自定中心振動篩設計
自定中心振動篩設計,自定中心振動篩,設計
一、 選題的依據(jù):
篩分作業(yè)是煤炭加工的重要環(huán)節(jié),它廣泛地應用于篩選廠和選煤廠,對煤炭進行粒度分級、脫水、脫泥、脫介。就煤炭加工而言,篩分技術和分選技術處于同等重要的地位。我國生產(chǎn)的原煤一半以上是動力用煤,不同用戶對動力用煤的粒度要求是不一樣的,尤其是化工,發(fā)電等部門,對煤炭粒度要求很嚴格,如果超過規(guī)定限度,不但影響這些部門的正常生產(chǎn),還會造成不小的浪費。例如在煤炭氣化的過程中,若使用粉煤含量過高的塊煤,不僅影響爐內氣流暢通,降低造氣量,嚴重時還導致氣化爐填塞;機車和船舶由于鍋爐通風強,煙簡短,如燃用含有較多粉煤的塊煤時,粉煤不僅燃燒不完全而且還隨著煙氣飛走,造成浪費和環(huán)境污染;大型火力發(fā)電廠,絕大部分使用粉煤鍋爐,若供應原煤和塊煤,顯然是不經(jīng)濟的??傊?,將原煤篩選成多種粒度的產(chǎn)品,對路供應給各類用戶,對合理利用煤炭資源是十分重要的。
篩分可以為其他選煤方案創(chuàng)造條件。目前的各種選煤方法和分選設備往往都受到粒度的限制,不同的選煤方法都有一定的入料限制,過粗的大塊不能分選,而粒度過細也很難回收。在選煤廠主要是將原煤分成塊煤和末煤兩種粒級,分別進行跳汰選煤和重介選煤。重介選煤對入料中的煤泥含量很敏感,它直接影響到介質系統(tǒng)的正常工作和重介分選的效果。通過分選去除細泥,減少煤泥對介質系統(tǒng)的污染,以及高暉泥對精煤產(chǎn)品的污染;也可使跳汰機洗水粘度降低,有利于細粒煤的分選,從而提高分選效果。
在動力煤選煤廠中,通常將小于6mm的干粒粉煤給發(fā)電廠或者其它用戶,而大于6mm的沒選入跳汰機分選,這也是依靠篩分作用來完成的。
總之,在選煤加工過程中,篩分作業(yè)不僅關系著動力煤產(chǎn)品對路供應,關系著動力煤,煉焦煤洗選產(chǎn)品質量的提高,也關系到煤炭資源的合理利用,環(huán)境保護和生產(chǎn)部門的經(jīng)濟效益。
二、 國內外研究概括及發(fā)展趨勢(含文獻綜述):
改革開放以后,我國各行業(yè)都得到長足的進步。振動篩的應用也越來越廣泛,但同時對振動篩的各項性能都有了新的要求。在此大背景下,我國振動篩技術通過自主研發(fā)和吸收消化國外先進技術,也得到了長足的進步。相繼研制出DYS大型圓振動篩、YA型圓振動篩、ZKX系列直線篩和SZZ型自定心振動篩等。
近幾年來,國內外對振動篩的研制越發(fā)重視。目前,振動篩的發(fā)展已經(jīng)朝著大型化、智能化、高效集中、使用壽命長方向發(fā)展。世界上振動機械產(chǎn)品處于領先地位的公司主要有德國的SCHENCK公司、美國的ALIS-CHALMERS公司、日本的HITACHI公司等,他們生產(chǎn)的產(chǎn)品代表了世界范圍內振動篩發(fā)展的主流趨勢。而在國內,只有太行公司、鞍山礦山機械股份有限公司、上海冶金礦山機械廠等少數(shù)幾家企業(yè)開始大型振動機械的研制、開發(fā)與生產(chǎn)。但基于振動機械的工業(yè)環(huán)境復雜、條件惡劣、生產(chǎn)企業(yè)小,再加上我國振動機械工業(yè)起步較晚,我國產(chǎn)品與國外產(chǎn)品還存在較大差距。但是,隨著改革開放的不斷發(fā)展,我國的振動篩技術要會不斷進步,逐步縮短與國外先進的差距。目前,河南新鄉(xiāng)眾多廠家生產(chǎn)的SZZ系列自定心振動篩,產(chǎn)品標準為QJ/AKJ02.08-89自定中心振動篩和QJ/AKJ02.09-89自定中心振動篩,已具有相當先進水平。
三、 研究內容及實驗方案:
本次設計的主要部件是單軸性振動的激振器。激振器的軸參與振動,結構簡單、容易制造。設計為自定中心,皮帶輪偏心,在工作過程中不參與振動,大大的延長皮帶的使用壽命,工作也較穩(wěn)定。設計內容還包括篩箱的設計,軸以及軸承的選擇和強度的校核。振動篩及零部件材料的選用和加工方法等。
研究的方法主要以理論計算為主,部分部件采用篩分設備的實踐經(jīng)驗,用比較法進行設計和簡單的計算。
四、 目標、主要特色及工作進度
目標:
主要參數(shù)
清篩進程 200m/h
中等粒度石碴占總量 50%
污土占總量 25%
每米道床石碴體積 1.5m3
石碴的緊方容量 2.0 t/m3
按以上要求完成振動篩設計。
主要特色:
具有結構可靠、激振力強、篩分效率高、振動噪音小、堅固耐用、維修方便、使用安全等特點。
工作進度:
1. 收集資料、外文資料翻譯、開題報告 (第1周—第2周)
2. 總體方案設計 (第3周—第4周)
3. 參數(shù)確定及設計計算 (第5周—第7周)
4. 振動篩裝配圖設計及零部件圖設計 (第8周—第15周)
5. 畢業(yè)設計論文 (第16周—第17周)
五、 參考文獻:
[1] 璞良貴,紀名剛主編.機械設計.第七版.北京:高等教育出版社,2001
[2] 孫桓,陳作模主編.機械原理.第六版.北京:高等教育出版社,2002
[3] 成大先主編.機械設計手冊.北京:化學工業(yè)出版社,2004
[4] 聞邦椿,劉樹英編著. 機械振動學.北京:冶金工業(yè)出版社,2000
[5] Ye Zhonghe, Lan Zhaohui. Mechanisms and Machine Theory. Higher Education Press, 2001.7
自定中心振動篩設計
學生姓名:劉城建 班級:0781052
指導老師:吳暉
