish these tasks—an expensive solution—one can use a rapidly deployable manipulator system. Consider the following scenario: as soon as a specific task is identified, the task based design software determinesthe task. This optimal configuration is thenassembled from the RMMS modules by a human or, in the future, possibly by another manipulator. The resulting manipulator is rapidly programmed by using the software assembly paradigm and our library of robotic skills. Finally,the manipulator is deployed to perform its task.
Although such a scenario is still futuristic, the development of the reconfigurable modular manipulator system, described in this paper, is a major step forward towards our goal of a rapidly deployable manipulator system.
Our approach could form the basis for the next generation of autonomous manipulators, in which the traditional notion of sensor-based autonomy is extended to configuration-based autonomy. Indeed, although a deployed system can have all the sensory and planning information it needs, it may still not be able to accomplish its task because the task is beyond the system’s physical capabilities. A rapidly deployable system, on the other hand, could adapt its physical capabilities based on task specifications and, with advanced sensing, control, and planning strategies, accomplish the task autonomously.
2 Design of self-contained hardware modules
In most industrial manipulators, the controller is a separate unit housing the sensor interfaces, power amplifiers, and control processors for all the joints of the manipulator.A large number of wires is necessary to connect this control unit with the sensors, actuators and brakes located in each of the joints of the manipulator. The large number of electrical connections and the non-extensible nature of such a system layout make it infeasible for modular manipulators. The solution we propose is to distribute the control hardware to each individual module of the manipulator. These modules then become self-contained units which include sensors, an actuator, a brake, a transmission, a sensor interface, a motor amplifier, and a communication interface, as is illustrated in Figure 3. As a result, only six wires are required for power distribution and data communication.
2.1 Mechanical design
The goal of the RMMS project is to have a wide variety of hardware modules available. So far, we have built four kinds of modules: the manipulator base, a link module, three pivot joint modules (one of which is shown in Figure 2), and one rotate joint module. The base module and the link module have no degrees-of-freedom; the joint modules have one degree-of-freedom each. The mechanical design of the joint modules compactly fits a DC-motor, a fail-safe brake, a tachometer, a harmonic drive and a resolver.
The pivot and rotate joint modules use different outside housings to provide the right-angle or in-line configuration respectively, but are identical internally. Figure 4 shows in cross-section the internal structure of a pivot joint. Each joint module includes a DC torque motor and 100:1 harmonic-drive speed reducer, and is rated at a maximum speed of 1.5rad/s and maximum torque of 270Nm. Each module has a mass of approximately 10.7kg. A single, compact, X-type bearing connects the two joint halves and provides the needed overturning rigidity. A hollow motor shaft passes through all the rotary components, and provides a channel for passage of cabling with minimal flexing.
2.2 Electronic design
The custom-designed on-board electronics are also designed according to the principle of modularity. Each RMMS module contains a motherboard which provides the basic functionality and onto which daughtercards can be stacked to add module specific functionality.
The motherboard consists of a Siemens 80C166 microcontroller, 64K of ROM, 64K of RAM, an SMC COM20020 universal local area network controller with an RS-485 driver, and an RS-232 driver. The function of the motherboard is to establish communication with the host interface via an RS-485 bus and to perform the lowlevel control of the module, as is explained in more detail in Section 4. The RS-232 serial bus driver allows for simple diagnostics and software prototyping.
A stacking connector permits the addition of an indefinite number of daughtercards with various functions, such as sensor interfaces, motor controllers, RAM expansion etc. In our current implementation, only modules with actuators include a daughtercard. This card contains a 16 bit resolver to digital converter, a 12 bit A/D converter to interface with the tachometer, and a 12 bit D/A converter to control the motor amplifier; we have used an ofthe-shelf motor amplifier (Galil Motion Control model SSA-8/80) to drive the DC-motor. For modules with more than one degree-of-freedom, for instance a wrist module, more than one such daughtercard can be stacked onto the same motherboard.
