基于Simulink的无人机六自由度仿真

加装滑翔增程组件的炸弹气动外形和无人机类似,研究无人机的运动特性将对研究滑翔增程组件起到重要作用。利用Simulink对无人机进行六自由度建模,分析无人机在滑翔过程当中的运动姿态特性,副翼对无人机运动的影响,无人机在风干扰的环境中的运动姿态特性,通过这些分析,可以对炸弹的滑翔增程组件的设计起到至关重要的作用,可为后续的控制、制导、导航研究打下基础。

Optimal measurement configurations for kinematic calibration of six-DOF serial robot

An optimal measurement pose number searching method was designed to improve the pose selection method.Several optimal robot measurement configurations were added to an initial pre-selected optimal configuration set to establish a new configuration set for robot calibration one by one.The root mean squares (RMS) of the errors of each end-effector poses after being calibrated by these configuration sets were calculated.The optimal number of the configuration set corresponding to the least RMS of pose error was then obtained.Calibration based on those poses selected by this algorithm can get higher end-effector accuracy,meanwhile consumes less time.An optimal pose set including optimal 25 measurement configurations is found during the simulation.Tracking errors after calibration by using these poses are 1.54,1.61 and 0.86 mm,and better than those before calibration which are 7.79,7.62 and 8.29 mm,even better than those calibrated by the random method which are 2.22,2.35 and 1.69 mm in directions X,Y and Z,respectively.

Synchronous tracking control of 6-DOF hydraulic parallel manipulator using cascade control method

The synchronous tracking control problem of a hydraulic parallel manipulator with six degrees of freedom (DOF) is complicated since the inclusion of hydraulic elements increases the order of the system.To solve this problem,cascade control method with an inner/outer-loop control structure is used,which masks the hydraulic dynamics with the inner-loop so that the designed controller takes into account of both the mechanical dynamics and the hydraulic dynamics of the manipulator.Furthermore,a cross-coupling control approach is introduced to the synchronous tracking control of the manipulator.The position synchronization error is developed by considering motion synchronization between each actuator joint and its adjacent ones based on the synchronous goal.Then,with the feedback of both position error and synchronization error,the tracking is proven to guarantee that both the position errors and synchronization errors asymptotically converge to zero.Moreover,the effectiveness of the proposed approach is verified by the experimental results performed with a 6-DOF hydraulic parallel manipulator.

Inverse kinematics of a heavy duty manipulator with 6-DOF based on dual quaternion

An iterative method is introduced successfully to solve the inverse kinematics of a 6-DOF manipulator of a tunnel drilling rig based on dual quaternion, which is difficult to get the solution by Denavit-Hartenberg(D-H) based methods. By the intuitive expression of dual quaternion to the orientation of rigid body, the coordinate frames assigned to each joint are established all in the same orientation, which does not need to use the D-H procedure. The compact and simple form of kinematic equations, consisting of position equations and orientation equations, is also the consequence of dual quaternion calculations. The iterative process is basically of two steps which are related to solving the position equations and orientation equations correspondingly. First, assume an initial value of the iterative variable; then, the position equations can be solved because of the reduced number of unknown variables in the position equations and the orientation equations can be solved by applying the solution from the position equations, which obtains an updated value for the iterative variable; finally, repeat the procedure by using the updated iterative variable to the position equations till the prescribed accuracy is obtained. The method proposed has a clear geometric meaning, and the algorithm is simple and direct. Simulation for 100 poses of the end frame shows that the average running time of inverse kinematics calculation for each demanded pose of end-effector is 7.2 ms on an ordinary laptop, which is good enough for practical use. The iteration counts 2-4 cycles generally, which is a quick convergence. The method proposed here has been successfully used in the project of automating a hydraulic rig.

Research on Optimizing Numerical Calculation of Posture Equations based on Six DOF Stewart Platform

The paper study position positive solution method based on 6-TPS parallel mechanism, and establish general kinematics model of 6-TPS parallel mechanism, gives the numerical method of positive solution based on a kind of position, deduced the forward position solution iteration format, and use MATLAB for the 6-TPS parallel mechanism kinematics to simulation, results show that solving program has stability, fast. effective.

