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Mobile manipulators collision-free trajectory planning with regard to end-effector vibrations elimination
Get PDFA sub-optimal point-to-point trajectory planning method for mobile manipulators operating in the workspace including obstacles taking into account the damping of the end-effector vibrations is presented. The proposed solution is based on extended Jacobian approach and redundancy resolution at the acceleration level. Fulfilment of the condition stopping the mobile manipulator at the destination point is guaranteed, which leads to elimination of the end-effector vibrations and significantly increases positioning accuracy. The effectiveness of the presented method is shown and compared to the classical Jacobian pseudo inverse approach. A computer example involving a mobile manipulator consisting of a nonholonomic platform (2, 0) class and SCARA-type holonomic manipulator operating in two-dimensional task space including obstacle is also presented
Nonlinear modelling and transient dynamics analysis of a hoist equipped with a two-stage planetary gear transmission system
Get PDFA system-level nonlinear dynamic model for a two-stage planetary gear transmission system of a hoist is established with the consideration of time-varying meshing stiffness, backlash, damping, and bearing stiffness. Vibrational test results are also presented in accordance with simulation results computed from the dynamic model, and engagement-impacting dynamic simulations are achieved by adapting a dynamic explicit algorithm based on this model. Accordingly, variation in the contact state in relation to the engaging position is obtained together with vibration characteristics of the transmission system. This study provides a theoretical basis for the reduction of vibration and noise for the transmission system
Simulation of dynamic vehicle load on road pavement
Get PDFNumerical simulation approach has recently grown in popularity due to its wide range of applications in the solving of random vehicle-pavement interaction (VPI). This study proposes a framework to simulate the dynamic vehicle load process due to a quarter-truck vehicle model moving along a rough road surface. A procedure used to generate artificial time histories of dynamic vehicle load on road pavement was developed. Example application of the proposed framework is presented and a comparison of calculated and experimental values demonstrates the effectiveness of the framework. To elucidate the relationship between dynamic vehicle load and road roughness, this study normalized the average maximum dynamic vehicle loads on road surfaces of different grades using standard deviation of dynamic vehicle load. Numerical results indicate that the normalized average maximum dynamic vehicle load is not associated with road roughness
Convenient displacement monitoring technique using smartphone
Get PDFIn this paper, a displacement monitoring APP called D-Viewer is proposed and developed. By means of common laser device and projection plate, structural displacement can be monitored dynamically, using the APP. Firstly, the laser spot centroid recognition method was studied. Second, the displacement monitoring APP was developed. Finally, in order to verify the feasibility of the method, a series of static and dynamic experiments using smartphone were conducted. Results show that this method can be used as a convenient, fast, low-cost structural displacement monitoring method
Research on liquid sloshing model of partially-filled tank by nonlinear external excitation
Get PDFThe parameters of elliptical tank can greatly affect the roll stability of the elliptical tank with different filled levels, the exact equations for the mass centre of the tank were developed. The solutions of the transient mass centre of sloshing liquid in a tank with modified elliptical cross sections were obtained by a new vehicle rollover model. To achieve Euler transform 6-degree of freedom (DOF) motion equation of tank, Liquid Sloshing model of partially-filled tank was built by Nonlinear External Excitation. In addition, MATLAB ODE was used to investigate the numerical simulation. According to the different filled level of the tank by simulating, force and moment about X, Y and Z-axis of the coordinates of the mass centre were obtained. It is shown that the nonlinear mathematical models of liquid sloshing and vehicle motion equation can accurately describe the tank truck dynamic response in turing. The finding of this study may provide a theoretical basis to improve the roll stability of the tank
The sensitivity analysis of the translation and the rotation angle of the first-order mode shape of the joints in frame structures
Get PDFWhen damage occurs, there are changes in the structural stiffness. This causes changes in the vibrational information, such as translation and rotation angle of the joints in the structure. This paper presents a sensitivity study of translation and slope of the first-order mode shape of the joints in the frame structure, and which will contribute to structural damage identification further. Starting from the equation of natural vibration of frame structure, and according to the characteristics of the stiffness matrix, derive sensitivity coefficient expression of translation and slope of first-order mode shape of the joints in the structure, and obtain the first-order relative sensitivity coefficient of the first story is always smaller than zero when single column of the first story damage occurs. The numerical analysis of the four stories three spans frame shows consistent results with the formula derivation
PD control for global stabilization of an n-TORA system
Get PDFThis paper concerns a global stabilization problem for an n-TORA (Translational Oscillator with a Rotational Actuator) system which consists of n carts connected to the fixed walls and each other by n+1 linear springs with each cart having an eccentric rotational proof-mass actuator moving in the horizontal plane. First, this paper derives the motion equation of the n-TORA system. Then, by using Lyapunov stability theory and physical properties of mechanical parameters of the n-TORA system, this paper proves that the global stabilization of the n-TORA system can be achieved by the PD control of the angle of the rotational proof-mass of each TORA. This paper presents numerical simulation results for 2- and 3-TORA systems to validate the result of the global stabilization
Multi-objective topology optimization for the measuring rod of gun barrel bore detecting system
Get PDFIn this paper, we focus on the measuring rod of the gun barrel bore detecting system. The topology optimization model of the measuring rod is set up based on the variable density continuum structural topology optimization method. In order to minimize the static flexibility and to maximize the low vibration frequency simultaneously, the compromise programming approach is employed to optimize multi-objective topology. Optimization results show that an ideal distribution of material is acquired, which enhances the natural frequency of structure and reduces the structure quality, thus a synchronized multi-objective optimization is achieved. We validate the ultimate optimized topology with statics and dynamics analysis. The results show that both global stiffness and low frequency of the optimized measuring rod have been improved significantly which verify the rationality of the design
Dynamic analysis of a train-bridge system to vessel collision and running safety of high-speed trains
Get PDFA dynamic analysis model is established for a train-bridge system subjected to a vessel collision-load. A (32+48+32) m continuous bridge with PC box girders and a CRH2 high-speed train are considered as a case study. The whole histories of the train running on the bridge are simulated while the vessel collision load acting on the pier, based on which the dynamic responses of the bridge and the running safety indices of the train on the bridge are evaluated. The results show that the dynamic responses of the bridge are greatly increased by the vessel collision load, resulting in a big influence on the running safety of high-speed train
Smartphone based public participant emergency rescue information platform for earthquake zone – “E-Explorer”
Get PDFDevastating earthquake can often cause the disaster area communication interrupt, traffic paralysis, etc. It is difficult for the emergency rescue force to get the disaster area in time. Therefore, active local participation in the quake-hit areas to aid each other appeals extremely important. The paper is based on a self-developed smartphone software called “E-Explorer”, study its significance and its working methods to help the public participate in the earthquake rescue actively when external network are cut off. “E-Explorer” can help deliver important information for personal survival, let rescue workers locate the positions of survivors trapped, creating an efficient self-help and mutual rescue platform for the earthquake-stricken people