機(jī)械外文文獻(xiàn)翻譯-無人駕駛電動(dòng)鏟越障車【中文2578字】【PDF+中文WORD】,中文2578字,PDF+中文WORD,機(jī)械,外文,文獻(xiàn),翻譯,無人駕駛,電動(dòng),越障,中文,2578,PDF,WORD Surmounting obstacles by arm maneuver for unmanned power shovel Abstract Large debris created after natural disasters restrict access to inner parts of affected regions, and slows down disaster relief operations. Power shovels are often used to clear wreckage but the process can take a lot of time. Moreover, it is dangerous to involve human workers operating heavy machinery in such unstable conditions. To speedup access to inner areas, obstacles can be surmounted with the assistance of carefully maneuvered power shovel arm, instead of removing them. In this work, an autonomous obstacle surmounting technique for an unmanned power shovel is proposed. Out of different sequences, the one that optimizes the total energy consumption is chosen as the best can- didate for surmounting a given step-like obstacle. Dynamic simulation results show the effectiveness of the proposed method. Background Each year many countries in the world are challenged by natural disasters such as earthquakes, floods, tsu- namis, typhoons and so on. While these disasters can cause loss of life, they also generate large amounts of debris, which further reduces access to inner parts of the affected regions. This results in slowing down of search and rescue missions as well as other disaster relief opera- tions. Power shovels are used in disaster stricken areas to remove wreckage and to clear up roads. Neverthe- less, it is a dangerous task to involve human workers to operate such heavy machines in these conditions as there is chance of tip over of these machines due to instabil- ity. Moreover, it can take a lot of time to clear up all the obstacles and finally get access to inner areas. In order to speed up disaster relief operations, large obstacles can be surmounted instead of clearing them. Using crawler wheels, power shovels have the ability to go over objects effectively compared to other vehi- cles. However, there exists several challenges to obsta- cle surmounting with power shovels as follows: only theobstacles that are within the climbing limit of the crawler can be overcome; crawler power can be easily saturated; power shovel can tip over and damage itself if not moved skillfully when it is on top of an obstacle; being heavy machines, power shovels are also difficult to get back to the original state at the event of tip over. To overcome the aforementioned problems, a power shovel can maneuver its arm effectively to assist the obstacle surmount operation. In fact, such arm assistance is being used nowadays to load small power shovels to trucks for transportation. As can be seen on [1], it can be achieved only with great level of skill and competency. Considering this scenario as a starting point, this work presents an autonomous arm maneuver based obstacle surmounting method to overcome a step-like structure for an unmanned power shovel (Fig. 1). Among different maneuver sequences, the best maneuver is chosen based on the minimum total energy consumption. Further- more, a smooth trajectory of the machine is preferred