實驗型數(shù)控銑床設(shè)計

實驗型數(shù)控銑床設(shè)計,實驗,試驗,數(shù)控,銑床,設(shè)計 生物啟發(fā)的運動策略:在機器人和機構(gòu)實驗室開發(fā)的新型地面移動機器人 生物啟發(fā)的運動策略： 在機器人和機構(gòu)實驗室開發(fā)的新型地面移動機器人 摘要-本文介紹了一些地面移動機器人，它們的發(fā)展是基于弗吉尼亞理工大學(xué)RoMeLa（機器人技術(shù)和機械實驗室）使用生物啟發(fā)的新型運動策略。我們通過學(xué)習(xí)自然模型，然后模仿或獲取來自這些設(shè)計和進程中的靈感，為移動機器人的移動，應(yīng)用和實施了新的方式。不同于大多數(shù)地面移動機器人使用的常規(guī)手段的運動，如車輪或軌道，這些機器人展示獨特的移動性特點，使在某些環(huán)境下運動困難的常規(guī)地面機器人變得適應(yīng)。這些新型的地面機器人，包括：整個皮膚運動機器人，它從似變形蟲的運動機械受到啟發(fā)；三條腿的步行機器人STriDER（自激三足動態(tài)實驗型機器人），利用驅(qū)動的被動式運動概念；六足機器人MARS（多附加的機器人系統(tǒng)）使用干粘合劑“壁虎腳”走在零重力的環(huán)境中；人形機器人DARwIn（動態(tài)擬人智能機器人）使用動態(tài)兩足步態(tài)；移動性高的機器人IMPASS（擁有積極會話系統(tǒng)的智能移動平臺）使用了一種新型車輪和腿混合運動的策略。對于上述每個機器人和所運用的新型運動策略，我們隨后將對它們的性能以及面臨的挑戰(zhàn)進行討論。 關(guān)鍵詞-生物的啟發(fā)，運動，移動機器人。 １.導(dǎo)言 9 / 11世界貿(mào)易中心的慘劇后，在歸零地（911恐怖襲擊中倒塌的世界貿(mào)易中心遺址），國防部聯(lián)合機器人計劃秘書辦公室從機器人輔助搜索和努力救援中得到教訓(xùn)，并在為此準備的一份報告中指出，機器人的移動性是指作為目前機器人技術(shù)的一個主要限制性內(nèi)容就是完成搜索和救援任務(wù)。該報告進一步指出，所有雇用機器人在歸零地網(wǎng)站使用軌道驅(qū)動器一般都優(yōu)于車輪在不平坦的地面，不過，其他更有效的運動策略必須作進一步調(diào)查。不同與空中或海上運輸?shù)能囕v在他們的旅行區(qū)域內(nèi)幾乎可以達到任何一個目的地，今天使用的大部分地面車輛，在穿越大障礙和攀登陡坡時有困難，這是由于其有限的移動性，尤其是在非結(jié)構(gòu)化環(huán)境下。 隨著機器人智能技術(shù)的進步，和移動機器人在新的應(yīng)用領(lǐng)域增加，機器人替換基礎(chǔ)運動機械的需要，這可以使它們在被調(diào)遣到復(fù)雜的非結(jié)構(gòu)化地形中時變得至關(guān)重要。目前地面車輛的運動的方法是基于車輪，鐵軌或兩條腿，每一個方法有其自身的長處和短處。為了使移動機器人適應(yīng)一個地區(qū)的復(fù)雜地形，一種新的運動方法是必要的。例如，為了能夠找到被困在倒塌大樓中的人，將需要身處狹窄拐角的機器人能夠在瓦礫下或之間移動。目前的運動方法，可以做到這項工作的一部分，但在實現(xiàn)所有這些功能時，他們卻只有有限的成功。 我們通過學(xué)習(xí)自然模型，然后模仿或獲取來自這些設(shè)計和進程中的靈感，為移動機器人的移動，應(yīng)用和實施了新的方式。在本文中，我們呈現(xiàn)了5個地面移動機器人，它們的發(fā)展是基于弗吉尼亞理工大學(xué)的RoMeLa（機器人技術(shù)和機械實驗室）使用的生物啟發(fā)的新型運動策略。不同于大多數(shù)地面移動機器人使用的常規(guī)手段的運動，如車輪或軌道，這些機器人展示獨特的移動性特點，使在某些環(huán)境下運動困難的常規(guī)地面機器人變得適應(yīng)。 2.生物啟發(fā)的新型運動的策略 2.1從似變形蟲的運動機械受到啟發(fā)的運動 WSL（整個皮膚運動）是指一個生物，有一細長圓環(huán)形狀的身體用來作為表面為牽引，皮膚是用來驅(qū)動通過循環(huán)的收縮與擴張。 圖1.一個單軸的變形蟲的動力機構(gòu) 這種啟發(fā)的新型運動策略，來自某些單一方式的細胞生物體， 例如該變形蟲 （巨變形蟲）的運動。這些生物體的運動是由細胞質(zhì)環(huán)流過程（圖1 ）所造成的，液態(tài)形式的細胞質(zhì)流在內(nèi)外質(zhì)管中流動，并轉(zhuǎn)化為凝膠狀的外質(zhì)前端的表層皮膚，最后在細胞質(zhì)的外皮膚后部回復(fù)到液態(tài)的形式。這連續(xù)細胞內(nèi)外質(zhì)的轉(zhuǎn)化是該變形蟲向前運動的有效動力。 如果不可能的話，直接用機器人模仿這細胞質(zhì)環(huán)流的過程是很困難的事。因此，代替使用細胞質(zhì)液體凝膠轉(zhuǎn)型的過程，WSL使用一個靈活的長圓環(huán)形狀的皮膚膜。這種皮膚可以拉長，然后在一個單一連續(xù)的運動中隨意內(nèi)外旋轉(zhuǎn)，在變形蟲外質(zhì)管中有效地生成整體的細胞質(zhì)環(huán)流運動（圖2 ）。 圖3和圖4顯示了一個簡單的實驗，它使用一個灌滿水的長的有彈性的有機硅皮膚環(huán)形管，以演示運動機構(gòu)的可行性。 圖2. 同心固體管整個皮膚運動模型 通過驅(qū)動環(huán)的收縮（1a，2a，3a ）及擴大（1b，2b，3b ）產(chǎn)生的反轉(zhuǎn)運動。 （ a ）在0.0秒 （ b ）在0.30秒 （ c ）在0.46秒 圖3.預(yù)拉力彈性皮膚模型運動的一系列照片 圖4. 拉緊的繩索驅(qū)動模型運動的一系列照片 機器人使用整個皮膚運動可以在與機器人相接觸的環(huán)境中的任何表面上移動，不論是地面，墻壁或兩邊的障礙物，或天花板，因為整個皮膚是用于運動。與一彈力膜或網(wǎng)狀的鏈接作為其外部皮膚，機器人可以很容易擠壓在障礙之間或在倒塌的天花板下，使用所有的接觸面為牽引向前邁進，或甚至擠壓本身通過直徑小于其名義寬度的孔。 2.2利用被動式運動驅(qū)動概念的三足運動 圖5. STriDER:自激三足動態(tài)實驗型機器人 STriDER（自激三足動態(tài)實驗型機器人）是一種新型的三足步行機器（圖五） ，利用被動動力驅(qū)動的運動概念，動態(tài)步行與高能源效率和最小控制使用其獨特的三足步態(tài)（圖6 ）。不像其他的被動動態(tài)行走的機器，這種獨特的三足運動機器人，是以三腳架位置達到固有的穩(wěn)定，它可以改變方向，和比較容易操作，使得它可實際地應(yīng)用于現(xiàn)實生活中。 圖6.單步三足步態(tài) 圖6顯示單步三足步態(tài)的概念。從開始的位置（圖6 （ a ）） ，機器人轉(zhuǎn)變其重心，通過調(diào)整它的兩個骨盆鏈接（圖6 （ b ）） ，機器人的身體能在跌倒的方向垂直于落地三角（圖6（ c ）） ，繞軸線旋轉(zhuǎn)定義為由兩個支持的雙腿。正像在機器人跌倒時，中間的腿（擺動腿） 自然擺動到兩落地腿之間（圖6 （ d ））防止跌倒（圖6 （ e ））。由于所有三腿接觸地面，機器人重置姿態(tài)通過激勵其連接，儲存勢能，為下次的步態(tài)（圖6 （ f ））作準備 。三足步態(tài)的關(guān)鍵是自然擺動運動的擺動腿，和機構(gòu)關(guān)于均衡骨盆關(guān)節(jié)連接的兩個落地腿。適當(dāng)?shù)臋C械設(shè)計參數(shù)（質(zhì)量和性能方面的聯(lián)系），用其動態(tài)結(jié)構(gòu)拓展驅(qū)動被動動力運動概念，以最低限度的控制和能源消耗進行反復(fù)運動。 