Abstract: The dynamic behavior of a reciprocating compressor transmission mechanism with joint clearance is studied in this paper. A transmission mechanism virtual prototype model is built under software ADAMS. Revolute joint between connecting rod and crosshead pin is modeled with clearance by contact model based on the so called Impact-function, and four processes of cylinder pressure load is simulated by the IF function. Cylinder pressure load, amplitude of joint clearance, crank speed and flexibility of connecting rod is taken as influence factors. Four different cases were simulated. Joint contact forces, accelerations of compressor block and journal centre path are used to analyze the dynamic behavior. The presented results show that these factors play a significant role of dynamic behavior of mechanisms.
Abstract: This paper presents a simplified method for the identification of quadratic Volterra systems. Since the higher order kernels often play a secondary role compared to the linear component of the system, it is worth establishing a balance between the calculation consumption of the higher order kernels and their effect on the model accuracy. The equivalent kernels are used to substitute original quadratic kernels, and therefore both the model complexity and identification computational requirement are significantly reduced. Then the identification algorithm based on least square minimization of model output error and random multi-tone excitation is designed. Simulations show this simplified method is of excellent generalization ability and has robustness against noise in output signals.
Abstract: In this paper the rotor dynamic characters of the bearing system in turbocharger are researched. The computing method of rotor dynamic is also analyzed. Through modeling the components and parts of bearing system and rotor dynamic model, the three critical speeds are computed and analyzed. By comparing the working speed and critical speed, we can judge that whether the turbocharger works nearby the critical speed or not. If it does, then how to make the turbocharger work stably is also researched. At the same time, how the key design parameters, such as the shaft length and diameter, impact on rotor dynamic character is discussed in detail. In the end, an optimization strategy of the rotor structure is proposed to make the working speed be away from the critical speed.
Abstract: Chart datum is a vertical reference of ocean depth, which can give the ocean vertical spatial information for Marine Geodesy. Due to time and resource constraints, it is a practical problem of how to determine the chart datum with high accuracy at the short-term tidal stations. In this paper, based on the least-square fitting model, the transfer algorithm for the chart datum at the short-term tidal stations is further developed. Both the accuracy of chart datum computed by this algorithm and the effect on those are presented. The findings of this paper are summarized as follows: The accuracy computed by the least-square fitting model can achieve the centimeter level. The accuracy values determined by the least-square fitting model can further be improved by using the instantaneous ratio of tidal range and selecting the short-distance permanent tidal station.
Abstract: The geometric models of the hydraulic turnover device are constructed by using three -dimensional modeling software UG, and then they are induced into simulation software ADAMS by a sharing data format. By using ADAMS, models are further simplified and the virtual prototype is established. By using the associated model, the simulation of the hydraulic turnover device is analyzed in ADAMS. Compared with the traditional methods of using physical prototypes, the movement processes and relevant parameters of the hydraulic turnover device can be effectively obtained by means of this method. Furthermore, the quality of the constraint relations between the parts is very important in terms of the accuracy of the model simulation analysis. This simulation results accord with the practical situation, which indicates that the operation is stable and the efficiency is high. It provides a theoretical basis for the practical design of the hydraulic turnover device, which shows that the combination of ADAMS and UG works well.
Abstract: Dynamic behaviors of a rotor with a transverse fatigue surface crack have been studied a lot in the past. In the present study the rotor containing a transverse crack with semi-elliptical fronted edge is considered since the crack grows in an elliptical path when the rotor is subjected to long time cyclic loads through fatigue experiments and realistic cases. Using the finite element method, the stiffness of the shaft with the semi-elliptical fronted transverse crack is calculated. Then, the vibration responses and the coupling mechanism of bending and torsional vibrations of the rotor with and without torsional excitation are analyzed. The result shows that there are slight differences between the dynamic responses of the straight fronted cracked rotor and the semi-elliptical fronted rotor in common frequency fields and high frequency fields. The similar contrast is obtained when the rotor system is applied by torsional excitation.
Abstract: In this paper, we take the vertical tool changer device as an example to study the reliability of the manipulator in the heavy tool case. Firstly, introduce the structure of the vertical tool changer device, and do a simple instruction for the functions of the main components; Secondly, analyze the mechanical properties of the manipulator theoretically, find out the maximum force in the tool changer processing and build a virtual platform of the automatic tool changer to simulate the processing and test the performance of the tool changer; Finally, analyze the performance of the manipulator by finite element method in the heavy tool case. The analysis result shows that the maximum stress is less than the allowable stress: when the manipulator grasps heavy tool, so it is safe in the tool changer processing.
Abstract: A jaw mechanism based on the biomechanical findings of human mastication system is being developed to simulate jaw motion and investigate its effect on jaw function to provide the basis for jaw model. Following an investigation into the biological process of mastication, a linear cylindrical actuator is used to replace a group of muscles, and it can act bio-directionally with both origin and insertion attached to the skull and the mandible via spherical joints. The trajectory of the incisal point can be reproduced through programming the six actuations. So it builds the functional `relation between incisal point and six actuators. Co-simulations for motion and control have been conducted using the ADMAS and SIMULINK and the results have indicated that the jaw mechanism enables the jaw behaviors to be reproduced perfectly.
Abstract: A passively suspended road vehicle rolls outwards under the influence of lateral acceleration when cornering, which is very dangerous under large lateral acceleration. In this paper, time lag between steering input and vehicle lateral acceleration response is systematically studied to implement the active roll control algorithm from the viewpoint of vehicle system dynamics. A 3 DOF yaw-roll vehicle model is established based on vehicle lateral, roll and yaw dynamics. Vehicle parameters of a 1997 Jeep Cherokee is used for parametric study, where the influences of vehicle velocity, steering frequency, mass, length, roll, yaw moment of inertia, position of vehicle centre of gravity, and tyre cornering stiffness are studied via numerical simulation. The analysis results will help improve the real time rollover warning/control algorithm design for vehicle safety.
Abstract: The dynamic analysis of a flexible-link-joint robot colliding with its environments is presented in this paper. Kinematics of both rotary-joint motion and link deformation is described by 4×4 homogenous transformation matrices. Both the stretching deformation, bending deformation and the torsional deformation of the flexible links are considered. Furthermore, the flexibility and the mass of the joint are considered too. The concept of impact force potential energy is introduced, so that the generalized forces due to the impact force can be computed easily. The Lagrange dynamic equations are used to establish the complete mathematic model of the system with impact. Dynamics simulation of a spatial flexible-link-joint manipulator arm is given as an example to validate the algorithm presented in this paper. And the numerical results indicate that the flexibility of the link and joint have distinguished influence on the impact dynamics of the flexible robots.