to avoid any vibrations and jerk exerted on itself and on its surroundings. Previous works on excavators can be found at [2–5]. Ref. [2] presents a dynamic model for an excavator with the intention of developing an automated excavation con- trol system for terrestrial, lunar, and planetary excavation. The kinematics of excavators having hydraulic actuatorsare investigated in detail in [3]. Ref. [4] mainly focuses on a system that completely automates the truck loading task. In that system the excavator’s software decides where to dig in the soil, where to dump in the truck, and how to quickly move between these points while detecting and stopping for obstacles. The nature of an excavation process and the way it may be controlled is investigated with the intention of automatic excavation in [5]. Among other related works, an autonomous stair- case climbing tracked mobile robot is introduced in [6]. However, it does not use any arms for assistance. Ref. [7] introduces a pilot system for a rescue robot to let a human operator suggest good directions to traverse on a 3D debris environment. In contrast, the proposed sys- tem seeks autonomous operation without any human intervention. Ref. [8] has proposed a wheeled robot with a movable center of mass (CoM) to ease the traverse over rough terrain. The proposed system also considers change of CoM, indirectly, by maneuvering its arm; how- ever, the main focus is on getting the reaction force at the bucket as a support to lift the power shovel crawler. Fig. 1 Basic parts of a power shovel. The coordinate frame convention is X forward, Y left and Z up X (forward) crawler step platform boom joint power shovel bucket bucket joint axis of platform rotation boom arm Z (up) arm joint Problem statement Given a step-like obstacle, the power shovel should maneuver its arm to climb up the obstacle in a smooth trajectory. Also, it should carry out the maneuver in such a way that the total energy consumption is minimized. The whole process is to be automated so that the risk for the human workers is eliminated. Nomenclature The basic parts of a power shovel are illustrated in Fig. 1; boom, arm and bucket are the main links considered, while each link is attached to the previous link by boom- joint, arm-joint and bucket-joint, respectively. These joints are individually controlled to achieve different poses similar to a serial link robot manipulator. There is a rotating platform, which can rotate around its local z axis (vertical) so that the whole boom-arm-bucket composite can be moved to its front and back, symmetrically. The vehicle stands on a crawler that provides better mobility on unstructured terrain. Methods b stage 2 Fig. 2 Obstacle surmount stages. The power shovel with dotted lines depicts the initial state while the the one with the regular lines depicts the final state for each stage. P1, P2, P3 and αF denote the parameters of the total maneuver. B and E denote bucket and step edge positions respectively B P3 E initial pose of stage 2 Pb P4 step Pb : bottom center position final pose of stage 2 αF P1 a stage 1 E initial pose of stage 1 Pb Pb : bottom center position P2 step B