步態(tài)改變方向是在一個相當(dāng)有趣的方式下執(zhí)行：通過改變選擇擺動腿的序列，三足步態(tài)可以在每一步60 °區(qū)間的方向移動機器人（圖7 ） 圖7. 轉(zhuǎn)變方向的步態(tài)戰(zhàn)略 簡單的三腳架配置和STriDER的三足步態(tài)有很多優(yōu)勢超過其它腿式機器人：它有一個簡單的運動結(jié)構(gòu)（對兩足動物 ，四足動物 ，或六足動物）防止其雙腿之間，一條腿和身體的沖突，相當(dāng)穩(wěn)定（如照相機三腳架）；簡單的控制（對兩足動物）正因該運動是一個在預(yù)定方向的簡單下降及控制其下降；它又是高效能源，在動力學(xué)上用其內(nèi)置開發(fā)驅(qū)動被動動力運動概念;它重量輕，使它能發(fā)射到難以進入的領(lǐng)域，例如，它使部署和定位傳感器在高的位置進行監(jiān)視變得非常理想。 圖8.一個單一步驟的三足步態(tài)的實驗裝備 2.3步行在零重力環(huán)境下的干膠粘劑壁虎腳 靈感來自美國航天局噴氣推進實驗室的LEMUR機器人（圖9 ） ，在弗吉尼亞理工大學(xué)的機器人技術(shù)和機械實驗室研制一種六足機器人的研究平臺，多肢運動和操縱。如圖10所示，MARS（多附庸的機器人系統(tǒng)）有6個4自由度的肢體軸對稱布置，機器人本體與動球節(jié)點在肩膀上有一個大的工作空間?？苫Q的末端執(zhí)行器/腳允許其用于研究各種研究方面例如走在非結(jié)構(gòu)化環(huán)境，攀登，和靈巧的操控任務(wù)。 圖9. 美國航天局噴氣推進實驗室的LEMUR IIa? 多附庸的機器人系統(tǒng)的六軸對稱安排，四肢均連接到機構(gòu)，由一個三自由度動球的聯(lián)合提供了一個廣泛的運動類似于肩髖關(guān)節(jié)。中途沿每個肢體是一種單自由度的聯(lián)合它提供了一系列類似的運動類似于肘或膝關(guān)節(jié)。這種安排使每個肢體有廣泛的工作空間。整個平臺是大約16英寸，直徑10英寸，身高與外表昆蟲或蜘蛛一樣。碳纖維復(fù)合體進行鋁聚合物電池， PC104的單板電腦，以及可互換的傳感器，包括立體視覺的接口相機。四肢由一個輕量級鋁框架和碳纖維復(fù)合材料外骨骼皮膚建造。每一聯(lián)合通過轉(zhuǎn)口貨品中最大芯直流電動機通過分布式可變方式控制驅(qū)動。在每個肢體端部，可互換末端執(zhí)行器/腳允許它用于各種實驗和應(yīng)用。 圖10. MARS:多附庸的機器人系統(tǒng) 與其他的機器人設(shè)計方法不同，它力求模仿生物學(xué)和工程兩者統(tǒng)一，LEMUR的起源缺乏一些必要的生物分子;生物分子專門用于作為一個設(shè)計工具。機器人的目的是沿著表面結(jié)構(gòu)移動，它的靈感來自于沿著底部和巖石之間移動的多肢靈巧的海洋生物。馬上可舉的例子便是章魚和海星，其中他們的顯著特點是軸對稱，相對身體尺寸來說四肢較長。軸對稱機器人是全方位的，面對一個特定方向的移動或操縱，節(jié)省其昂貴運動。此外，長的四肢又能產(chǎn)生一個廣闊的工作空間。 其中MARS的一個重要應(yīng)用領(lǐng)域是在零重力情況下自主地在太空中檢查維修車輛和結(jié)構(gòu)。使用有肢的機器人是最有前途的技術(shù)，例如共聚物技術(shù); 使用機器腿在空間車輛或結(jié)構(gòu)的外表面爬行檢查和維修操作。不過，使用有肢的機器人在零重力的環(huán)境中創(chuàng)造了一整套新的問題和要求。在零重力環(huán)境中運動需要使用確保其腳步行于表面的方法，這可能是通過抓住在表面上利用磁鐵，吸杯的某些功能來完成。它的靈感來自壁虎在垂直墻壁上爬行和在天花板上下步行的能力，未來版本的MARS將使用干膠粘劑腳在零重力的環(huán)境下行走于表面，因為這是最有前途的技術(shù)，使機器人行走表面的運動和操作過程變的穩(wěn)定。 2.4一種新型車輪腿混合運動策略 智能平臺的流動性與積極語言系統(tǒng)是一種非結(jié)構(gòu)化環(huán)境無人系統(tǒng)，新型高流動性運動平臺（圖11 ） 。利用單獨驅(qū)動無框車輪輻條，它可以按照輪廓不均勻的表面，如路軌，并越過大的障礙，如有腿車輛，保留簡單的車輪（圖12 ）。因為它缺乏復(fù)雜的腿和擁有一個大型有效的（輪）直徑，這個高度自適應(yīng)性系統(tǒng)可以輕易地移動到極端的地形，同時保持一定的運行速度，從而在搜索和救援任務(wù)，科學(xué)探索，和進行反恐的應(yīng)用中有很大的潛力。 圖11.此渲染圖象是IMPASS的版本，使用了兩個驅(qū)動車輪，并進行模擬 圖12.IMPASS關(guān)于移動和適應(yīng)地形的一些例子 我們分析了運動學(xué)和模擬機器人用兩個驅(qū)動車輪在平坦地形上的運動，它們利用每個車輪結(jié)構(gòu)上的一個，兩個，三個點相接觸（圖13 ）。這表明一個點接觸模式有兩個自由度，運動的輸出可以任意選定。這種模式將允許機器人移動，同時為質(zhì)量中心保持恒定的高度，我們已經(jīng)通過模擬進行了證明。至于這個模式的結(jié)果表明，通過改變方位角發(fā)生離散，采取措施改變不同的長度和左右車輪。兩個點的接觸方式顯示有一個自由度，選擇一個步長，將徑向平面的中心軸軌道視為確定的車輪角度函數(shù)。這種運動模式只用兩個輪子便能靜態(tài)地穩(wěn)定行走，還可用于承受有效重載荷。 三點接觸結(jié)構(gòu)顯示為零的自由度，但是在固定的任務(wù)中，它將有額外的穩(wěn)定性，讓機器人擁有更廣泛的立足之地。 圖13.一個單一的驅(qū)動車輪及其自由度的不同模式的運動系統(tǒng)圖 關(guān)于瞬態(tài)轉(zhuǎn)變的概念隨后得到開發(fā)，在逐漸轉(zhuǎn)變過程中有三個接觸點，迫使基準線與機器人的軸線斜交（圖14 ）。深入了解此結(jié)構(gòu)，通過在此機構(gòu)中分析機器人獲得作為一個SPPS的空間機構(gòu)。從空間分析獲得的見解能形容一個更一般的運動學(xué)模型可以用來分析共面基準軸線和斜交基準線的兩種情況，以及允許分析影響駕駛兩個驅(qū)動輪輻車輪差異。 圖14.輪輻車輪驅(qū)動的轉(zhuǎn)向策略? 要驗證我們的模型分析和在下一階段項目的概念評估，我們已設(shè)計并制作了第一個輪輻車輪驅(qū)動的樣機（圖15 ）將用于IMPASS。 圖15.輪輻車輪驅(qū)動的樣機 2.5 兩足運動的仿人機器人 ?DARwIn（動態(tài)擬人機器人與情報）是一種仿人機器人能兩足行走和表演，像人類一樣，它已發(fā)展成一個為研究機器人運動的研究平臺，同時也成為弗吉尼亞理工大學(xué)的首次進入2007年機器人世界杯競爭的基礎(chǔ)平臺（圖16，17）。該高600毫米，重4公斤的機器人有21個自由度（DOF），每一關(guān)節(jié)通過分布式控制與可控順序的無芯直流電動機進行驅(qū)動。利用計算機視覺系統(tǒng)對頭部，在軀干上的慣性測量組合，和在腳上的多力傳感器，DARwIn可以在超越障礙時完成人類一樣的步態(tài)，能夠越過不平坦的復(fù)雜地形，完成復(fù)雜行為，如踢足球。 圖16.運動系統(tǒng)圖和DARwIn的CAD模型 ?對這個項目的持續(xù)研究的目標是發(fā)展機器人平臺，并研究與參加2007年機器人世界杯比賽相關(guān)的問題，（產(chǎn)生和實現(xiàn)一個動態(tài)步態(tài)，使用零力矩點控制，為了智能運動規(guī)劃和避障，基于視覺的控制，在不平坦地形下散步，踢足球的復(fù)雜行為等發(fā)展算法和策略）。 