摘要:目前我國各種選煤廠使用的設備中,振動篩是問題較多、維修量較大的設備之一。這些問題突出表現(xiàn)在篩箱斷梁、裂幫,稀油潤滑的箱式振動器漏油、齒輪打齒、軸承溫升過高、噪聲大等問題,同時伴有傳動帶跳帶斷帶等故障。這類問題直接影響了振動篩的使用壽命,嚴重影響了生產(chǎn)。自定中心振動篩可以很好的解決此類問題,因此本次設計的振動篩為自定中心振動篩,該系列振動篩主要用于煤炭行業(yè)中物料分級、脫水、脫泥、脫介等作業(yè)。其工作可靠,篩分效率高,但設備自身較重。設計分析論述了設計方案,包括振動篩的分類與特點和設計方案的確定;對物料的運動分析,對振動篩的動力學分析及動力學參數(shù)的計算,合理設計振動篩的結構尺寸;進行了激振器的偏心塊等設計與計算,包括原始的設計參數(shù),電動機的設計與校核;進行了主要零部件的設計與計算,皮帶的設計計算與校核,彈簧的設計計算,軸的強度計算,軸承的選擇與計算,然后進行了設備維修、安裝、潤滑及密封的設計,最后進行了振動篩的環(huán)保以及經(jīng)濟分析。
關鍵詞:振動篩;激振器;自定中心
指導老師簽名:
Custom Design Center Shaker
Student name: Liu Chengjian Class:0781052
Supervisor: Wu Hui
Abstract: At present, China's coal preparation plant all the equipment used in the shaker is more problems, maintenance of one of the larger equipment. These issues in sieve outstanding performance me off beam, crack help, lubrication oil dilute the box-type vibrator oil spills, fighting tooth gear, bearing temperature rise too high, major issues such as noise, accompanied by dancing with broken belts, such as fault zone. Such issues directly affecting the life of the shaker, which has seriously affected the production. 2YAH1548-round good shaker can solve such problems, so this shaker designed for round 2 YAH1548-shaker, the series of major shaker in the materials used in the coal industry classification, dehydration, desliming, such as referrals from
Operations. Its reliable, efficient screening, but their heavy equipment. Design analysis on the design options, including the classification and shaker features and design programmes to be confirmed; materials on the movement of the shaker and the dynamics of the parameters, to design the structure of vibrating screen size; conduct The eccentric block of the exciter, such as design and calculation, including the original design parameters, motor design and verification; were the main components of the design and calculation, belts and check the design and calculation, the design of spring, the axis of Strength, the choice of bearings and calculation and then proceed to the maintenance of equipment, installation, lubrication and seal the design, a shaker final environmental and economic analysis.
Key words: shaker; Vibrator; Self-centering
Signature of Supervisor:
南昌航空大學科技學院學士學位論文
低能耗機器人懸浮機構的應用
摘要 (文檔摘要)
本文給出一種采用懸浮裝置直接驅動機器人手臂來操縱重型物體的低能量操縱方法??紤]到在水平面內懸吊工具的操作,利用懸吊在水平面內的工具的動態(tài)行為給出了混合位置/力跟蹤計劃的運算法則,為了垂直操縱懸浮機器人手臂,由考慮到彈簧秤的重力補償,這種混合位置/力的動力學模型已經(jīng)發(fā)展。為了顯示應用于工業(yè)的可能性,這種模型在倒角作業(yè)領域已經(jīng)展開。模擬和實驗證明了此擬議系統(tǒng)的可行性。
文本全文?(5295個字)
著作權MCB UP Limited (MCB) 2000截至2000小型斷路器有限公司(簡稱MCB)
Mohammad Jashim Uddin: 博士, 山形大學系統(tǒng)和信息工程系, 日立 4-3-16, 日本Yonezawa 992-8510,電話: +81 238 26 3237; 傳真: +81 238 26 3205.
