A method for selecting driving system parameters of a new electric shovel's excavating mechanism with three-DOF

2011 ◽  
Vol 225 (11) ◽  
pp. 2661-2672 ◽  
Author(s):  
B Wei ◽  
F Gao ◽  
J Chen ◽  
J He ◽  
X Zhao
Keyword(s):  
Dynamic Model ◽  
Degrees Of Freedom ◽  
Virtual Work ◽  
Transmission Ratio ◽  
Principle Of Virtual Work ◽  
Driving System ◽  
Generalized Coordinates ◽  
System Parameters ◽  
Three Degrees Of Freedom ◽  
Selection Of

Driving system parameters include motor parameters and transmission ratio of the reducer. In this study, a new three-degrees-of-freedom parallel excavating mechanism of electric shovel is analysed for the selection of its driving system which consists of three sub-driving parts. Based on the principle of virtual work in the form of generalized coordinates, the dynamic model of the excavating mechanism is established to calculate the external inertia loads and force (or torque) loads. For this parallel excavating mechanism which has three sub-drives, the external inertia loads cannot be fully divided into three independent parts with respect to these three sub-driving systems. Hence, the dynamic model of the system is employed to get loads characteristic of three sub-driving systems in the excavating process. Thus, the parameters' range of the motors can be obtained and then the best transmission ratio of every reducer can be obtained.

A Measure for Evaluation of Maximum Acceleration of Redundant and Nonredundant Parallel Manipulators

2015 ◽  
Vol 8 (2) ◽  
Author(s):  
Jun Wu ◽  
Binbin Zhang ◽  
Liping Wang
Keyword(s):  
Dynamic Model ◽  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Virtual Work ◽  
Parallel Manipulators ◽  
Maximum Acceleration ◽  
Virtual Work Principle ◽  
Joint Force ◽  
Joint Forces ◽  
Three Degrees Of Freedom

The paper deals with the evaluation of acceleration of redundant and nonredundant parallel manipulators. The dynamic model of three degrees-of-freedom (3DOF) parallel manipulator is derived by using the virtual work principle. Based on the dynamic model, a measure is proposed for the acceleration evaluation of the redundant parallel manipulator and its nonredundant counterpart. The measure is designed on the basis of the maximum acceleration of the mobile platform when one actuated joint force is unit and other actuated joint forces are less than or equal to a unit force. The measure for evaluation of acceleration can be used to evaluate the acceleration of both redundant parallel manipulators and nonredundant parallel manipulators. Furthermore, the acceleration of the 4-PSS-PU parallel manipulator and its nonredundant counterpart are compared.

Partially conforming plate bending elements for static and dynamic analyses

1973 ◽  
Vol 8 (4) ◽  
pp. 260-263 ◽  
Author(s):  
C T F Ross
Keyword(s):  
Degrees Of Freedom ◽  
Natural Frequencies ◽  
Virtual Work ◽  
Plate Bending ◽  
Principle Of Virtual Work ◽  
Displacement Method ◽  
Dynamic Analyses ◽  
The Matrix ◽  
Three Degrees Of Freedom ◽  
General Convergence

Two partially conforming flat-plate bending elements have been developed for static and dynamic analyses through the principle of virtual work. One of these elements is triangular and the other quadrilateral and both have corner nodes only, with three degrees of freedom per node. By use of these elements in the matrix displacement method, the natural frequencies of vibration of a square cantilevered plate have been calculated; these calculated results have been compared with experimental results. Agreement has been found to be good, and in general, convergence appears to take place.

Torsional Vibrations and Dynamic Loads in a Basic Planetary Gear System

1986 ◽  
Vol 108 (3) ◽  
pp. 348-353 ◽  
Author(s):  
R. August ◽  
R. Kasuba
Keyword(s):  
Dynamic Model ◽  
Degrees Of Freedom ◽  
Planetary Gear ◽  
Gear System ◽  
Dynamic Loads ◽  
Ring Gear ◽  
Gear Mesh ◽  
Input And Output ◽  
Planetary Gear System ◽  
Three Degrees Of Freedom

An interative method has been developed for analyzing dynamic loads in a light weight basic planetary gear system. The effects of fixed, semi-floating, and fully-floating sun gear conditions have been emphasized. The load dependent variable gear mesh stiffnesses were incorporated into a practical torsional dynamic model of a planetary gear system. The dynamic model consists of input and output units, shafts, and a planetary train. In this model, the sun gear has three degrees of freedom; two transverse and one rotational. The planets, ring gear, and the input and output units have one degree of freedom, (rotation) thus giving a total of nine degrees of freedoms for the basic system. The ring gear has a continuous radial support. The results indicate that the fixed sun gear arrangement with accurate or errorless gearing offers in general better performance than the floating sun gear system.