圖17. DARwIn：動態(tài)擬人智能機器人 DARwIn有一個輕巧的鋁骨骼結(jié)構(gòu)與快速成型塑膠皮膚表面。它的胳膊和腿連接到機構(gòu)由三自由度動球節(jié)點提供了廣泛的運動，與肩和髖關(guān)節(jié)類似。每一關(guān)節(jié)是Maxon的轉(zhuǎn)口貨品中最大芯直流電動機通過分布式控制與可變原則驅(qū)動。該機器人有兩個2100 mAh/7.4v鋁聚合物電池作為其電源， PC104的單板電腦處理，三率陀螺儀，跟蹤機體的方向和各種傳感器包括一個視覺接口相機和腳下八個力傳感器。目前新版本的DARwIn正在發(fā)展，在弗吉尼亞理工大學(xué)，2007年機器人世界杯正在設(shè)計進行中，來自機械工程系和建筑設(shè)計學(xué)院的研究生和高級本科生相互協(xié)作。 3.結(jié)論 在本文中，我們呈現(xiàn)了5個獨特的地面移動機器人，在RoMeLa的發(fā)展下，在弗吉尼亞理工大學(xué)使用了新型運動策略有高度的移動性。作為證明，為發(fā)展這些機器人使用生物靈感和仿生學(xué)是關(guān)鍵。通過學(xué)習(xí)自然模型，然后模仿或獲取來自這些設(shè)計和進程中的靈感，為移動機器人在各種環(huán)境中具有獨特移動性的移動，我們已經(jīng)成功地應(yīng)用和實施了新方式。 鳴謝 作者想感謝美國國家科學(xué)基金會（No.IIS-0535012）、海軍研究辦公室（No.N00014-05-1-0828）、美國宇航局噴氣推進實驗室（美國航天局學(xué)院獎學(xué)金項目）以及弗吉尼亞理工大學(xué)辦公室和副總統(tǒng)辦公室負責(zé)人的研究（ASPIRES），感謝他們對軍隊的研究和開發(fā)， 感謝工程司令部（RDECOM）為繼續(xù)支持這項工作，通過弗吉尼亞理工大學(xué)聯(lián)合無人操作系統(tǒng)所做的測試、實驗及研究（JOUSTER），并感謝作者的研究生道格拉內(nèi)、馬克英格拉姆、馬克肖瓦爾特、杰里米西斯頓和卡爾米艾克就這些項目所做的工作。 - 13 - Biologically Inspired Locomotion Strategies: Novel Ground Mobile Robots at RoMeLa Biologically Inspired Locomotion Strategies: Novel Ground Mobile Robots at RoMeLa Abstract-This paper presents some of the ground mobile robots under development at the Robotics and Mechanisms Laboratory (RoMeLa) at Virginia Tech that use biologically inspired novel locomotion strategies. By studying nature's models and then imitating or taking inspiration from these designs and processes, we apply and implement new ways for mobile robots to move. Unlike most ground mobile robots that use conventional means of locomotion such as wheels or tracks, these robots display unique mobility characteristics that make them suitable for certain environments where conventional ground robots have difficulty moving. These novel ground robots include; the whole skin locomotion robot inspired by amoeboid motility mechanisms, the three-legged walking machine STriDER (Self-excited Tripedal Dynamic Experimental Robot) that utilizes the concept of actuated passive-dynamic locomotion, the hexapod robot MARS (Multi Appendage Robotic System) that uses dry-adhesive “gecko feet” for walking in zero-gravity environments, the humanoid robot DARwIn (Dynamic Anthropomorphic Robot with Intelligence) that uses dynamic bipedal gaits, and the high mobility robot IMPASS (Intelligent Mobility Platform with Active Spoke System) that uses a novel wheel-leg hybrid locomotion strategy. Each robot and the novel locomotion strategies it uses are described, followed by a discussion of their capabilities and challenges. Keywords - Bio-inspiration, locomotion, mobile robots. 1. Introduction In a report [1] prepared for the Office of the Secretary of Defense Joint Robotics Program on the lessons learned from the robot assisted search and rescue efforts at Ground Zero following the 9/11 World Trade Center tragedy, robot mobility is noted as one of the major limitations of current robotic technology for such missions. The report further states that all the robots employed at the Ground Zero site used track drives which are generally superior to wheels on uneven ground; however, other alternative locomotion strategies which are more effective must be further investigated. Unlike aerial or marine vehicles which can reach almost any destination point