第一篇：論文題目多自由度非線性機械系統(tǒng)的全局分叉和混沌動力學研究

論文題目：多自由度非線性機械系統(tǒng)的全局分叉和混沌動力學研究 作者簡介：姚明輝，女，1971年11月出生，2002年09月師從于北京工業(yè)大學張偉教授，于2006年06月獲博士學位。

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摘要

在機械系統(tǒng)中，有許多問題的數(shù)學模型和動力學方程都可用高維非線性系統(tǒng)來描述，對于高維非線性動力系統(tǒng)來說，其研究難度比低維非線性動力系統(tǒng)要大得多，不僅理論方法上有困難，幾何描述和數(shù)值計算都有困難。目前研究高維非線性系統(tǒng)的全局分叉和混沌動力學的理論方法還不是很多，國際上處于發(fā)展階段，國內(nèi)尚處于起步階段，因此發(fā)展處理高維非線性動力學系統(tǒng)的理論研究方法是非常重要和迫切的。在高維非線性動力學的全局分叉和混沌動力學問題中，除了單脈沖混沌運動外，還有多脈沖混沌運動，目前研究多脈沖混沌運動的解析方法主要有兩種，即廣義Melnikov方法和能量相位法。

本論文改進和推廣了Kovacic、Haller和Wiggins等人提出的廣義Melnikov方法和能量相位法，利用這兩種全局攝動解析方法首次研究了非線性非平面運動懸臂梁、粘彈性傳動帶非平面運動和面內(nèi)載荷和橫向載荷聯(lián)合作用下四邊簡支薄板的多脈沖軌道和Shilnikov型混沌運動。理論研究發(fā)現(xiàn)這些系統(tǒng)存在多脈沖混沌運動；利用數(shù)值方法模擬、驗證了理論分析的結果。論文的研究內(nèi)容及取得的創(chuàng)新性成果有以下幾個方面。

(1)綜述了高維非線性系統(tǒng)的分叉和混沌動力學的國內(nèi)外研究現(xiàn)狀；簡要介紹了Melnikov方法的發(fā)展，高維Melnikov方法的應用，以及廣義Melnikov方法的提出和建立；概括了能量相位法的國內(nèi)外主要研究進展；介紹了研究高維非線性系統(tǒng)的全局分叉和混沌運動的其它方法。總結了能量相位法和廣義Melnikov方法的研究進展、成果及存在的不足和有待深入研究的問題。

(2)介紹了由Haller和Wiggins提出的能量相位法；以及由Kovacic等人提出的廣義Melnikov方法。由于能量相位法和廣義Melnikov方法提出和發(fā)展的時間較短，而且一直是獨立的兩種解析方法，在本論文中，首次詳細地研究了兩種全局攝動解析方法的區(qū)別和聯(lián)系。

(3)Haller和Wiggins提出的能量相位法在計算能量差分函數(shù)時，所引入的變換改變了原來系統(tǒng)的拓撲結構。為了使原來系統(tǒng)的拓撲結構不發(fā)生變化，我們改進了能量相位法。利用改進的能量相位法，首次研究了非線性非平面運動懸臂梁、粘彈性傳動帶和四邊簡支薄板的全局分叉和混沌動力學，發(fā)現(xiàn)這些系統(tǒng)存在多脈沖混沌運動。

(4)由于廣義Melnikov方法在理解、計算和開折條件的證明上，存在很大的難度，因此，一直沒有應用到實際工程中分析一些具體的模型。本文首次把廣義Melnikov方法推廣到實際工程中，利用廣義Melnikov方法研究具有實際工程背景的三個高維非線性機械系統(tǒng)，從理論上給出了這些系統(tǒng)產(chǎn)生Shilnikov型混沌運動的必要條件。

(5)首次研究了非線性非平面運動懸臂梁的多脈沖異宿軌道和混沌動力學。在主共振-主參數(shù)共振-1:2內(nèi)共振情形的平均方程的基礎上，利用規(guī)范形理論進行化簡；利用能量相位法，首次從理論上得到了非線性非平面運動懸臂梁產(chǎn)生Shilnikov型混沌的必要條件，發(fā)現(xiàn)在這個系統(tǒng)中存在著Shilnikov型混沌運動。數(shù)值分析表明非線性非平面運動懸臂梁的平均方程確實存在Shilnikov型多脈沖混沌運動，發(fā)現(xiàn)系統(tǒng)的阻尼和激勵兩個參數(shù)對系統(tǒng)出現(xiàn)多脈沖混沌運動影響較大，進一步驗證了理論分析的結果，在三維相空間里存在Shilnikov型多脈沖混沌運動軌線。

