摩擦、动态棘轮和执行器的多模态主动控制
Multi-mode active control of friction, dynamic ratchets and actuators
摘要：
通过超声振动主动控制摩擦是一种众所周知的效果，具有从冲压成形到微机械致动器的许多技术应用。在三个可能的方向（垂直于接触平面、运动方向和平面内横向）中的任何一个方向上施加振动，都可以观察到摩擦力的降低。在这项工作中，我们考虑的多模式主动控制的滑动摩擦，在两个或多个方向的相移振荡同时作用。我们的分析是基于一个宏观的接触力学模型，最近被证明是非常适合描述动态摩擦过程。为了简单起见，我们限制我们的分析，一个恒定的，独立于负载的正常和切向刚度和两个叠加的相移谐波振荡，其中一个是垂直于平面和其他的运动方向。在以前的作品利用本模型，我们假设一个恒定的局部摩擦系数，减少所观察到的摩擦力完全从系统的宏观动力学。我们的数值模拟结果表明，摩擦定律是由三个无量纲参数。根据这些参数的值，观察到三种性质不同的行为类型：（a）摩擦系数的对称速度依赖性（正速度和负速度相同），（b）相对于速度符号的非对称依赖性，但在零速度时为零力，以及（c）在零速度时为非零力的非对称依赖性。后两种情况可以解释为“动态棘轮”（b）和致动器（c）。
英文摘要：
Active control of friction by ultrasonic vibration is a well-known effect with numerous technical applications ranging from press forming to micromechanical actuators. Reduction of friction is observed with vibration applied in any of the three possible directions (normal to the contact plane, in the direction of motion and in-plane transverse). In this work, we consider the multi-mode active control of sliding friction, where phase-shifted oscillations in two or more directions act at the same time. Our analysis is based on a macroscopic contact-mechanical model that was recently shown to be well-suited for describing dynamic frictional processes. For simplicity, we limit our analysis to a constant, load-independent normal and tangential stiffness and two superimposed phase-shifted harmonic oscillations, one of them being normal to the plane and the other in the direction of motion. As in previous works utilizing the present model, we assume a constant local coefficient of friction, with reduction of the observed force of friction arising entirely from the macroscopic dynamics of the system. Our numerical simulations show that the resulting law of friction is determined by just three dimensionless parameters. Depending on the values of these parameters, three qualitatively different types of behavior are observed: (a) symmetric velocity-dependence of the coefficient of friction (same for positive and negative velocities), (b) asymmetric dependence with respect to the sign of the velocity, but with zero force at zero velocity, and (c) asymmetric dependence with non-zero force at zero velocity. The latter two cases can be interpreted as a "dynamic ratchet" (b) and an actuator (c).
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