微结构表面金刚石车削加工过程中快速伺服刀架的控制

Control of Fast Tool Servo When Diamond Turning Micro-structured Surfaces

微结构表面金刚石车削加工过程中由于切削深度突变而易于引起切削力干扰,采用滑模变结构控制算法来解决这一问题。研制了用于微结构表面加工的快速伺服刀架,建立了快速伺服刀架动力学模型,并设计了基于连续时域模型的滑模变结构控制器,它与系统的参数变化及扰动无关,因此在切削过程中具有很好的鲁棒性。另外,滑模变结构控制系统快速性好,无超调,计算量小,实时性强,很适合于加工控制。针对滑模变结构控制算法与常规PID控制算法进行了阶跃响应对比实验,结果表明滑模变结构控制算法比常规PID控制算法的超调小,稳态误差小于20nm。最后以微菲涅耳透镜作为微结构表面的实例进行加工实验,实验结果进一步验证了滑模变结构控制算法的有效性。

Aiming at that the cutting force disturbance is easy to be induced when diamond turning micro-structured surfaces because of the mutational cutting depth, a variable structure sliding-mode control algorithm is proposed to solve the problem. A fast tool servo for micro-structured surface machining is developed, and the corresponding dynamic model is established. A continuous time domain based variable-structure sliding-mode controller is designed. It is robust against changes of system parameters in the cutting process and disturbances of cutting forces. It is also quick to track the command position accurately. So it is adapt to turning process without overshoot. Comparison step response test is conducted between conventional PID and variable-structure sliding-mode algorithm. The result shows that the variable-structure sliding-mode controller has less overshoot than the PID controller, and the steady-state error is less than 20 nm. At last, the effectiveness of this controller is further verified by machining test of micro Fresnel lens as the example of micro-structured surfaces.