International Journal of Advanced Design and Manufacturing Technology
Volume:15 Issue: 4, Dec 2022

Researchers have a special fondness for continuum robots (CRs) due to their various applications. CRs have been modeled in different ways. One of these methods is called lumped model. Although the lumped modeling of CRs needs multiple degrees of freedom, researchers have considered only a few degrees of freedom. But considering such structures led to some issues in the accuracy of the controller. Therefore, in this paper, the dynamic modeling of a CR which is based on the lumped model is developed in a general form. Additionally, a control strategy based on sliding mode back-stepping control is proposed after introducing the first and second Lyapunov functions for stability proof. Moreover, a new function in the control law is used to avoid chattering phenomena. The proposed controller can reduce the settling time, which is one of the most important factors in controlling such robots. To demonstrate the efficiency of the proposed method, three different case studies are conducted for a planar 8-DOF continuum manipulator and the simulations are compared with the feedback linearization method (FL). The simulations show the effectiveness of the proposed method for controlling the continuum robot.

In this paper, the rigid four-bar linkage with clearance joint has been examined. The effects of design parameters have been analyzed separately. Considering chaotic behaviour and undesirable vibrations of the system induced by joint clearance, it has been suggested to use compliant joints for improving these undesirable behaviours. Therefore, rigid four-bar linkage with clearance joint and compliant joint is investigated by pseudo-rigid-body model. Subsequently, the nonlinear behaviour of the compliant mechanism is examined, using fast Fourier transform analysis, Poincare sections, and bifurcation diagram. Comparative analysis of results clearly shows that using appropriate compliant joints causes notable improvements in the behaviour of the system, reduction of sudden impacts, and lower accelerations. 6 cycles simulations of mechanisms demonstrate the decreasing 207 impacts to 33 impacts using compliant joint. Moreover, the results report 87% decrease in follower top acceleration and 64% in clearance joint top contact force. Although using the compliant joint makes limitations in the workspace, but the appropriate and optimized design of the compliant joint results in good improvement in the performance of the system.

In the present study, novel channel geometries in a wavy channel heat sink (HS) are investigated using ANSYS-FLUENT software. The Ag/water-ethylene glycol (50%) nanofluid is selected for cooling the CPU in this HS. The second-order upwind method is employed to discretize the momentum Equation and the SIMPLEC algorithm is employed for coupling velocity and pressure fields. Comparison of the two HSs with and without microtube shows that the presence of the microtube increases the uniformity of the CPU surface temperature distribution and decreases the mean surface temperature of the CPU (TCPU-Mean). However, the pumping power consumption of the system increases about 10 times. The results also demonstrate that the addition of nanoparticles results in intensification in the Performance Evaluation Criterion (PEC) of the system and up to 30%, especially at high Reynolds numbers.

Sheet metal forming is widely used in automotive and aerospace industry. In this paper analysis of sheet metal forming process by deep drawing was discussed. Static analysis on the deep drawing operation was carried out to find the stresses, strains and total deformation of deep drawing cup. CAD models are generated using CATIA from the dimensions obtained by theoretical calculations and analysis is carried out using ANSYS software. The force required to develop the cup, deformation and defect like tearing, wrinkles etc. can be obtained through simulation. By using this method it is easy to make stress and strain analysis for different materials. From the analysis, it is observed that Titanium has the maximum stress with standing ability when compared to copper and Aluminum.

In his research article, several models of heatsink were optimally designed in fin length, width and height along with pin placement which consists of 4 pin fin heatsink models heatsink (including square with different pin angles, circular, truncated cone, and cone pin heatsinks and one model of the plate-fin heatsink (PFHS)) in order to achieve better thermal performance as well as less energy consumption and were numerically investigated under high air velocity and heat fluxes. Different parameters such as peak temperature, Nusselt number, heat resistance, pressure drop, and energy consumption were compared. The results show that the square PPFHS with the pin angle of 45 degrees has the highest thermal performance compared to the rest of the models while also having the highest pressure drop and energy consumption between the models consuming more than 255 and 358 percent more energy in order to have the same air velocity in the pathway, while the truncated and the fully formed cone model despite having 25% and 30% less thermal performance, have the least pressure drop between the pin models of the heatsinks and therefore consume the least energy out of the PPFHS.

The roll forming process plays a critical role in producing various sections used in industries. Also, the quality of these products is strongly affected by the thickness of the strip, the distance between stands, the section web, the flower pattern, and the plastic anisotropy. Therefore, the influences of practical factors on the bowing defect of the symmetrical U-section are experimentally and mathematically characterized in the present research. The investigated material is DC03 (1.0347) steel. Different prediction models such as linear and non-linear model based on the general full-factorial design of experiment are used to predict the effect of following factors on the bowing defect. Accuracy of the analytical model was verified by comparing the output results with the practical data. Results show that the strip thickness of investigated material, the flower pattern, and the section web have the most significant effect on the bowing defect. Also, the anisotropic properties of the investigated material and the inter distance have the minor impact on the bowing defect, but the effect of material with considering the anisotropic properties on increasing the accuracy of process simulation results is very impressive and increases the accuracy of simulation results from 84% to 91%. Finally, the predicted bowing defect using the modified two-factor model was in 91% agreement with the experimental results.