3 Integrated quick-coupling connectors
To make a modular manipulator be reconfigurable, it is necessary that the modules can be easily connected with each other. We have developed a quick-coupling mechanism with which a secure mechanical connection between modules can be achieved by simply turning a ring handtight; no tools are required. As shown in Figure 5, keyed flanges provide precise registration of the two modules. Turning of the locking collar on the male end produces two distinct motions: first the fingers of the locking ring rotate (with the collar) about 22.5 degrees and capture the fingers on the flanges; second, the collar rotates relative to the locking ring, while a cam mechanism forces the fingers inward to securely grip the mating flanges. A ball- transfer mechanism between the collar and locking ring automatically produces this sequence of motions.
At the same time the mechanical connection is made,pneumatic and electronic connections are also established. Inside the locking ring is a modular connector that has 30 male electrical pins plus a pneumatic coupler in the middle. These correspond to matching female components on the mating connector. Sets of pins are wired in parallel to carry the 72V-25A power for motors and brakes, and 48V–6A power for the electronics. Additional pins carry signals for two RS-485 serial communication busses and four video busses. A plastic guide collar plus six alignment pins prevent damage to the connector pins and assure proper alignment. The plastic block holding the female pins can rotate in the housing to accommodate the eight different possible connection orientations (8@45 degrees). The relative orientation is automatically registered by means of an infrared LED in the female connector and eight photodetectors in the male connector.
4 ARMbus communication system
Each of the modules of the RMMS communicates with a VME-based host interface over a local area network called the ARMbus; each module is a node of the network. The communication is done in a serial fashion over an RS-485 bus which runs through the length of the manipulator. We use the ARCNET protocol [1] implemented on a dedicated IC (SMC COM20020). ARCNET is a deterministic token-passing network scheme which avoids network collisions and guarantees each node its time to access the network. Blocks of information called packets may be sent from any node on the network to any one of the other nodes, or to all nodes simultaneously (broadcast). Each node may send one packet each time it gets the token. The maximum network throughput is 5Mb/s.
The first node of the network resides on the host interface card, as is depicted in Figure 6. In addition to a VME address decoder, this card contains essentially the same hardware one can find on a module motherboard. The communication between the VME side of the card and the ARCNET side occurs through dual-port RAM.
There are two kinds of data passed over the local area network. During the manipulator initialization phase, the modules connect to the network one by one, starting at the base and ending at the end-effector. On joining the network, each module sends a data-packet to the host interface containing its serial number and its relative orientation with respect to the previous module. This information allows us to automatically determine the current manipulator configuration.
During the operation phase, the host interface communicates with each of the nodes at 400Hz. The data that is exchanged depends on the control mode—centralized or distributed. In centralized control mode, the torques for all the joints are computed on the VME-based real-time processing unit (RTPU), assembled into a data-packet by the microcontroller on the host interface card and broadcast over the ARMbus to all the nodes of the network. Each node extracts its torque value from the packet and replies by sending a data-packet containing the resolver and tachometer readings. In distributed control mode, on the other hand, the host computer broadcasts the desired joint values and feed-forward torques. Locally, in each module, the control loop can then be closed at a frequency much higher than 400Hz. The modules still send sensor readings back to the host interface to be used in the computation of the subsequent feed-forward torque.
5 Modular and reconfigurable control software
The control software for the RMMS has been developed using the Chimera real-time operating system, which supports reconfigurable and reusable software components [15]. The software components used to control the RMMS are listed in Table 1. The trjjline, dls, and grav_comp components require the knowledge of certain configuration dependent parameters of the RMMS, such as the number of degrees-of-freedom, the Denavit-Hartenberg parameters etc. During the initialization phase, the RMMS interface establishes contact with each of the hardware modules to determine automatically which modules are being used and in which order and orientation they have been assembled. For each module, a data file with a parametric model is read. By combining this information for all the modules, kinematic and dynamic models of the entire manipulator are built.