(6)首次研究了變張力粘彈性傳動帶非平面運動時多脈沖同宿軌道和混沌動力學。建立了粘彈性傳動帶非平面運動的偏微分方程，應用Galerkin法和多尺度方法得到主參數(shù)共振-1:1內(nèi)共振情形的平均方程，利用規(guī)范形理論化簡平均方程；首次利用能量相位法研究粘彈性傳動帶的多脈沖同宿軌道和混沌動力學，驗證Shilnikov多脈沖軌道的存在性。數(shù)值模擬了粘彈性傳動帶的多脈沖同宿軌道的混沌運動，數(shù)值計算脈沖個數(shù)、區(qū)域直徑和相位漂移之間的關系，發(fā)現(xiàn)隨著脈沖個數(shù)的增加，Shilnikov型多脈沖軌道的區(qū)域直徑減小。

(7)首次研究了面內(nèi)載荷和橫向載荷聯(lián)合作用下四邊簡支矩形薄板的多脈沖異宿軌道和混沌動力學。在四邊簡支矩形薄板的運動偏微分方程基礎之上，應用Galerkin法和多尺度方法得到主參數(shù)共振-基本參數(shù)共振-1:2內(nèi)共振情形的平均方程，利用規(guī)范形理論進行化簡，首次利用能量相位法研究薄板的Shilnikov型多脈沖異宿軌道和混沌動力學，理論分析發(fā)現(xiàn)系統(tǒng)存在多脈沖跳躍而導致的Smale馬蹄意義的混沌。數(shù)值分析表明四邊簡支矩形薄板的平均方程存在Shilnikov型多脈沖混沌運動，發(fā)現(xiàn)系統(tǒng)的阻尼和激勵兩個參數(shù)對系統(tǒng)出現(xiàn)多脈沖混沌運動影響較大，進一步驗證了理論研究的結果，在三維相空間里存在Shilnikov多脈沖混沌運動。

(8)首次利用近可積Hamilton系統(tǒng)的廣義Melnikov方法研究懸臂梁的多脈沖同宿軌道和混沌動力學，得到了在共振情況下判斷非線性非平面運動懸臂梁產(chǎn)生多脈沖混沌運動的廣義Melnikov函數(shù)，求解滿足開折條件的零點。從理論上給出了這個系統(tǒng)產(chǎn)生Shilnikov型混沌的必要條件。數(shù)值模擬了非線性非平面運動懸臂梁的多脈沖混沌運動。

(9)利用近可積Hamilton系統(tǒng)的廣義Melnikov方法首次研究了粘彈性傳動帶空間運動和面內(nèi)載荷與橫向載荷聯(lián)合作用下四邊簡支矩形薄板的多脈沖異宿軌道和混沌動力學。得到了在共振情況下判斷這些系統(tǒng)產(chǎn)生多脈沖混沌運動的廣義Melnikov函數(shù)，求解滿足開折條件的零點，從理論上給出了這些系統(tǒng)產(chǎn)生Shilnikov型混沌的必要條件。理論分析發(fā)現(xiàn)這些系統(tǒng)存在多脈沖跳躍而導致的Smale馬蹄意義的混沌。數(shù)值結果說明了理論結果的正確性，并且發(fā)現(xiàn)一些參數(shù)和初始條件對于這些系統(tǒng)產(chǎn)生多脈沖混沌運動有著較大的影響。

(10)用數(shù)值方法研究了一個二自由度機械系統(tǒng)的多脈沖混沌運動，發(fā)現(xiàn)了一種新的多脈沖混沌吸引子。

能量相位法和廣義Melnikov方法提出和發(fā)展的時間較短，理論體系較新而復雜，能量相位法是從多脈沖跳躍軌道的能量耗散方面來研究多脈沖混沌運動，而廣義Melnikov方法則是從多脈沖奇異橫截面中的穩(wěn)定流形和不穩(wěn)定流形來研究多脈沖混沌運動。研究表明，這兩種方法分別只研究了多脈沖軌道的一個方面，如果能夠把兩者結合起來研究多脈沖混沌運動，則其結論將更加完整。

