In the control of the vibration structure, active vibration control is an important topic during these years. In this thesis, an active vibration control strategy is proposed to improve the vibration problem in a linear motor positioning system. The main purpose of the present research is to reduce the vibration of the positioning system. A force estimator is applied to suppress extra force produced from a linear motor positioning system. However, uncertain parameters of the system and external disturbance degrade the accuracy of the force estimator. A sliding controller has been designed to enhance the performance of the control system. The performance of the force estimator and the improvement of the control strategy have been discussed thoroughly in this research. The computer simulation and experiments both show encouraging results of the proposed control strategy. The vibration induced from a linear motor positioning system can be suppressed to the expected amplitude 0.0956 when the linear motor position completed.

No description available.

Vibration in metal cutting is a common problem in the manufacturing industry, especially when long and slender tool holders or boring bars are involved in the manufacturing process. Vibration has a detrimental effect on machining. In particular the surface finish is likely to suffer, but tool life is also most likely to be reduced. Tool vibration also results in loud noise that may disturb the working environment. The first part of this thesis describes the development of a robust and manually adjustable analog controller capable of actively controlling boring bar vibrations related to internal turning. This controller is compared with an adaptive digital feedback filtered-x LMS controller and it displays similar performance with a vibration attenuation of up to 50 dB. A thorough experimental investigation of the influence of the clamping properties on the dynamic properties of clamped boring bars is also carried out in second part of the thesis. In relation to this, it is demonstrated that the number of clamping screws, the clamping screw diameter size, the screw tightening torque and the order the screws are tightened, have a significant influence on a clamped boring bar’s eigenfrequencies as well as on its mode shape orientation in the cutting speed - cutting depth plane. Also, an initial investigation of nonlinear dynamic properties of clamped boring bars was carried out. Furthermore, vibration in milling has also been studied in relation to millingtool holders with a long overhang. A basic investigation concerning the spatial dynamic properties of the tool holders of milling machines, both when not cutting and during cutting, has been carried out. Also, active control of milling tool holder vibration has been investigated and a first prototype of an active milling tool holder was implemented and tested. The challenge of transferring electrical power while maintaining good signal quality to and from a rotating object is addressed and a solution to this is proposed. Finally, vibration is also a problem for the hydroelectric power industry. In Sweden, hydroelectric power plants stand for approximately half of Sweden’s electrical power production and are also considered to be a so-called green source of energy. When renovating water turbines in small-scale hydroelectric power plants and modifying them to optimize efficiency, it is not uncommon that disturbing vibrations occur in the power plant. These vibrations have a negative influence on the production capacity and will wear various components quickly. Occasionally, these vibrations may cause severe damage to the power plant. To identify this vibration problem, experimental modal analysis and operating deflection shape analysis were utilized. To reduce the vibration problem, active control using inertial mass actuators was investigated. Preliminary results indicate a significant attenuation of the vibrations.

The objective of this research is to develop a wearable device that could harvest waste mechanical energy of the human hand movement and utilize this energy to suppress wrist tremors. Piezoelectric material is used to measure the hand movement signals, and the signal of wrist tremor is filtered to be utilized to suppress the tremor. In order to conduct the experiment of energy harvesting and tremor suppression, an experimental rig was fabricated. Two types of piezoelectric materials, PVDF (polyvinylidene fluoride) films and MFC (macro fiber composite) films, are used to harvest mechanical energy and used as actuators to suppress hand tremors. However, due to some shortages of the materials, these two types of materials are not used as actuators to suppress the wrist tremors. Thus, we use Matlab Simulink to simulate the tremor suppression with AVC (active vibration control) algorithm.

We use the elitist and extinction policies to improve the simple genetic algorithm in this study. We expect that the search technique can avoid falling into the local maximum due to the premature convergence, and the chance of finding the near-optimal parameter in the larger searching space could be obviously increased. The accelerometer is then taken as the sensor for output measurement, and the designed controller is implemented to actively suppress the vibration of the plain that is due to the excitation effect of the high-speed and precision positioning of the linear motor. From the computer simulations and the experimented results, it is obvious that the near-optimal controller designed by using genetic approach with elitist and extinction can improve the effect of vibration suppression; the settling time is also decrease. For the vibration suppressions of high-speed precision positioning problems, the results are satisfactory in the cases of short, middle and long distance.

Abstract We use the non-binary coding ,elitist strategy, increasing mutation rate, extinction, and immigration strategy to improve the simple genetic algorithms in this study. We expect that the search technique can avoid falling into the local optimum due to the premature convergence, and purse the chance that finding the near-optimal parameters in the larger searching space could be obviously increased. The accelerometer is then taken as the feedback sensor for output measurement, and the designed actuator and the PID fuzzy logic controller (PIDFLC) is implemented to actively suppress the vibration of the supporting mechanism that is due to the excitation effect of the high-speed and precision positioning action of the linear motor. From the computer simulations and the experimental results, it is obvious that the near-optimal PIDFLC controller designed by modified genetic algorithms can improve the effect of the vibration suppression; the settling time is also decrease. For the vibration suppressions of high-speed precision positioning problems, the vibrating supporting mechanism can quickly be stabilized.

