ABSTRACT First of all Xing and Liu have to be congratulated for their interesting paper [1]. In the paper, the authors claimed to find an exact solution for thin orthotropic rectangular plates with CCCC boundary conditions which has not... more
ABSTRACT First of all Xing and Liu have to be congratulated for their interesting paper [1]. In the paper, the authors claimed to find an exact solution for thin orthotropic rectangular plates with CCCC boundary conditions which has not been solved for ages. The frequency values can be obtained exactly according to the paper but, the key point is that, the proposed method is not an exact solution claimed by the authors. As a result, the values are not exact. Eqs. (A3)–(A6) defined in [1] are four conditions. They should be satisfied at the same time if the solution is an exact solution. It will be shown that only three of four conditions (A3)–(A6) can be satisfied at the same time.
ABSTRACT This paper presents simulation and optimization of a spatial six-cable robot. For various points on the paths, tension in the cables and stiffness of the robot are determined before optimization. By selecting a function related... more
ABSTRACT This paper presents simulation and optimization of a spatial six-cable robot. For various points on the paths, tension in the cables and stiffness of the robot are determined before optimization. By selecting a function related to the stiffness matrix of the robot as the objective function of genetic algorithm, vertical positions of the connection points on the base platform as the optimization variables for each point on the paths can be determined in a way that the related function is optimized and a tension reduction in all the cables can be observed for most of the paths. Finally, the results of using different objective functions are presented for three different criteria: workspace volume, kinematic performance indices and actuating energy of the robot. The results indicate which function has the largest workspace volume with tension reduction property in all the six cables, which has the highest values for the kinematic performance indices and which has the lowest actuating energy
ABSTRACT It is well known that anode and cathode pressures, cell temperature and channel geometry are the effective parameters in the performance of DMFC (direct methanol fuel cell). In the present paper, the GA (genetic algorithm) as one... more
ABSTRACT It is well known that anode and cathode pressures, cell temperature and channel geometry are the effective parameters in the performance of DMFC (direct methanol fuel cell). In the present paper, the GA (genetic algorithm) as one of the most powerful optimization tools is applied to determine the optimal values for these parameters which result in maximum power density of a DMFC. The predominant part of the genetic algorithm is the fitness function. For the fitness function calculation, calculation of more than one thousand cases is necessary. Unfortunately, large numbers of experiments are needed, which is very time-consuming and costly. To overcome this challenge, a quasi two dimensional, isothermal model is used to obtain the power of DMFC as the fitness function of GA. For validation of this model, the results of the model are compared with experimental results and literature and shown to be in good agreement with them.
ABSTRACT In this paper, the problem involving rotating half-space or rotating an infinite space with cylindrical or spherical cavity. The material is elastic and has an inhomogeneity in the direction r-axis. The fundamental equations are... more
ABSTRACT In this paper, the problem involving rotating half-space or rotating an infinite space with cylindrical or spherical cavity. The material is elastic and has an inhomogeneity in the direction r-axis. The fundamental equations are solved by using finite-difference method. A numerical method is used to calculate the temperature, displacement and the components of stresses with time and through the radial of the body. Numerical results are given and illustrated graphically for each case considered. The results indicate that the effect of rotation and non-homogeneity is very pronounced. Comparison made with the results in the absence of rotation and non-homogeneity media.
This paper presents a simulation study aimed at investigating the potential of using fuzzy controller for active vibration control in a piezoelectric Stewart platform. The focus of the study is to assess, through simulation, the control... more
This paper presents a simulation study aimed at investigating the potential of using fuzzy controller for active vibration control in a piezoelectric Stewart platform. The focus of the study is to assess, through simulation, the control authority of the piezo stack actuators for effectively controlling the Stewart platform vibration. Dynamic analysis of the structure is performed using Matlab/Simulink. Each leg of the active interface consists of a linear piezo stack actuator, a collocated velocity sensor and flexible tips for the connections with the two end plates. The piezoelectric stack is modeled as a bar element and the electro-mechanical coupling property is simulated. The open loop and closed loop dynamic response simulations are done in Matlab/Simulink. The closed loop implementation is aimed at achieving maximum damping of the six rigid body modes of the system, through six local fuzzy velocity feedback controllers. Simulations are carried out to characterize the effect of...
This paper demonstrates the potential of applying PD like fuzzy logic controller for active vibration control of piezoelectric Stewart platforms. Through simulation, the control authority of the piezo stack actuators for effectively... more
This paper demonstrates the potential of applying PD like fuzzy logic controller for active vibration control of piezoelectric Stewart platforms. Through simulation, the control authority of the piezo stack actuators for effectively damping the Stewart platform vibration can be evaluated for further implementation of the system. Each leg of the piezoelectric Stewart platform consists of a linear piezo stack actuator, a collocated velocity sensor, a collocated displacement sensor and flexible tips for the connections with the two end plates. The piezoelectric stack is modeled as a bar element and the electro-mechanical coupling property is simulated using Matlab/Simulink software. Then, the open loop and closed loop dynamic responses are performed for the system to characterize the effect of the control on the vibration of the piezoelectric Stewart platform. A significant improvement in the damping of the structure can be observed by using the PD-like fuzzy controller
This paper presents a simulation study aimed at investigating the potential of using fuzzy controller for active vibration control in a piezoelectric Stewart platform. The focus of the study is to assess, through simulation, the control... more
This paper presents a simulation study aimed at investigating the potential of using fuzzy controller for active vibration control in a piezoelectric Stewart platform. The focus of the study is to assess, through simulation, the control authority of the piezo stack actuators for effectively controlling the Stewart platform vibration. Dynamic analysis of the structure is performed using Matlab/Simulink. Each leg of the active interface consists of a linear piezo stack actuator, a collocated force sensor and flexible tips for the connections with the two end plates. The piezoelectric stack is modeled as a bar element and the electro-mechanical coupling property is simulated. The open loop and closed loop dynamic response simulations are done in Matlab/Simulink. The closed loop implementation is aimed at achieving maximum damping of the six rigid body modes of the system, through six local fuzzy force feedback controllers. Simulations are carried out in Matlab/Simulink to characterize ...