final pose of stage 1 In the proposed method the obstacle surmount operation is divided into two stages. In the 1st stage, the bucket is kept at the front of the power shovel and it provides the required reaction force to lift the front of the crawler to climb up the step-like structure; the rear of the crawler maintains contact with the ground level. This is illus- trated in Fig. 2a. After the 1st stage is completed, the platform rotates 180° to move the boom-arm-bucket composite to the back of the power shovel to initiate the 2nd stage. Similar to the 1st stage, the bucket provides the required reaction force to lift the rear of the crawler to complete the total surmount operation in the 2nd stage. This is illustrated in Fig. 2b. Throughout 1st and 2nd stages, the bucket maintains fixed ground position either by using friction force [1] or anchored by bucket teeth, which acts as a pivot for stable maneuver; the suit- able anchoring method can be chosen depending on the environment. Discussion It can be observed that the CFSQP result compare well with the result obtained in the exhaustive slow batch simulation. In fact, CFSQP had captured the continuous nature of the objective function (energy) and as a result had been able to obtain the most energy efficient param- eters, which cannot be seized even when exhaustive batch simulations are run based on smaller parameter incre- ments. This is evident from CFSQP energy result being smaller than that of the exhaustive slow batch simulations. To make CFSQP running, a modification had to be included into the original algorithm. That is, when the gradient of the objective function is calculated by finite Angle [deg] difference approximation, the algorithm tends to use nearby points, which can even violate the given con- straints. This can make ODE crash due to ill-defined inputs. To overcome this problem, a large cost was injected when ill-defined points were tested. The joint trajectories for boom, arm and bucket joints (Figs. 11, 12, 13) confirm that the joints undergo smooth transition. However, the discontinuity of each figure needs special mention. After the 1st stage has finished the platform rotates to the back of the power shovel to start the 2nd stage. It is assumed that this trivial operation can be done by constant energy and therefore omitted from the analysis for simplicity. As a result, a discontinuity can be seen due to the mismatch of final and initial joint posi- tions between sequence 1 and sequence 2–1. The parameter P4 is considered to be constant in thesimulation. The only requirement for P4 is such that the power shovel should be able to maintain stability once it lifts the bucket after sequence 2–2 is completed. There- fore, as long as this requirement is fulfilled, P4 can be set to an empirical value and not be included in the optimi- zation process. The open dynamics engine (ODE) [9] consists of two default solvers namely, (1) Dantzig’s Agorithm solver, and(2) Successive Over-Relaxation (SOR) Projected Gauss- Seidel (PGS) LCP solver. Dantzig’s Agorithm solver has been used in this work as it attempts to achieve anumerically exact solution, even though