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dynamic modeling of a Non-Uniform Flexible Tail for a Robotic Fish

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Journal of Bionic Engineering 2013年第2期10卷 201-209页

作者： Phi Luan Nguyen Van Phu Do Byung Ryong Lee Intelligent Control and Mechatronics Lab School of Mechanical Engineering University of Ulsan Ulsan 680-749 Korea School of Mechanical Engineering University of Ulsan Ulsan 680-749 Korea

In this paper, a non-uniform flexible tail of a fish robot was presented and the dynamic model was developed. In this model, the non-uniform flexible tail was modeled by a rotary slender beam. The hydrodynamics forces, including the reactive force and resistive force, were analyzed in order to derive the governing equation. This equation is a fourth-order in space and second-order in time Partial Differential Equation （PDE） of the lateral movement function. The coefficients of this PDE were not constants because of the non-uniform beams, so they were approximated by exponential functions in order to obtain an analytical solution. This solution describes the lateral movement of the flexible tail as a function of material, geometrical and actuator properties. Experiments were then carried out and compared to simulations. It was proved that the proposed model is suitable for predicting the real behavior of fish robots.

关键词： fish robot flexible tail dynamic modeling kinematic lateral movement

dynamic modeling and Eigenvalue Evaluation of a 3-DOF PKM Module

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Chinese Journal of Mechanical Engineering 2010年第2期23卷 166-173页

作者： ZHANG Jun LI Yonggang HUANG Tian School of Mechanical Engineering Tianjin University Tianjin 300072 China Tianjin University of Technology and Education Tianjin 300222 China

Due to the structural complexity, the dynamic modeling and quick performance evaluation for the parallel kinematic machines （PKMs） are still to be remained as two challenges in the stage of conceptual design. By using the finite element method and substructure synthesis, this paper mainly deals with the dynamic modeling and eigenvalue evaluation of a novel 3-DOF spindle head named the A3 head. The topological architecture behind the proposed A3 head is a 3-RPS parallel mechanism, which possesses one translational and two rotational capabilities. The mechanical features of the A3 head are briefly addressed in the first place followed by inverse position analysis. In the dynamic modeling, the platform is treated as a rigid body, the RPS limbs as the continuous uniform beams and the joints as lumped virtual springs. With the combination of substructure synthesis and finite element method, an analytical approach is then proposed to formulate the governing equations of motion of system using the compatibility conditions at interface between the limbs and the platform. Consequently, by solving the eigenvalue problem of the governing equations of motion, the distribution of lower natural frequencies of the A3 head throughout the entire workspace can be predicted in a quick manner. Modal analysis for the A3 head reveals that the distributions of lower natural frequencies are strongly related to the mechanism configuration and are axially symmetric due to system kinematic and structural features. The sensitivity analysis of the system indicates that the dimensional parameters of the 3-RPS mechanism have a slight effect on system lower natural frequencies while the joint compliances affect the distributions of lower natural frequencies significantly. The proposed dynamic modeling method can also be applied to other PKMs and can effectively evaluate the PKM＇s dynamic performance throughout the entire workspace.

关键词： dynamic modeling parallel kinematic machine natural frequency

dynamic modeling and Experiment of a New Type of Parallel Servo Press Considering Gravity Counterbalance

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Chinese Journal of Mechanical Engineering 2013年第6期26卷 1222-1233页

作者： HE Jun GAO Feng BAI Yongjun WU Shengfu State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong University China First Heavy Industries

The large capacity servo press is traditionally realized by means of redundant actuation, however there exist the over-constraint problem and interference among actuators, which increases the control difficulty and the product cost. A new type of press mechanism with parallel topology is presented to develop the mechanical servo press with high stamping capacity. The dynamic model considering gravity counterbalance is proposed based on the virtual work principle, and then the effect of counterbalance cylinder on the dynamic performance of the servo press is studied. It is found that the motor torque required to operate the press is a lot less than the others when the ratio of the counterbalance force to the gravity of ram is in the vicinity of 1.0. The stamping force of the real press prototype can reach up to 25 MN on the position of 13 mm away from the bottom dead center. The typical deep-drawing process with 1 200 mm stroke at 8 strokes per minute is proposed by means of five order polynomial. On this process condition, the driving torques are calculated based on the above dynamic model and the torque measuring test is also carried out on the prototype. It is shown that the curve trend of calculation torque is consistent to the measured result and that the average error is less than 15%. The parallel mechanism is introduced into the development of large capacity servo press to avoid the over-constraint and interference of traditional redundant actuation, and its dynamic characteristics with gravity counterbalance are presented.

