Helder Lacerda | Universidade Federal de Uberlândia (original) (raw)
Papers by Helder Lacerda
IFAC Proceedings Volumes, 1998
In this paper, PlO controllers primarily control the axes of a biaxial table. A contour error con... more In this paper, PlO controllers primarily control the axes of a biaxial table. A contour error controller (CEC) works simultaneously, helping them. The calculus of the orthogonal path deviation (contour error) is performed with an additional term in the equation, resulting in a more accurate value and enabling the use of this type of motion controller at higher feedrate. The response results are compared with those of common PlOs and non-corrected CEC in order to analyse the effectiveness of this controller over the system.
Structural Health Monitoring 2015, 2015
The Impedance-based Structural Health Monitoring (ISHM) technique has become a promising and attr... more The Impedance-based Structural Health Monitoring (ISHM) technique has become a promising and attractive tool for damage identification in the field of nondestructive evaluation techniques. This method takes into account the variations of the electromechanical impedance (EMI) of the structure as caused by the presence of damage by using piezoelectric transducers bonded on the structure surface (or embedded into it). However, temperature effects are a critical challenge to a practical implementation of an ISHM system. In this technique, the EMI, which is directly related to the mechanical impedance of the structure, is obtained as a frequency domain dynamic response. Based on the variation of the impedance signals, the presence of damage can be detected. In this work, a reliability assessment is performed on a monitored structured (aircraft Al panel) aiming at determining threshold indexes associated with damage. The diagnostic, which is obtained from a statistics-based methodology, uses a temperature compensated damage metric in order to simulate a structure in its actual operational conditions. doi: 10.12783/SHM2015/90
Mechanical Systems and Signal Processing, 2019
The nonlinear dynamic analysis of viscoelastic systems is not an easy task. In some cases, it is ... more The nonlinear dynamic analysis of viscoelastic systems is not an easy task. In some cases, it is due to the difficulty in dealing with the temperature-and frequency-dependent properties of the viscoelastic substructure. Also, since the real-life viscoelastic treatments are characterized by inherent uncertainties affecting their efficiency, their handling in the nonlinear modeling is essential from an engineering point of view. In this contribution, a stochastic modeling based on the Karhunen-Loève expansion is proposed for a three-layer sandwich beam having nonlinear behavior using the concept of complex modulus and shift factor. The nonlinear frequency responses were obtained by using an approximated harmonic balance method with the Galerkin bases. Due to the difficulty in solving the resulting complex nonlinear eigenproblem with a frequency-dependent stiffness, making the stochastic nonlinear analyses very costly, it is proposed an iterative reduction method to approximate the complex eigenmodes. The influence of the forcing amplitude and temperature on the computed nonlinear frequency responses has been confirmed by performing laboratory experiments with a three-layer sandwich beam specimen placed inside an environmental chamber. Also, a curve-fitting has been performed to calibrate the deterministic nonlinear model using optimization tools. The envelopes of nonlinear responses demonstrate the relevance of considering the uncertainties in design variables.
ABSTRACT It has been demonstrated by many authors that the internal damping mechanism of the visc... more ABSTRACT It has been demonstrated by many authors that the internal damping mechanism of the viscoelastic materials offers many possibilities for practical engineering applications. However, in traditional procedures of analysis and design of viscoelastic dampers subjected to cyclic loadings, uniform, constant temperature is generally assumed and do not take into account the self-heating phenomenon. Moreover, for viscoelastic materials subjected to dynamic loadings superimposed on static preloads, such as engine mounts, these procedures can lead to poor designs or even severe failures since the energy dissipated within the volume of the material leads to temperature rises. In this paper, a hybrid numerical–experimental investigation of effects of the static preloads on the self-heating phenomenon in viscoelastic dampers subjected to harmonic loadings is reported. After presenting the theoretical foundations, the numerical and experimental results obtained in terms of the temperature evolutions at different points within the volume of the viscoelastic material for various static preloads are compared, and the main features of the methodology are discussed.
Latin American Journal of Solids and Structures
The good damping performance and inherent stability of viscoelastic materials in relatively broad... more The good damping performance and inherent stability of viscoelastic materials in relatively broad frequency bands, besides cost effectiveness, offers many possibilities for practical engineering applications. However, for viscoelastic dampers subjected to dynamic loadings superimposed on static preloads, especially when good isolation characteristics are required at high frequencies, traditional design guidelines can lead to poor designs due to the rapidly increasing rate of temperature change inside the material. This paper is devoted to the numerical and experimental investigation in the degradation of the stiffness and capacity of a viscoelastic material induced by the thermal runaway phase, when it is subjected to dynamic and static loads simultaneously. After the theoretical background, the obtained results in terms of the temperature evolutions at different points within the volume of the material and the hysteresis loops for various static preloads are compared and the main features of the proposed study are highlighted.