本論文的創(chuàng)新點有以下幾個方面。

(1)首次利用能量相位法和廣義Melnikov方法研究了非線性非平面運動懸臂梁、粘彈性傳動帶非平面運動和面內(nèi)載荷與橫向載荷聯(lián)合作用下四邊簡支薄板的多脈沖軌道和Shilnikov型混沌運動，發(fā)現(xiàn)在三個機械系統(tǒng)中存在著Shilnikov型混沌運動。

(2)Haller與Wiggins利用能量相位法計算能量差分函數(shù)時，他們所引入的變換改變了原系統(tǒng)的拓撲結構。為了使原系統(tǒng)的拓撲結構不發(fā)生變化，我們改進了能量相位法。

(3)由于廣義Melnikov方法在理解、計算和開折條件的證明上，存在很大的難度，因此，一直未應用于實際工程系統(tǒng)。本文首次把廣義Melnikov方法應用于三個機械系統(tǒng)，從理論上給出了這些系統(tǒng)產(chǎn)生Shilnikov型混沌運動的必要條件。

(4)用數(shù)值方法研究了一個二自由度非線性機械系統(tǒng)，在這個系統(tǒng)中發(fā)現(xiàn)了一種新的多脈沖混沌吸引子。

本論文利用能量相位法和廣義Melnikov方法研究了非線性非平面運動懸臂梁、粘彈性傳動帶非平面運動和面內(nèi)載荷與橫向載荷聯(lián)合作用下四邊簡支矩形薄板的多脈沖軌道和混沌動力學。通過本文的研究，發(fā)現(xiàn)能量相位法和廣義Melnikov方法有一些有待于進一步改進和完善的方面。下述幾個問題值得進一步的研究。

(1)如何把能量相位法和廣義Melnikov方法推廣到高維非自治系統(tǒng)和高于四維的更高維非線性系統(tǒng)。

(2)利用能量相位法分析非線性系統(tǒng)的多脈沖軌道和混沌動力學的關鍵在于定義耗散因子，而耗散因子是阻尼與外激勵的比值。目前，能量相位法只能用來分析單阻尼、單激勵單耗散因子的系統(tǒng)，如何把能量相位法擴展到多阻尼、多激勵多耗散因子的系統(tǒng)，有待進一步的研究。

(3)能量相位法和廣義Melnikov方法理論體系比較復雜，不利于工程科學家用來解決工程實際問題。如何進一步改進和簡化這兩種方法，提出新的多脈沖軌道和混沌動力學的判定準則，使這兩種全局攝動方法更好地應用于工程實際問題。

關鍵詞：

廣義Melnikov方法，能量相位法，Shilnikov型多脈沖軌道，全局分叉，混沌動力學，規(guī)范形，懸臂梁，粘彈性傳動帶，薄板

Studies on Global Bifurcations and Chaotic Dynamics in Multi-Degree of Freedom Nonlinear Mechanical Systems

