空间机械手的跟踪捕捉操作.doc

毕业设计外文资料翻译题 目 空间机械手的跟踪捕捉操作 学 院 机械工程学院 专 业 机械工程及自动化 班 级 机自0917班 学 生 廉开发 学 号 20090421170 指导教师 苏东宁 二一 三 年 四月 一 日 Tracking Trajectory Planning of Space Manipulator for Capturing Operation Panfeng Huang1; Yangsheng Xu2 and Bin Liang3 College of Astronautics, Northwestern Polytechnical University, China 2 Department of Automation and Computer-Aided Engineerging, The Chinese University of Hong Kong, Hong Kong Shenzhen Space Technology Center, Harbin Instute of Technology, China Abstract: On-orbit rescuing uncontrolled spinning satellite (USS) using space robot is a greatchallenge for future space service. This paper mainly present a trajectory planning method of space manipulator that can track, approach and catch the USS in free-floating situation. According to the motion characteristics of USS, we plan a spiral ascending trajectory for space manipulator to approach towards USS in Cartesian space. However, it is difficult to map this trajectory into the joint space and realize feasible motion in joint space because of dynamics singularities and dynamics couple of space robot system. Therefore, we utilize interval algorithm to handle these difficulties. The simulation study verifies that the spiral ascending trajectory can been realized. Moreover, the motion of manipulator is smooth and stable, the disturbance to the base is so limited that the attitude control can compensate it.Keywords: Space manipulator, tracking trajectory planning, interval algorithms, polynominal spline functionIntroductionThis paper deals with a special problem oftrackitrjectoryplanningofspacemanipulatofor capturing the uncontrolled spinning satellites. On-orbit capturingisachallengeworkforspacerobotsystem in the future space service. The space robot science has gotten big progress in the pastdecade.T herefore, on-orbit service for uncontrolled satellite will be a main application of space robot in orderreduce the space cost in the future. When human being launched the first space robot and operated itto accomplish the space mission, space robot began to be utilized in differentspacetasks. Nowadays space robots are aiding to construct and maintain the InternationalSpaceStatio andservicingthspace telescope. Therefore space robotic servicing forsatellitsuchrescue,repairrefuelling and maintenance, promise to extendsatellitelifeandreducecostsmakesitoneofthemostattractiveareasofdevelopingtechnology.Spacerobots are likelytoplay more and more important roles insatelliteservicingmissionandspaceconstructionmission in the future. The approach ancaptureoperation must be solved firstly in order to accomplish all these missions. A well known space robot, the Shuttle Remote Manipulator System (SRMSorCanadarm) D. Zimpfer and P. Spehar, 1996 was operated to assist capture and berth the satellite from the shuttle by the astronaut. NASA missions STS-61, STS-82, and STS-103 repaired the Hubble Japan demonstratedthe space manipulator to capture acooperative satellite whose attitude is stabilized during the demonstration viatele-operationfromthegroundcontrolstationKawano,I.,etal.1998,NoriyasuInaba,etal,2000.Allmentiabovespacerobotic technologies demonstrate the usefulness of space robot for space servicing. However their use is limited to capture the satellites that are cooperative and attitude stabilized. For instance, the rotatedattwodeg/sec.NASAmissionThereforethecaptureandrecovery of a valuable uncontrolled satellite can be a class of future missionforthefuturespacerobot.Nearlyallofsatelliteservicingmissionsoccurredhavebeen executed by Extra-Vehicular Activity (EVA) of the astronaut with the limited help of space robotic manipulator. It is very expensive and dangerous for the astronauts to capture an uncontrolled spinning satellite, even forslowlyspinning satellite. On the other hand, space robotic technologybecomesmoreandmore advancrecently. The space robot carries out such satellite servicing mission automatically or with limited human support in the future. However, the first step of the capture is how to track and approach the target satellite. Stephen Jacobsen et al Jacobsen, S., et al. (2002) presented to plan a safekinematicstrajectory f or free flying robots approaching an uncontrolled spinning satellite, they address how to let the space robot approach to the workspace of robotic manipulator in whichthemanipulatorcanoperate and capture the USS. Therefore,this paper assumes that the target satellite isintheworkspaceof space manipulator. it is desirable to contrive a new tracking and approach trajectory for space manipulator to capture the target satellite.So far, there are many studies on trajectory planning of space robot. S. Dubowsky and Kazuya Yoshida K.HashizumKyoshidandKHashizume (2001) utilized the ETS-VII as Yangsheng Xu Om P. Agrawal and Yangsheng Xu (1994) introduced a global optimum path planning forredundantspace manipulator. All examples mentioned interacHowever,onlyfewresearchers work on tracking trajectory planningofspacemanipulatorforcapturingthuncontrolledsatelliteinfact.HiroyukietalHiroyukiNagamatus,et al. (1996) presented a capture strategy for retrieval of a tumbling satellite by a space robotic manipulator. Zhenghua Luo and Yoshiyuki sakawa Zhenghua Luo and Yoshiyuki Sakawa(1990)discussed the control law of capturing a tumbling object by a space manipulator. Therefore, how oplanfeasible tracking trajectory becomes ator based onspacebaseisdifferentwithterrestrialmanipulatorintrajectoryplanning and control.Hence it is necessary to plan the tracking