in their travel domain, most ground vehicles used today have difficulty traversing overobstacles and climbing steep inclines due to their limited mobility, especially in unstructured environments. As the technology of robotics intelligence advances, and new application areas for mobile robots increase, the need for alternative fundamental locomotion mechanisms for robots that can enable them to maneuver into complex unstructured terrain becomes critical. Current methods of ground vehicle locomotion are based on wheels, tracks or legs, and each of these methods has its own strengths and weaknesses [2, 3]. In order to move a robot into an area of complex terrain a new method of locomotion is needed. For example, to be able to find people trapped in a collapsed building, a robot would need to be able to move over, under and between rubble, and maneuver itself into tight corners. Current methods of locomotion can do some part of this, but they have only had limited success in achieving all of these capabilities [4]. By studying nature's models and then imitating or taking inspiration from these designs and processes, we apply and implement new ways for mobile robots to move. In this paper we present five of the ground mobile robots under development at the Robotics and Mechanisms Laboratory (RoMeLa) at Virginia Tech that use biologically inspired novel locomotion strategies. Unlike most ground mobile robots that use conventional means of locomotion such as wheels or tracks, these robots display unique mobility characteristics that make them suitable for certain environments whereconventional ground robots have difficulty moving. 2. Biologically Inspired Novel Locomotion Strategies 2.1 Locomotion inspired by amoeboid motility mechanisms Whole Skin Locomotion (WSL) [5, 6] is a biologically which has a body of a shape of an elongated torus, is used as a surface for traction and that the skin is used for the actuation by cycling through contraction and expansion. Fig. 1. Motility mechanism of a monopodial amoeba The inspiration for this novel locomotion strategy comes from the way certain single celled organisms, such as the Amoeba proteus (giant amoeba) move. The motion of these organisms is caused by the process of cytoplasmic streaming (Fig. 1) where the liquid form endoplasm that flows inside the ectoplasmic tube transforms into the gel-like ectoplasm outer skin at the front, and the ectoplasm outer skin at the end transforms back into the liquid form endoplasm at the rear. The net effect of this continuous ectoplasm-endoplasm transformation is the forward motion of the amoeba [7, 8]. Directly imitating this cytoplasmic streaming process with a robot is very difficult to do if not possiblee. Thus, instead of using the process of liquid to gel transformation of cytoplasm, the WSL is implemented by a flexible membrane skin in the shape of a long torus. The skin of this elongated torus can then rotate in a fashion of turning itself inside out in a single continuous motion, effectively generating the overall motion of the cytoplasmic streaming ectoplasmic tube in amoebae (Fig. 2). Fig. 2. Everting motion generated by the contracting (1a, 2a, 3a) and expanding (1b, 2b, 3b) actuator rings for the concentric solid tube WSL model. Figures 3 and 4 show simple experiments