Yes / This paper presents an investigation into the development of an intelligent active vibration control (AVC) system. Evolutionary Genetic algorithms (GAs) and Adaptive Neuro-Fuzzy Inference system (ANFIS) algorithms are used to develop mechanisms of an AVC system, where the controller is designed on the basis of optimal vibration suppression using the plant model. A simulation platform of a flexible beam system in transverse vibration using finite difference (FD) method is considered to demonstrate the capabilities of the AVC system using GAs and ANFIS. MATLAB GA tool box for GAs and Fuzzy Logic tool box for ANFIS function are used for AVC system design. The system is then implemented, tested and its performance assessed for GAs and ANFIS based design. Finally a comparative performance of the algorithm in implementing AVC system using GAs and ANFIS is presented and discussed through a set of experiments.

We use the adaptive probabilities of crossover and mutation, elitist strategy, and extinction and immigration strategy to improve the simple genetic algorithm in this study. We expect that the search technique can avoid falling into the local maximum due to the premature convergence, and the chance of finding the near-optimal parameter in the larger searching space could be obviously increased. The accelerometer is then taken as the sensor for output measurement, and the designed actuator and digital PID controller is implemented to actively suppress the vibration of the plain that is due to the excitation effect of the high-speed and precision positioning of the linear motor. From the computer simulations and the experimented results, it is obvious that the near-optimal digital PID controller designed by modified genetic approach can improve the effect of vibration suppression; the settling time is also decrease. For the vibration suppressions of high-speed precision positioning problems, the vibrating plain system can fastly be stabilized.

Biodynamic feedthrough occurs in many types of operator controlled machines where the operator is a passenger and the motion of the controlled machine excites motion of the human operator, creating unwanted feedback. It is a significant cause for control performance degradation in backhoes. In this research, the problem of biodynamic feedthrough is investigated in a backhoe control system. For simplification, the system is limited to a single degree of freedom. Several controller based approaches are investigated to reduce cab vibration, while maintaining cylinder tracking performance. These controllers are tested in hardware, with and without the human operator and associated biodynamic feedthrough. The effect of this cab vibration reduction on biodynamic feedthrough is tested in a small set of human subject tests. The results indicate that some vibration reduction and improvement in the operator's control performance can be achieved by adding cab vibration compensation.

Nas últimas décadas, intensas pesquisas estão sendo desenvolvidas na área de controle ativo de vibrações utilizando estruturas flexíveis e transdutores piezoelétricos distribuídos em sua superfície. Este trabalho possui como objetivo a implementação, identificação e a aplicação do controle ativo de vibrações em barras engastadas. Os transdutores piezoelétricos são fixados próximos à extremidade fixa da barra. Um sistema de aquisição de sinais e de controle é utilizado para gravar os dados experimentais e implementar os projetos dos controladores de vibrações. Para a implementação computacional foi utilizado o software Matlab operando em conjunto com uma placa dSpace DS1104. A identificação do sistema, efetuada a partir da resposta em frequência das barras, é realizada considerando apenas os três primeiros modos de vibração das barras. Um modelo teórico que representa a dinâmica do sistema é apresentado e seus parâmetros são ajustados de acordo com dados experimentais, obtidos em ensaios, com a estrutura flexível. Para o problema de rejeição a perturbações e regulação de posição, são aplicados os métodos de controle conhecidos como Positive Position Feedback (PPF) e de Alocação de Pólos. Resultados experimentais são apresentados para demonstrar a eficácia do controle ativo de vibrações, utilizando transdutores piezoelétricos. / In recent decades, intensive researches have been developed in the area of active vibration control making use of flexible structures and piezoelectric transducers distributed on its surface. This work aims to identify, implement and apply the active control of vibrations in cantilevers beams. The piezoelectric transducers are surface-bonded near the fixed end of cantilever beam. A data acquisition and control system is used to record experimental data and to implement the design of a vibration controller. The software Matlab operating in conjunction with a board dSpace DS1104 was used for the computational implementation. The identification system, made from the frequency response of the cantilevers beams, is performed by considering only the first three modes of vibration of the cantilevers beams. A theoretical model representing the system dynamics is presented and its parameters are adjusted according to experimental data, obtained in tests, with the flexible structure. As for the problem of disturbance rejection and regulation position, control methods known as Positive Position Feedback (PPF) and Pole Placement are applied. Experimental results are presented to demonstrate the effectiveness of active control of vibration using piezoelectric transducers.