关键词： mechanical press parallel mechanism dynamic modeling virtual work principle

dynamic modeling and Experiment of a Fish Robot with a Flexible Tail Fin

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Journal of Bionic Engineering 2013年第1期10卷 39-45页

作者： Phi Luan Nguyen Van Phu Do Byung Ryong Lee ~ Intelligent Control and Mechatronics Lab School of Mechanical Engineering University of Ulsan Daehak-ro 93 Nam-gu Ulsan 680-749 South Korea School of Mechanical Engineering University of Ulsan Daehak-ro 93 Nam-gu Ulsan 680-749 South Korea

This paper presents the dynamic modeling of a flexible tail for a robotic fish. For this purpose firstly, the flexible tail was simplified as a slewing beam actuated by a driving moment. The governing equation of the flexible tail was derived by using the Euler-Bernoulli theory. In this equation, the resistive forces were estimated as a term analogous to viscous damping. Then, the modal analysis method was applied in order to derive an analytical solution of the governing equation, by which the relationship between the driving moment and the lateral movement of the flexible tail was described. Finally, simulations and experiments were carried out and the results were compared to verify the accuracy of the dynamic model. It was proved that the dynamic model of a fish robot with a flexible tail fin well explains the real behavior of robotic fish in underwater environment.

关键词： robotic fish flexible tail dynamic modeling lateral movement

dynamic modeling and Analysis of 9-DOF Omnidirectional Legged Vehicle

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Chinese Journal of Mechanical Engineering 2011年第4期24卷 515-521页

作者： GAO Feng WANG Guofu CUI Ying YANG Xinhong School of Transportation Science ＆ Engineering Beihang University Beijing 100191 China

The omnidirectional legged vehicle with steering-rails has a specific mechanism feature, and it can be controlled flexibly and accurately in omnidirectional motion. Currently there lacks further research in this area. In this paper, the mechanical characteristics of independent walking control and steering control and its kinematics principle are introduced, and a vehicle has a composite motion mode of parallel link mechanism and steering mechanism is presented. The motion direction control of the proposed vehicle is only dependant on its steering rails, so its motion is simple and effective to control. When the relative motion between the walking and steering is controlled cooperatively, the vehicle can walk perfectly. By controlling the steering rails, the vehicle can walk along arbitrary trajectory on the ground. To achieve a good result of motion control, an equivalent manipulator model needs to be built. In terms of the mechanism feature and the kinematic principle, the simplified manipulator model consists of a rail in stance phase, a rail in swing phase, and an equivalent leg. Considering the ground surface slope during walking, a parameter of inclination angle is added. Based on such a RPP manipulator model, the equations of motion are derived by means of Lagrangian dynamic approach. To verify the dynamic equations, the motion of the manipulator model is simulated based on linear and nonlinear motion planning. With the same model and motion parameters, the dynamic equations can be solved by Matlab and the calculation data can be gained. Compared with the simulation data, the result confirms the manipulator dynamic equations are correct. As a result of such special characteristics of the legged mechanism with steering rails, it has a potential broad application prospects. The derivation of dynamics equation could benefit the motion control of the mechanism.

关键词： legged vehicle omnidirectional motion steering rails dynamic modeling dynamic simulation

dynamic modeling of thermal conditions for hot-water district-heating networks

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Journal of Hydrodynamics 2014年第4期26卷 531-537页

作者：周守军田茂诚赵有恩郭敏 School of Thermal Energy Engineering Shandong Jianzhu University School of Energy and Power Engineering Shandong University Department of Computer Science and Technology Shandong University of Finance and Economics

To investigate the dynamic characteristics of the thermal conditions of hot-water district-heating networks, a dynamic modeling method is proposed with consideration of the heat dissipations in pipes and the characteristic line method is adopted to solve it. Besides, the influences of different errors, space steps and initial values on the convergence of the dynamic model results are analyzed for a model network. Finally, a part of a certain city district-heating system is simulated and the results are compared with the actual operation data in half an hour from 6 secondary heat stations. The results indicate that the relative errors for the supply pressure and temperature in 5 stations are all within 2%, except in one station, where the relative error approaches 4%. So the proposed model and algorithm are validated.