trajectory of space manipulatorforapturing USS from the engineering point of view. This paper aims to address an innovative trackingrajectory planning method of space robot manipulator capturing the USS according .This paper is organized as follows. The section two describes the main problem and assumption,thesectionthree simplyreviewsthekinematicsanddynamicsquationofspacemanipulator.Then,weaddressthemotionestimation of USS in section four. The section five addresses ourtrajectoryplanningmethod.In section six, the computer simulation study and result are showed. The section seven summarizes the whole paper and educes the conclusion.2. Problem Formulation2.1. Description of ProblemOn-orbit capturing USS has not successful examples so far, as a typical example of on-orbit operation. Here, the authors mainly assume a capture operation in order to describe the problem. Fig.1 shows a schematic illustration of a tracking operation in which a space manipulator is tracking and approaching towards the target satellite. This operation can almost been solved for terrestrial robotic manipulator. However, in space environment, it isvery difficult problem for robotic manipulator to capturUSS because of the dynamics couple and dynamic singularities which result in the big error of desired trajectory and real trajectory, this error possibly causes the catastrophic affair and demolish the space robot system completely. On the other hand, it is very important problem to plan a trajectory for space manipulator to track and approach the USS. This paper will focus on this problem. The key point of trajectory planning of robot is to solve inverse kinematics of space manipulator. The drawback in kinematics problems of free-flying space manipulator is that, as Longman et al R. W. Longman, R. E. LindBerg, and M. F. Zedd (1987) and Vafa et al Z. Vafa and S. Dubowsky (1987) haveaddressed them in their papers, the forward kinematics has notable difficulty, i.e., the position and orientation of the manipulator end-effector do not have a closed form solution since they depend on the inertia property that changes according to the configuration of space manipulator. Therefore, the history of the postural change must be considered in order to derive the solution, all these problems make the inverse kinematics more difficult.In order to cope with tracking trajectory planning problem, the present paper describes a tracking trajectory according to the features of the USS and the space manipulator. As discussed in detail in section five.2.2. AssumptionIn this paper, the authors assume a model of space robot system which is composed of a space base and a robotic manipulator arm mounted on the space base. Fig.2 shows a simple model of space robot system with a single manipulator arm. In order to clarify the point at issue, they present the following assumption. a) The space robot system consists of n+1 links connected with n active joints, each joint has one rotational degree of freedom (DOF) and is controlled. The attitude or position of the space base can be controlled or not be controlled respectively. b) No mechanical restriction and external force or torque to the space manipulator system, i.e. the gravity isignored, so that the total momentum of the mechanical system is always conserved. The kinematics and dynamics analysis during the motion is in the inertial coordinate system. Therefore, the DOF of the space manipulator system in inertial coordinate is n+6, that is the attitude of the base has three DOFs, the position of the base has three DOFs, n represents the DOF number of the manipulator arm. c) For simplification, the whole system is composed of rigid bodies, thus, the space manipulator system is regarded a free-flying mechanical chain consisted of n+1 rigid bodies d) The motion state of USS can be estimated by the sensors of the space robot system. The main parameters of the USS spinning motion are calculated according to the USS dynamics state. i.e. the spinning velocity can be estimated and the mark points of USS motions the circle trajectory.Kinematics and Dynamics of Space Manipulator3.1 Kinematics of Space Robo The kinematics of robotic manipulator maps the relationship between Joint space and Cartesian space, the space-based kinematics is different form the terrestrial robot, the kinematics of ground robotic manipulator only depends on the joint variables, position and orientation of the end-effector respectively. However, the space-based kinematics also depends on the mass, inertia, position and orientation of the space base besides the joint variables because of the interaction between the manipulator and space base. We will simply review it that has been described by Yoji Umetani et al Yoji Umetani and Kazuya Yoshida (1989). As shown in Fig.2, we define the vector relation of whole space robot model. The model assumed can be treated as a set of n+1 rigid bodies connected with n joints that form a tree configuration, each joint is numbered in series of 1 to n. We define two coordinate systems, one is the inertial coordinate system I in the orbit, the other is the base coordinate system 0 attached on the base body with its origin at the centroid of the base. The COM is the center of total system mass, all vectors in this paper are expressed in terms of coordinate I. We use three appropriate parameters such as Roll, Pitch, and Yaw to describe the attitude of base. Therefore, we use the vector principle to describe theDifferentiate the kinematics equation (1) with respect