Research On System Of The Grinding Tools Based On Compliant Control

1.IntroductionThe grinding and finish machining on free-form Surface needs many processes using the grinding tools system. It needs the identification and modeling to the machining process, and also needs to ensure and control the movement and location of the grinding tools system in machining process, also needs to control the contact state and contact force between the grinding tools system(grinding cutting tools) and rigidity environment(workpiece surface).Compliant control of grinding system is a general technology, which is in the process of theory research and on the way of technology realizing, so it becomes the bottle-neck of grinding and finish machining on the free-form surface. The free-form grinding and finish machining is blank in our country by the way of compliant grinding technology of force\location isomorphism combined NC. So, the paper realizes the function of series-parallel connection machine tools making use of the manufacturing entity composed of the grinding compliant control entity and NC. The design characteristics and control strategies of series-parallel connection machine tools are considered, and moreover, many factors are considered including the advancement of compliant control technology and the realization cost.2. The design of grinding tools systemThrough the analysis of the work theory and framework characteristics of series-parallel connection machine, the paper builds the entity model of every components of grinding tools system by means of UG(Unigraphics).Moreover, the paper builds macro model of two-degree of freedom by means of UG assembly function.The framework entity document is put out in the format of parasolid after UG finishs, and is saved by the correct format while putting in ADAMS. Then the virtual grinding sample machine is builded adding to restriction and load. Finally the performance and the feasibility are tested in order to make sure how to operate in next step.3. The transfer function solution of grinding tool systemThe orthogonal of force and location is used in the paper, that is to say force does not affect the location and force space is one-dimension vector that the experimental force is single-dimension.The single-dimension force, which is X direction notified in the figure , is controlled. The transfer function in the grinding terminal performer needed to be solved only.(1).The transfer function establishment of grinding tools systemThe functions in every direction of grinding terminal performer is listed as follows.m,c,k denotes equivalent quality,equivalent damping,equivalent stiffness.After a series of resolution, the transfer function of grinding tools system is:(2). The transfer function resolution while grinding tools system contacts with the outside environment.The system could contact with outside environment when force is gathered and controlled. Fx , which is produced, needs to controlled. Meantime,the transfer function changes with outside environment. So, the transfer function needs to be resolved while grinding tools system contacts with the outside environment.Now.the transfer function of grinding terminal performer is adjusted as:If we assume exterior stiffness k e equal to 10N/m,102N/m,103N/m,104N/m,we can get the relation of force and location in the next expression.4.The design and simulation of the non-linear PD controllerIn the non-linear PD controller, the output control is:The non-linear PD controller is constructed by means of simulink toolboxes in MATLAB in the figure 2.The result of simulink analysis indicates that the non-linear PD controller can go well in grinding tools system of different environment. Moreover, if the stiffness changes continuously with the given range, the controller can retain good effect.5.The movement simulation of grinding tools systemWhether the design of the grinding tools system is reasonable and the movement parts intervenes with each other or not, can be proved through helix movement simulation and the virtual workpiece machining experiment of grinding tools system.The figure 3 is the simulation curve of helix movement. The system structure design of grinding tools system is proved reasonable by means of the movement simulation analysis of the grinding tools system.6. ConclusionA kind of two-degree of freedom grinding tools system with compliant control is designed in the paper in order to combine with NC to realize the function of series-parallel connection machine tool.The movement track dynamic performance of grinding tools system is analyzed and the design of framework entity is reasonable through the machining of virtual workpiece, which of theory anlysis is made in the paper.The paper does the research on the model of grinding tools system based on its characteristics regarding to the conditions and adjustment of compliant PID control stability. The non-linear PD control strategies are adopted in the framework system .The method is designed based on the Popov's stability, and it is simple and stable entirely.It is proved effective through constructing non-linear PD control structure using Simulink(Dynamic System Simulink) toolboxes in MATLAB.