A Novel Parameter Optimization Method for the Driving System of High-Speed Parallel Robots

2018 ◽  
Vol 10 (4) ◽  
Author(s):  
Xin-Jun Liu ◽  
Gang Han ◽  
Fugui Xie ◽  
Qizhi Meng ◽  
Sai Zhang
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Dynamic Performance ◽  
Optimization Method ◽  
Parallel Robots ◽  
Parameters Optimization ◽  
Driving System ◽  
System Parameters ◽  
Driving Torque ◽  
Instantaneous Acceleration

Driving system parameters optimization, especially the optimal selection of specifications of motor and gearbox, is very important for improving high-speed parallel robots' performance. A very challenging issue is parallel robots' performance evaluation that should be able to illustrate robots' performance accurately and guide driving system parameters optimization effectively. However, this issue is complicated by parallel robots' anisotropic translational and rotational dynamic performance, and the multiparameters of motors and gearboxes. In this paper, by separating the influence of translational and rotational degrees-of-freedom (DOFs) on robots' performance, a new dynamic performance index is proposed to reflect the driving torque in instantaneous acceleration. Then, the influence of driving system's multiparameters on robots' driving torque in instantaneous acceleration and cycle time in continuous motion is investigated. Based on the investigation, an inertia matching index is further derived which is more suitable for minimizing the driving torque of parallel robots with translational and rotational DOFs. A comprehensive parameterized performance atlas is finally established. Based on this atlas, the performance of a high-speed parallel robot developed in this paper can be clearly evaluated, and the optimal combination of motors and gearboxes can be quickly selected to ensure low driving torque and high pick-and-place frequency.

A Study on Vibrations of Hexarot-Based High-G Centrifugal Simulators

Robotica ◽  
2019 ◽  
Vol 38 (2) ◽  
pp. 299-316 ◽  
Author(s):  
Siamak Pedrammehr ◽  
Houshyar Asadi ◽  
Saeid Nahavandi
Keyword(s):  
Dynamic Model ◽  
Virtual Work ◽  
Viscous Friction ◽  
Stability Index ◽  
Flexible Manipulator ◽  
Kinematics And Dynamics ◽  
Principle Of Virtual Work ◽  
End Effector ◽  
Dynamic Formulation ◽  
Different Parts

SummaryThis paper investigates the vibrations of hexarot simulators. The generalized modeling of kinematics and dynamics formulation of a hexarot mechanism is addressed. This model considers the flexible manipulator with the base motion. The dynamic formulation has been developed based on the principle of virtual work. The dynamic model consists of the stiffness of the different parts of the mechanism, the effects of gravity and inertia, torque and force related to the joints viscous friction. Finally, the response of the end effector at various frequencies has been presented, and the vibrations of the mechanism and the dynamic stability index have been investigated.

Dynamic performances analysis of hybrid press based on dependent generalized coordinates

2014 ◽  
Vol 229 (12) ◽  
pp. 2187-2194
Author(s):  
Jinliang Gong ◽  
Xiaoming Wang ◽  
Fengan Huang ◽  
Yanfei Zhang
Keyword(s):  
Dynamic Model ◽  
Virtual Work ◽  
Single Degree Of Freedom ◽  
Virtual Work Principle ◽  
Generalized Coordinates ◽  
Hybrid Mechanism ◽  
Adams Simulation ◽  
Angular Velocities ◽  
Dynamic Performances ◽  
Angular Displacements

A kind of multi-link hybrid press mechanism is brought forth. It adopts three motors as actuations to fulfill the single degree of freedom output of end effector. For hybrid press mechanism, the forward kinematics is usually complicated and its numerical solution is computation-intensive and time-consuming. Therefore, the dynamic model is difficult to build up when it needs to analyze the input function’s effect on system dynamic performances. Concept of dependent generalized coordinates is adpoted here and a kind of dynamic modeling method of multi-link hybrid mechanism is presented based on the virtual work principle. The linear and angular displacements of every component can be expressed concisely in the form of dependent generalized coordinates. They are much simpler than that of independent generalized coordinates. Accordingly, linear and angular velocities will be derived by differentiating with respect to displacements. Velocity Jacobian matrix will be simplified under dependent generalized coordinates system and the virtual work principle-based dynamic model will also be simplified accordingly. Then it needs to introduce constraint conditions and multiplier in order to acquire actuation forces. Introduction of the constraints guarantees the real kinetic characteristics of mechanism. In the end, the curves of actuation forces and spherical joints’ inner forces variations are presented using Matlab. By comparing with Adams simulation results, validity of the method has been proved.