Yasuo Nasu:山形大學機械系統(tǒng)工程部教授,日立 4-3-16, 日本Yonezawa 992-8510,
Kazuhisa Mitobe: 副教授, 山形大學機械系統(tǒng)工程部教授,日立 4-3-16, 日本Yonezawa 992-8510,
Kou Yamada: 副研究員, 山形大學電子及信息工程系, 日立 4-3-16, 日本Yonezawa 992-8510,
鳴謝: 在此作者真誠的感謝Yoshihiro Ishihara先生, Yoshiyasu Hariu先生, Hidekazu Satou先生, 及 Kazuo Abe先生在機器人的制作和控制軟件的執(zhí)行中所做出的努力Mohammad Jashim Uddin還將感謝教育部,科學會,運動商及(MONBUSHO)給出的獎學金, Japan. Received: 5 January 2000 Accepted: 7 February 2000
1. 簡介:
在水平的運動中,工具重量在連接摩擦上有相當大的影響,它直接地影響推進時的轉動力矩。在垂直的運動中,地心引力效果在操作體的動力學上有相當大的影響。機器人的操縱應該在推進轉力矩的可允許極限和力量感應器的能力里面。懸浮工具系統(tǒng)(STS)是一種新提議的橫向操縱重型工具的處理策略,懸吊機器人手臂系統(tǒng)(SRAS)是一種新提議的機器人手臂用在垂直面實現(xiàn)低功率驅動和小容量感應器的操作方法。由于和傳統(tǒng)的系統(tǒng)比起來具有很多優(yōu)點,懸浮工具系統(tǒng)和懸吊機器人手臂系統(tǒng)已經(jīng)成為工業(yè)應用領域越來越感興趣的話題。
當需要結構的堅硬性和高性能動態(tài)的時候,并聯(lián)操作結構與現(xiàn)有的機器人系列相比,提供了許多明顯的優(yōu)點。因此, 這種機制在過去二十年受到了一定的關注(自1983). 一般說來,直接驅動式機械手, ,容易出現(xiàn)過快的操作幅度, 然而其輸出動力卻很小。為了使其能拿起物體,在多個機械手的協(xié)調性控制方面做了很多研究(Schneider and Cannon, 1992; Walker et al., 1988). 當兩個或更多機器人手臂用來完成一單一的任務時,其承載、處理、操縱能力會得到增強。 然而, 一個單一的機械手不能操縱重物,因為其驅動轉矩滯留在一個固定的極限。當前,許多工業(yè)機器人被用于研磨作業(yè)。大部分的研磨機器人操作受限于環(huán)境. 許多研究人員開展了工業(yè)機器人的力量控制(Kashiwagi et al., 1990; Whitney and Brown, 1987). 然而, 在那些系統(tǒng)中,研墨工具以傳統(tǒng)的方式直接裝在機器人手臂上,而且需要一個很大的驅動力,雖然對有關在垂直面內機器人手臂的操作有所研究 (Nemec, 1994), 但沒考慮到重力的補償,一般,由一個或多個機械手完成一個任務的可能性取決于其運動學和動態(tài)的能力。
自動化機器人的修邊已經(jīng)在(Her and Kazerooni, 1991)被描述。在惠特尼等地報道,美洲獅 560 機器人的機械手焊珠研磨系統(tǒng)已經(jīng)具有視覺系統(tǒng) (1990). 在所有先前的修邊或研磨的研究中,大功率驅動器被應用于機器人系統(tǒng)。在垂直面內,由于機械手的巨大的重力的影響,研磨加工過程變得非常困難,尤其是當驅動器的轉矩極限小于重力的影響范圍。
機器人系統(tǒng)通常應用于一個受約束的環(huán)境,所以,要控制最終受力器在自由方向的位置和在被約束方向的觸點壓力 。由Raibert 和Craig (1981)提出的混合位置/力控制方案在別的現(xiàn)存的控制方案上擁有相當大的聲望。
本文中, 將闡述具有一種懸吊工具系統(tǒng)的機械手混合位置/力控制方案??紤]到懸浮工具在水平面內的動態(tài)性能,我們將延伸說明到混合控制方案的基本原理。在垂直的運動中,討論由彈簧秤引起的重力補償?shù)膭討B(tài)性能。
2. 系統(tǒng)描述:
Asada和Ro (1985) 設計了直接驅動五桿并聯(lián)機器人,具有如下許多優(yōu)點:沒有后沖,微小的摩擦,高機械硬度以及精確的運動。這種實驗裝置系統(tǒng)包含一個兩自由度機器人,具有一個五桿連接結構和懸架系統(tǒng)。圖1和圖2展示了機器人結構的計算機輔助設計,在水平面和豎直面內分別附帶一個彈簧平衡器。表一顯示了五桿連接機制的一些重要性能。
2.1. 運動學和動力學方程:
本節(jié)討論的連接結構是一個五桿閉環(huán)連桿機構,如圖3。有兩個輸出環(huán)節(jié),分別由兩個獨立的直驅馬達驅動,兩個馬達安裝在底架上, 1,2,3,4桿的長度分別由[sub]1,\ l[sub]2,\ l[sub]3,\ & l[sub]4表示。輸入桿的角度由q[sub]1 和 q[sub]2表示,從Y軸測量所得。終點坐標(見方程式1)(見方程式2),從方程 (1)和 (2)得該機器人的反轉運動學為:(見方程式3)( 見方程式4),工作空間是一個Jacobian矩陣2×2矩陣,可以表示為:(見方程式5),機器人手臂的慣量矩陣是一個2 x 2 矩陣,可以表示為 (見方程式6)
A=I[sub]1+m[sub]1l[sup]2[sub]C1+I[sub]3+m[sub]3l[sup]2[sub]C3+m[sub]4l[sup]2[sub]1
B m= (m[sub]3l[sub]2l[sub]C3+m[sub]4l[sub]1l[sub]C4)cos(q[sub]1-q[sub]2)
C m= (m[sub]3l[sub]2l[sub]C3+m[sub]4l[sub]1l[sub]C4)cos (q[sub]1-q[sub]2) Dm=I[sub]2+m[sub]2l[sup]2[sub]C2+I[sub]4+m[sub]4l[sup]2[sub]C4+m[sub]3l[sup]2[sub]2
科里奧利公式和向心力矩陣是一個 2 x 1 矩陣,可表達為:(見方程式 7)(見方程式 8),重利矩陣是一個2 x 1矩陣,可以表示為:( (見方程式9)( (見方程式10),g是由重力引起的重力加速度。
2.2.硬件描述:
控制系統(tǒng)的一個硬件示意圖如圖4,一部奔騰微型計算機, 133 兆赫, 被用來控制此系統(tǒng)。輸入(A/D)和輸出(D/A)轉換具有八條通道和12字節(jié)的處理能力。伺服系統(tǒng)驅動器有三種控制模式:位置控制模式速度控制模式和轉矩控制模式。此計算機主板具有三個端口和24字節(jié)脈沖處理。一個低容量的三軸力傳感器 (逐漸校正到19.62 N) 裝在機器人手臂頂端和氣動夾子之間。運算放大器與一個低通濾過器設計在一起,以消除預想不到的噪音,表2顯示了直驅馬達的一些重要性能。
2.3. 工作空間與異常:
對于一個給定的末端受動器位置,反轉運動學一般具有兩個可行的解決方案。異常的結構會分開這兩種解決方案,在異常的結構中,操縱器的最終受動器不能在一個特定的方向移動。異常分為兩種:固定異常和不定異常。一個閉環(huán)操縱器可能既有固定異常又有不定異常,在一個靜止的異常中, Jacobian 點陣具有零決定因素,然而在一個不定異常中,Jacobian點陣的決定因素為無窮大。Ting (1992) 、 Asada和 Ro (1985) 指出了五桿閉環(huán)連桿機構的異常問題。
對于五連桿結構,Jacobian 矩陣的決定因素J被定義為(見方程式11);對于五連桿機構,當( 見方程式12)的情況時,固定異常存在。由方程式 (10)知,固定異常發(fā)生在工作空間的邊界,所以,籍由選擇鏈環(huán)尺寸來獲得一個自由空間的寬闊異常。機器人手臂的笛卡爾工作空間是最終受力器的總電子掃頻量,同時機器人手臂執(zhí)行所有的可行的動作,最終受力器伴有一種特殊的力,即法向力和切向力。
迪卡爾工作空間受限于機器人手臂的幾何學分析和鉸鏈的機械約束以及驅動器的旋轉極限。力量工作空間受限于最終受力器的發(fā)向力和切向力。實際上,力量工作空間是機械人手臂的一個笛卡爾工作空間的子集。
當驅動器的旋轉力矩在如下范圍內時:0[sup]- <= q[sub]1\ <=180[sup]- & 0[sup]- <= q[sub]2 <=180[sup]-.圖5展示了五連桿機構在水平面內的模擬卡迪爾工作空間。笛卡爾總工作空間應付 5.0 N 的力量工作空間,在10.0 N的力量工作空間情況下是卡迪爾工作空間的一個子集。當彈簧秤的提升力設為9.81 N 和驅動器的旋轉力在以下范圍時:0[sup]- <= q[sub]1 <=180[sup]- and 180[sup]- <= q[sub]2 <=360[sup]-.圖6展示展示了五連桿機構在豎直面內的模擬卡迪爾工作空間。笛卡爾總工作空間應付 5.0 N 的力量工作空間,在10.0 N的力量工作空間情況下是卡迪爾工作空間的一個子集。
3. 懸浮動態(tài)
懸浮工具系統(tǒng)和懸浮機器人手臂系統(tǒng)的模型分別如圖7圖8 所示。 彈簧秤的性能參數(shù)見表III 。在懸浮系統(tǒng)中, [phi]是旋轉角度, [psi] 是方位角。為了將懸浮系統(tǒng)形象化,我們考慮做如下假設:高架鐵路的彈性變形,鋼索的質量,滾動阻力,風力以及忽略噪音。最終受力器的卡迪爾坐標定義如下: (見方程式13)( 見方程式14),有效的提升力F[sub]取決于彈簧秤的設置,與懸浮的質量有關而不是鋼絲繩的長度變化。在懸浮工具上的有效力被定義為: (見方程式15)( 見方程式16)。現(xiàn)在,水平面內的懸浮力為:(見方程式17)。在豎直面內的有效力F[sub]vy和 F[sub]vz 被定義為:(見方程式18)( 見方程式19)。此時,在豎直面內來自彈簧秤的補償力可被定義為:(見方程式20)