using a long elastic silicone skin toroid filled with water to demonstrate the feasibility of the locomotion mechanism. (a) At 0.0 sec (b) At 0.30 sec (c) At 0.46 sec Fig. 3. Sequence of pictures of the locomotion of the pre tensioned elastic skin model Fig. 4. Sequence of pictures of the tension cord actuated model locomotion A robot that uses WSL can move as long as any surface of the robot is in contact with the environment, be it the ground, walls or obstacles on the side, or the ceiling, since the entire skin is used for locomotion. With an elastic membrane or a mesh of links acting as its outer skin, the robot can easily squeeze between obstacles or under a collapsed ceiling, and move forward using all of its contact surfaces for traction, or even squeeze itself through holes with diameters smaller than its nominal width as demonstrated in [5]. 2.2 Tripedal locomotion utilizing the concept of actuated passive-dynamic locomotion Fig. 5. STriDER: Self-excited Tripedal Dynamic Experimental Robot STriDER (Self-excited Tripedal Dynamic Experimental Robot) is a novel three-legged walking machine (Fig. 5) that exploits the concept of actuated passive dynamic locomotion [9 to 11], to dynamically walk with high energy efficiency and minimal control using its unique tripedal gait (Fig. 6). Unlike other passive dynamic walking machines, this unique tripedal locomotion robot is inherently stable with its tripod stance, can change directions, and is relatively easy to implement, making it practical to be used for real life applications. Fig. 6. Single step tripedal gait Fig. 6 shows the concept of the single step tripedal gait. From its starting position (Fig. 6 (a)), as the robot shifts its center of gravity by aligning two of its pelvis links (Fig. 6 (b)), the body of the robot can fall over in the direction perpendicular to the stance triangle (Fig. 6 (c)), pivoting about the line defined by the two supporting legs. As the robot falls over, the leg in the middle (swing leg) naturally swings between the two stance legs (Fig. 6 (d))and catches the fall (Fig. 6 (e)). As all three legs contact the ground, the robot resets its posture by actuating its joint, storing potential energy for its next gait (Fig. 6 (f)). The key to this tripedal gait is the natural swinging motion of the swing leg, and the flipping of the body about the aligned pelvis joints connecting the two stance legs. With the appropriate mechanical design parameters (mass properties and dimension of the links), this motion is repeated with minimal control and power consumption exploiting the actuated passive dynamic locomotion concept utilizing its built in dynamics. Gaits for changing directions are implemented in a rather interesting way: by changing the sequence of choice of the swing leg, the tripedal gait can move the robot in 60°interval directions for each step (Fig. 7) Fig. 7. Gait strategies for changing directions The simple tripod configuration and tripedal gait of STriDER has many advantages over other legged robots; it has a simple kinematic structure (vs. bipeds, quadrupeds, or hexapods) that prevents conflicts among its legs and between a leg and the body; it is inherently stable (like a camera tripod); it is simple to control (vs. bipeds) as the motion is a simple falling in a predetermined