to time. Then, we can obtain the kinematics relationship in velocity level. The detail derivation sees the concerned articles Yoji Umetani and Kazuya Yoshida (1989).where: pe: The position vector of the end-effector in coordinate system I r0: The position vector of the centroid of the space base body in I systeml0 : Vector pointing from the centroid of space base to the joint one. li : vector pointing from joint i to joint i+1 Jb: Jacobian matrix for the space base variables Jm: Jacobian matrix for the manipulatorxb: The position/orientation of the space base xe: The position/orientation of the end-effector : : Joint variable of the manipulator3.2 Dynamics of Space Robot It is a general problem to derive the dynamics equation of space robotstem. Wutilize Roberson-Wittenburgs method Robert E. Roberson (1997) to derive the rigid dynamics of multi-body system. This method utilizes the mathematical graph theory Jens Wittenburg (1997)escribe the interconnecting of the multi-body. The advantage of this method is that the various multi-body systems can be described by the uniform mathematical model. So far, there are many studies on the dynamics of space robot system. Therefore we will directly express the dynamic equation according to the assumed model. The motion equation of the space robot system is expressed in the following form Y. Xu and T. Kanade (1992).The symbols in the above equations are defined asfollowings:mi: The mass of link i of the space manipulator: The total mass of the whole space robot systemri : The position vector of centroid of the link ipi : The position vector of joint iki: Unit vector indicating joint axis direction of the link i rg: The position vector of the total centroid of the space robot systemIi:Inetia tenor of the link i with respect to its masscentercb: Velocity dependent non-linear term for these cm: Velocitydependentnon-linearterm for he manipulator armFb: The External force and torque on the space base Fh: The external force and torque on the end-effector : The joint torque of the manipulator armHb: The inertial matrix of the space baseHm: The inertial matrix for the manipulatorHbm: The coupling inertial matrix between the space base and manipulatorAll vectors are described with respect to the inertial coordinate systemI, cb and cm can be obtained by inverse dynamic. The inverse dynamic computation is useful for a computed torque control. Here, the authors use n-order recursive Newton-Euler approach J. S. Y.Luh, M. W. Walker and R. P. C.Paul (1980) K. Yoshida (1997) to compute inverse dynamics. In addition, calculating inverse dynamics can obtain the reaction force/moment on the space base.where: Fi, Ni are inertial force and moment exterting onthe centroid of link i. Otherwise we define force andmoment fi, ni exterting on the joint, fci and nci exterting onthe end-effector. Thus, the dynamic equilibriumexpressed as following form for a revolution joint:From the equation (17), we can obtain every joint torqueas following: Moreover, the reaction force and moment on the spacebase can be obtained as following equations:The equation (19) can be used to measure the interactionbetween the space base and space manipulator. These parameters are very important reference for designing the attitude control system and orbit control system. Moreover, the coordinate control of space base and space manipulator needs these parameters.The symbols in equation (17), (18) and (19) are defined as followings: sij: the elementofIncidencematrixs,thedetaileddefinitioseesmathematicalgraphtheory. sei: the element of Incidence matrix sej (j = 1,n), that represents a j is -link. lij:vector from joint i to joint j, from Fig.2, we know lij =cij-cii. cij : vector from the centroid of link i to joint j.For whole space robot system, the external force or torque on the space base Fb, which can be generated by jet thrusters or reaction wheels, and Fe can be assumed zero before the end-effector contacts the objective. Therefore the linear and angular momenta of whole system are conservative when Fh= 0. The motion of system isgoverned by only inertial force/torque on the manipulator joint . Thus, we can obtain the following momenta equation from equation (3)At the beginning, assume0 for simplification, thus,from equation (20), we obtain, the matrix Jg is calledGeneralized Jacobian Matrix (GJM) or Space JacobianMatrix (SJG). GJM is used to calculate the joint angularvelocity and end-effector velocity. Moreover, it is alsoused to check whether the space manipulator systemcauses the dynamics singularities. When the determinantof GJM is equal to zero or the GJM loses full rank, themanipulator appears the dynamics singularities. Inaddition, the GJM can be used to design controller usually.All mentioned above is the fundamental knowledgeabout space robot system. The following trackingtrajectory planning and control is base on this dynamicMotion Estimation of USSIn this section, we describe to estimate the motion state and equation of USS. The USS to be rescued has unique characteristics as follows: the orbital information such as altitude and inclination of the USS will be known by the ground control station. The size, shape and mass property of the USS are also well known in advance from design phase information. The handle location will be identified by human decision. Therefore we also assume that the USS is equipped with visual marker, signal reflectors, GPS, and so on for simplification.Here, we assume that the USS is nearly axis-symmetric shape with