关键词： district-heating network thermal conditions dynamic modeling characteristic line method

dynamic modeling and Simulation of a Commercial Naphtha Catalytic Reforming Process

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Chinese Journal of Chemical Engineering 2005年第1期13卷 74-80页

作者：胡永有 iit.edu 徐巍华侯卫锋苏宏业褚健 His current address is Department of Chemical and Environmental Engineering Illinois Institute of Technology Chicago IL 60616 USA. E-mail: huyongy National Laboratory of Industrial Control Technology Institute of Advanced Process Control Zhejiang University Hangzhou 310027 China

A first principles-based dynamic model for a continuous catalyst regeneration (CCR) platforming process, the UOP commercial naphtha catalytic reforming process, is developed in this paper. The lumping details of the naphtha feed and reaction scheme of the reaction model are given. The process model is composed of the reforming reaction model with catalyst deactivation, the furnace model and the separator model, which is capable of capturing the major dynamics that occurs in this process system. dynamic simulations are performed based on Gear numerical algorithm and method of lines (MOL), a numerical technique dealing with partial differential equations (PDEs). The results of simulation are also presented. dynamic responses caused by disturbances in the process system can be correctly predicted through simulations.

关键词： catalytic reforming dynamic modeling simulation method of lines process control

dynamic modeling of a Roller Chain Drive System Considering the Flexibility of Input Shaft

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Chinese Journal of Mechanical Engineering 2010年第3期23卷 367-374页

作者： XU Lixin YANG Yuhu1 CHANG Zongyu LIU Jianping School of Mechanical Engineering Tianjin University 23anjin 300072 China College of Engineering Ocean University of China Qingdao 266100 China

Roller chain drives are widely used in various high-speed, high-load and power transmission applications, but their complex dynamic behavior is not well researched. Most studies were only focused on the analysis of the vibration of chain tight span, and in these models, many factors are neglected. In this paper, a mathematical model is developed to calculate the dynamic response of a roller chain drive working at constant or variable speed condition. In the model, the complete chain transmission with two sprockets and the necessary tight and slack spans is used. The effect of the flexibility of input shaft on dynamic response of the chain system is taken into account, as well as the elastic deformation in the chain, the inertial forces, the gravity and the torque on driven shaft. The nonlinear equations of movement are derived from using Lagrange equations and solved numerically. Given the center distance and the two initial position angles of teeth on driving and driven sprockets corresponding to the first seating roller on each side of the tight span, dynamics of any roller chain drive with two sprockets and two spans can be analyzed by the procedure. Finally, a numerical example is given and the validity of the procedure developed is demonstrated by analyzing the dynamic behavior of a typical roller chain drive. The model can well simulate the transverse and longitudinal vibration of the chain spans and the torsional vibration of the sprockets. This study can provide an effective method for the analysis of the dynamic characteristics of all the chain drive systems.

关键词： roller chain dynamic modeling Lagrange equations

dynamic modeling and analysis of the 3-PRS power head based on the screw theory and rigid multipoint constraints

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Science China(Technological Sciences) 2023年第7期66卷 1869-1882页

作者： MA YiWei TIAN YanLing LIU XianPing LU ChengHao School of Engineering The University of WarwickCoventryCV47ALUK School of Mechanical Engineering Tianjin UniversityTianjin300072China

This study presents a dynamic modeling and analysis methodology for the 3-PRS parallel ***,an improved reduced dynamic model of component substructures is proposed using the dynamic condensation technique and the rigid multipoint constraints at the joint/interface level,leading to a minimum set of generalized coordinates for external ***,the mapping between interface constraint stiffness and global stiffness is illustrated,resulting in an analytical stiffness model of joint ***,the derived component and joint substructures are synthesized into the entire mechanism based on the Lagrange ***,a case study illustrates that the lower-order dynamic performances predicted within the proposed approach have the same trend as those obtained from a complete-order finite element *** root mean square discrepancy of the lower-order natural frequencies between the two models is less than 5.92%,indicating the accuracy and effectiveness of the proposed *** developed approach can highly and efficiently predict the dynamic performance distributions across the entire workspace and guide the optimal functional design under the virtual machine framework.

关键词： dynamic modeling parallel kinematic machines screw theory substructure synthesis rigid multipoint constraints