Font Size: a A A

Dynamic Modeling And Performance Optimization Design Of The Forging Manipulator

Posted on:2015-12-06Degree:DoctorType:Dissertation
Country:ChinaCandidate:W J SunFull Text:PDF
GTID:1221330467487190Subject:Engineering Mechanics
Abstract/Summary:PDF Full Text Request
Large forgings are key parts of the heavy technical equipment, whose manufacturing level demonstrates the comprehensive national power. The production of the large forging depends on heavy-duty manufacturing equipment, which includes machining equipment such as forging press and operating equipment such as forging manipulator. The forging manipulator is the key basic equipment for forging mechanization and automation. Nowdays, ten thousand ton level forging hydraulic press can be designed and manufactured indenpendtly in our country, but the large forging manipulator, as the auxiliary tool for the forging press, depends on the foreign design technologies. The backward operating equipment seriously restricts the manufacturing capacity and production efficiency of the large forging in our country. Therefore, it is significant to carry out the research on the basic sciences and key technologies of the forging manipulator, in order to improve the domestic manufacturing level of heavy equipment.Taking the functional requirements and working safety of the forging manipulator into account, some key issues about its kinematics, statics and dynamics modelings are studied in the thesis, and the related performance optimization designs are also performed, which provides theoretical guidance and technical support for design of the manipulator. The main contributions of the thesis are listed as follows:(1) During the forging operation, huge and complex impact loads will be generated at the manipulator clamp. A modification to the dynamic model is presented for the case that the manipulator clamps a slender bar workpiece for metal forming, and the forging system is simplified as a single degree of freedom (SDOF) model with considering the plastic deformation of the workpiece. A comparison with the commercial software LS-DYNA simulations and some previous work is performed to validate the proposed model. It is shown that the contact condition has significant influence on the dynamic behavior of the forging system. A parametric study is conducted to examine the effects of the material property of workpiece on the maximum dynamic loads exerted to the clamp. In addition, the other dynamic model of the forging system, based on an elastic-plastic discrete spring model and the Timoshenko beam element model, is also developed to further improve the prediction accuracy of the maximum bending moment and dynamic force exerted to the clamp for the short workpiece. (2) To meet the performance requirements better in different cases, a multiobjective optimization method for comprehensive manipulation performance indexes of the manipulator is proposed on the basis of the previous work. Three main manipulation performances, including velocity, force capability and kinematic decoupling performance, are analyzed using the concept of the manipulability ellipsoid. Moreover, the velocity and force capability directional manipulability measures are defined in terms of the requirement of manipulation performances. Two global performance indices, which consider the mean value and standard deviation of manipulation performance, are used to measure the performance over the entire workspace of the manipulator. The performance indices-based multiobjective optimization is performed using NSGA Ⅱ algorithm. The goal of this paper is to present an effective way to improve the comprehensive performance of the manipulator by parameter optimization of the main-motion mechanism. Compared with the original design, it shows that the proposed performance evaluation and optimization method is feasible.(3) The forging manipulator is heavy-duty equipment and usually needs to clamp a heavy workpiece to cooperate with the forging press. In order to prevent local excessive forces from endangering the safety of the mechanical structure, the mechanical performance design for the forging manipulator is carried out based on the above manipulation performance optimization. According to the sensitivity analysis of the design parameters, the average forces acting on some key parts of the mechanism during the whole work space are chosen as optimization objectives, which are minimized simultaneously to properly distribute the forces of the mechanism. The results of the manipulation performance optimization are introduced into the proposed optimization model as constraint conditions. The optimization result shows that the mechanism has better mechanical behavior with the guaranteed manipulation performances.(4) In order to reduce the dynamic loads exerted to the clamp during the forging process, an optimization strategy is presented with considering dynamic performance of the forging manipulator. Firstly, the equivalent SDOF model of the main-motion mechanism is established so as to improve the computational efficiency in solving the dynamic equation of the mechanism. Then the thesis investigates the effects of the geometry change and motion components of the mechanism on its equivalent mass and stiffness briefly. Combined with the above research results, a multiobjective optimization design is proposed to satisfy not only the requirements of the manipulation performance and mechanical performance but also the passive compliance performance.
Keywords/Search Tags:Forging Manipulator, Passive compliance, Dynamic Modeling, Perform-ance Analysis, Multiobjective Optimization
PDF Full Text Request
Related items