Farrokh Sassani
University of British Columbia, Mechanical Engineering, Faculty Member
In this paper the use of a heart-tracking hand support is proposed to allow coronary artery bypass grafting surgery to take place on the beating heart. This method eliminates the tissue damage associated with the use of physical heart... more
In this paper the use of a heart-tracking hand support is proposed to allow coronary artery bypass grafting surgery to take place on the beating heart. This method eliminates the tissue damage associated with the use of physical heart stabilizers.
Research Interests:
Material requirement planning (MRP) is used as an important technique in production planning topics. Several researches have been carried out in MRP systems, however in the case of fuzzy lead time (FLT), there are few researches available... more
Material requirement planning (MRP) is used as an important technique in production planning topics. Several researches have been carried out in MRP systems, however in the case of fuzzy lead time (FLT), there are few researches available in the literature. In this paper, fuzzy lead time is discussed to cover an uncertainty condition in MRP systems. Hereby, the history of a vendor delivery and the volume of an order are considered as inputs and lead time is considered as an output of the proposed fuzzy system. Finally, lead time is estimated based on generating fuzzy rule bases and some linguistic rules, which are logical relationships between inputs and output. To establish the validation of the proposed approach, results of lead time obtained by the Monte Carlo simulation are compared with fuzzy lead times, both in 20 independent observations, each in 1000 simulation runs, using two-way analysis of variance (ANOVA). This statistical analysis also confirms the superiority of the pr...
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Heaters are one of the central parts of natural gas reduction stations using turboexpanders to prevent the formation of hydrate and corrosion failure. This study intends to design a fired heater by applying a combustion sub-model to... more
Heaters are one of the central parts of natural gas reduction stations using turboexpanders to prevent the formation of hydrate and corrosion failure. This study intends to design a fired heater by applying a combustion sub-model to derive an optimal model for this kind of application. This model is developed to accurately consider all subsections of the fired heater namely radiation, convection, and shield sections, as well as flue gas composition, and its volume. Within this context, a multi-objective optimization is employed to identify the optimal design of the gas-fired heater in the natural gas reduction station for the Ramin power plant case study. The total economic and environmental costs, together with modified exergy efficiency, are selected as objective functions. Multi-criteria-decision-making-method is employed on Pareto frontiers optimal curve to suggest the optimal solution. Results show that the developed model can outperform previous models in thermal efficiency wi...
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In this paper, the kinematic isotropy has been considered as the performance evaluation criterion for optimal design of robotic manipulators. The Global Isotropy Index or GII has been used as the measure of isotropy, which is based on the... more
In this paper, the kinematic isotropy has been considered as the performance evaluation criterion for optimal design of robotic manipulators. The Global Isotropy Index or GII has been used as the measure of isotropy, which is based on the robot’s behavior in its entire workspace. A “Genetic Algorithm” has been developed to solve the minimax optimization formulation of robot design in order to find the optimal design parameters such as link lengths of the best isotropic robot configurations at optimal working points of the end-effector. Later, the algorithm is implemented to optimize globally throughout the whole robot workspace. The method has been demonstrated for 2 DOF robotic manipulators.
Adaptive control of peak forces in milling with slender cutters is addressed. The dynamics of the milling process is modelled as a first order discrete system. A systematic design of adaptive PID and Pole-Placement controllers is... more
Adaptive control of peak forces in milling with slender cutters is addressed. The dynamics of the milling process is modelled as a first order discrete system. A systematic design of adaptive PID and Pole-Placement controllers is presented. The performances of the two controllers are compared using simulations and real time machining experiments. It is shown that when the time varying cutting process and time invariant feed drive transfer functions are accurately identified and decoupled, the adaptive controllers can be successfully applied to machining processes.
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Abstract This study attempts to provide an improved insight into the significant role of inherent coupling in the mechanical behavior of woven fabric composites. In particular, applying yarns tension to postpone the wrinkling defect has... more
Abstract This study attempts to provide an improved insight into the significant role of inherent coupling in the mechanical behavior of woven fabric composites. In particular, applying yarns tension to postpone the wrinkling defect has now become a common technique in industry during shear forming of fabric reinforcements. Yet, in-depth understanding of this coupling characteristics is rather limited. The article first distinguishes between the meso-level (inherent) coupling and the macro-level coupling expressed by the general Hook’s law. Then, specific types of inherent couplings are identified, including tension–tension, tension-shear, and shear-tension. A fixture capable of performing combined loadings was employed to characterize the coupling modes in a typical glass/polypropylene plain weave. Results revealed a highly dominant influence of tension-shear coupling on the effective mechanical properties of the fabric, followed by the tension-tension and shear-tension couplings. Discussions are made as to how these macro-level observations may be linked to underlying deformation mechanisms at lower material scales.