it is about one order of magnitude slower than SOR PGS LCP solver. From Fig. 14, it can be observed that the joint tor- ques undergo certain transients at different stages. At the beginning of 1st stage, torque transients occur due to two reasons: (1) front of the crawler looses the contact with ground, and (2) internal forces generated when the bucket starts pushing the step or ground. A similar condition occurs at the beginning of the 2nd stage where the back of the crawler (however, seen as the front of the crawler due to platform rotation) starts moving upwards and looses contact with the ground. Another important observation is that the gravity terms (mass of each link) have dominated over other terms such as Coriolis, centripetal and inertial terms because of the relatively small joint velocities and accelerations. As the first step of obstacle surmount operation a sim- ple step-like structure was chosen as the obstacle. How- ever, one should not forget that power shovels have the advantage of modifying the terrain using its arm and bucket. As a result, it can pave the unstructured terrain in front of it to shape it to a step-like structure using fast methods like bench cut method and employ the proposed method; totally modifying the terrain into a smooth slope would take a considerable amount of time, which negates the original purpose.  無人駕駛電動(dòng)鏟越障車 摘要 在自然災(zāi)害發(fā)生后會(huì)產(chǎn)生大量的廢墟，阻礙了救援人員解救被困人員，延緩了救災(zāi)行動(dòng)。動(dòng)力鏟通常用來清理廢墟殘骸，但這個(gè)過程可能需要很多時(shí)間。此外，在這種不穩(wěn)定的條件下，讓救援人員操作重型機(jī)械是非常危險(xiǎn)的。為了加快進(jìn)入被困人員區(qū)域，可以通過靈活機(jī)動(dòng)的無人駕駛動(dòng)力鏟臂來執(zhí)行，而不是將其淘汰，在這項(xiàng)工作中，無人駕駛動(dòng)力鏟的自主障礙技術(shù)是至關(guān)重要的。在不同的序列中，優(yōu)化總能量消耗的方法被選為克服給定步驟障礙的最佳方法，動(dòng)態(tài)仿真結(jié)果表明了該方法的有效性。 關(guān)鍵詞:動(dòng)力鏟；障礙超越；無人駕駛；優(yōu)化 背景 每年世界上許多國家都受到地震、洪水、臺(tái)風(fēng)等自然災(zāi)害的侵襲，這些災(zāi)害不僅造成生命損失，而且它們也會(huì)產(chǎn)生大量的廢墟，這導(dǎo)致了搜索和救援任務(wù)緩慢及救援困難度加大。在受災(zāi)地區(qū)，讓人們操作動(dòng)力鏟操作清理廢墟，是一項(xiàng)危險(xiǎn)的任務(wù)，因?yàn)檫@些機(jī)器有可能因安裝的不穩(wěn)定而發(fā)生故障，對人們造成傷害。此外，清除所有的障礙并最終進(jìn)入內(nèi)部區(qū)域需要花費(fèi)大量的時(shí)間。 為了加快救援行動(dòng)的速度，越過巨大的障礙物，而不是清除它們，這時(shí)使用履帶輪，動(dòng)力鐵鍬能有效地解決這一問題。然而，在使用動(dòng)力鏟的情況下，有幾個(gè)難題需要克服:只有在履帶車的爬坡范圍內(nèi)的障礙物才能被克服;履帶越障車的力量可以很容易的飽和;當(dāng)它處于障礙物的頂部時(shí)，如果沒有靈巧地移動(dòng)，它可以翻倒并損壞自己。作為重型機(jī)械，在翻倒的時(shí)候，動(dòng)力鏟也很難回到原來的狀態(tài)。 以前在挖掘機(jī)上的工作可以在[2-5]找到。參考文獻(xiàn)[2]提出了一種挖掘器的動(dòng)態(tài)模型，目的是開發(fā)一個(gè)用于地面、月球和行星挖掘的自動(dòng)挖掘控制系統(tǒng)。[3]詳細(xì)研究了具有液壓執(zhí)行機(jī)構(gòu)的挖掘機(jī)的運(yùn)動(dòng)學(xué)。參考文獻(xiàn)[4]主要集中在一個(gè)完全自動(dòng)化卡車裝載任務(wù)的系統(tǒng)上。在這個(gè)系統(tǒng)中，挖掘機(jī)的軟件決定了在哪里挖掘，在哪里傾倒卡車，以及如何快速在這些點(diǎn)之間移動(dòng)，同時(shí)檢測和停止障礙物。研究了開挖過程的性質(zhì)和控制方法，并在[5]中進(jìn)行了自動(dòng)開挖的目的。 在其他相關(guān)的工作中，一種自動(dòng)爬樓梯的履帶機(jī)器人被引入[6]。但是，它不使用任何武器援助。參考文獻(xiàn)[7]介紹了一種救援機(jī)器人的試驗(yàn)系統(tǒng)，該系統(tǒng)允許人類操作員在三維碎片環(huán)境中提出正確的方向。相比之下，擬議的sys- tem則尋求無需人工干預(yù)的自動(dòng)操作。參考文獻(xiàn)[8]提出了一種可移動(dòng)的質(zhì)心(CoM)的輪式機(jī)器人，以方便在崎嶇的地形上行走。擬議的系統(tǒng)也考慮通過操縱它的手臂來間接地改變CoM;如何-永遠(yuǎn)，主要的焦點(diǎn)是在桶中得到反應(yīng)力作為支撐來舉起動(dòng)力鏟履帶。 Fig. 1 Basic parts of a power shovel. The coordinate frame convention is X forward, Y left and Z up X (forward) crawler step platform boom joint power shovel bucket bucket joint axis of platform rotation boom arm Z (up) arm joint 問題陳述 如果有一個(gè)類似階梯狀的障礙物，動(dòng)力鏟應(yīng)該機(jī)動(dòng)它的手臂以平穩(wěn)的軌跡爬上障礙物。