Yao Minghui ABSTRACT

The governing equations of motion for a number of engineering problems can be described by high-dimensional nonlinear systems.Comparing with low-dimensional nonlinear systems, the theory method, geometrical description and numerical simulation on the complicated dynamic behavior of high dimensional nonlinear systems were more difficult.The global bifurcations and chaotic dynamics of high-dimensional nonlinear systems have been at the forefront of nonlinear dynamics for the last two decades.Due to lack of analytical tools and methods to study the global bifurcations and chaotic dynamics for high-dimensional nonlinear systems, it is extremely challenging to develop the theories of the global bifurcations and chaotic dynamics for high-dimensional nonlinear systems and to give systematic applications to engineering problems.Therefore, the global bifurcations and chaotic dynamics of high-dimensional nonlinear systems are important theoretical problems in science and engineering applications as they can reveal the instabilities of motion and complicated dynamical behaviors in high-dimensional nonlinear systems.Besides the Shilnikov type single-pulse global bifurcations and chaotic dynamics of high-dimensional nonlinear systems, the Shilnikov type multi-pulse homoclinic and heteroclinic bifurcations and chaotic dynamics were investigated.Two main methods for studying the Shilnikov type multi-pulse homoclinic and heteroclinic orbits in high-dimensional nonlinear systems are the energy-phase method and the generalized Melnikov method.In this dissertation, we improve and expand the energy-phase method and the generalized Melnikov method presented by Haller, Kovacic and Wiggins.These two methods are utilized to investigate the Shilnikov type multi-pulse heteroclinic and homoclinic bifurcations and chaotic dynamics for three high-dimensional nonlinear mechanical systems which the nonlinear non-planar oscillations of a cantilever beam, a parametrically excited viscoelastic moving belt and a parametrically and externally excited thin plate.The analysis of global dynamics indicates that there exist the multi-pulse jumping orbits in the perturbed phase space of the averaged equation for three high-dimensional nonlinear mechanical systems.These results show that the multi-pulse Shilnikov orbits chaotic motions can occur for three high-dimensional nonlinear mechanical systems.Numerical simulations are also given to verify the analytical predictions.The research contents and the innovative contributions of this dissertation are as follows:(1)We give a review of the researches on the global bifurcations and chaotic dynamics of high-dimensional nonlinear systems and summarize the developments and results achieved on studies the Shilnikov type multi-pulse chaotic dynamics with the energy-phase method and the generalized Melnikov method in the past two decades.We indicate the unsolved problems at present and the developing directions in the energy-phase method and the generalized Melnikov method in the future.(2)We give a briefly description on the energy-phase method and the generalized Melnikov method based on the research work given by Haller, Kovacic and Wiggins et al.in the theoretical frame.Due to the short time of the development and independence of the two methods, we analyze the difference and relation between the two global singular perturbation methods in detail for the first time.(3)Based on research obtained in this dissertation, we think that the symplectic transformations used by Haller et al.do not have topological equivalence because they will change the topology of the phase space and the types of multi-pulse connections.The energy-phase method is further improved to ensure the equivalence of topological structure for the phase portraits.The multi-pulse Shilnikov orbits and chaotic dynamics with the energy-phase method in three high-dimensional nonlinear mechanical systems are studied in this dissertation for the first time.These results show that the multi-pulse Shilnikov orbits chaotic motions can occur for three high-dimensional nonlinear mechanical systems.(4)Due to difficulties of comprehension and computation of the generalized Melnikov method, it is not always applied to engineering problems.We expand and apply the generalized Melnikov method to study the Shilnikov type multi-pulse orbits to resonance bands in three high-dimensional nonlinear mechanical systems for the first time.These results show that the multi-pulse Shilnikov orbits chaotic motions can occur for three high-dimensional nonlinear mechanical systems.(5)The many pulses orbits with the energy-phase method chaotic dynamics for the nonlinear non-planar oscillations of a cantilever beam are studied in this dissertation for the first time.The resonant case considered here is principal parametric resonance-1/2 sub-harmonic resonance for the first mode and fundamental parametric resonance-primary resonance for the second mode.Based on normal form obtained, the improved energy-phase method is utilized to analyze the multi-pulse global heteroclinic bifurcations and chaotic dynamics for the nonlinear non-planar oscillations of the cantilever beam for the first time.The chaotic motions of the nonlinear non-planar oscillations of a cantilever beam are also found by using numerical simulation.(6)The multi-pulse orbits and chaotic dynamics of parametrically excited viscoelastic moving belt are studied in detail for the first time.Using Kelvin-type viscoelastic constitutive law, the equations of motion for viscoelastic moving belt with the external damping and parametric excitation are determined.The four-dimensional averaged equation under the case of 1:1 internal resonance and primary parametric resonance is obtained by directly using the method of multiple scales and Galerkin’s approach to the partial differential governing equation of viscoelastic moving belt.From the averaged equations obtained here, the theory of normal form is used to give the explicit expressions of normal form with a double zero and a pair of pure imaginary eigenvalues.Based on the normal form, the improved energy-phrase method is employed to analyze the global homoclinic bifurcations and chaotic dynamics in parametrically excited viscoelastic moving belt.The global analysis indicates that there exist the Shilnikov type multi-pulse orbits in the averaged equation.The results obtained above mean the existence of the chaos for the Smale horseshoe sense in motion of parametrically excited viscoelastic moving belt.The chaotic motions of viscoelastic moving belts are also found by using numerical simulation.It is also found from the results of numerical simulation of the relationship of the width of the layers and the lowest number of pulses that the width of the layers decreases with the augment of the lowest number of pulses.