4. 系統(tǒng)動力學
混合位置/力控制方案以一個工作空間的直角分解為基礎。在平面運動中,考慮到懸浮工具的動態(tài)影響,我們討論位置/力控制模型 。在這部分中,豎直面中的混合位置/力控制模型從彈簧秤的重力補償方面來描述。
5. 仿真結果
為了探討機器人手臂在橫向和縱向面內的執(zhí)行性能,利用前面章節(jié)的MATLAB仿真程序進行了動態(tài)模型模擬,仿真框圖如圖10。軌跡發(fā)生器,運動器,控制器,操作器動力, 以及約束條件都在MATLAB函數(shù)中被描述了。端口用來連接標量或矢量信號匯集成一個更大的矢量信號。轉換器用來選擇輸出矢量的有用信號。
5.1.水平面內
為顯示工具重力的影響,利用混合位置/力模擬以實現(xiàn)水平面運動。在模擬過程中,總操作時間為10秒,混合的時間為0.5秒,要求速度為0.02米/秒。最終受力器的軌跡在一個被約束的表面,從(0.0, 0.3) 到 (0.2, 0.3) 。模型工具的重量是2.0 kg 。 假設是特制鋼,彈簧秤的提升力看作是19.62 N ,所需的力為5.0 N 。從圖11可看出, 與傳統(tǒng)的工具系統(tǒng)相比,由于特制鋼工具系統(tǒng)具有更小的連接摩擦,故其位置誤差更小。 此外,從圖12可看出,由于小的懸浮力作用于此懸浮工具系統(tǒng),故其引起力的誤差更小。
5.2. 豎直面內
在豎直面內,當驅動器力矩極限在重力影響范圍之內時,彈簧秤的提升力是必要的,用以補償重力。一個特征曲線圖用來說明提升力的必要性以使機械手在力矩的極限內保持在一個預設的速度。圖13表示了在速度為0.01米/秒時彈簧秤的提升力和馬達的驅動力矩之間的關系F[sub]b。 在此特征曲線圖里,提升力達到5.0 N ,由于假想摩擦力的影響(方向力河切向力),馬達驅動力保持不變。此時,由于受到提升力的影響,馬達的驅動力將增加。從此特征圖可以看出,當提升力從5.2 N變到16.5 N時,在驅動力極限內機器人手臂能夠被操作。
我們進行了懸浮機器人手臂操作的混合位置/力控制模擬實驗。在模擬實驗中,總操作時間為10秒,混合的時間為0.5秒,最大速度為0.01米/秒,從特征曲線圖可知,提升力設定為9.81 N ,要求的力是5.0 N。在垂直向上的運動中,機械手的軌跡在一個被約束的表面,從(0.3, 0.0) 到(0.3, 0.1) 。圖14 展示了機械手的有效的提升力和重力 。在豎直面的運動,彈簧秤的提升力是補償重力的主要部分,以及有效力非常小。圖15和圖16分別展示了位置軌跡和力的軌跡。輸出的位置軌跡與要求的位置軌跡之間存在一個小的固定誤差以及力的輸出與要求的力輸出有一個小的時間滯后。
6. 實驗結果
為了證明以上系統(tǒng)地有效性和正確性,我們在水平面和豎直面都進行了實驗,實驗結果如下部分所示。
6.1. 靜力
圖17和圖18分別展示了在靜態(tài)時沿X軸和Y軸的有效力F[sub]hx 和F[sub]hy。很明顯, 當機器人手臂抓住懸浮工具時,有效的靜態(tài)力大小接近最佳,但是當機器人手臂抓住工具而沒有懸浮時,由于工具自身重量的影響,有效力將非常高。由于工具自身重量,機械手頂端會偏離引起位置誤差。有效的靜態(tài)力造成連接摩擦影響驅動器的驅動力矩。
6.2.水平運動
在本實驗中,機械手抓取一個2.0千克的懸浮工具的運動軌跡在一條從(0.1, 0.34) 到 (0.2, 0.34)的線上。速度指令為0.02米/秒,所需的力是10.0牛。從彈簧秤上懸吊起工具所需的力為19.62 N 。在實驗開始之前,最終受力器與一個被約束的表面接觸,圖19展示了本實驗的位置軌跡,圖20展示了力的軌跡。實際的位置軌跡與所需的位置軌跡存在一個穩(wěn)定的小誤差,以及實際力與要求的力輸出有一個小的時間滯后。
6.3. 豎直運動
在豎直平面內,當驅動器的驅動力矩極限在重力影響范圍之內時,機器人手臂不能進行自動操作。在本實驗中,彈簧秤的提升力設定為15.0 N,足夠將在低速運行的機器人手臂懸吊起來。機械手的軌跡在一個從(0.28, 0.22) 到 (0.28, 0.26)的被約束表面上。指令速度為0.005米/秒,所需的力為2.0牛 。圖21和圖22分別展示了位置軌跡和力的軌跡。實際的位置軌跡與要求的位置軌跡之間存在一個小的固定誤差以及實際的力的與所需的力軌跡有一個小的時間滯后。圖23 說明了所需的驅動力矩,此力矩在驅動器的最大極限之內。
7.工業(yè)應用
為證實上述被應用于工業(yè)的機器人系統(tǒng)的低能耗,倒角作業(yè)已經(jīng)實行。圖24 展示了在豎直平面內的實驗裝備,在傳統(tǒng)的系統(tǒng)中,用旋轉的鐵碳銼刀修毛刺的結果顯示,在304不銹鋼上用0.88牛的解點壓力和0.01米/秒的速度可生成一個可令人接受的倒角。
