رسول فشارکی فرد

In this paper, the error of tool deflection in perpendicular to a milling process feed direction is investigated and novel compensation method to this error is proposed. While the end mill tool is machining, due to the existence of perpendicular disturbing force on the feed path while the endmill tool is machining, a deflection which reduces machining accuracy. If a compensation force is exerted to the middle of tool, the deflection can be reduced. By using a hydraulic actuator, the compensation force would be proportional to the disturbing machining force, in the opposite direction so that this error can be reduced. It is necessary to estimate disturbing forces and tool deflection magnitude in lateral side of machining precisely before applying the proportional force to the endmill. The first step endmill is modeled on SolidWorks and in the next step The machining operation is simulated to calculate the error causing force in which both the milling tool and the workpiece are 3D flexible. By obtaining the force results of the tool under different machining modes from Abaqus, a semi -analytical model is established on Simscape Multibody module of matlab software. By comparing Abaqus results the parameters of the lumped model are adjusted. The output force is extracted from Abaqus and put in tabular form the tool deflection is extracted from MATLAB SimScape which calculation speed is faster than the numerical model in this method. To find the compensating force, the beam theory obtains a factor of 3.2 times the machining force applied to the middle of the tool. This force is applied in open loop to the MATLAB model and the result indicates almost 70 percent reduction in the tool tip lateral deflection.

Choosing the right equipment in terms of price, performance and reliability, is one of the main challenges in the automation industry. Among these equipments, electric motors are the most important elements which are widely used in the industries. Electro motors selection is made according to certain rules and principles, and it is very important to know the governing conditions. Using amotor with less power than required will lead to system failure and a motor with much more power will result in extra costs. In this article, scientific selection of an electric motor for the bending process in an automation system has been discussed. Using real conditions of a manufacturer and available data in articles and books, the necessary relationships were extracted .28 number of motors (among the available ones) were nominated in the first stage of preliminary monitoring. Then, by applying other prevailing conditions and characteristics, 3 motors with different powers selected for final investigations. Eventually, after using Simscape simulations & exerting less energy consumption criteria, the 5RK90GE-CW2ML2 motor (manufactured by Oriental Motor Company) was selected and was approved after satisfying the power, quality and safety conditions.

Nowadays, the need of welding industry's to improve weld quality has led to the consideration of robotic welding. The use of articulated industrial robots for welding has many challenges. Because some robots do not have the capability of online error compensating of the seam track. Therefore, in order to remove the welding seam tracking error, the use of an auxiliary mechanism is proposed in this article. This mechanism is a table with 1-degree of freedom (dof), which produces a continuous motion in workpiece under the welding torch. The rotational motion of the motor is transformed into a translational motion of the workpiece by a ball-screw system, where this linear motion compensates the tracking error. Since in the welding process, relative motion accuracy of the workpiece and the welding torch is crucial, proper control of the interface table ensures the weld quality. In this paper, two different methods for controlling the table with 1-dof are studied. In the first method, due to the complexity of friction model of the ball-screw mechanism and the presence of nonlinear terms, this part of the model is considered as an external disturbance, and, then, a PID controller for the linear part is designed. In the second method, known as feedback linearization, a control law is designed for that the tracking error tends to zero by passing time. Throught a comparison between the simulation results, the second control method demonstrates better precision relating the first controller. While the error of PID controller equals to 3 mm and the second controller’s error does not go beyond 0.5 mm. At last, the experimental cell used for the robotic welding is introduced to evaluate the mentioned results.

This paper focuses on the dynamic modeling of quadrotor with respect to changes in operating conditions. The main objective of this investigation is to provide complete governing quadrotor dynamic equations using the Euler-Lagrange method considering all aerodynamic forces which affect it's motion. In previous papers, dynamical equations are never considered comprehensively. The study of quadrotor's dynamics permits to understand it's physics and behavior and provides a precise model of the system. Once such a model is obtained, the control of quadrotor turns much simpler than current inaccurate models. In order to take into account, the set of forces and torques involved in quadrotor dynamics, the previous studies are used and after describing each of the forces and their precise terms, the complete dynamic quadrature model is presented. At the end, the system's performance is simulated in two different operating conditions, one regardless of the external object coupled with quadrotor, and the other in the coupled condition with a camera, and by this means, the achieved dynamic model is validated. In the first operating conditions in two different tests, the dynamic equations of the present work will be compared against the previous ones. In the second operating conditions, the quadrotor performance under influence of a connected camera whose motion changes continuously the system dynamic equations is studied.

In this article, thermal analysis of sheet metals during arc welding is studied by an adaptive finite element method to construct a welding process simulator. This simulator can be developed to reduce the cost of weld training. By increasing the calculation speed of heat transfer in comparison with the usual methods, this approach analyzes the process in real-time and permits the development of the simulator. So, it can be used as the main calculation engine of a welding simulator. The most crucial parameter in evaluation of real-time analysis is the calculation accuracy. Hence an adaptive mesh method based on H-refinement is applied and the heat transfer is analyzed by both constant and adaptive mesh methods. First, the heat transfer equations will be derived and solved, then the stiffness and capacity matrix and the other parameters will be obtained. The linear 3D tetrahedral elements are used and considered by means of 3 dimensional cartesian coordinates. The heat flux of the arc is studied through Pavelic model. The parameters of interest in the equations are welding voltage, current, speed and sheet specifications which are time dependant. A comparison between the calculation times and accuracy of the results demonstrates that an adequate calculation speed is achieved without any considerable effect on the accuracy.

In electromagnetic motors, increase in output torque leads to increase in rotor inertia. Various robotics applications, especially haptic interfaces, oblige convenient dynamic performances of electromagnetic motors which are strongly in turn influenced by the rotor’s inertia. In the present paper, a robust control method for a viscous hybrid actuator is developed which supplies a desired varying torque while maintaining a constant low inertia. This hybrid actuator includes two dc motors with the shafts coupled through a rotational damper using a viscous non-contact coupler. This coupling method is based on Eddy current to provide the required performances. The large far motor eliminates or reduces the inertial forces and external dynamics effects on the actuator. The small near motor provides the desired output torque. Since the system is essentially linear, the applied robust control method is based on Hꝏ and parametric uncertainties and physical constraints including motors’ voltages saturation, rotary damper’s speed saturation, fastest user’s speed and acceleration applied to the actuator and force sensor noise are considered in its design. Also the robust method of µ-synthesis for the system in presence of parameteric uncertainties and other physical constraints are studied. The implementation of the controller on a 1 dof haptic interface model validate the achievement of the desired performances.