纳米三坐标测量机接触式测头触发控制

为高灵敏度纳米三坐标测量机(nano-CMM)接触式测头提出了一种高精度高效率的触发控制策略。该策略使用了一种自行研制的4-DVD接触式测头,工件接触测头产生的微小变形会导致测头产生灵敏度极高的触发信号。系统使用超声波马达整合不同驱动模式,实现了高速逼近和低速触发的有效结合。触发过程使用了二次触发策略,即第一次触发获得接触位置的范围,第二次触发用极低的速度,详细记录触发点附近的触发信号,并通过线性拟合的方式求得信号曲线转折点,即为触发位置。该方法解决了驱动分辨率和行程大小的矛盾。实验结果显示:该方法可以有效地避免测头系统的塑性形变,触发位置的重复性可在10 nm以内。结果表明,本文提出的nano-CMM接触式测头触发控制策略在保证精度和稳定性的前提下,表现出了良好的控制效率。

Trigger control of touch probe for nano-CMM

A high precision and high efficiency trigger control scheme for the touch probe in a high-sensitive nano Coordinate Measurement Machine(nano-CMM) is developed,and a self-developed 4-DVD touch probe is used in the proposed scheme. When the probe touches the workepiece, the tiny deformation of the probing system will generate a high-sensitive trigger signal. By integrating different driving modes of an ultrasonic motor, the trigger control scheme realizes the combination of high-speed approaching and low-speed touching.Furthermore, a double-trigger method is used in the touching process. The first trigger is to determine the rough range of the trigger point and the second trigger is to record the trigger signal in detail by a very low speed and to work out the turning point of the trigger signal curve by a linear fitting i.e. the trigger position. This method solves the paradox between traveling range and driving resolution. Experimental results show that the proposed method will avoid the permanent deformation during touching process and the repeatability of the trigger point is within 10 nm . It concludes that this trigger control method for a nano-CMM touch trigger probe not only offers the higher precision and reliability,but also shows the acceptable control efficiency.