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When two bodies slide on each other the asperities are engaged and friction is created. By superposing ultrasonic vibrations to one of the bodies, the friction force is reduced .This phenomenon is widely used in metal forming and metal cutting. In this research, experimental study of the effect of ultrasonic vibrations has been on sliding friction force in longitudinal direction. For this purpose, set-up was designed and fabricated. The main components of the set-up, including generators, transducers, first engaged body and second engaged body. The Set-up was installed on the machine lathe for investigation of the effect of ultrasonic vibrations on sliding friction force in longitudinal direction. The experiments were performed for eight different performance conditions. Next, the effect of each parameter ultrasonic wave velocity, roughness and material of contact surfaces were studied on the reduction of the friction force due to addition of ultrasonic vibrations. The result show that range of reduction friction force due to addition of ultrasonic vibrations in longitudinal direction is between 40 to 100% for the different performance conditions also friction force significantly reduced by increasing ultrasonic wave velocity so that friction force can be brought to zero by significant increase in ultrasonic wave velocity. The results also show that friction force has a more reduction for the surface has a less roughness. Aluminum-aluminum surfaces can be more reduction friction force from aluminum – steel surfaces.

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The aims of this research paper are modeling, control and development of a mobile micro-robot equipped with vibratory actuators and investigating the effect of stiffness of microrobot's bases as well as friction coefficient on the robot dynamics. Accordingly, the motion principle of stick-slip is used and two small vibrating motors are utilized to run this micro-robot. First, the differential equations governing the micro-robotic platform are extracted and analyzed. Then, friction forces are calculated by modeling the micro-robot as a lumped system, consisting of three point masses connected together via stiff springs. Next, using mechanical and electrical coupled equations, an appropriate model for the vibratory actuators is obtained. In the next step, simulation process with SIMULINK and MATLAB is carried out and the simulation results are presented. Afterward, the influences of the stiffness of robot's bases as well as the friction coefficient on the motion of robot are investigated. A proportional-integral-derivative (PID) controller is applied to the micro-robot to precisely control its motion. Finally, the construction process and experimental evaluation of the micro-robot are presented. According to the simulation result, the positioning accuracy of the micro robot is about 17 m at its maximum translational velocity. Furthermore, a translational velocity of about 4mm/s corresponding to the reference voltage of 1 V is acquired using experiment.