可配置型五坐标B样条插补控制器的研制

针对采用五轴联动数控机床的线性插补功能进行数控加工存在的不足,提出了一种B样条插补控制策略用于五轴联动数控机床以实现复杂曲面零部件的高速高精数控加工。参考开放式、模块化体系结构控制器(OMAC)标准,开发了具有B样条插补功能的五轴联动数控机床运动控制器。该控制器将控制任务按照实时性要求进行划分。人机交互、代码解析及参数映射关系构造等过程离线完成,插补运算、离散逻辑控制及逆运动学变换等过程由实时线程执行,保证了数控系统的硬实时性。为简化NC程序的编制过程,控制器设计为接收工件坐标系下的加工信息。通过开发适应各种形式数控机床的逆运动学变换模块,并将机床参数设计为可用户定制,使得控制器具有良好的通用性。在控制器内部建立NC程序文件中位置曲线和方位曲线间的参数映射关系,使得机床平动轴与转动轴间的运动规划符合实际加工要求,并可保证加工精度。实际加工实验中,在采用B样条插补算法的NC程序量降低为线性插补NC程序量15%倍时,其插补误差为线性插补误差的45%,控制器插补精度为0.68,表明该B样条插补控制器可以满足五坐标数控加工的要求。

Development of configurable motion controller with 5-axis B-spline interpolation function

To improve the machining speed and precision of mechanical parts with complex shapes by Computer Numerical Control (CNC) machining, a B spline interpolation method for 5-axis CNC machine tools is proposed. By taking the Open and Modular Architecture Controller (OMAC) as a reference, a motion controller with B-spline interpolation function is developed.The controller divides the controlling tasks in accordance with real-time request, executes the man-machine interactive, code analysis and parameter mapping in an offline environment and runs the interpolation operation, discrete logic control and inverse kinematic transformation in a real-time thread.Therefore,the real-time performance of the controller is well realized by methods above. To simplify the procedure of NC program, the machining information received by the controller are vectors in a part coordinate system.Furthermore, the controller can offer a good generality by developing Inverse Kinematic Transformation Module (IKTM) units suitable for various 5-axis machine tools and designing the parameters of machine tools as the customizable parameters.The mapping relation between the orientation and the position parameters in the NC program is established by the controller. As a result, the motions of linear axes and motion of rotary axis meet the machining requirement well and good machining accuracy is obtained. In a machining process, when the NC program capacity for B spline interpolation is 15% that of the NC program capacity for linear interpolation, its interpolation error is 0.45% that of the linear one. The interpolation accuracy of the controller is 0.68.These results show that the developed B spline interpolation controller can well meet demands of NC machining and has a good controlling performance.