Frictional Characteristics of Plain Bearing Guideway in Minute and Transient Motion

研究了平面轴承导轨在滑动运动的微小过渡区的位移-摩擦力特性。滑动轴承导轨上的滑块质量为150 kg，并由力操作定位机构驱动，其进给分辨率为1纳米，进给刚度为每纳米几牛顿。在不同的两种运动模式下，载玻片的最大行程范围为16 μ m。一种是连续运动，进给速度为50 ~ 5000 nm/min，另一种是步进运动，步长为1 ~ 1000 nm。平均进给速度和行程设置与连续运动中的相同。研究结果如下：1.在进给方向反转之后，在已知的稳态区域之前，位移-摩擦力特性中存在瞬态区域，在该稳态区域中，摩擦力对于位移的增加是恒定的。瞬态区开始后，反向的进给方向到几百纳米的位移，具有几牛顿每纳米的等效刚度，其次是稳定状态区与零等效刚度.提出了位移-摩擦力特性曲线的数学模型.在由步进运动组成的数控运动中，摩擦力在本质上可以很小，与一般公认的值相比可以是负值.微小步进运动中的小值和负值是由振荡运动引起的; 5.瞬态区和稳态区位移对摩擦力特性的差异必然影响数控运动的可控性

Displacement-frictional force characteristics of a plan bearing guideway was investigated in minute and transient region of sliding motion. A slide on plain bearing guideways was 150 kg in mass and was driven by a force-operated positioning mechanism with feed resolution of one nanometer and feed stiffness of several Newton per nanometer. The slide was reciprocally fed for maximum travel range of 16 mum in different two motion modes. The one was continuous motion in feed rate of 50 to 5000 nm/min. The other was stepwise motion in step size of 1 to 1000 nm. The average feed rate and the travel range were set up as same as the one in the continuous motion. The results are as follows.1. A transient region exists in displacement-frictional force characteristics after reversing of feed direction before the known steady state region in which frictional force is constant for increase in displacement. The transient region starts just after reversing of feed direction to a few hundred nanometer displacement, has the equivalent stiffness of several Newton per nanometer and is followed by the steady state region with zero equivalent stiffness.2. A mathematical model of the displacement-frictional force characteristic curve was proposed.3. In numerically controlled motion composed of stepwise motion in nature frictional force can be very small and negative in comparison with generally recognized value.4. The small value and negative one are caused by oscillating motion in minute stepwise motion.5.The difference between the transient region and the steady state one in displacement to frictional force characteristics definitely affects controllability of numerically controlled motion