International Journal of Advanced Design and Manufacturing Technology
Volume:14 Issue: 1, Mar 2021

In this paper, a new robotic gripper is proposed and modeled which is able to bear a high amount of load and it can be used as the claws of climbing robots. As the climbing robots are usually heavy and their configuration should be kept in height against the gravity, firm grippers with no slippage possibility should be designed in order to guarantee the stability. The proposed new gripper is essentially required for the grip-based climbing robots which are heavy and are supposed to accomplish a specific operational task while they are grasping the pipe-shaped structures. The kinematic and quasi-static modeling of the proposed gripper is extracted and its related parameters are optimized to provide the maximum gripping force and the minimum slippage probability. Since these robust grippers are usually actuated by high torque motors, the reaction effect of the actuators force on the arm of the robot model is investigated here as a new study. Hence, the corresponding mechanical arm is also controlled, using a robust nonlinear controller to neutralize the destructive effect of extreme reaction forces or torques from the gripper motors to the robot arm during its mission. Thus, a robust controller is designed and implemented on the arm joint to cover the required positioning accuracy of the arm movement during the climbing motion. Afterward, the applicability of the proposed gripper and also the efficiency of the designed controller is verified by the aid of some analytic and comparative simulation scenarios performed in MATLAB-SIMULINK and MSC-ADAMS simulation. It is shown that the proposed gripper together with its related controlling algorithm for the arm can successfully provide a proper climbing mechanism for these kinds of robots which are supposed to climb through the structures and perform a special manipulating task.

The Electro-discharge coating process is an efficient method for improvement of the surface quality of the parts used in molds. In this process, Material Transfer Rate (MTR), an average Layer Thickness (LT) are important factors, and tuning the input process parameters to obtain the desired value of them is a crucial issue. Due to the wide range of the input parameters and nonlinearity of this system, the establishment of a mathematical model is a complicated mathematical problem. Although many efforts have been made to model this process, research is still ongoing to improve the modeling of this process. To this end, in the present study, three powerful machine learning algorithms, namely, Relevance Vector Machine (RVM), Extreme Learning Machine (ELM) and the Least Squares Support Vector Machine (LS-SVM) that have not been used to model this process, have been used. The values R2 above 0.99 for the training data and above 0.97 for the test data show the high accuracy and generalization capability degree related to the LS-SVM models, which can be applied for the input parameters tuning in order to attain a preferred value of the outputs.

The equilibrium position of a deformable bubble in a combined Couette-Poiseuille flow is investigated numerically by solving the full Navier-Stokes equations using a finite-difference/front-tracking method. The present approach is examined to predict the migration of a bubble in a combined Couette-Poiseuille flow at finite Reynolds numbers of 5, 10, and 15. The related unsteady incompressible full Navier-Stokes equations are solved using a conventional finite-difference method with a structured staggered grid. The purpose of this study is to evaluate ANN and ANFIS methods in study of the lateral migration of the bubble. Evaluation criteria of accuracy in test set derived from ANFIS demonstrates that estimated values of correlation coefficient (r), Mean Absolute Error (MAE), and Root Mean Square Error (RMSE) are 0.97, 0.001, and 0.0014, respectively. The ANN model with RMSE of 0.0007, MAE of 0.0004 and r of 0.99, is better than ANFIS model. It is also demonstrated that the bubble position estimated by the ANN and ANFIS models closely follows the one achieved from front tracking method.

In this study, hole-flanging of a dual-phase steel sheet is conducted using incremental forming approach. In this process, a hole with a certain diameter is pre-cut on a sheet. Then, this hole is transformed into a cylindrical flange shapes, by contacting the forming tool with the hole edges. During the process, the tool is moved in spiral paths. The parameters affecting the height and thickness distribution of the formed flange include axial step, radial step, and rotational speed of the tool. Results show that the axial step has the most significant effect on the process, among other parameters; when the axial step is tripled, the flange thickness increases by 19%. On the other hand, a decrease in the radial step decreases the flange edge thickness. When the radial step is tripled, the flange thickness increases by 8%, while the flange height decreases about 3%.

The purpose of this research is to construct and investigate the stability of the ball and beam control system with PID coefficients derived from the simulation and compare them. In this research, by first obtaining the mathematical model of the mechanical system and its simulation, the best PID coefficients are selected for it to minimize the settling time and the error. Then, to create this system, the types of mechanisms provided for the ball and beam control system are examined. Depending on the equipment and facilities available, the best design is chosen and built. The best design is the use of the four_bar mechanism using the servo motor and the ultrasonic sensor. The appropriate design is first developed in SolidWorks software to provide accurate measurements for the production of components. Laser cutting and 3D printers are used to produce system components. After the control system is built, the simulation coefficients in the MATLAB software are inserted into the system microcontroller program to check the system responses to the various control coefficients obtained. So doing multiple experiments indicated that the best PID coefficients for this system are PD coefficient. The difference between the experimental graph and the simulation graph is their overshoot. They also have different settling times. One of the reasons for this difference is the use of some approximations as well as disregarding friction.

