Case Studies in Mechanical Systems and Signal Processing

Small experimental test-rigs are often used to investigate active vibration control concepts in the laboratory because of ease of construction and implementation. However, in marine applications, there is a large gap between this type of experiment and full-scale implementation onboard a ship. In this article a large-scale laboratory based active vibration control system is demonstrated. It involves a floating raft system attached to a hull-like structure by way of four hydraulic actuators, which are placed in parallel with eighteen passive resilient isolators. The flexible hull-like structure is supported on twenty six pneumatic springs to simulate a floating ship. A decentralized feedforward control strategy was implemented resulting in the reduction of vibration levels on the flexible hull-like receiving structure of up to 36 dB at some tonal excitation frequencies. The passive isolation results in broadband control and is most effective at higher frequencies.

Tiejun Yang

Yao Sun

Liubin Zhou

Michael J. Brennan

Zhigang Liu

Practical demonstration of a large-scale active vibration isolation system

大规模主动隔振系统的实际演示

The increasing importance of human joints study as complex mechanical systems involves medical data processing, system fluid dynamic modelling and the establishing of reliable boundary conditions. Understanding the dynamical behaviour of joints is crucial to face prosthesis design and the associated research. This process is presented in a case study of the human ankle joint. From a proper medical image segmentation, bone surfaces are 2D-modelled as constant curvature surfaces (circles) under different criteria. The fluid dynamic problem is solved under different boundary conditions. Finally, the pressure field is obtained inside the joint and the sensitivity of the system with respect to the fitting methodology is consequently analyzed. Concluding remarks outline the findings for practical use in system study.

R. D’Amato

R. Calvo

E. Gómez

Sensitivity study of the morphometric fitting on the pressure field inside ankle joints

踝关节内部压力场形态学拟合的敏感性研究

This case study presents two diagnostic methods for the detection of broken bars in induction motors with squirrel-cage type rotors: FFT method and wavelet method. The FFT method allows detecting broken rotor bar when the motor operates under a load, but if the machine is decoupled from the mechanical load, the side band components associated with broken bars do not appear. The WT is a powerful signal-processing tool used in power systems and other areas. New wavelet-based detection methods that are focused on the analysis of the startup current have been proposed for the detection of broken bars. Since the transient stator current signal is not periodic, it is not amenable to analyze the signal by FFT method. In addition, it is impossible to estimate the time of the fault occurrence using the FFT. In this paper, our main goal is to find out the advantages of wavelet transform method compared to Fourier transform method in rotor failure detection of induction motors.

Cesar da Costa

Masamori Kashiwagi

Mauro Hugo Mathias

Rotor failure detection of induction motors by wavelet transform and Fourier transform in non-stationary condition

非平稳条件下基于小波变换和傅里叶变换的感应电机转子故障检测

This paper proposes a low-cost, high precision and efficient throttle-less hydraulic circuit that utilizes off-the-shelf industrial elements to control single rod hydraulic cylinders. The circuit uses an on/off solenoid valve to redirect the differential flow of a single rod hydraulic cylinder, and two counterbalance valves to manage switching (resistive–assistive) loads. Conducted experiments on a prototype system indicated a maximum steady state positional error of 0.2 mm. The circuit consumes only 20% of energy that is required by a valve controlled circuit to follow the same tracking signal. A simple proportional controller, that uses readings of a linear position transducer, is employed for all experiments, which makes the designed circuit easy to be implemented.

Ehsan Jalayeri

Ahmed Imam

Nariman Sepehri

A throttle-less single rod hydraulic cylinder positioning system for switching loads

无节流单杆液压缸定位系统用于切换负载

In the automotive field, size optimization procedures can be combined with concept modelling approaches, in order to design a vehicle Body-In-White (BIW) model with optimal static and dynamic performances already in the early design stages. However, this specific optimization problem, with hundreds of design variables, limited design space and often conflicting objectives, makes the choice of the appropriate optimization method really difficult. The aim of this paper is to show an industrial case study, where two different implementations of the classical gradient-based (GB) method are used in combination with a technique for vehicle body concept modelling to achieve a multi-objective BIW optimization of a passenger car.