direction and catching its fall; it is energy efficient, exploiting the actuated passive dynamic locomotion concept utilizing its built in dynamics; it is lightweight enabling it to be launched to difficult to access areas; and it is tall making it ideal for deploying and positioning sensors at high position for surveillance, for example. Fig. 8. Experiment setup for a single step tripedal gait 2.3 Dry-adhesive gecko feet for walking in zero gravity environments Inspired by NASA JPL’s LEMUR class robots [12, 13] (Fig. 9), RoMeLa at Virginia Tech is developing a hexapod robotic platform for research in multi-limbed ocomotion and manipulation. Shown in figure 10, the Multi Appendage Robotic System (MARS) has six 4-degree-of-freedom (DOF) limbs arranged xi-symmetrically about the robot body with kinematically spherical joints at the shoulder for a large workspace. Interchangeable end-effector/feet allow it to be used for studying various research areas such as walking in unstructured environments, climbing, and for dexterous manipulation tasks. Fig. 9. NASA JPL’s LEMUR IIa MARS’s six axi-symmetrically arranged limbs are each connected to the body by a 3 DOF kinematically spherical joint which provides a wide range of motion similar to a shoulder of hip joint. Midway along each limb is a single DOF joint which provides a range of motion similar to an elbow or knee joint. This arrangement allows each limb to have a wide workspace. The entire platform is approximately 16 inches in diameter standing 10 inches tall with the appearance of an insect or spider. The carbon fiber composite body carries Li-Poly batteries, a PC104 single board computer, and interchangeable sensors including stereovision Firewire cameras. The limbs are constructed with a lightweight aluminum frame and carbon fiber composite exoskeleton skin for stiffness. Each joint is actuated by Maxon’s RE-max coreless DC motors via distributed control withvariable compliance. At the end of each limb, interchangeable end-effector/feet allow it to be used for various experiments and applications. Fig. 10. MARS: Multi Appendage Robotic System Unlike other robot design approaches that seek to mimic biology and engineering together, LEMUR’s origins lack any necessary biological elements [12]; biological elements are used exclusively as a design tool. As the robot is intended to move along the surface of the structure, inspiration was taken from multi-limbed, dexterous sea creatures that tend to move along the bottom and among rocks. Immediately applicable examples are octopi and starfish which are notable for their axi-symmetry. The creatures’ limbs are long relative to body size. Being axi-symmetric, the robot is omni directional, saving operationally expensive movement to face a particular direction for mobility or manipulation. Also, the long limbs generate a generous workspace. One of the key application areas of MARS is autonomous in-space inspection and maintenance of space vehicles and structures in zero gravity. Using limbed robots is the most promising technology for such EVA tasks; to crawl outside on the outer surface of space vehicles or structures using legs for inspection and maintenance operations. However using limbed robots in zero gravity environments creates a whole new set of problems and