rasul fesharakifard

In recent years, the navigation of mobile robots has been of great interest. One of the important challenges in the navigation of mobile robots is the obstacle avoidance problem so that the robots do not collide with each other and obstacles, during their movement. Hence, for good navigation, a reliable obstacle avoidance methodology is needed. On the other hand, some of the other most important challenges in robot control are in the field of motion planning. The main goal of motion planning is to compile (interpret) high-level languages into a series of primary low-level movements. In this paper, a novel online sensor-based motion planning algorithm that employs the Adaptive Neuro-Fuzzy Inference  System (ANFIS) controller is proposed. Also, this algorithm is able to distance the robots from the obstacles (i.e. it  provides a solution to the obstacle avoidance problem). In the proposed motion planning algorithm, three distances (i.e. the distance of the robot from the obstacles in three directions: right, left, and front) have been used to prioritize the goal search behavior and obstacle avoidance behavior and to determine the appropriate angle of rotation. Then, for  determining the linear velocity, the nearest distance from obstacles and distance from the goal have been used. Theproposed motion planning algorithm has been implemented in the gazebo simulator (by using Turtlebot) and its performance has been evaluated. Finally, to improve the performance of the proposed motion planning algorithm, We have used type-1, interval type-2, and interval type-3 fuzzy sets, then, we have evaluated and compared the efficiency of the proposed algorithm for each of these fuzzy sets under specific criteria.

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.

Quadrotors provide exclusive performances like vertical landing and taking off, load carrying capacity, and possibility of remote control. A pertinent deficiency of them however concerns their underactuated configuration, which is one of the inherent characteristics of these robots. A dependency between different movements of quadrotor is unavoidable due to this characteristic. To eliminate the dependencies between linear and rotational motions and so increase the number of controllable degrees of freedom, a novel configuration has been presented for the fully-actuated quadrotor. The rotors have the ability to rotate around two perpendicular directions and two degrees of freedom have been added to the system. The motion dependencies between linear and angular degrees are omitted. To investigate the capability of the fully-actuated quadrotor, the novel configuration is introduced and the capabilities of this configuration in eliminating movement dependencies are discussed. To this end, after extracting the motion equations governing the fully-actuated quadrotor using Newton-Euler method and applying a proportional-derivative controller to the model, the performance of this configuration in eliminating the motion dependencies is compared against a conventional underactuated type. It is shown that this configuration is capable of eliminating motion dependencies to a great extent within various simulation results. Finally, by designing a back-stepping controller and applying different trajectories to the proposed fully-actuated quadrotor, its motion capabilities and limitations are thoroughly investigated.

Bottom-up stereolithography is included among the additive manufacturing methods, which gives many advantages over top-down stereolithography. The major advantages are related to better fabrication resolution, higher material feed-rate, shorter production time and less material waste. During this process, a separation force is generated as a solidified layer separates from the base of resin container. This force leads to product delamination which in turn stimulates the product failure. An efficient solution to this problem is achieved by studying the interaction force on the specimen contact zone. The approach proposed in this study is based on experimental measurements of the force exerted during the process. Different parameters regarding process characteristics are varied in several tests and a comprehensive analysis is conducted to correspond test condition to the resulting separation force. The significant parameters are process speed, cross-section area, the complexity of geometry and orientation of solidification. For some different cases, the separation force varies between 3 and 36N, and the highest difference between the simulated and experimental results remains beyond 5%. It is observed that higher velocity, larger cross-section area or more part geometry complexity increase the separation force. Another novelty concerns the study of the producing orientation on the separation force. Related experimentation is performed to determine the effect of cross-sectional and geometrical complexity. This article finally gives some preliminary propositions for the part design.

Training is usually carried out throughout traditional methods which impose enormous costs. Virtual reality is one of the most suitable methods that has been presented in this application and improves many of the weak points of traditional training such as high cost of welding. Previous studies were conducted on virtual welding with the use of virtual reality techniques in welding training. The novelty of this article is that uses Kinect for tracking and Adaptive meshing for thermal analysis. The dimension of workpiece is 70x50x10 and the material is low carbon steel. The user performs real-time welding in the virtual environment by moving the electrode clamp. Since process parameters like current, hand motion speed, arc length, and welding voltage make changes in generated heat, and color of molten-solid zone, a graphic interface updates the color in each part of the model. The process is modeled in two different ways of fixed and adaptive mesh finite element approaches which manifests good precision and calculation of speed, respectively. All calculations in the simulation environment and the thermal analysis engine performed in the C# program. One of the positive features of the simulator is self-learning. A novice welder could take enough time to learn the manual arc welding simulator without any extra cost or danger. This simulator provides a good training ability to control the welding parameters.

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 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.