G. De Gaetano

D. Mundo

C. Maletta

M. Kroiss

L. Cremers

Multi-objective optimization of a vehicle body by combining gradient-based methods and vehicle concept modelling

基于梯度方法和车辆概念建模的车辆车身多目标优化

This paper presents a proposal for a minimum energy feedforward control technique for flexible structures to suppress residual vibrations in point-to-point (PTP) motion. In the proposed method, the trajectory profile of the PTP motion is generated through a cycloidal function whose input is the output of a polynomial function. The obtained trajectory is dependent upon the coefficients of the polynomial function. To achieve the suppression of the residual vibration as well as the operating energy of this PTP motion, the coefficients are tuned by metaheuristic algorithms. In the numerical simulations, we investigated the PTP motions of a single-link flexible manipulator and a robotic arm attached to a flexible link. The simulation results were compared with those of previous studies, revealing the effectiveness of the proposed method.

Akira Abe

An effective trajectory planning method for simultaneously suppressing residual vibration and energy consumption of flexible structures

一种同时抑制柔性结构残余振动和能耗的有效轨迹规划方法

Rotor imbalance is the most common cause of machine vibration. In practice, rotors can never be balanced perfectly owing to manufacturing errors such as porosity in casting, non-uniform density of materials, manufacturing tolerances, and gain or loss of material during operation. Mass imbalance leads to the generation of a centrifugal force, which must be counteracted by bearings and support structures. A full spectrum analysis is presented for vibration signal to reveal the fault specific whirl signatures. The results clearly indicate the potential and feasibility of the discussed approach for the rotor imbalance diagnosis in a rotor shaft system coupled with a three phase induction motor. This paper presents a smart experimental method for vibration measurement and imbalance fault detection in rotating machinery.

Guilherme Kenji Yamamoto

João Sinohara da Silva Sousa

A smart experimental setup for vibration measurement and imbalance fault detection in rotating machinery

旋转机械振动测量与不平衡故障检测的智能实验装置

The diagnosis of bearing faults at the earliest stage is critical in avoiding future catastrophic failures. Many diagnostic techniques have been developed and applied in for such purposes, however, these traditional diagnostic techniques are not always successful when the bearing fault occurs within a gearbox where the vibration response is complex; under such circumstances it may be necessary to separate the bearing vibration signature. This paper presents a comparative study of four different techniques for bearing signature separation within a gearbox. The effectiveness of these individual techniques were compared in diagnosing a bearing defect within a gearbox employed for endurance tests of an aircraft control system. The techniques investigated include the least mean square (LMS), self-adaptive noise cancellation (SANC) and the fast block LMS (FBLMS). All three techniques were applied to measured vibration signals taken throughout the endurance test. In conclusion it is shown that the LMS technique detected the bearing fault earliest.

Faris Elasha

David Mba

Cristobal Ruiz-Carcel

A comparative study of adaptive filters in detecting a naturally degraded bearing within a gearbox

齿轮箱内自然退化轴承检测中自适应滤波器的比较研究

During high level vibration test on a high mass specimen, the test engineer is often facing difficulty to pass properly the specified vibration level due to coupling between the specimen and the shaker. The present paper present a methodology to define a virtual shaker testing simulator. The first step involves the dynamic identification of a 80 kN shaker performed thanks to measurements (modal analysis and sine sweep). The second step is the definition of the physic represented in the simulator and the translation of the electromechanical equations in a home-made simulator. Controller developed by SIEMENS LMS and supplied to V2i for a use in the framework of the AOC project is introduced to close the loop. Two test cases are described to demonstrate the possibilities offered by the simulator.

Sébastien Hoffait

Frédéric Marin

Daniel Simon

Bart Peeters

Jean-Claude Golinval

Measured-based shaker model to virtually simulate vibration sine test

基于测量的振动台模型用于虚拟模拟正弦振动测试

The study deals with an experimental campaign to analyze the effects on an automatic machine for plastic cap assembly of the increased vibrations occurring when speeding up its operation. The new velocity specifications are required by the machine manufacturer for raising the production capacity. The analysis successfully identified the functional units critically affected by elastodynamic issues related to the speed increment. Hence it permitted to focus the redesign process on the critical groups in order to implement the desired machine upgrade by means of limited modifications to the current machine version. The most relevant experimental results are presented and discussed. The paper also reports data provided by further tests carried out on a machine variant (obtained after the implementation of the first design modifications), which prove the effectiveness of the proposed solutions to improve the machine performance.

Alberto Martini

Marco Troncossi

Upgrade of an automated line for plastic cap manufacture based on experimental vibration analysis

基于实验振动分析的塑料瓶盖生产线升级

Publication Information	Publisher: Elsevier B.V.，Publishing cycle: ，Journal Type: journal，Open Access Journals: No
Basic data	Year of publication: 2015，Proportion of original research papers: ，Self Citation Rate:， Gold OA Rate:

Case Studies in Mechanical Systems and Signal Processing

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