Latin American Journal of Solids and Structures
The good damping performance and inherent stability of viscoelastic materials in relatively broad... more The good damping performance and inherent stability of viscoelastic materials in relatively broad frequency bands, besides cost effectiveness, offers many possibilities for practical engineering applications. However, for viscoelastic dampers subjected to dynamic loadings superimposed on static preloads, especially when good isolation characteristics are required at high frequencies, traditional design guidelines can lead to poor designs due to the rapidly increasing rate of temperature change inside the material. This paper is devoted to the numerical and experimental investigation in the degradation of the stiffness and capacity of a viscoelastic material induced by the thermal runaway phase, when it is subjected to dynamic and static loads simultaneously. After the theoretical background, the obtained results in terms of the temperature evolutions at different points within the volume of the material and the hysteresis loops for various static preloads are compared and the main features of the proposed study are highlighted.
Structural Health Monitoring: An International Journal
Resumo: Os sistemas de controle dos movimentos de baixo custo, para motores de passo, utilizam a ... more Resumo: Os sistemas de controle dos movimentos de baixo custo, para motores de passo, utilizam a porta paralela de um micro computador e o sistema operacional MS-DOS e tem a desvantagem de apresentar uma interface ruim, pouco amigável, pouco informativa e sem estética, devida às limitações do DOS . O objetivo deste trabalho é desenvolver uma placa de circuito impresso e uma interface gráfica no ambiente Windows ® para acionar os motores de passo de uma mesa X-Y (destinada a corte e solda de chapas metálicas), através da porta USB de um microcomputador rodando o programa AutoCAD ® . A interface gráfica desenvolvida é mais funcional e amigável, utiliza o sistema operacional Windows98 ® e comandos adicionados ao menu do programa AutoCAD ® para o acionamento dos motores. Os testes experimentais envolveram interpolação linear e circular, de modo a acionar os motores de passo, reproduzindo o projeto desenvolvido no AutoCAD ® . Os resultados mostraram que o sistema desenvolvido é capaz de traçar qualquer trajetória desejada com boa exatidão. Para o microcomputador, este sistema é um dispositivo de interface humana (HID), em que a velocidade máxima de transferência de dados é limitada a 800 bytes/s, o que fez com que a velocidade máxima de acionamento dos motores de passo ficasse aquém do esperado. Palavras chave: mesa X-Y, porta USB, sistema de controle dos movimentos, AutoCAD .
Matemática aplicada à indústria: problemas e métodos de solução, 2016
Optimization techniques are used for balancing flexible rotors: modal information is used to redu... more Optimization techniques are used for balancing flexible rotors: modal information is used to reduce the number of experimental readings and global strain energy minimization is used to determine correction masses and their corresponding angle positions. Optimization results are compared to those obtained using influence coefficients. Experimental results validate the simulations procedures.
Anais do Congresso Nacional de Matemática Aplicada à Indústria, 2015
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2004
Journal of the Brazilian Society of Mechanical Sciences, 2000
ABSTRACT This article deals with a contour error controller (CEC) applied in a high speed biaxial... more ABSTRACT This article deals with a contour error controller (CEC) applied in a high speed biaxial table. It works simultaneously with the table axes controllers, helping them. In the early stages of the investigation, it was observed that its main problem is imprecision when tracking non-linear contours at high speeds. The objectives of this work are to show that this problem is caused by the lack of exactness of the contour error mathematical model and to propose modifications in it. An additional term is included, resulting in a more accurate value of the contour error, enabling the use of this type of motion controller at higher feedrate. The response results from simulated and experimental tests are compared with those of common PID and non-corrected CEC in order to analyse the effectiveness of this controller over the system. The main conclusions are that the proposed contour error mathematical model is simple, accurate, almost insensible to the feedrate and that a 20:1 reduction of the integral absolute contour error is possible.
The International Journal of Advanced Manufacturing Technology, 2012
ABSTRACT This work deals with an hybrid PID+fuzzy logic controller applied to control the machine... more ABSTRACT This work deals with an hybrid PID+fuzzy logic controller applied to control the machine tool biaxial table motions. The non-linear model includes backlash and the axis elasticity. Two PID controllers do the primary table control. A third PID+fuzzy controller has a cross coupled structure whose function is to minimise the trajectory contour errors. Once with the three PID controllers tuned, the system is simulated with and without the third controller. The responses results are plotted and compared to analyse the effectiveness of this hybrid controller over the system. They show that the proposed methodology reduces the contour error in a proportion of 70:1.
