Hassan Yousefi

Pressure drop in micro T-mixers

Results are presented from a numerical study examining the pressure drop of the liquid phase inside micro T-mixers at moderate Reynolds numbers. The effects on the pressure gradient of changes to design and operating parameters such as the aspect ratio of the mixing channel and the volume flow rate are studied. To understand the influence of geometrical parameters on flow resistance and the mixing zone, a wide range of dimensions of micro T-mixers is studied. A broad range of Reynolds numbers is investigated so that the flow is either in the vortex or in the engulfment regimes. Explicit equations are proposed to predict the friction factor for both vortex and engulfment flow regimes inside T-mixers. In addition, a model is proposed to determine the mixing zone in micro T-mixers. A set of experiments were carried out to support the simulation results. The model results were found to be consistent with the experimental findings.

Optimization of unknown parameters of adaptive backstepping in position tracking of a permanent magnet linear motor

In the current paper a non-linear load control method is developed and implemented for a permanent magnet linear synchronous motor (PMLSM) with a flexible load. The proposed controller tracks a flexible load to the desired reference position as fast as possible and without awkward oscillation. The control method is based on an adaptive backstepping algorithm whose stability is ensured by the Lyapunov stability theorem. The unknown parameters of the controller were estimated by means of a differential evolution algorithm. The needed states of the system that are used by controller are estimated by using the Kalman filter. The proposed controller is implemented and tested in a linear motor test drive and responses are presented.

Usability Test in a Virtual Environment: A Case Study Based on a Mining Machine

Put During the concept phase of product development, designers must evaluate complex engineering scenarios. The usability test is an effective method to find out the design correctness regarding to use of the certain technical solutions. The commonly used usability test is performed on the physical mock-ups, and it is expensive test for new designed machines. Performance predictions and functional evaluations are possible long before real prototype test results become available. However, with the rise in model complexity, data quantity, computing performance, and accuracy, we increasingly find ourselves lacking the tools, methods, and metaphors to deal with the information generated. One of the most important applications of virtual reality (VR) technology has been for requirements analysis using virtual prototypes. The appeal of using VR is from saving the cost of physical mock-ups and prototypes, especially for complex systems. The paper presents a Virtual Reality (VR) technique as environment for the 3D model of the new designed systems and performs the usability tests to improve the designed system performance. The paper presents and investigates the results of applying usability test in a virtual environment for a sample mining machine.Copyright

Human Centered Design of Mobile Machines by a Virtual Environment

Psychomechatronics is a new holistic discipline that integrates mechatronics and cognitive science, offering innovative methods that lead to the concurrent design of human---machine systems. According to current methods, mechatronics features are designed first and human factors are considered thereafter. A problem with this approach is that it is often too late to impose significant changes in the mechatronics design at that time. Psychomechatronics, on the other hand, takes the nature of human cognition as the starting point of systems design and therefore it is a human-centered design principle. It does not adhere to the conventional sequential approach but applies simultaneously both mechatronics and cognitive science at the same conceptual stage, which optimizes the design of hybrid human---machine systems. The paper presents the key ideas of psychomechatronics design method with special reference to mobile machinery. The required virtual environment for carrying out the psychomechatronics design of mobile machines is described. The paper presents the results of applying usability test in a virtual environment for a sample mining machine.

Application of Fuzzy Gain-Scheduling in Position Control of a Servo Hydraulic System with a Flexible Load

Abstract The control of hydraulic servo-systems has been the focus of intense research over the past decades. Hydraulic position servos with an asymmetrical cylinder are commonly used in industry. These kinds of systems are nonlinear in nature and generally difficult to control. Changing system parameters using the same gains will cause overshoot or even loss of system stability. The highly non-linear behaviour of these devices makes them ideal subjects for applying different types of sophisticated controllers. The paper is concerned with a second order model reference to positioning control of a flexible load servo-hydraulic system using fuzzy gain-scheduling. In the present study, to compensate the lack of damping in a hydraulic system, an acceleration feedback was used. To compare the results, a p-controller with feedforward acceleration and different gains in extension and retraction is used. The design procedure for the controller and experimental results are discussed. The results suggest that using the fuzzy gain-scheduling controller decrease the error of position reference tracking.