Effect of Prestress on Bridge–Vehicle Interactions

2015 ◽  
Author(s):  
Hai Zhong ◽  
Mijia Yang
Keyword(s):  
Degrees Of Freedom ◽  
Virtual Work ◽  
Interaction Model ◽  
Dynamic Interaction ◽  
Vertical Acceleration ◽  
Vehicle Speed ◽  
Principle Of Virtual Work ◽  
Vehicle Model ◽  
Multiple Vehicles ◽  
4 Degrees Of Freedom

Prestress applied on bridges affects the dynamic interaction between bridges and vehicles traveling over them. In this paper, the prestressed bridge is modeled as a beam subjected to eccentric prestress force at the two ends, and a half-vehicle model with 4 degrees of freedom is used to represent the vehicle passing the bridge. A new bridge–vehicle interaction model considering the effect of prestress with eccentricity is developed through the principle of virtual work. The correctness and accuracy of the model are validated with literature results. Based on the developed model, numerical simulations have been conducted using the Newmark’s β method to study the effects of vehicle speed, eccentricity and amplitude of the prestress, and presence of multiple vehicles. It is shown that prestress has an important effect on the maximum vertical acceleration of vehicles, which may provide a good index for detecting the change of prestress. It is also interesting to find that the later-entering vehicle on the prestressed bridge will largely reduce the maximum vertical acceleration of the vehicle ahead of it.

scholarly journals Generalized Lagrange-D’Alembert principle

2012 ◽  
Vol 91 (105) ◽  
pp. 49-58
Author(s):  
Djordje Djukic
Keyword(s):  
Dynamic Equilibrium ◽  
Virtual Work ◽  
Analytical Mechanics ◽  
Principle Of Virtual Work ◽  
Constraint Forces ◽  
Lagrange Equations ◽  
Virtual Displacement ◽  
Generalized Coordinates ◽  
D’Alembert Principle ◽  
Applied Forces

The major issues in the analysis of the motion of a constrained dynamic system are to determine this motion and calculate constraint forces. In the analytical mechanics, only the first of the two problems is analyzed. Here, the problem is solved simultaneously using: 1) Principle of liberation of constraints; 2) Principle of generalized virtual displacement; 3) Idea of ideal constraints; 4) Concept of generalized and ?supplementary" generalized coordinates. The Lagrange-D?Alembert principle of virtual work is generalized introducing virtual displacement as vectorial sum of the classical virtual displacement and virtual displacement in the ?supplementary" directions. From such principle of virtual work we derived Lagrange equations of the second kind and equations of dynamical equilibrium in the ?supplementary" directions. Constrained forces are calculated from the equations of dynamic equilibrium. At the same time, this principle can be used for consideration of equilibrium of system of material particles. This principle simultaneously gives the connection between applied forces at equilibrium state and the constrained forces. Finally, the principle is applied to a few particular problems.

Dynamical Characteristics of a Hydraulic Soft Actuator With Three Degrees of Freedom

2021 ◽  
Author(s):  
Qing Xie ◽  
Tao Wang ◽  
Shiqiang Zhu
Keyword(s):  
Dynamic Model ◽  
Degrees Of Freedom ◽  
Soft Actuator ◽  
Dynamical Characteristics ◽  
Geometrical Features ◽  
Highly Nonlinear ◽  
Series Of Experiments ◽  
Soft Actuators ◽  
Modeling Of Dynamics ◽  
Three Degrees Of Freedom

Abstract In recent years, increasing attention and expanding research have been devoted to the study and application of soft actuators. Inherent compliance equips soft actuators with such advantages as incomparable flexibility, good environmental adaptability, safe interaction with the environment, etc. However, the highly nonlinear also bring challenges to modeling of dynamics. This study aims to explore the dynamical characteristics of an underwater hydraulic soft actuator. The actuator has three fiber-reinforced elastomer chambers distributed symmetrically inside. By controlling the pressure in the chambers through a hydraulic power system, the actuator can achieve spatial motion with three degrees of freedom. To describe the relationship between the input pressure combination and the actuator movement, a dynamic model considering the nonlinearity of viscoelastic material is developed based on Lagrangian method and constant curvature hypothesis. A series of experiments are carried out, including single-chamber actuation and multi-chamber actuation. The test results verify the effectiveness and precision of the model. Finally, the effects of the geometrical features on dynamic response are investigated through model-based simulation, which can provide guidance to parameter optimization. The proposed dynamic model can also contribute to behavior analysis, performance prediction, and motion control of the hydraulic soft actuator.

Sign in / Sign up

Export Citation Format

Share Document