In this paper, the problems arising from determining the modal properties of large and complex structures are investigated. For this purpose, the free interface component mode synthesis method has been used. In the following, Singular-Value Decomposition (SVD) is applied as a powerful mathematical tool to determine the appropriate coordinates to participate in the coupling process. Also, the effective error resources including modal shear error and the continuous systems overlapping error and their solution are introduced. Initially, a discrete system has been employed to investigate the free interface component mode synthesis method. Eventually, the studied main samples in this research are beam, plate and cylindrical shell. It is worth noting that the application of this method on the cylindrical shell has not been observed in previous researches.

In this paper, the effect of pre-stress condition on the resonance frequency of the transducer is studied by using numerical and analytical methods. To compare the obtained results, two sandwich-type transducers with nominal frequency of 25 kHz and 30 kHz are considered. Experimental determination of pre-stress value in transducer is described and measured. Then resonance frequency of transducers in the presence of pre-stress is determined by impedance analyser. Numerical analysis is conducted by modelling three-dimensional transducer in details at ABAQUS software. The resonance frequency is determined with and without pre-stress. The FE results show that by applying pre-stress on the transducers, the resonance frequency of transducers decreased. Furthermore, the FE results are very close to experimental results. Furthermore, a systematic analytical solution is presented based on one-dimensional wave propagation. The resultant displacement for each sub-section of the transducer is calculated and then all of them are assembled and solved by considering the continuity conditions of displacement and force components. It is found that pre-load condition that is produced by central bolt reduces resonance frequency of the transducer. The obtained analytical results provide fast and reliable model for predicting resonance frequency of transducer.

The bicycle helmet has a significant role in reducing and preventing impact because of reducing the deceleration of the skull, spreading the area over which the forces of the impact reach them and preventing direct contact between the skull and the impacting object. Honeycomb structure, due to its elastic properties, extends the energy absorption time of the whole structure and also increases the ability of the whole structure to absorb energy. Therefore, it can be used in the liner designing of a helmet to reduce velocity, energy, and acceleration in impacts. In this paper, intending to identify the minimum stress transmitted to the helmet during an impact, we used Rhino software to model a helmet with honeycomb liner and outer shell and then analyzed it in Abaqus software. Due to the fact that the size of various parts of the head is different in people, so for more comfort and safety, the use of customized-helmet is emphasized. To design and make a customized-helmet, the materials used in designing the helmet are ABS and PETg filaments, which can be used in 3D printing. These two materials have been analyzed with four compositions for the liner and the shell of the helmet. The results show that the best combination of the helmet with Minimum stress transmission and appropriate plastic strain due to impact is the helmet case with honeycomb liner of PETg and a shell made of ABS.

In this paper, vibrations reduction of piston engine of ultralight aircrafts was studied with considering a combination of experimental, analytical and numerical methods. Analytical equations of dynamic absorber were obtained. Afterward, experimental test was used to determine the system torque. Due to the difficulty of obtaining experimental data, the amount of angular acceleration and then velocity and angular displacement were calculated numerically using MATLAB software and verified with experimental results with a difference of less than 2%. Different components of the system were designed with reverse engineering method using SolidWorks software. After data transmission to Adams software, vibrational analysis of the system was performed and validated with analytical results with a difference of less than 1.91%. A suitable dynamic absorber was selected. The results showed that engine vibrations is reduced up to 40%.

This article investigates the buckling behavior of orthotropic annular/circular bilayer graphene sheet embedded in Winkler–Pasternak elastic medium under mechanical loading. Using the nonlocal elasticity theory, the bilayer graphene sheet is modeled as a nonlocal orthotropic plate which contains small scale effect and van der Waals interaction forces. Differential Quadrature Method (DQM) is employed to solve the governing equations for various combinations of simply supported or clamped boundary conditions. The results show that small scale parameter does not have any effect on critical buckling load of cases without elastic medium in simply supported boundary condition. Also, increase of vdW coefficient leads to increase of critical buckling load smoothly then it has no impact on critical buckling load after a certain value.

The paper studied the analysis of vibrations of rectangular carbon nanotube-reinforced composite plates. To this end, a three-layer nanocomposite plate - two layers with the targeted distribution of carbon nanotubes as FG-X at the top and bottom and a layer without an amplifier in the middle of the plate - were analyzed. The governing equations for this problem are based on First-order Shear Deformation Theory (FSDT). The distribution of nanotubes on these plates is as targeted FG-X. The effect of various types of SWCNTs distributions in the direction of thickness on the vibrational behavior of nanocomposite plates was examined. The effective properties of nanocomposite materials Functionally Graded Carbon Nanotube-Reinforced Composite (FG-CNTRC) were estimated using the rule of mixtures. Detailed parametric studies were performed to determine the effects of the volume fraction of carbon nanotubes and the thickness-to-length ratio of the plate on the natural frequency responses and the shape of the plate mode. The equations obtained in this problem were coded in MATLAB software, the nanocomposite plate was modelled in ABAQUS software, and the comparison of the results obtained from the numerical solution with ABAQUS software showed relatively right consistency with the results obtained from the analytical solution.