| In recent years, with the development of automobile industry, electronics industry, aeronautics and astronautics industry and some new high-tech industries, higher and higher requirements are made for quality and efficiency in machining die and mould with free-curved surfaces. And the requirements on the die and mould technology for high quality,high efficiency and low cost have been the focus of the manufacture. But at present, processes of precision machining die and mould with free-curved surface still depends mainly on the handwork of skilled workman. Because the handwork is low efficiency and unstably machining quality, it is difficult to adapt with requirements of free-curved surfaces for low cost,short period and high quality. So guaranteeing the precision of processes of precision machining die and mould with free-curved surface, we must accelerative develop advanced technology and the equipment on mold with free-curved surface of the automatically polished precision machining. Enhancing its efficiency already is imperative. This article breaks the fetter and limit between the traditional numerical control lathe and the industry robot, proposes the brand-new technical mentality, and realizes with the small equipment charring on the processing to the large-scale free curved surface goal. Micro-polishing-robot that is orientated by free curved surface realizes processing to the large-scale free curved surface.Because polishing-robot has specific function cell, the idea of modularization design is used. The different modules are designed by function requirement and various modules are achieved as an organic whole through the chassis. This robot is mainly composed of the main body organization, the walking organization, the polishing machining system and the electromagnetism cupule. The whole picture can be seen from figure 1. The walking organization of micro-polishing-robot adopts the tricycle structure, among them the front is an orientation wheel, and two rears are traditional wheels. Driving system of the robot car uses two direct current machines actuating separately two fast pulleys through the transmitting gear. Therefore its movement form is differential movement way. The different movement motion of the car is realized through different rotational speed of right and left wheels.This text has designed and developed the polishing machining system, which is made up of the polishing organization and the adjustment organization of polishing tool (the swinging organization). The three-dimensional modeling of every part made by CATIA software is virtually assembled and then the machining system is made to interfere examining. So the designed machining system is rational.Polishing way is one kind of constant pressure polishing processing method. The curved surface normal force (polishing pressure) is difficult to control and most important in these factors influencing polishing quality. For this reason the polishing pressure model of the micro-polishing-robot is set up: Setting up the kinematics model of the polishing machining system, as shown in fig. 2. Fig. 2 the kinematical structure picture of the polishing machining systemTherefore obtaining the kinematics mathematics expression formula of the machining system:According to the rotational pace of the driving wheel, we can get the movement pace of the polishing machining system, utilizing the relational expression. At the same time due to the swinging situation of the machining system, the pace and the location-stance situation of the tool can be understudied. Due to the motorial state of machining system, the rotational speed that electrical machinery should have can be get utilizing the contrary motion relational expression.In order to prove the kinematics the polishing machining system of micro-polishing-robot, it is carried on the computer simulation experiment by MATLAB. Fig. 3 showed movement simulation path curve of executive body of the robot. Fig. 4 provided the robot of left and right driving gear speed change process simulation result in the rate process. From the artificial result, we fund out the changes of two drive wheels of paces when the executive body walked according to the artificial kinematical orbit. The robot according to assigned the path to walk was realized through controlling the two driving gears speeds .Simultaneously the orientation angle of robot was change too. Fig. 3 The kinematical simulation picture Fig. 4 curve graph of driving wheelAccording to fig.5 the dynamic equation of polishing installment is: mz + cz+kz=F (3)Then the duplicate frequency response function oscillation amplitude of polishing installment is:We could know through the formula (4) that increasing k value could reduce H (ω) value, namely increasing the coefficient of elasticity of the spring is advantageous for the increasing system stability.In the polishing course the information of curved surface is very important. So the track of the curved surface and the polishing angle are researched. In the machining course the phenomenon of interfering emergence is prevented from. When keeping the polishing angle identical, the polishing pressure is kept immovably and the better surface quality is obtained, commonly gettingθfrom 5 o to 30o.Controlling system of micro-polishing-robot mainly was composed of machine upside, communication module and machine underside. The servo pneumatic system was composed of the air cylinder, pressure proportion valve, pressure transducer, unite one (divide water and strain angry device, relief pressure valve, oil fog device), Two electromagnetic valves of three direct links and silencers. Adopting the pressure proportion regulator was used as controlling regulator of the servo pneumatic system, the air cylinder as the carrying out component. Fig. 4 was the return circuit structure chart of the atmospheric pressure. Studying the mathematical model of the servo system, making simplify further to pneumatic servo model of controlling system, getting transmission function of controlling pneumatic servo system. |
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