Research And Implementation On Trajectory Planning Algorithm Based On PH Curve

The interpolation method of free-form curve machining is the mainly researchaspects of the numerical control system and CAD/CAM system. At the present,although the commonly CAD/CAM system has the modeling functions offree-form curve and surface, most of the numerical control system has only thefunction of line and arc interpolators. In the process of machining the complicationcurve, the traditional method is use small lines and arcs to approximately fit thetool path. The approximate methods have many shortcomings, such as a largercontour error, a longer processing program code, and larger data transmission andso on. So it is not suffice to content the requirement of high speed precisionprocessing. Hereby, it is much important to study the free–form curve and surfaceinterpolation methods of numerical control system.The main aim of the thesis is to study the real-time interpolation algorithm ofPH curve. A motion controller with the function of direct interpolation of PH curveis studied to eliminate the above shortcoming in traditional CNC system.The general scheme of numerical control system is designed in the thesiswhich has the functions of free curve direct interpolation. It is mainly divided intotwo aspects, such as the software structure and the hardware structure.Quintic PH curve has the same shape freedom with the cubic B spline at thesame initial conditions, but the former is much smoother. So the interpolatoralgorithms with C1Hermite and C~2spline curve are mainly studied. And thesimulation and test work of the algorithm are carried out based on MATLAB andVC6.0.Trajectory planning and velocity planning are also realized. The thesis adoptsthe improved ADAMS interpolation operator to plan the trajectory. The calculationis smaller and the precision is higher compared with the Taylor operator. Thevelocity planning with S curve is adopted by digital convolution. It reduces theprocess of calculation and improves the efficiency. And the velocity planningprocess is limited by the chord error.A motion controller prototype is setup and the tests are carried out based onthe numerical control system in the lab.