此外，它還應(yīng)該以這樣一種方式進(jìn)行機(jī)動(dòng)，使總能量消耗降到最低。整個(gè)過程是自動(dòng)化的，這樣就消除了人類工人的風(fēng)險(xiǎn)。 b stage 2 Fig. 2 Obstacle surmount stages. The power shovel with dotted lines depicts the initial state while the the one with the regular lines depicts the final state for each stage. P1, P2, P3 and αF denote the parameters of the total maneuver. B and E denote bucket and step edge positions respectively B P3 E initial pose of stage 2 Pb P4 step Pb : bottom center position final pose of stage 2 αF P1 a stage 1 E initial pose of stage 1 Pb Pb : bottom center position P2 step B final pose of stage 1 方法 在提出的方法中，障礙超越操作分為兩個(gè)階段。在第一階段，鏟斗保持在動(dòng)力鏟的前部，并提供所需的反作用力，使爬蟲的正面向上爬升到階梯狀結(jié)構(gòu);爬蟲的尾部保持與地面水平的接觸。如圖2a所示。第一階段完成后,平臺(tái)旋轉(zhuǎn)180°boom-arm-bucket復(fù)合移動(dòng)到后面的電鏟啟動(dòng)第二階段。與第一階段類似，吊桶提供了所需的反作用力，以提升爬蟲的尾部，完成第2階段的全部surmount操作。如圖2b所示。在第一和第二階段，水桶保持固定的地面位置，使用摩擦力[1]或由斗齒錨定，這是穩(wěn)定機(jī)動(dòng)的支點(diǎn);可根據(jù)環(huán)境選擇適合的錨固方法。 討論 可以看出，CFSQP結(jié)果與完全慢批量模擬得到的結(jié)果比較好。事實(shí)上，CFSQP已經(jīng)捕獲了目標(biāo)函數(shù)(能量)的連續(xù)性質(zhì)，因此能夠獲得最高效的param- eters，即使在基于較小參數(shù)的情況下，也不能被捕獲。從CFSQP的能量結(jié)果來看，這是明顯的，比徹底的慢批量模擬的結(jié)果要小。為了使CFSQP運(yùn)行，必須將修改包含到原始算法中。也就是說，當(dāng)目標(biāo)函數(shù)的梯度是有限的。 差分逼近,算法傾向于使用附近的點(diǎn),甚至可以違反給定con?-制度化。這可能會(huì)導(dǎo)致ODE崩潰，因?yàn)檩斎氲亩x不明確。為了克服這個(gè)問題，在測試不確定的點(diǎn)時(shí)注入了大量的成本。 吊桿、臂和桶接頭的關(guān)節(jié)軌跡(圖11、12、13)確認(rèn)關(guān)節(jié)平穩(wěn)過渡。然而，每個(gè)數(shù)字的不連續(xù)性需要特別的說明。第一階段完成后，平臺(tái)旋轉(zhuǎn)到動(dòng)力鏟的背面開始第二階段。假設(shè)這個(gè)簡單的操作可以通過恒定的能量來完成，因此為了簡單起見，我們省略了分析。因此，由于序列1和序列2-1之間的最終和初始關(guān)節(jié)的不匹配，可以看到間斷。 參數(shù)P4被認(rèn)為是常量。 模擬。P4的唯一要求是，當(dāng)2-2序列完成后，電鏟在提升吊桶后能夠保持穩(wěn)定。在此之前，只要滿足這一要求，P4就可以被設(shè)定為一個(gè)經(jīng)驗(yàn)值，而不被包含在優(yōu)化過程中。 open dynamics engine (ODE)[9]包括兩個(gè)默認(rèn)求解器，即(1)Dantzig的agm solver。 (2)連續(xù)超松弛(SOR)投影高斯- Seidel (PGS) LCP求解器。在這個(gè)工作中，Dantzig的agm solver已經(jīng)被用于實(shí)現(xiàn)a。 數(shù)值精確解，即使它大約是一個(gè)數(shù)量級的慢于或PGS LCP求解器。 從圖14可以看出，關(guān)節(jié)突在不同的階段經(jīng)歷一定的瞬態(tài)。在第一階段的開始階段，由于兩個(gè)原因?qū)е罗D(zhuǎn)矩瞬變:(1)履帶前的接觸與地面接觸，(2)當(dāng)桶開始推臺(tái)階或地面時(shí)產(chǎn)生的內(nèi)力。類似的情況出現(xiàn)在第二階段的開始階段，爬蟲的背部(但由于平臺(tái)旋轉(zhuǎn)而被視為爬蟲的前部)開始向上移動(dòng)并與地面失去聯(lián)系。另一個(gè)重要的觀察是重力條件(每一個(gè)連桿的質(zhì)量)在其他術(shù)語上占主導(dǎo)地位，比如科里奧利力、向心和慣性項(xiàng)，因?yàn)樗鼈兊年P(guān)節(jié)速度和加速度相對較小。 作為障礙物的第一步，將一個(gè)類似于sim的階梯狀結(jié)構(gòu)作為障礙物。如何——永遠(yuǎn)不要忘記，使用它的手臂和水桶來改變地形是有好處的。其結(jié)果是，它可以將非結(jié)構(gòu)化的地形鋪在前面，利用臺(tái)階切割法等快速方法將其塑造成階梯狀結(jié)構(gòu)，并采用所提出的方法;將地形完全修改成光滑的邊坡需要相當(dāng)長的時(shí)間，這就否定了原來的目的。 未來的工作 提出的方法是解決這一問題的第一步，因此選擇了一個(gè)簡單的階梯狀障礙物。由于問題的對稱性，在模擬中可以忽略y坐標(biāo)運(yùn)動(dòng)。此外，臂和桶連接軸相互平行，這使得cor-響應(yīng)的連接在飛機(jī)上移動(dòng)。這也使我們將三維運(yùn)動(dòng)簡化為二維空間。然而，在自然災(zāi)害之后產(chǎn)生的碎片有非常復(fù)雜的形狀。作者希望在未來解決各種障礙的問題，這就需要對全三維運(yùn)動(dòng)進(jìn)行分析。克服復(fù)雜障礙的另一個(gè)方面是穩(wěn)定性問題。電鏟在整個(gè)操作過程中應(yīng)保持其穩(wěn)定性，在任何情況下都不應(yīng)傾斜。 在軌跡規(guī)劃中采用簡單的高階多項(xiàng)式，因?yàn)樗唵我子?，沒有遇到任何問題。然而，spline(分段連續(xù)多項(xiàng)式)在軌跡規(guī)劃中得到了popu- larity，作者希望通過將簡單的多項(xiàng)式在未來改變?yōu)闃訔l函數(shù)來觀察其改進(jìn)。 作為下一步，作者希望在未來使用真實(shí)的硬件進(jìn)行擴(kuò)展，以確認(rèn)通過模擬獲得的結(jié)果。 11