Research On Motional Smoothness And Contour Precision Control Technology Based On CNC System

With the development of virtual technology, cloud computing, the internet of things, cloudmanufacturing, high speed cutting, and precision machining technology, the advanced manufacturingtechnology puts higher request on CNC system. For meeting the requirement of the advancedmanufacturing technology, various interdisciplinary theories and methods are applied synthetically.By centering on motional smoothness and contouring error control of CNC system, the paperresearches about continuous micro line contour machining technology, model identification andmodeling technology of the servo control system, independent-axis position servo control technology,and multi-axis position servo control technology. The main research work and results of this paper areas follows:(1) For the issue of continuous micro line contour machining, the traditional method takes eachprogram segment of micro line as a unit to deal with the problems, which leads to lower turningvelocity of the connective points, causes losing motional smoothness, influences processing efficiency,and machining quality. To improve turning velocity, the transition method of cubic parametric splinecurve is presented. Two type of approach about inscribed transition and external transition aredesigned according to the characteristics of the transitional line, and realizes high smooth transition ofturning velocity according to gradual change characteristics of the parameters spline curve tangent.The calculation of traditional S-curve velocity planning algorithm is so complex, that cannot meetreal-time requirement of the embedded CNC system. To solve this problem, a simplified fast S-curveplanning algorithm is proposed, which realizes high smooth machining. The simulative andexperimental results verify the feasibility and validity of the proposed approach.(2) In order to improve the system modeling accuracy, various theories and methods ofinterdisciplinary are applying synthetically, such as support vector machine, granular computing,immune algorithm, particle swarm optimization algorithm, and genetic algorithm. The modelstructures of the CNC servo control system are identified with2-dimensional searching algorithmand support vector machine. In order to improve model identification accuracy, a method ofinformation granular support vector machine is proposed to identify the model parameter of theservo control system, and the immune particle swarm optimization algorithm with crossover andmutation operator is presented to improve identification effect. The experimental results show thatthe proposed method can effectively improve the accuracy of the system model.(3) In order to improve motional smoothness and precision of the independent axis, the compound mode control strategy of improved generalized predictive control and nonlinear adaptive fuzzy controlare proposed by using generalized predictive control and fuzzy control theory methodcomprehensively. To advance the control performance of the servo control system, a performanceoptimization index of generalized predictive control is improved. To improve the control performanceof the system, an algorithm that adaptively adjusts parameters of improved generalized predictivecontrol is put forward. To meet the requirement of real-time system, a simplified calculation model ispresented to solve control input. To improve anti-interference ability of the system, an adaptive fuzzycontrol algorithm of variable structure parameters is proposed, which adaptively adjusts fuzzyquantitative domain and fuzzy control rules. The experiments show that the proposed compoundcontrol strategy effectively improves the dynamic response ability, steady performance and robustnessof the independent-axis position servo control system, and enhances the independent-axis motionsmoothness and precision of CNC system.(4) Research about multi-axis position servo control technology. Contour error model, velocityerror model and acceleration error model are established. To improve motional smoothness andcontouring precision of the multi-axis CNC system, the compound mode control strategy, which baseson parameter model predictive control and nonlinear adaptive fuzzy PID control, is proposed. Toguarantee minimum contouring error, tracking error, velocity error, and acceleration error duringnumerical control machining, a performance optimization index is proposed. To solve the real-timeproblem of control system, a simplified calculation model is presented to solve control signal by usingthe idea of sliding filter. To strengthen the robustness of the multi-axis CNC system, a nonlinearadaptive fuzzy PID control method is presented. The experiments show that the proposed methodeffectively improves the control performance and robustness of the multi-axis position servo controlsystem, and enhances motion smoothness and contouring precision of CNC system.(5) The corresponding CNC system is independently designed and exploited with milling andcarved machine platform. The engineering verifications are implemented for cubic parametric splinecurve transition algorithm of continuous micro line contour machining, the model identification andmodeling of the servo control system, control methods of independent-axis position servo controlsystem, and control strategies of multi-axis position servo control system. Through data acquisitionand physical processing, the feasibility and effectiveness of the proposed methods are certified.