在上述被提議的機器人手臂系統(tǒng)中,已經(jīng)應用于SS400倒角作業(yè)。懸吊此低能耗機器人手臂的提升力為15.0牛。用一個重0.13千克(直徑為16 mm)的氣動砂輪以最大旋轉速度為每秒30000轉的速度進行銑削 ,倒角表面的照片如圖25所示,圖26 顯示了在勻速為0.01米/秒的法向摩擦力f[sub]n及切向磨削力f[sub]t。法向磨削力保持在所需的大小2.0牛,因為在毛坯尺寸中沒有大的變化。切向力大約是法向力的一半,圖27展示了通過一次單一的磨削倒角表面的剖切圖。倒角結果顯示了倒角面的寬度0.36 +- 0.07 mm ,此結果在公差范圍內。
8. 結論
上述提議的懸浮系統(tǒng)的主要目標是用能耗操作器完成中午的作業(yè)。在水平面和豎直面內都已經(jīng)討論過。在水平運動中,懸浮系統(tǒng)具有一些優(yōu)點,當重型工具超出驅動器的驅動力矩極限時,它可以利用彈簧秤的提升力進行操作。此系統(tǒng)的連接摩擦力小于傳統(tǒng)的系統(tǒng),在橈腕關節(jié)產(chǎn)生的阻力更小,這對小容量的力傳感器來說更是一大益處。此外,在豎直運動中,懸浮力補償了作用在操作器上的重力。
懸浮工具的動態(tài)模型和懸浮機器人手臂系統(tǒng)已經(jīng)發(fā)展和執(zhí)行,利用當前的動力學公式,開展了模擬和實驗以證明上述提議的系統(tǒng)的有效性。在豎直平面內,倒角作業(yè)已經(jīng)開展了。在豎直平面內操作機器人手臂需要一個大力矩驅動的驅動器以克服重力。彈簧秤的提升力補償了工具在豎直平面內的重力。倒角表面的結果證明了懸浮機器人手臂的自動磨削系統(tǒng)可以以低功率驅動力傳感器和低能量驅動器在大尺寸的金屬切削過程中具有廣泛的可應用性。
Application of suspension mechanisms for low powered robot tasks
Abstract: The manipulation methods of a low powered direct-drive robot-arm for heavy object manipulation using a suspension device are presented. Manipulation of a suspended tool in the horizontal plane is considered. The algorithm is presented of the hybrid position/force tracking scheme with respect to the dynamic behavior of suspended tools in the horizontal plane. To manipulate the suspended robot-arm vertically, the hybrid position/force dynamic model has been developed by considering the gravity compensation of the spring balancer. In order to show the possible industrial applications chamfering operations have been carried out. Simulations and experiments demonstrate the feasibility of the proposed systems.
Introduction
Copyright MCB UP Limited (MCB) 2000
Mohammad Jashim Uddin: PhD student, Department of Systems and Information Engineering, Yamagata University, Jonan 4-3-16, Yonezawa 992-8510, Japan. Tel: +81 238 26 3237; Fax: +81 238 26 3205.
Yasuo Nasu: Professor, Department of Mechanical Systems Engineering, Yamagata University, Jonan 4-3-16, Yonezawa 992-8510, Japan.
Kazuhisa Mitobe: Associate Professor, Department of Mechanical Systems Engineering, Yamagata University, Jonan 4-3-16, Yonezawa 992-8510, Japan.
Kou Yamada: Research Associate, Department of Electrical and Information Engineering, Yamagata University, Jonan 4-3-16, Yonezawa 992-8510, Japan.