Simulation and Experimental Study in Position Control of Servo Hydraulic System With Flexible Load Using Adaptive Neural Network and Differential Evolution Strategy

Hydraulic position servos with an asymmetrical cylinder are commonly used in industry. These kinds of systems are nonlinear in nature and generally difficult to control. Because of parameters changing during extending and retracting, using constant gain will cause overshoot, poor performance or even loss of system stability. The highly nonlinear behaviour of these devices makes them ideal subjects for applying different types of sophisticated controllers. This paper is concerned with a second order adaptive model reference and an artificial neural network controller to position tracking of a servo hydraulic with a flexible load. In present study, a neural network with two outputs is presented. One of the outputs of neural network is used for system’s dynamic compensator and another one for gain scheduling controller. To avoid the local minimum problem, Differential Evolution Algorithm (DEA) is used to find the weights and biases of neural network. The proposed controller is verified with a common used p-controller. The simulation and experimental results suggest that if the neural network is chosen and trained well, it improves all performance evaluation criteria such as stability, fast response, and accurate reference model tracking in servo hydraulic systems.Copyright

Adaptive Fuzzy Gain Scheduling in Position Control of Servo Hydraulic System With Flexible Load

The control of hydraulic servo-systems has been the focus of intense research over the past decades. Hydraulic position servos with an asymmetrical cylinder are commonly used in industry. These kinds of systems are nonlinear in nature and generally difficult to control. Because of changing system parameters using the same gains will cause overshoot or even loss of system stability. The highly non-linear behavior of these devices makes them idea subjects for applying different types of sophisticated controllers. This paper is concerned with a second order model reference adaptive position control of a flexible load servo-hydraulic system using a fuzzy gain scheduling. In present study, to compensate the lack of damping in hydraulic system, an acceleration feedback was used. The proposed controller was verified with a common used p-controller. The results suggest that using fuzzy controller improves all performance evaluation criteria such as stability, fast response, and accurate reference model tracking in hydraulic systems.Copyright

Adaptive Neural Network in Compensation the Dynamics and Position Control of a Servo-Hydraulic System With a Flexible Load

Asymmetrical servo-hydraulic systems are commonly used in industry. These kinds of systems are nonlinear in nature and generally difficult to control. Because of changing system parameters, using the same gain will cause overshoot or even loss of system stability. The highly nonlinear behavior of these devises makes them idea subjects for applying different types of sophisticated controllers. This paper is concerned with using two artificial neural networks in compensation the dynamics and position tracking of a second order model reference in a flexible servo-hydraulic system. In present study, a neural network as an acceleration feedforward and another one as a gain scheduling of a proportional controller are proposed. Differential evolution algorithm is used to find the weights and biases to avoid the local minima. The proposed controller was verified with a commonly used p-controller. The results suggest that if the neural networks choose and train well, they improve all performance evaluation criteria such as stability, fast response, and accurate reference model tracking in servo-hydraulic systems.Copyright

Flow Dynamics of Vibrated Dense Granular Materials in the Presence of Ambient Gas

Results are presented from a numerical study examining the flow dynamics of condensed granular materials in the presence of an interstitial gas in a narrow gap between two concentric cylindrical buckets subjected to sinusoidal oscillation in the vertical direction of the form z = Asin(ωt), where the parameter Γ = Aω2 /g exceeds a critical value, Γc , above which the system becomes fluidized. Using a recently developed expression for the stress tensor of particle phase, a set of conservation equations were derived for the particle and fluid phases interacting via an interfacial drag force. Numerical integration of the continuum equations for the granular material in buckets revealed that above Γc , granular materials may exhibit liquid-like behavior and convection can occur creating a heap similar to that previously observed experimentally.Copyright