(7)The multi-pulse Shilnikov orbits and chaotic dynamics in a parametrically and externally excited thin plate are studied in this dissertation for the first time.The thin plate is subjected to transversal and in-plane excitations, simultaneously.The formulas of the thin plate are derived from the von Kármán equation and Galerkin’s method.The method of multiple scales is used to find the averaged equation.The theory of normal form, based on the averaged equation, is used to obtain the explicit expressions of normal form associated with a double zero and a pair of purely imaginary eigenvalues from the Maple program.Based on the normal form obtained above, the dissipative version of the improved energy-phase method is utilized to analyze the multi-pulse global heteroclinic bifurcations and chaotic dynamics in a parametrically and externally excited thin plate.The global dynamics analysis indicates that there exist the multi-pulse jumping orbits in the perturbed phase space of the averaged equations for a parametrically and externally excited thin plate.These results show that the chaotic motions of the multi-pulse Shilnikov type can occur in a parametrically and externally excited thin plate.Numerical simulations are given to verify the analytical predictions.It is also found from the results of numerical simulation that the multi-pulse Shilnikov type orbits exist in a parametrically and externally excited thin plate.(8)The generalized Melnikov method of near-integral Hamiltonian system is applied to study the multi-pulse global homoclinic bifurcations and chaotic dynamics for the nonlinear non-planar oscillations of the cantilever beam for the first time.The analysis of global dynamics indicates that there exist the multi-pulse jumping orbits in the perturbed phase space of the averaged equation for the nonlinear non-planar oscillations of the cantilever beam.Numerical simulations are given to verify the analytical predictions.It is also found from the results of numerical simulation in three-dimensional phase space that the multi-pulse orbits exist for the nonlinear non-planar oscillations of the cantilever beam.(9)The generalized Melnikov method of near-integral Hamiltonian system is applied to study the multi-pulse global heteroclinic bifurcations and chaotic dynamics for parametrically excited viscoelastic moving belt and a parametrically and externally excited thin plate for the first time.The analysis of global dynamics indicates that there exist the multi-pulse jumping orbits in the perturbed phase space of the averaged equation for these systems.Numerical simulations are given to verify the analytical predictions.It is also found from the results of numerical simulation in three-dimensional phase space that the multi-pulse orbits exist for these systems.(10)The results of numerical simulation show that the chaotic motion of the new Shilnikov type multi-pulse orbits can occur for a two-degree-of-freedom nonlinear mechanical system.Generalized Melnikov method and the energy-phase method developed in the short time.The energy-phase method studies dissipative energy of multi-pulse orbits, while generalized Melnikov method analyses the distance of the stable manifold and unstable manifold of multi-pulse orbits.They have merit and defect respectively.If we can combine these both methods to study multi-orbits, we will draw a conclusion completely.The innovative achievements of this dissertation mainly are as follows:(1)The Shilnikov type multi-pulse orbits with the energy-phase method and generalized Melnikov method chaotic dynamics for the nonlinear non-planar oscillations of a cantilever beam, parametrically excited viscoelastic moving belt and a parametrically and externally excited thin plate are studied in this dissertation for the first time.The Shilnikov type chaotic dynamics are found in the three high-dimensional nonlinear mechanical systems.(2)Based on research obtained in this dissertation, we think that the symplectic transformations used by Haller et al.do not have topological equivalence because they will change the topology of the phase space and the types of multi-pulse connections.The energy-phase method is further improved to ensure the equivalence of topological structure for the phase portraits.(3)Due to difficulties of comprehension and computation of the generalized Melnikov method, it is not always applied to engineering problems.We expand and apply the generalized Melnikov method to study the Shilnikov type multi-pulse orbits to resonance bands in three high-dimensional nonlinear mechanical systems for the first time.These results show that the multi-pulse Shilnikov orbits chaotic motions can occur for three high-dimensional nonlinear mechanical systems.(4)The results of numerical simulation show that the chaotic motion of the new Shilnikov type multi-pulse orbits can occur for a two-degree-of-freedom nonlinear mechanical system.The Shilnikov type multi-pulse orbits with the energy-phase method and generalized Melnikov method chaotic dynamics for the nonlinear non-planar oscillations of a cantilever beam, parametrically excited viscoelastic moving belt and a parametrically and externally excited thin plate are studied in this dissertation.We find the energy-phase method and generalized Melnikov method needing to improve further through our research.The three aspects as follows need further study:(1)How to expand the energy-phase method and generalized Melnikov method to high-dimensional non-autonomous nonlinear systems and high-dimensional which are higher than four dimensional nonlinear systems?(2)Using the energy-phase method to analyze multi-pulse orbits for high-dimensional nonlinear systems is important to define a dissipative factor which is the ratio of the damping coefficient to the excited force.Until now the energy-phase method can only study single dissipative factor, while can not analyze many dissipative factors which are the ratio of the damping coefficients to the excited forces.How to deal with many dissipative factors?(3)The theory of the energy-phase method and generalized Melnikov method is too complicated to apply to engineering problems conveniently.How to improve and simplify these two methods to apply engineering field well? How to present new criterion of the multi-pulse orbits?