ACKNOWLEDGMENT: The authors gratefully acknowledge Mr Yoshihiro Ishihara, Mr Yoshiyasu Hariu, Mr Hidekazu Satou, and Mr Kazuo Abe's efforts during fabrication of the robot and implementation of the control software. Mohammad Jashim Uddin would like to acknowledge his scholarship by the Ministry of Education, Science, Sports, and Culture (MONBUSHO), Japan. Received: 5 January 2000 Accepted: 7 February 2000
1. Introduction
In horizontal motion, tool weight has a considerable effect on joint friction. It affects directly the driving torque. In vertical motion, the gravity effect has a considerable influence on the dynamics of the manipulator. Robotic manipulation should be within the allowable limits of the driving torque and capacity of the force sensors. Suspended tool system (STS) is a newly proposed object handling strategy to manipulate heavy tools horizontally and suspended robot-arm system (SRAS) is a newly proposed robot-arm manipulation method in the vertical plane using low power actuators and small capacity force sensors. Due to their many advantages compared to conventional systems, STS and SRAS have become topics of growing interest for applications in industry.
Parallel manipulators offer significant advantages over current serial manipulators when structural stiffness and high-performance dynamic properties are required. Therefore, such mechanisms have received some attention over the last two decades (Hunt, 1983). Direct-drive arms, in general, tend to have excessively fast operating ranges, whereas the output forces are extremely small (Asada and Ro, 1985). For object handling, there are many researches on the coordinated control of multiple robot-arms (Schneider and Cannon, 1992; Walker et al., 1988). When two or more robot-arms are used to perform a single task, an increased load carrying, handling, and manipulating capability can be achieved. However, a single manipulator cannot manipulate a heavy object because the actuator torque stays within a fixed limit. Many industrial robots are currently used in automated grinding operations. Most of the grinding robots operate in a constrained environment. Force controlled grinding robots for industrial uses are developed by many researchers (Kashiwagi et al., 1990; Whitney and Brown, 1987). However, in those systems, the grinding tool is directly mounted on the robot-arm in a conventional way and requires a large actuator power. There are some researches on robot-arm manipulation in the vertical plane (Nemec, 1994), but compensation for gravity was not considered. In general, the feasibility of a task to be performed by one or more arms depends on both the kinematic and dynamic abilities of the manipulators.
Automated robotic deburring has been described in (Her and Kazerooni, 1991). Robotic weld bead grinding system by PUMA 560 robot with vision system has been reported in Whitney et al. (1990). In all the previous deburring or grinding researches, big power actuators were used in the robot system. In the vertical plane, the grinding process is very difficult due to the enormous gravity effects of the manipulator, especially when the actuator torque limit is beyond the range of the gravity effects.
Robotic systems usually operate in a constrained environment. So, it is necessary to control the position of the end-effector in the free direction and the contact force in the constrained direction. The hybrid position/force control scheme proposed by Raibert and Craig (1981) has gained considerable popularity over the other existing force control schemes.
In this paper, hybrid position/force control scheme of robot-arm with a suspended tool system is described. We extend the basis of hybrid control scheme by considering the dynamics of the suspended tool system in horizontal motion. In vertical motion, the dynamics of gravity compensation by spring balancer is discussed.
2. System description
Asada and Ro (1985) designed a direct-drive five-bar parallel drive manipulator, which has many advantages such as: no backlash, small friction, high mechanical stiffness, and accuracy of motion. The experimental system consists of a robot with two degrees of freedom (DOF) having a five-bar link configuration and a suspension system. Figures 1 and Figure 2 show the CAD design of the robot configuration with a spring balancer in the horizontal and vertical plane, respectively. Table I shows some important properties of the five-bar link mechanism.
2.1. Kinematic and dynamic equations
The link mechanism discussed in this section is a closed-loop five-bar link mechanism as shown in Figure 3. There are two input links that are driven by two independent direct-drive motors. Both motors are fixed to the base frame. The length of links 1, 2, 3, and 4 are denoted by l[sub]1,\ l[sub]2,\ l[sub]3,\ & l[sub]4, respectively. The angles of the input links are denoted by q[sub]1 and q[sub]2 measured from Y-axis. The end point coordinates are given by:(see equation 1)(see equation 2)From equations (1) and (2) the inverse kinematics of the manipulator is obtained as:(see equation 3)(see equation 4)The task space Jacobian matrix is a 2 x 2 matrix and can be expressed as:(see equation 5)The inertia matrix of the robot-arm is a 2 x 2 matrix and can be expressed as:(see equation 6)where
A = I[sub]1+m[sub]1l[sup]2[sub]C1+I[sub]3+m[sub]3l[sup]2[sub]C3+m[sub]4l[sup]2[sub]1
B m= (m[sub]3l[sub]2l[sub]C3+m[sub]4l[sub]1l[sub]C4)cos(q[sub]1-q[sub]2)
C m= (m[sub]3l[sub]2l[sub]C3+m[sub]4l[sub]1l[sub]C4)cos (q[sub]1-q[sub]2)
D m= I[sub]2+m[sub]2l[sup]2[sub]C2+I[sub]4+m[sub]4l[sup]2[sub]C4+m[sub]3l[sup]2[sub]2
The Coriolis and centripetal forces matrix is a 2 x 1 matrix and can be expressed as:(see equation 7)(see equation 8)The gravity matrix is a 2 x 1 matrix and can be expressed as:(see equation 9)(see equation 10)where g is the acceleration due to gravity.
