A. A. Mat Isa

Analytical and experimental study on balancing using influence coefficient method

Unbalance effect on rotating element happens as a result of an off centered mass concentration which will generate centrifugal forces with increasing running speeds. This unwanted situation requires correction to avoid failure due to excessive vibration. In this study, unbalance problem are studied by using theoretical influence coefficient method followed by the experimental verification. Experimental procedure is performed by using trial mass to calculate the influence coefficient and the corrected mass values as well as the phase angles. Finally, the vibration reduction of the rotor is compared theoretically and experimentally. Based on the results, the improved vibration reduction could be obtained reasonably for both single and two-plane balancing by using influence coefficient method.

Control of Flexible Beam with Unmodelled Dynamics Using Second-Order Pole Placement and LQR Techniques

Control of a flexible beam such as that in flexible-link robot manipulators in many mechanical devices is very challenging, due in part to its intrinsic nature of unmodelled dynamics in a system. Such a system is said to be subjected to nonholonomic constraints, hence its feedback control is difficult to realize. This paper presents the application of control design based on second-order pole placement and LQR approaches to a single-link flexible robotic arm. In this case, a controller considering the flexibility of highly-flexible arm is employed to suppress the tip vibration of the manipulator. The effectiveness of the method is verified through computer simulations and consequently, the adequateness of the control performance and the feasibility of the system with a super-light link are shown.

Frequency response function (FRF) based updating of a laser spot welded structure

The objective of this paper is to present frequency response function (FRF) based updating as a method for matching the finite element (FE) model of a laser spot welded structure with a physical test structure. The FE model of the welded structure was developed using CQUAD4 and CWELD element connectors, and NASTRAN was used to calculate the natural frequencies, mode shapes and FRF. Minimization of the discrepancies between the finite element and experimental FRFs was carried out using the exceptional numerical capability of NASTRAN Sol 200. The experimental work was performed under free-free boundary conditions using LMS SCADAS. Avast improvement in the finite element FRF was achieved using the frequency response function (FRF) based updating with two different objective functions proposed.

Kinematic and Dexterity Analysis of a 3-DOF Parallel Manipulator

A new three Degree Of Freedom (3-DOF) parallel manipulator has been proposed in this study. Because the parallel manipulator has three Degree Of Freedom (DOF), one translation degree of freedom and two rotational degrees of freedom, it has received considerable attention from both researchers and manufacturers over the past years. The inverse kinematic and Jacobain matrix were derived. The dexterity of the parallel manipulator is presented. The key issue of how the kinematic performance in term of dexterity varies with differences in the structural parameters of the parallel manipulator is investigated. The simulation results, using MATLAB, testify the validity of the analytic model and illustrate the structural parameters have direct effect upon dexterity characteristic of the 3-DOF parallel manipulator.

PID controller design for trailer suspension based on linear model

A quarter of an active trailer suspension system having the characteristics of a double wishbone type was modeled as a complex multi-body dynamic system in MSC.ADAMS. Due to the complexity of the model, a linearized version is considered in this paper. A model reduction technique is applied to the linear model, resulting in a reduced-order model. Based on this simplified model, a Proportional-Integral-Derivative (PID) controller was designed in MATLAB/Simulink environment; primarily to reduce excessive roll motions and thus improving the ride comfort. Simulation results show that the output signal closely imitates the input signal in multiple cases – demonstrating the effectiveness of the controller.

Ambient Response Modal Analysis on a CEM-1 Single-Layer Printed Circuit Board

Since the level of vibration always depends on the natural frequencies of the system, it is important to know the modal parameters of such system to control failure and provide prevention actions. The demand for structurally reliable Printed Circuit Boards (PCB) has increased as more functions are required from electronic products along with less weight and smaller size. This imposes certain limitations and critical requirements. In this paper, investigation on the dynamic characteristics of CEM-1 Single-layer PCB using Operational Modal Analysis (OMA, or often called Output-Only or Ambient Modal analysis), is presented. The Frequency Domain Decomposition (FDD) and Enhanced Frequency Domain Decomposition (EFDD) techniques are applied on the PCB with free-free end condition. Comparison of results between both techniques and also with the result from Experimental Modal Analysis (EMA), will be shown. The understanding on dynamic behaviour of this structure provides valuable insight into the nature of the response and remarkable enhancement of its model, strength and vibration.