Friction moments in single and double contact points in deep prerolling: Precision positioning under oscillatory motion condition

Ultra-precision positioning to better than nanometer in accuracy with low level of vibration is of great interest to various applications such as actuators for precision positioning of mobile stages in CNC machines, robotics in medical applications towards large scale devices like very large telescopes (VLT). The paper reports on recent pre-rolling experimental measurements of moment friction during the phase of pre-rolling i.e., at start and at finish. The development resulted in a single-point contact system set up and double points contact setup in a form of a pendulum generating pure pre-rolling and to study the laws of rolling resistance to contacting bodies at a distance significantly reduced compared to the elastic contact spot size. Phenomenological effects have been observed during both extensive tests. It is noted that the single point pendulum posed several technical challenges to secure perfect balancing and hence allow for pre-rolling to occur and precisely measured characteristics. The surface tension of solids on the contact zone, parameters of the frequency-independent internal friction and the pressure of the adhesion forces are found. The sensitivity of measuring rolling friction moments is of the order of 10-10 Nm, the measurement error does not exceed 10% with for example 120 nm minimum displacement of the ball Peel adhesion density extremely low. The swing of the pendulum with a maximum period has a stable swing plane. In the deep pre-rolling (DPR) zone before full rolling, there is an effect of a sharp decrease in the swing period of the pendulum with a decrease in the swing amplitude. In this case, the rolling friction also decreases and tends to its minimum final value, determined by the work of adhesion forces on separation. In the study of rolling resistance in the DPR zone, it is necessary to measure not only the reliance of the swing amplitude on the time, but also the reliance of the swing period of the pendulum on time. The developed phenomenological theory and measurement procedure allowed us for the first time to build a simple instrument for direct measurements with high sensitivity and accuracy of the surface energy density of the adhesion forces (or surface tension) in the case of a solid body, and the parameters of internal frequencyindependent friction and the pressure generated by adhesion forces.