After the initialization, the rmms software component operates in a distributed control mode in which the microcontrollers of each of the RMMS modules perform PID control locally at 1900Hz. The communication between the modules and the host interface is at 400Hz, which can differ from the cycle frequency of the rmms software component. Since we use a triple buffer mechanism [16] for the communication through the dual-port RAM on the ARMbus host interface, no synchronization or handshaking is necessary.
Because closed form inverse kinematics do not exist for all possible RMMS configurations, we use a damped least-squares kinematic controller to do the inverse kinematics computation numerically..
6 Seamless integration of simulation
To assist the user in evaluating whether an RMMS con- figuration can successfully complete a given task, we have built a simulator. The simulator is based on the TeleGrip robot simulation software from Deneb Inc., and runs on an SGI Crimson which is connected with the real-time processing unit through a Bit3 VME-to-VME adaptor, as is shown in Figure 6. A graphical user interface allows the user to assemble simulated RMMS configurations very much like assembling the real hardware. Completed configurations can be tested and programmed using the TeleGrip functions for robot devices. The configurations can also be interfaced with the Chimera real-time softwarerunning on the same RTPUs used to control the actual hardware. As a result, it is possible to evaluate not only the movements of the manipulator but also the realtime CPU usage and load balancing. Figure 7 shows an RMMS simulation compared with the actual task execution.
7 Summary
We have developed a Reconfigurable Modular Manipulator System which currently consists of six hardware modules, with a total of four degrees-of-freedom. These modules can be assembled in a large number of different configurations to tailor the kinematic and dynamic properties of the manipulator to the task at hand. The control software for the RMMS automatically adapts to the assembly configuration by building kinematic and dynamic models of the manipulator; this is totally transparent to the user. To assist the user in evaluating whether a manipulator configuration is well suited for a given task, we have also built a simulator.
