| At present many CAD/CAM digital systems have the abilities of modeling freecurve interpolation, however, most of them merely realize the process of line and circleinterpolation, which are unable to meet the demands of high-speed and high-accuracyperformance of free curve models. So the research on motion controller with thefunction of free curve interpolation is of great significance. Based on DSP and FPGA,this thesis studies the open motion controller, which is able to realize NURBS curve.Due to the advantages on fast digital process of DSP, calculations of free curveinterpolation are achieved. Besides, FPGA has the feature of high reliability, shortdevelopment cycle and reprogrammable performance, which overcame limitations ofhardware and software, such as low interpolation speed on software and complexmodifying and updating process on hardware.The main research work is given as follows:The NURBS curve interpolation processes are divided into rough interpolation andfine interpolation according to the calculation processes and assignments of the curveinterpolation. Rough interpolation of NURBS curve is the data intensive, fineinterpolation is further intensive work base on rough interpolation. So the systemstructure based on DSP and FPGA technologies is respectively by the features ofNURBS curve interpolation.The federate scheduling method of the NURBS curve is proposed constrained bychord tolerance, acceleration and jerk limitations. The proposed method first scans aNURBS curve and finds out the crucial points with large curvature and breakpoints.Then, the NURBS curve is divided into several NURBS sub-curve using curve splittingmethod which guarantees the convergence of predictor-corrector interpolation algorithm.The suitable federate at critical point is adjusted according to the limits of chord error,centripetal acceleration and jerk, and at breakpoint is adjusted based on the formulationof velocity variation. The federate profile corresponding to each NURBS curve isconstructed according to the length and the given limits of acceleration and jerk.The linear and circular interpolation models based on point-to-point comparisonmethod, minimum deviation and digital integration method are designed using thehardware description language on FPGA. Implementation of the NURBS curveinterpolation is used C code. Simulations and experiments are conducted to verify thefeasibility and applicability of the proposed method. |