Structural Health Monitoring 2015, 2015
IFAC Proceedings Volumes, 1998
In this paper, PlO controllers primarily control the axes of a biaxial table. A contour error con... more In this paper, PlO controllers primarily control the axes of a biaxial table. A contour error controller (CEC) works simultaneously, helping them. The calculus of the orthogonal path deviation (contour error) is performed with an additional term in the equation, resulting in a more accurate value and enabling the use of this type of motion controller at higher feedrate. The response results are compared with those of common PlOs and non-corrected CEC in order to analyse the effectiveness of this controller over the system.
Structural Health Monitoring 2015, 2015
The Impedance-based Structural Health Monitoring (ISHM) technique has become a promising and attr... more The Impedance-based Structural Health Monitoring (ISHM) technique has become a promising and attractive tool for damage identification in the field of nondestructive evaluation techniques. This method takes into account the variations of the electromechanical impedance (EMI) of the structure as caused by the presence of damage by using piezoelectric transducers bonded on the structure surface (or embedded into it). However, temperature effects are a critical challenge to a practical implementation of an ISHM system. In this technique, the EMI, which is directly related to the mechanical impedance of the structure, is obtained as a frequency domain dynamic response. Based on the variation of the impedance signals, the presence of damage can be detected. In this work, a reliability assessment is performed on a monitored structured (aircraft Al panel) aiming at determining threshold indexes associated with damage. The diagnostic, which is obtained from a statistics-based methodology, uses a temperature compensated damage metric in order to simulate a structure in its actual operational conditions. doi: 10.12783/SHM2015/90
Mechanical Systems and Signal Processing, 2019
The nonlinear dynamic analysis of viscoelastic systems is not an easy task. In some cases, it is ... more The nonlinear dynamic analysis of viscoelastic systems is not an easy task. In some cases, it is due to the difficulty in dealing with the temperature-and frequency-dependent properties of the viscoelastic substructure. Also, since the real-life viscoelastic treatments are characterized by inherent uncertainties affecting their efficiency, their handling in the nonlinear modeling is essential from an engineering point of view. In this contribution, a stochastic modeling based on the Karhunen-Loève expansion is proposed for a three-layer sandwich beam having nonlinear behavior using the concept of complex modulus and shift factor. The nonlinear frequency responses were obtained by using an approximated harmonic balance method with the Galerkin bases. Due to the difficulty in solving the resulting complex nonlinear eigenproblem with a frequency-dependent stiffness, making the stochastic nonlinear analyses very costly, it is proposed an iterative reduction method to approximate the complex eigenmodes. The influence of the forcing amplitude and temperature on the computed nonlinear frequency responses has been confirmed by performing laboratory experiments with a three-layer sandwich beam specimen placed inside an environmental chamber. Also, a curve-fitting has been performed to calibrate the deterministic nonlinear model using optimization tools. The envelopes of nonlinear responses demonstrate the relevance of considering the uncertainties in design variables.
ABSTRACT It has been demonstrated by many authors that the internal damping mechanism of the visc... more ABSTRACT It has been demonstrated by many authors that the internal damping mechanism of the viscoelastic materials offers many possibilities for practical engineering applications. However, in traditional procedures of analysis and design of viscoelastic dampers subjected to cyclic loadings, uniform, constant temperature is generally assumed and do not take into account the self-heating phenomenon. Moreover, for viscoelastic materials subjected to dynamic loadings superimposed on static preloads, such as engine mounts, these procedures can lead to poor designs or even severe failures since the energy dissipated within the volume of the material leads to temperature rises. In this paper, a hybrid numerical–experimental investigation of effects of the static preloads on the self-heating phenomenon in viscoelastic dampers subjected to harmonic loadings is reported. After presenting the theoretical foundations, the numerical and experimental results obtained in terms of the temperature evolutions at different points within the volume of the viscoelastic material for various static preloads are compared, and the main features of the methodology are discussed.
Latin American Journal of Solids and Structures
The good damping performance and inherent stability of viscoelastic materials in relatively broad... more The good damping performance and inherent stability of viscoelastic materials in relatively broad frequency bands, besides cost effectiveness, offers many possibilities for practical engineering applications. However, for viscoelastic dampers subjected to dynamic loadings superimposed on static preloads, especially when good isolation characteristics are required at high frequencies, traditional design guidelines can lead to poor designs due to the rapidly increasing rate of temperature change inside the material. This paper is devoted to the numerical and experimental investigation in the degradation of the stiffness and capacity of a viscoelastic material induced by the thermal runaway phase, when it is subjected to dynamic and static loads simultaneously. After the theoretical background, the obtained results in terms of the temperature evolutions at different points within the volume of the material and the hysteresis loops for various static preloads are compared and the main features of the proposed study are highlighted.