Acknowledgment
This research was funded in part by DOE under grant DE-F902-89ER14042, by Sandia National Laboratories under contract AL-3020, by the Department of Electrical and Computer Engineering, and by The Robotics Institute, Carnegie Mellon University.
The authors would also like to thank Randy Casciola, Mark DeLouis, Eric Hoffman, and Jim Moody for their valuable contributions to the design of the RMMS system.
可迅速布置的機械手系統(tǒng)
作者：Christiaan J.J. Paredis, H. Benjamin Brown, Pradeep K. Khosla
摘 要：
一個迅速可部署的機械手系統(tǒng)，可以使再組合的標(biāo)準(zhǔn)化的硬件的靈活性用標(biāo)準(zhǔn)化的編程工具結(jié)合，允許用戶迅速建立為一項規(guī)定的任務(wù)來通常地控制機械手。這篇文章描述這樣的一個系統(tǒng)的兩個主要方面，即，再組合的標(biāo)準(zhǔn)化的機械手系統(tǒng)(RMMS)硬件和相應(yīng)控制軟件。
1 介紹
機器人操縱裝置可能容易被程序重調(diào)執(zhí)行不同的任務(wù)， 然而一個機械手可以執(zhí)行的任務(wù)的范圍已經(jīng)被它的機械結(jié)構(gòu)限制。例如，一個很適合準(zhǔn)確的運動的機械手在一張桌子上部或許將不能朝著垂直的方向舉起重物。因此，執(zhí)行規(guī)定的任務(wù)，需要有一個合適的機械結(jié)構(gòu)來選擇機械手。
我們提議一個迅速可部署的機械手系統(tǒng)的概念來處理固定構(gòu)造的機械手的上述的缺點。一迅速可部署機械手系統(tǒng)由迅速建造的軟件和硬件組成，是適合一規(guī)定任務(wù)的一個機械手。
一個迅速可部署的系統(tǒng)的中心的組成部分是一個再組合的標(biāo)準(zhǔn)化的機械手系統(tǒng)(RMMS)。 RMMS利用一可交換的連接的和各種尺寸和性能的共同模件。通過結(jié)合這些多功能的模件，大范圍專用機械手可以被收集。 最近，有相當(dāng)多的對機械手標(biāo)準(zhǔn)化的想法的興趣。但是，對于研究應(yīng)用以及為工業(yè)應(yīng)用來說， 大多數(shù)這些系統(tǒng)缺乏的必要的能力，這是迅速可部署的體制的概念的關(guān)鍵。
有效的使用RMMS需要基于任務(wù)的設(shè)計軟件。 這軟件認(rèn)為是任務(wù)和可得到的操縱者模件的輸入描述；作為一標(biāo)準(zhǔn)化會議構(gòu)造最佳適合執(zhí)行規(guī)定任務(wù)的業(yè)務(wù)的產(chǎn)量產(chǎn)生。幾種不同的方法已經(jīng)被成功使用解決這個錯綜復(fù)雜的問題的。
一個迅速可部署的機械手系統(tǒng)的第3 個重要的組成部分是控制軟件的代的一種框架。為實時基于傳感器的控制系統(tǒng)降低軟件生成的復(fù)雜性， 一個軟件范例叫軟件為會議已經(jīng)在CMU先進(jìn)的操縱者實驗室里被提出。這個范例結(jié)合可重復(fù)使用和再組合的軟件成分的概念，象妄想實時操作系統(tǒng)支持的那樣,用一個圖形用戶界面和可視程序設(shè)計語言而實施.
雖然軟件會議范例提供迅速編程操縱者系統(tǒng)的軟件基礎(chǔ)設(shè)施，但是它不解決編程問題?；趥鞲衅鞯臋C械手系統(tǒng)的明確編程由于必須被為機器人指定執(zhí)行任務(wù)的廣大數(shù)量的細(xì)節(jié)是麻煩的。基于傳感器的機器人的軟件綜合問題可以被簡化，通過提供堅固的機器人技能， 即，為在機器人任務(wù)域完成普通任務(wù)封裝策略. 這樣機器人技能能在而不需要考慮任何低級的細(xì)節(jié)的任務(wù)步計劃階段使用。