requirements. Locomotion in zero gravity environments requires using methods of securing its feet to the walking surface. This may be accomplished by grabbing certain features on the surface, using magnets, suction cups. Inspired by the ability of geckos to climb vertical walls and walk upside down on the ceiling, future version of MARS will be using dry adhesive feet to walk on surfaces in zero gravity environments as this is the most promising technology for stabilizing the robot on its walking surface for locomotion and for manipulation tasks. 2.4 A novel wheel-leg hybrid locomotion strategy IMPASS (Intelligent Mobility Platform with Active Spoke System) is a novel high mobility locomotion platform for unmanned systems in unstructured environments [14 to 16] (Fig. 11). Utilizing rimless wheels with individually actuated spokes, it can followthe contour of uneven surfaces like tracks and step over large obstacles like legged vehicles while retaining the simplicity of wheels (Fig. 12). Since it lacks the complexity of legs and has a large effective (wheel) diameter, this highly adaptive system can move over extreme terrain with ease while maintaining respectable travel speeds, and thus has great potential for search-and-rescue missions, scientific exploration, and anti-terror response applications. Fig. 11. Rendered image of a version of IMPASS using two actuated spoke wheels and a mock up of the system Fig. 12. Some examples of the mobility and terrain adaptability of IMPASS We have analyzed the kinematics and simulated the motion of a robot using two actuated spoke wheels on flat terrain using a one-, two-, and three-point contact per wheel scheme (Fig. 13). It is shown that the one-point contact mode has two degrees of freedom and that the motion output can be arbitrarily selected. This mode would allow for moving while maintaining a constant height for the center of mass, which we have demonstrated by simulation. Turning for this mode is shown to occur discretely by changing the heading angle for every step by taking steps of different lengths with the right and left wheels. The two-point contact mode is shown to have one degree of freedom, and that by choosing a step length, the path of the center of the axle in the sagittal plane is determined as a function of the wheel angle. This mode of locomotion allows for statically stable walking with only two wheels, and could be used for carrying heavy payloads. The three-point contact scheme is shown to have zero degrees of freedom,but would allow for additional stability during stationary tasks by letting the robot assume a wide stance. Fig. 13. Kinematic diagram of a single actuated spoke wheel and its degrees of freedom for different modes The concept for transient turning was then developed by having three contact points at the step transition, forcing the pivot line to be skew with the axle of the robot (Fig. 14). Insight into this configuration was gained by analyzing the robot in this configuration as an SPPS spatial mechanism. The insight gained from the spatial analysis is used to describe a more general kinematic model that could be used to analyze both cases of the coplanar pivot line and the skew pivot line, as well as allow analysis of the effects of differentially driving the two actuated spoke wheels. Fig. 