Papers by Keyword: Modal Approach

Abstract: This study contributes to the development of more resilient and responsive control systems for industrial robotics. Industrial robot arms are subject to various vibrational forces during various operations, which can limit their accuracy and response time. This paper studies the vibration characteristics of a robotic arm through real world measurement and Finite Element Analysis (FEA). The robot arm is the MELFA RV-2SDB15. In this paper, the authors determine the dynamic parameters of the examined manipulator. Experimental measurement is carried out with a modal approach. Optimization techniques are employed to develop an accurate CAD model of the robotic arm.

Abstract: This paper presents a new strategy for the design of radiation mode sensors by using shaped PVDF films for one-dimension structures. Based on a modal approach, the shape of a PVDF sensor is analytically determined in such a way that the output signal of the sensor is directly proportional to amplitude of a particular radiation mode. Other modes are filtered out. A general expression of the PVDF sensor shape is obtained. It is found that the modal sensor shape can be expressed as a function of the second spatial derivative of the structural mode shape function. Finally, with an example of a vibrating beam, the proposed PVDF radiation mode sensor is used in an active structural acoustic control system for reduction of the structural-borne noise.

Abstract: The aim of this paper is the determination of the evolution of the modal stress intensity factor (MSIF) for a non-propagating crack subjected to dynamic loading using the extended finite element method (X-FEM). The main advantage of this method coupled with the modal analysis is its capability in modeling cracks independently of the mesh and in a reduced computational time compared to the finite element method coupled with dynamic iterative method. The proposed procedure is applied to a reference problem (cracked plate). The MSIFs obtained agree well with those found by indirect boundary element (IBEM), weight function and Newmark’s explicit methods.

Abstract: This paper presents a method for the vibration of a beam with a breathing crack under harmonic excitation. The infinitely thin crack is characterised by a parameter that takes into account the shape and the depth of the crack. The closed- and open-crack states are both modelled by a modal approach: two sets of equations of motion cast in the modal coordinates of their individual mode shapes. The state change (from closed to open or vice versa) involves the calculation of the modal coordinates associated with the new state from the modal coordinates of the previous state. By imposing the continuity of displacement and velocity the beam at the instant of the state change, the matrix that transforms the modal coordinates from one state to the other is determined and proved to be the Modal Scale Factor matrix. This analytical approach takes advantage of exact nature and mathematical convenience of beam modes and is time-efficient. Forced vibration at various values of crack parameter is determined. It is found that as decreases (crack length increases) the vibration becomes increasingly erratic and finally chaotic.