Research On Dynamic Control Accuracy Test Planning Of Five-axis Machine Tool Aiming For Complex Curved Surface Machining

Five-axis CNC machine tool is an advanced manufacturing equipment specially for complex curved surface machining.In the precise high-speed machining process of fiveaxis machine tool for complex curved surface,the dynamic tracking error due to tracking delay discrepancy between the servo systems is a main cause of processing inaccuracy.Comprehensive measurement of dynamic tracking error in the five-axis machining process,otherwise known as dynamic control accuracy test,is very meaningful for analysis of curved surface machining accuracy and research of dynamic tracking error reduction.There have been more and more researchers and engineers paying attention on dynamic control accuracy test of five-axis machine tools in recent years.Planning the motions of axes during the dynamic control accuracy test process(dynamic control accuracy test planning,for short),is the core step to relate to the dynamic control accuracy test capability.For dynamic control accuracy test planning,there are many useful test planning examples from current international standard and recent researches.However,there are yet some shortcomings or problems,such as the relationship between test planning method and test capability is not yet clear,there is a lack of theory basis in the test planning process,the capability to reflect dynamic control accuracy may be insufficient,and so on.Thus,it is worth to explore dynamic control accuracy test planning of five-axis machine.In this dissertation,dynamic control accuracy test planning method to detect dynamic tracking error of five-axis machining for complex curved surface is researched.The two popular dynamic control accuracy tests,circular test with DBB(double ballbar)and RTCP(rotation tool centre point)test,will both be researched and improved on dynamic control accuracy test capability.The researches of this dissertation were conducted as followed:(1)The dynamic control accuracy test planning method and corresponding test capability are researched to reveal the correlation between complexity of planning and test capability.RTCP test planning is researched as an example.The existing RTCP test planning examples are summarized and sorted from point of view of planning method.The test capability of planning cases by different planning methods is compared by simulation and experiments.Compared with simple command planning method,complex method,such as point-based spline method or function-based method,can provide a clear advantage on dynamic control accuracy test capability.(2)For circular test with DBB,to overcome existing problems of five-axis motion state lack and inefficient dynamic control accuracy test capability,the test planning method introducing complex multi-axis motions is researched.The 8-shape complicated synchronous motions of two rotary axes are proposed in the circular test planning.By application of 8-shape motions,the two rotary axes will run in complicated synchronous motion states,which result in synchronous and complicated movements of all the five motion axes during test process.By simulation and experiments,compared with the existing circular test planning case,the circular test planned with 8-shape complex multiaxis motions,called circle-8 test,shows the advantages on dynamic control accuracy test capability.(3)For RTCP test,to overcome existing problems of insufficient theory basis and inefficiency of reflecting dynamic control accuracy,the test planning method based on sensitive test point optimization by modified genetic algorithm is proposed.The mapping relationship between servo tracking error occurring and dynamic tracking error reflected in machining process is established,and error observation matrix and its corresponding observability index based on singular value are defined.A modified genetic algorithm,which considers error observability as optimization index,is established to select sensitive test points and motion directions,and cubic spline interpolation is applied to plan RTCP test from the sensitive test points and motion directions.By simulation and experiments,compared with the existing RTCP test planning cases,the RTCP tests planned by sensitive point optimization show the advantages on dynamic control accuracy test capability.(4)For RTCP test planning based on multiple trigonometric functions,aiming at existing problems of unclear correlation between trigonometric parameter setting and test capability and insufficient theory basis of parameter combination selecting,the selection of trigonometric parameter combinations in the test planning process is researched.Effect of different trigonometric parameter combinations on rotary axis motion in the test process are analyzed,and the feasible trigonometric parameter combinations for RTCP test planning are listed.By simulation,the effects of different trigonometric parameter collections on dynamic control accuracy test capability are summarized,and the valid trigonometric parameter combinations for strong test capability are obtained.By simulation and experiments,the RTCP tests planned from above obtained parameter combinations show the advantages on dynamic control accuracy test capability.