Key words: Generalized Melnikov method, the energy-phase method, Shilnikov type multi-pulse, global bifurcations, chaotic dynamics, theory of normal form, cantilever beam, viscoelastic moving belt, thin plate

第二篇：平行多連桿樣品抓取機構的動力學仿真研究論文

引言

樣品抓取與轉(zhuǎn)移是深空探測的主要任務之一，平行多連桿樣品抓取機構是實現(xiàn)上述任務的執(zhí)行機構，也是最為關鍵的復雜系統(tǒng).平行多連桿樣品抓取機構是在軌道交會對接任務階段，實現(xiàn)追蹤飛行器與目標飛行器之間的對接、保持和樣品轉(zhuǎn)移等任務的重要部分.在完成在軌對接之后，平行多連桿樣品抓取機構將在追蹤飛行器與目標飛行器構成的組合體飛行期間，按程序指令將樣品從追蹤飛行器轉(zhuǎn)移到目標飛行器，保證樣品能夠進入后續(xù)的任務工作環(huán)節(jié).平行多連桿樣品抓取機構能成功捕獲抓取樣品，并順利將其轉(zhuǎn)移至返回艙內(nèi)，是一個復雜的動力學過程.地面驗證試驗很難模擬空間零重力環(huán)境，因此采用仿真技術建立虛擬數(shù)字樣機研究整個樣品抓取與轉(zhuǎn)移過程的動力學問題成為關鍵和主要的手段.本文以平行多連桿樣品抓取機構為研究對象，在Adams多體動力學仿真環(huán)境中建立了動力學仿真模型，詳細分析了樣品抓取與轉(zhuǎn)移整個工作過程中的動力學特性與規(guī)律，并分析了冗余設計工況，為平行多連桿樣品抓取機構的研究和設計提供了參考作用.1工作原理

對接機構主動件安裝在追蹤飛行器上，被動件安裝在目標飛行器上，對接機構完成后進行樣品抓取與轉(zhuǎn)移過程.平行多連桿抓取機構的功能要求是對樣品進行捕獲，然后將其轉(zhuǎn)移至安裝在目標飛行器內(nèi)的返回艙內(nèi).主要由抓取機構、連桿機構、驅(qū)動機構、傳動機構等組成.因兩套平行多連桿抓取機構呈夾角式分布，且樣品采集器不規(guī)則，在轉(zhuǎn)移過程中樣品勢必會發(fā)生翻轉(zhuǎn).為了使樣品轉(zhuǎn)移過程平穩(wěn)安全，故在對接機構被動件部分、主動件部分、返回艙部分均設置了能為樣品提供導向功能的導向槽.通過對導向槽及導向槽與樣品采集器之間的間隙的優(yōu)化設計，可以降低轉(zhuǎn)移機構與樣品之間的接觸力，提高轉(zhuǎn)移機構的動力學特性.轉(zhuǎn)移功能的實現(xiàn)主要利用了連桿機構的行程放大特性及抓取機構的單向鎖緊釋放特性，通過連桿機構的反復收合，由抓取機構進行鎖緊和釋放工作，從而將樣品采集器移動至目標位置.2動力學建模

在平行多連桿樣品抓取機構設計原理與動力學分析的基礎上，采用adams軟件建立了動力學模型.在該模型中，假設追蹤飛行器和目標飛行器的幾何中心在向坐標相同，在整個樣品抓取與轉(zhuǎn)移過程中，平行多連桿樣品抓取機構在恒定的電機的驅(qū)動下經(jīng)過四次張開收合的過程，在每套機構上的3組抓取機構與樣品采集器的接觸力作用下將樣品采集器從追蹤飛行器移動到目標飛行器內(nèi)，而樣品采集器與導向槽之間的接觸力將保證樣品采集器在運動過程中不至翻轉(zhuǎn).在目標飛行器上設計了止動鎖緊裝置，使得樣品采集器在轉(zhuǎn)移機構收合過程中不至反向運動，同時調(diào)整其姿態(tài).整個模型中包括轉(zhuǎn)動副(Revolute Joint)、平移副(RevoluteJoint)、驅(qū)動速度(motion)、樣品采集器與棘爪之間的碰撞接觸力(contact)、樣品采集器與導向槽之間的碰撞接觸力(contact)、樣品采集器與止動鎖緊裝置之間的碰撞接觸力(contact)等.3仿真算例