Effect of Suppressed DOF on a Rigid RC Bridge Response under Strong Earthquake Motion

NLTHA （nonlinear time history analysis） is impractical for widespread used by the professional engineer because it requires long and inefficient computational time involving complexities when six DOF （degree of freedom） per node is applied. The NLTHA nowadays is predicted by MPA （modal pushover analysis）. In this method, effects of higher modes on the dynamic response are considered to estimate seismic demands for structures. In this study, the effect of the reduction of number of DOF is analyzed using 3D NLTHA together with MPA of a rigid connection RC bridge under large earthquake motion. The results are compared with the 6 DOF NLTHA in terms of response of the structure and CPU time to obtain the most efficient computational effort. Result of NLTHA showed that the computational time of the structure both for 4 DOF （without two lateral torsional effects） and 3 DOF （without two lateral torsional and vertical displacements） was reduced significantly compared to the structure using 6 DOF. The reduction of computational time was close to fifty percent both for 4 and 3 DOF＇s. When the maximum responses between NLTHA and MPA are compared, it is found that the differences are insignificant.

Implementing kinematics computation in FPGA co-processor for a 6-DOF space manipulator

Based on the coordinate rotation digital computer(CORDIC)algorithm,the high-speed kinematicscalculation for a six degree of freedom(DOF)space manipulator is implemented in a field programmablegate array(FPGA)co-processor.A pipeline architecture is adopted to reduce the complexity and time-consumption of the kinematics calculation .The CORDIC soft-core and the CORDIC-based pipelined kine-matics calculation co-processor are described with the very-high-speed integrated circuit hardware descrip-tion language(VHDL)language and realized in the FPGA .Finally,the feasibility of the design is vali-dated in the Spartan-3 FPGA of Xilinx Inc.,and the performance specifications of FPGA co-processor arediscussed.The results show that time-consumption of the kinematics calculation is greatly reduced.

Full scale measurement for FPSO on motions in six-degrees of freedom and environmental loads and deduction of mooring system loads

A joint industry project on a full scale measurement of Fenjin FPSO,headed by Shanghai Jiao Tong University and sponsored by CNOOC,was initiated in October 2007 and has been going on for more than 25 months.The purpose of the project is to measure and collect the motions in six-degrees of freedom of an FPSO,and to collect the environmental loads at the offshore oil-field.A motion data measuring system is designed and installed on the FPSO.Another environmental data measuring system is installed on a fixed jacket platform nearby.A large quantity of valuable first-hand data is obtained.With the data collected,motion characteristics of the FPSO in a long-term period are concluded.A short-term analysis for the FPSO in one of the typhoons is also completed.The mean periods of wave-frequency motions are calculated by the spectrum analysis.The tension loads of the mooring system,which is of great concern,are calculated by the decoupled technique.

Analysis of the Sloshing Flows of a LNG Cargo Tank

The sloshing flows in a LNG cargo tank model （1/50 scale） of a ship are measured by an embedded pano- ramicPIV system. The measurement system consists of a Nd-Yag laser（120mJ, 15Hz）, two cameras（lk x lk） and a host computer. Four experimental cases were tested for the tank model, in which swaying motions are made by a 6 DOF-motion platform. The amplitudes of swaying are 9.76mm and 29.29mm, and the swaying frequencies are 0.633Hz and 0.828Hz. The measurement regions are the vertical plane 50ram away from the front wall of the tank where a pump tower is installed. It was verified that the flow patterns of the sloshing are similar to each other when the swaying amplitudes are similar.

Unsteady analysis of six-DOF motion of a 6:1 prolate spheroid in viscous fluid

Free-moving simulations of airplanes, submarines and other automobiles under extreme and emergency conditions are becoming increasingly important from operational and tactical perspectives. Such simulations are fairly challenging due to the extreme unsteady motions and high Re(Reynolds) numbers. The aim of this study is to perform a six-DOF motion simulation of a 6:1prolate spheroid that is falling in a fluid field. Prior to conducting the six-DOF simulation, some verification simulations were performed. First, a laminar flow past an inclined prolate spheroid at a Re number of 1000 and incidence angle of 45. with a tetrahedral mesh was simulated to verify the relevant targeted discrete method for an unstructured mesh. Second, to verify the LES(large eddy simulation) models and dependent parameters for the DDES(delayed detached eddy simulation), a turbulent flow past a sphere was performed at a subcritical Re number of 10000. Third, a steady maneuvering problem about a prolate spheroid pitching up from 0. to 30. incidence at a uniform angular velocity was established based on a dynamic tetrahedral mesh with changing topology and the ALE(arbitrary Lagrangian-Eulerian) method of fluid-structure coupling at a Re number of 4.2 × 10~6.Finally, two six-DOF motions of an inclined 6:1 prolate spheroid at an initial incidence of 45. were simulated at different Re numbers of 10000 and 4.2 × 10~6.