Latin American Journal of Solids and Structures
The good damping performance and inherent stability of viscoelastic materials in relatively broad... more The good damping performance and inherent stability of viscoelastic materials in relatively broad frequency bands, besides cost effectiveness, offers many possibilities for practical engineering applications. However, for viscoelastic dampers subjected to dynamic loadings superimposed on static preloads, especially when good isolation characteristics are required at high frequencies, traditional design guidelines can lead to poor designs due to the rapidly increasing rate of temperature change inside the material. This paper is devoted to the numerical and experimental investigation in the degradation of the stiffness and capacity of a viscoelastic material induced by the thermal runaway phase, when it is subjected to dynamic and static loads simultaneously. After the theoretical background, the obtained results in terms of the temperature evolutions at different points within the volume of the material and the hysteresis loops for various static preloads are compared and the main features of the proposed study are highlighted.
Structural Health Monitoring: An International Journal
Resumo: Os sistemas de controle dos movimentos de baixo custo, para motores de passo, utilizam a ... more Resumo: Os sistemas de controle dos movimentos de baixo custo, para motores de passo, utilizam a porta paralela de um micro computador e o sistema operacional MS-DOS e tem a desvantagem de apresentar uma interface ruim, pouco amigável, pouco informativa e sem estética, devida às limitações do DOS . O objetivo deste trabalho é desenvolver uma placa de circuito impresso e uma interface gráfica no ambiente Windows ® para acionar os motores de passo de uma mesa X-Y (destinada a corte e solda de chapas metálicas), através da porta USB de um microcomputador rodando o programa AutoCAD ® . A interface gráfica desenvolvida é mais funcional e amigável, utiliza o sistema operacional Windows98 ® e comandos adicionados ao menu do programa AutoCAD ® para o acionamento dos motores. Os testes experimentais envolveram interpolação linear e circular, de modo a acionar os motores de passo, reproduzindo o projeto desenvolvido no AutoCAD ® . Os resultados mostraram que o sistema desenvolvido é capaz de traçar qualquer trajetória desejada com boa exatidão. Para o microcomputador, este sistema é um dispositivo de interface humana (HID), em que a velocidade máxima de transferência de dados é limitada a 800 bytes/s, o que fez com que a velocidade máxima de acionamento dos motores de passo ficasse aquém do esperado. Palavras chave: mesa X-Y, porta USB, sistema de controle dos movimentos, AutoCAD .
Matemática aplicada à indústria: problemas e métodos de solução, 2016
Optimization techniques are used for balancing flexible rotors: modal information is used to redu... more Optimization techniques are used for balancing flexible rotors: modal information is used to reduce the number of experimental readings and global strain energy minimization is used to determine correction masses and their corresponding angle positions. Optimization results are compared to those obtained using influence coefficients. Experimental results validate the simulations procedures.
Anais do Congresso Nacional de Matemática Aplicada à Indústria, 2015
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2004
Journal of the Brazilian Society of Mechanical Sciences, 2000
ABSTRACT This article deals with a contour error controller (CEC) applied in a high speed biaxial... more ABSTRACT This article deals with a contour error controller (CEC) applied in a high speed biaxial table. It works simultaneously with the table axes controllers, helping them. In the early stages of the investigation, it was observed that its main problem is imprecision when tracking non-linear contours at high speeds. The objectives of this work are to show that this problem is caused by the lack of exactness of the contour error mathematical model and to propose modifications in it. An additional term is included, resulting in a more accurate value of the contour error, enabling the use of this type of motion controller at higher feedrate. The response results from simulated and experimental tests are compared with those of common PID and non-corrected CEC in order to analyse the effectiveness of this controller over the system. The main conclusions are that the proposed contour error mathematical model is simple, accurate, almost insensible to the feedrate and that a 20:1 reduction of the integral absolute contour error is possible.
The International Journal of Advanced Manufacturing Technology, 2012
ABSTRACT This work deals with an hybrid PID+fuzzy logic controller applied to control the machine... more ABSTRACT This work deals with an hybrid PID+fuzzy logic controller applied to control the machine tool biaxial table motions. The non-linear model includes backlash and the axis elasticity. Two PID controllers do the primary table control. A third PID+fuzzy controller has a cross coupled structure whose function is to minimise the trajectory contour errors. Once with the three PID controllers tuned, the system is simulated with and without the third controller. The responses results are plotted and compared to analyse the effectiveness of this hybrid controller over the system. They show that the proposed methodology reduces the contour error in a proportion of 70:1.
Structural Health Monitoring 2015, 2015