3.1 正常工作

3.1.1接觸力計算值

通過計算可以求得在樣品抓取與轉(zhuǎn)移過程中，抓取機構與樣品采集器之間的碰撞接觸力隨時間變化的曲線，反映了平行多連桿樣品抓取機構的動力學特性，其中，后端抓取機構與樣品采集器的碰撞接觸力計算值.可以看出后端抓取機構與樣品采集器之間碰撞接觸力最大值為64.1N樣品采集器導向槽與樣品采集器碰撞接觸力計算最大值為61.8N追蹤飛行器導向槽與樣品采集器碰撞接觸力計算最大值為20.8N，目標飛行器導向槽與樣品采集器碰撞接觸力計算最大值為28.2N當樣品采集器被轉(zhuǎn)移到目標飛行器內(nèi)之后，經(jīng)過一段時間，樣品采集器與目標飛行器之間的碰撞接觸力趨于平衡.3.2冗余設計分析

3.2.1樣品采集器位置與姿態(tài)偏移

經(jīng)仿真計算，當只有一套平行多連桿樣品抓取機構正常工作時，也能順利完成樣品轉(zhuǎn)移任務.在這種工況下，姿態(tài)偏移量，經(jīng)過轉(zhuǎn)移過程，樣品采集器的位移與姿態(tài)都發(fā)生了變化，其中，樣品采集器X方向位置偏移為-1mm;Y方向位移為-565.8 mm;Z方向位置偏移量計算值為-0.005 mm;X方向轉(zhuǎn)角為2.09度，Y方向轉(zhuǎn)角為-1.08度，Z方向轉(zhuǎn)角為0度.3.2.2接觸力計算值

通過計算可以求得在樣品轉(zhuǎn)移過程中，后端抓取機構與樣品采集器之間的碰撞接觸力以及樣品采集器與導向槽之間的碰撞接觸力隨時間變化的曲線，反映了平行多連桿樣品抓取機構的動力學，其中，后端抓取機構與樣品采集器的碰撞接觸力計算值.從圖中可以看出，正常工作的后端抓取機構與樣品采集器之間的碰撞接觸力有尖峰值出現(xiàn)，最大值為2006.8 N;樣品采集器導向槽與樣品采集器碰撞接觸力較小，追蹤飛行器導向槽與樣品采集器碰撞接觸力有尖峰值出現(xiàn)，最大值1102.7N，目標飛行器導向槽與樣品采集器碰撞接觸力也有尖峰值出現(xiàn)，最大值為4342.5 N.當樣品采集器被轉(zhuǎn)移到目標飛行器內(nèi)之后，經(jīng)過一段時間，樣品采集器與目標飛行器之間的碰撞接觸力趨于平衡，且平衡值為0.由此可以看出，當平行多連桿樣品抓取機構正常工作時，后端抓取機構與樣品采集器之間的碰撞接觸力、追蹤飛行器導向槽與樣品采集器碰撞接觸力以及目標飛行器導向槽與樣品采集器碰撞接觸力均有較大的尖峰值出現(xiàn)，但樣品采集器位置與姿態(tài)偏移量并不明顯，因此，在材料剛度強度足夠的情況下，單套平行多連桿樣品抓取機構也能正常完成樣品轉(zhuǎn)移任務.4結論

本文采用adams軟件建立了平行多連桿樣品抓取機構的動力學模型，詳細分析了整個樣品抓取與轉(zhuǎn)移工作的動力學過程，通過計算得到了經(jīng)過樣品轉(zhuǎn)移過程之后，樣品采集器的位置和姿態(tài)的偏移情況，以及抓取機構與樣品采集器碰撞接觸力和樣品采集器與導向槽之間的碰撞接觸力，同時對冗余設計進行了分析，對空間飛行器平行多連桿樣品抓取機構的設計起到了分析指導作用.