作為使用一個迅速可部署的系統(tǒng)的例子， 在一種核環(huán)境里，在那里它必須檢查材料和放射性污染的空間，或者集合和修理設(shè)備考慮一個操縱者。在這樣的一種環(huán)境里， 廣泛改變的動態(tài)的(例如，工作區(qū))和動態(tài)的(例如，速度，凈載重量)性能被要求， 并且這些要求可能不被知道priori。不得不準(zhǔn)備大套要完成這幾次任務(wù)的不同操縱者一昂貴解決辦法一使用迅速可部署操縱者系統(tǒng)能。 考慮下列腳本：一項具體的任務(wù)一被鑒定，基于任務(wù)的設(shè)計軟件就使最佳的標(biāo)準(zhǔn)化的會議構(gòu)造下決心進(jìn)行任務(wù)。人們?nèi)缓髲腞MMS 模件裝配這個最佳的構(gòu)造或者，將來，也許到另一個操縱者。導(dǎo)致的操縱者被迅速通過使用軟件裝配范例和我們的機器人技能的信息庫編程序。 最后，操縱者被有效地使用執(zhí)行它的任務(wù)。雖然這樣的腳本仍然是未來的， 再組合的標(biāo)準(zhǔn)化的操縱者系統(tǒng)的發(fā)展，在這篇文章里描述，是向我們的一個迅速可部署的機械手系統(tǒng)的目標(biāo)的一個向前的主要的臺階。
我們的方法能為自治機械手的下一代形成基礎(chǔ)，其中基于傳感器的自治權(quán)的傳統(tǒng)的觀念被給予基于構(gòu)造的自治權(quán)。的確， 雖然一個部署的系統(tǒng)能有它需要的全部感覺并且計劃的信息， 它可能仍然不能完成它的任務(wù)，因為任務(wù)是在系統(tǒng)的物理能力以外。一個迅速可部署的系統(tǒng)， 另一方面， 能改編它的基于任務(wù)說明的物理能力和帶有先進(jìn)的感覺，控制，以及計劃策略，自動完成任務(wù)。
2硬件模塊的2種設(shè)計
在通常工業(yè)機械手里， 那些控制器單獨接在那些傳感器接口，功率放大器，并且因機械手全部關(guān)節(jié)那些機械手而控制處理器。許多電線連接這個控制單位和傳感器，位于機械手的每個關(guān)節(jié)的作動器和剎車是必要的。大量電氣裝線和這樣的一次系統(tǒng)平面布置的非可擴展性，為標(biāo)準(zhǔn)化的機械手使它不能實行。我們提出的這個解決辦法是將控制硬件分配給操縱者的每個個別的模件。 包括傳感器的這些模件然后成為整裝組件，作動器，一個剎車，一次輸送，一個傳感器接口，一個電動機放大器和一個通信接口。
2.1機械設(shè)計
RMMS 工程的目標(biāo)是有可提供的多種硬件模塊。迄今，我們已經(jīng)建造4 種模件： 操縱者基礎(chǔ)，一連接模塊，樞共同模件(一在身材顯示)，并且一旋轉(zhuǎn)共同模件。底部模件和連接模塊沒有自由度； 共同模件各自有一自由度。共同模件的機械設(shè)計緊密適合一臺直流電動機，一個有自動防故障設(shè)備的剎車，一臺轉(zhuǎn)速表，諧波運動。
那些樞和旋轉(zhuǎn)共同模件在外部使用提供那些直角不同或者成隊構(gòu)造分別，但是相同內(nèi)部，在典型地方顯示一共同的樞的內(nèi)部結(jié)構(gòu)。 每個共同模件包括一臺直流力矩電動機和100：1的諧波駕駛速度減壓器， 并且被在1.5rad /s 和270納米的最高轉(zhuǎn)矩的最高速度下。不是每個模件都有塊大約10.7公斤一單個，小型，耐壓的X 類型提供需要的剛性連結(jié)并且相連在一起。一根空的電動機軸通過全部旋轉(zhuǎn)的零部件，并且為最小的屈曲電信號的傳送提供一條通道。
2.2 電子設(shè)計
通俗設(shè)計的艙中的電子也被根據(jù)的原則設(shè)計。每個RMMS 模件包含主板，提供基本的功能性和可以被堆積增加模件具體的功能性。
主板由西門子80C 166組成， 64 K ROM，RAM，一SMC COM20020的64 K 有一臺RS-485 驅(qū)動器和一臺RS-232 驅(qū)動器的普遍的局部地區(qū)網(wǎng)絡(luò)控制器。主板的功能是通過一種RS-485公共系統(tǒng)建立與主接口的聯(lián)系和進(jìn)行程序控制模件， 象在第4 部分被更詳細(xì)解釋的那樣。RS-232 連續(xù)的公共汽車司機考慮到單純的診斷和軟件原型法。
一個堆積的連接器有各種各樣的功能允許模糊的數(shù)量的增加，例如傳感器接口，電動機控制器，RAM 擴大器等等，在我們的當(dāng)今的實施里，只是有作動器的模件包括daughtercard。 這張卡片到數(shù)字化的變換器包含一16位resolver，要與轉(zhuǎn)速表和一臺12 位D/A變換器接口控制電動機放大器的一臺12 位模數(shù)轉(zhuǎn)換器；我們已經(jīng)使用一個ofthe 架子電動機放大器(Galil運動控制模型SSA 8/80)驅(qū)動直流電動機。對有超過一自由度，例如一個腕模件的模件來說，不止一這樣的daughtercard可以被堆積到相同的主板上。
3 綜合連合的連接器
為了使一個標(biāo)準(zhǔn)化的機械手再組合，模件可能容易被彼此連
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