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If the point of application of an axial force on a column falls inside a certain area within the cross-section, only stresses of one sign arise on the cross-section. This area is called the kern of the cross-section. For regular... more
If the point of application of an axial force on a column falls inside a certain area within the cross-section, only stresses of one sign arise on the cross-section. This area is called the kern of the cross-section. For regular cross-sectional shapes, the dimensions of the kern can be determined analytically. In the case of irregular shapes graphical or computer techniques can be used. In this article the kern of an ellipse is analytically determined.
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Color parameters were used in this study to develop a machine learning model for predicting the mechanical properties of artificially weathered fir, alder, oak, and poplar wood. A CIELAB color measuring system was employed to study the... more
Color parameters were used in this study to develop a machine learning model for predicting the mechanical properties of artificially weathered fir, alder, oak, and poplar wood. A CIELAB color measuring system was employed to study the color changes in wood samples. The color parameters were fed into a decision tree model for predicting the MOE and MOR values of the wood samples. The results indicated a reduction in the mechanical properties of the samples, where fir and alder were the most and least degraded wood under weathering conditions, respectively. The mechanical degradation was correlated with the color change, where the most resistant wood to color change exhibited less reduction in the mechanical properties. The predictive machine learning model estimated the MOE and MOR values with a maximum R2 of 0.87 and 0.88, respectively. Thus, variations in the color parameters of wood can be considered informative features linked to the mechanical properties of small-sized and clea...
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Manual wheelchair propulsion (MWP) is an inefficient and physically straining process. A reliably fabricated and instrumented wheel can help researchers to accurately calculate the forces and moments exerted by the wheelchair users and... more
Manual wheelchair propulsion (MWP) is an inefficient and physically straining process. A reliably fabricated and instrumented wheel can help researchers to accurately calculate the forces and moments exerted by the wheelchair users and propose strategies to improve MWP. In this study, an instrumented wheel is designed, fabricated, and validated by using general uncertainty analysis. A six-component transducer is used to measure three-dimensional forces and moments applied by the wheelchair user on the handrim. The output of the transducer are forces and moments, which are directly transmitted to a PC using a USB port. By developing the transformation equations, the actual forces and moments on the hand of the wheelchair user are calculated. The angular position of the hand on the handrim is calculated from the kinetic data obtained through the instrumented wheel, and the derived equations. The general uncertainty analysis method is used to calculate the uncertainty values for the va...
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In this paper the use of a heart-tracking hand support is proposed to allow coronary artery bypass grafting surgery to take place on the beating heart. This method eliminates the tissue damage associated with the use of physical heart... more
In this paper the use of a heart-tracking hand support is proposed to allow coronary artery bypass grafting surgery to take place on the beating heart. This method eliminates the tissue damage associated with the use of physical heart stabilizers.
Research Interests:
Research Interests:
Research Interests:
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A new global isotropy index (GII) is proposed to quantify the configuration independent isotropy of a robot's Jacobian or mass matrix. A new discrete global optimization algorithm is also proposed to optimize either the GII or some... more
A new global isotropy index (GII) is proposed to quantify the configuration independent isotropy of a robot's Jacobian or mass matrix. A new discrete global optimization algorithm is also proposed to optimize either the GII or some local measure without placing any conditions on the objective function. The algorithm is used to establish design guidelines and a globally optimal architecture for a planar haptic interface from both a kinematic and dynamic perspective and to choose the optimum geometry for a 6-DOF Stewart Platform. The algorithm demonstrates consistent effort reductons of up to six orders of magnitude over global searching with low sensitivity to initial conditions.
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This paper presents a study of the stick-slip frictional phenomenon when large contact areas subjected to uneven contact loads, such as the rotating platform of excavators and large robotic manipulators, are involved. The objective of the... more
This paper presents a study of the stick-slip frictional phenomenon when large contact areas subjected to uneven contact loads, such as the rotating platform of excavators and large robotic manipulators, are involved. The objective of the investigation is to a gain better understanding of the phenomenon from experimental observations and to develop a mathematical representation that can be used for modeling, simulation and design purposes. A dynamic integral-model has been proposed and simulations have been carried out. The effects of various system parameters on the behavior of the system have been studied experimentally and analytically. The simulation results using the proposed integral-model are in good agreement with the experimental results. The latter also show that stick-slip vibrations can be influenced by the loading conditions.
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This paper proposes a technique to model uncertainties associated with linear time-invariant systems. It is assumed that the uncertainties are only due to parametric variations caused by independent uncertain variables. By assuming that a... more
This paper proposes a technique to model uncertainties associated with linear time-invariant systems. It is assumed that the uncertainties are only due to parametric variations caused by independent uncertain variables. By assuming that a set of a finite number of rational transfer functions of a fixed order is given, as well as the number of independent uncertain variables that affect the parametric uncertainties, the proposed technique seeks an optimal parametric uncertainty model as a function of uncertain variables that explains the set of transfer functions. Finding such an optimal parametric uncertainty model is formulated as a noncovex optimization problem, which is then solved by a combination of a linear matrix inequality and a nonlinear optimization technique. To find an initial condition for solving this nonconvex problem, the nonlinear principal component analysis based on the multidimensional principal curve is employed. The effectiveness of the proposed technique is ve...