In the present study, the response surface methodology is used to predict the bubble departure frequency of pure liquids using experimental data. Water, ethanol and methanol pure liquids were used as the testing fluid. The effects of vapor and liquid density difference, vapor and liquid viscosity, surface tension, thermal conductivity, heat flux on the vapor bubbles departure frequency on the heat transfer of boiling pool of pure liquids were investigated by response surface methodology. The results showed that the output of the Response surface methodology had a good overlap with the data of bubbles departure frequency of pure liquids. Also, the results for the bubble departure frequency show a good overlap between the models presented by the researchers and the experimental data and have good accuracy. In this research, a new model for the prediction of vapor bubble departure frequency, based on the Buckingham theory, in nucleate boiling is proposed, which predicts the experimental data with a satisfactory accuracy (9%).

The two factors of track irregularity and train speed affect the dynamic behavior of rail vehicles and can lead to an increase in dynamic forces, a decrease in ride comfort, and derailment in some cases. In this paper, the effect of train speed increase and different conditions of track irregularity on ride comfort and ride quality are investigated. For this purpose, first, two freight and passenger train models have been modeled in UM software, and then the effect of train speed increase and track irregularities (different US federal classes) have been studied with Sperling’s index. A freight train with the model of 18-100 and 3-piece bogie and a TGV high-speed train with 10 wagons were simulated. The results showed that in Sperling’s index, with the increase in the train speed and irregularity amplitude, the value of ride comfort and ride quality generally increased. For example, in the passenger train and irregularity classes 5 and 4, with the increase in train speed from 10 to 100 m/s, the Sperling’s index values changed from 0.66 to 1.99 and from 0.78 to 2.25, and increased 200% and 188%, respectively. In other words, at a speed of 10 m/s, passengers' comfort is just noticeable, while at a speed of 100 m/s and class 4, the situation is more pronounced but not unpleasant and the system should be monitored.

The length values selection for a determined type of linkage to achieve the necessary task, dimensional synthesis, is classified into three classes based on the mechanism’s task: function generation, path generation, and motion generation. The case considered in this study, Function generation synthesis, aims to create a relation between the angular motions of the input and output links of the mechanism. For this problem, a semi-analytical method called the Newton-HCM is used for numerical solutions, which combines Newton’s method with the semi-analytical Homotopy Continuation Method (HCM). Function generation synthesis of a planar four-bar linkage for four and five precision points is the main challenge of the current study, which is highly nonlinear and complicated to solve. Numerical examples of the function generation problem for a four-bar linkage with four and five precision points are presented and authenticate the excellent performance of the proposed algorithm.

In this study, a couple of 3PRR parallel robot is used for the rehabilitation process of a patient to eliminate a walking disability and leads to his treatment. The 3PRR robot has three degrees of freedom, provided by three prismatic actuators. Also using a couple of them, can quickly rehabilitate and provide the rehabilitation movements of a patient in the walking process. In this study, the extraction of kinematic and dynamic Equations of the robot was investigated, and a fuzzy-logic-based controller is performed. This controller has the ability to repel unwanted disturbances to follow the desired path. All modelling was simulated by MATLAB software. The simulation results show that using the mathematical model and controller, it is easy to go any desired path in the workspace; and this controller will be able to repel environmental disturbances like the sudden movement of patients.

The mesh generation process as a time-consuming and computational effort in the numerical methods always has been paid attention to by researchers to provide more accurate and fast methods. In this study, an accurate, fast, and user-friendly method of mesh generation has been developed by combining the image processing method with Computational Fluid Dynamics (CFD). For this purpose, a turbulent flow around a single square as a bluff body is simulated by homemade code using MATLAB software as a test case to illustrate the mentioned method. The conservative Equations have been discretized using the finite volume method based on the Power-la scheme. Utilizing useful filters on the imported gray-scale digital image provides edge detection of the obstacle in the computational domain. After the edge detection step, an orthogonal, structured, and staggered mesh is generated.

Fused Deposition Modeling and Sintering (FDMS) is one of the indirect and emerging processes of Additive Manufacturing (AM) for the production of metal parts, which is a combination of AM process and Metal Injection Molding (MIM). This study laboratory made a raw material (Feed Stock) composing of high percentage of metal powder (particle in nano-scale) and polymeric materials; and then, designed an extruder to simulate melting and extruding process by Computational Fluid Dynamic (CFD). The different variables such as the nozzle diameter (D) of 1, 2, 3 and 4 mm and compression zone length (L2) of 100, 200 and 300 mm were simulated to investigate their impacts on flow rate and required torque to rotate screw. The findings showed that components of feed stock for high physical and mechanical properties of FDMS should account for 55 wt.% of paraffin wax, 25 wt.% of polypropylene, 15 wt.% of carnauba wax and 5 wt.% of stearic acid with optimum percentage of metal powder of 90 wt.%. Also, the optimum value of extruder diameter and compression zone length were 2mm and 200 mm, respectively.