14. Turning strategy for the actuated spoke wheel To verify our analytical model and to evaluate the concept in the next phase of the project, we have designed and fabricated our first prototype of the actuated spoke wheel (Fig. 15) to be used for IMPASS. Fig. 15. Prototype of the actuated spoke wheel 2.5 Bipedal locomotion for humanoid robots DARwIn (Dynamic Anthropomorphic Robot with Intelligence) is a humanoid robot capable of bipedal walking and performing human like motions, developed as a research platform for studying robot locomotion and also as the base platform for Virginia Tech’s first entry to the 2007 Robocup competition (Fig.s 16, 17). The 600 mm tall, 4 Kg robot has 21 degree-of-freedom (DOF) with each joint actuated by coreless DC motors via distributed control with controllable compliance. Using a computer vision system on the head, IMU in the torso, and multiple force sensors on the foot, DARwIn can implement human-like gaits while navigating obstacles and will be able to traverse uneven terrain while implementing complex behaviors such as playing soccer. Fig. 16. Kinematic diagram and the CAD model of DARwIn The goal of this on going research project is to develop the robotic platform for, and study the issues related to participating in the 2007 Robocup competition (generating and implementing a dynamic walking gait using Zero Moment Point control, developing algorithms and strategies for intelligent motion planning and obstacle avoidance, vision based control, uneven terrain walking, complex behaviors for playing soccer, etc.) Fig. 17. DARwIn: Dynamic Anthropomorphic Robot with Intelligence DARwIn has a lightweight aluminum skeletal structure with rapid prototyped plastic skin covers. The arms and legs are connected to the body by 3 DOF kinematically spherical joints which provide a wide range of motion similar to a shoulder and hip joint. Each joint is actuated by Maxon’s RE-max coreless DC motors via distributedcontrol with variable compliance. The robot carries two 2100 mAh/7.4V Li-Poly batteries as its power source, a PC104 single board computer for processing, three rate gyros to track orientation of the body, and various sensors including a Firewire camera for vision and eight force sensors on the foot. The new version of DARwIn currently under development for the 2007 Robocup is being designed through collaboration of graduate students and senior undergraduate students from both the Department of Mechanical Engineering and the School of Architecture + Design at Virginia Tech. 3. Conclusion In this paper, we have presented five of the unique ground mobile robots under development at the RoMeLa at Virginia Tech that use novel locomotion strategies for high mobility. As demonstrated, using bioinspiration was the key for the development of these robots. By studying nature's models and then imitating or taking inspiration from these designs and processes, we have successfully applied and implemented new ways for mobile robots to move in various environments with unique mobility. Acknowledgements The author would like to thank the National Science Foundation (No. IIS-0535012), Office of Naval Research (No. N00014-05-1-0828), NASA’s Jet Propulsion Laboratory (NASA Faculty Fellowship Program), and Virginia Tech’s Office of the Provost and the Offic