2.2. Hardware description
A hardware schematic diagram of the control system is shown in Figure 4. A Pentium based microcomputer, 133 MHz, is used to control the system. The A/D and D/A converter has eight channels and 12-bit resolution. The servo driver has three control modes: position control mode, velocity control mode, and torque control mode. The counter board has three ports and 24-bit pulse resolution. A low capacity three-axis force sensor (calibrated to work up to 19.62 N) is mounted between the robot-arm tip and the pneumatic gripper. The operational amplifier is designed with a low pass filter to eliminate unexpected noise. Table II shows some important properties of direct-drive motors.
2.3. Work space and singularity
For a given end-effector position, there are in general two possible solutions to the inverse kinematics. The singular configuration separates these two solutions. At the singular configuration, the manipulator end-effector cannot move in certain directions. There are two types of singularities, stationary singularity and uncertainty singularity. A closed-loop manipulator may have both stationary and uncertainty singularities. At a stationary singularity, the Jacobian matrix has zero determinant, whereas at an uncertainty singularity, the determinant of Jacobian matrix is infinity. Ting (1992) and Asada and Ro (1985) pointed out the singularity problem for the five-bar closed link manipulator.
For the five-bar link configuration, the determinant of Jacobian matrix, J, is defined as follows:(see equation 11)For five-bar link configuration the stationary singularity will exist when:(see equation 12)From equation (10), the stationary singularity occurs on the boundary of the workspace. Thus, by selecting link dimensions, a wide singularity free workspace can be obtained. The Cartesian workspace of a robot-arm is the total volume swept out by the end-effector as the robot-arm executes all possible motions. The force workspace of a robot-arm is the total volume swept out by the end-effector as the robot-arm executes all possible motions with a specific force at the end-effector, normal force and tangential force.
The Cartesian workspace is constrained by the geometry of the robot-arm as well as mechanical constraints of the joints and the limit of the actuator's rotation. The force workspace is constrained by the normal and tangential force applied at the end-effector. Actually, the force workspace is a subset of Cartesian workspace of a robot-arm.
Figure 5 shows the simulated Cartesian workspace of the five-bar link mechanism in the horizontal plane when the actuator rotation is limited within the following ranges: 0[sup]- <= q[sub]1\ <=180[sup]- & 0[sup]- <= q[sub]2 <=180[sup]-. The total Cartesian workspace copes with 5.0 N force workspace, where the 10.0 N force workspace is a subset of Cartesian workspace. Figure 6 shows the simulated Cartesian workspace of the five-bar link mechanism in the vertical plane when the lifting force of the spring balancer is set to a force of 9.81 N and the actuator rotation is limited within the following ranges: 0[sup]- <= q[sub]1 <=180[sup]- and 180[sup]- <= q[sub]2 <=360[sup]-. The total Cartesian workspace copes with 5.0 N force workspace, where the 10.0 N force workspace is a subset of Cartesian workspace.
3. Suspension dynamics
The models of the suspended tool system and the suspended robot-arm system are shown in Figure 7 and Figure 8, respectively. The properties of the spring balancer are shown in Table III. In the suspension system, [phi] is swing angle, and [psi] is orientation angle. In order to simplify the suspension system, the following assumptions are considered. The elastic deformation of the overhead rail, the mass of the wire rope, rolling resistance, wind forces, and noise are neglected. The Cartesian coordinates of the end-effector are defined as follows:(see equation 13)(see equation 14)The active lifting force, F[sub]b, in the wire rope depends on the setting of the spring balancer, which is related to the suspended mass but independent of the variation of the rope length. The active forces on the suspended tool are defined as follows:(see equation 15)(see equation 16)Now, the suspension force in the horizontal plane is:(see equation 17)The effective forces F[sub]vy, and F[sub]vz in the vertical plane are defined as follows:(see equation 18)(see equation 19)Then, the compensation force from the spring balancer in the vertical plane can be defined as follows:(see equation 20)
4. System dynamics
The hybrid position/force control scheme is based on an orthogonal decomposition of task space. The hybrid position/force control model is discussed for planar motion by considering the dynamic effect of the suspended tool. In this section, hybrid position/force control model for vertical motion is described by gravity compensation of the spring balancer.
5. Simulation results
In order to investigate the performance of robot-arm in the horizontal and vertical planes, simulations have been carried out using the dynamic models developed in the preceding sections by MATLAB Simulink program. The Simulink block diagram is shown in Figure 10. The trajectory generator, kinematics, controller, manipulator dynamics, and constraint conditions are described in MATLAB functions. The ports are used to combine scalar or vector signals into a larger vector. The switches are used to select the desired signals of the output vector.
5.1. The horizontal plane
Hybrid position/force simulation is carried out for horizontal motion to show the effect of tool weight. In simulation, total manip
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