Vision-Based Microtribological Characterization of Linear Microball Bearings

Abstract

ISR develops, applies and teaches advanced methodologies of design and analysis to solve complex, hierarchical, heterogeneous and dynamic problems of engineering technology and systems for industry and government. ISR is a permanent institute of the University of Maryland ABSTRACTMicroball bearings can potentially provide robust and low friction support in micromachines such as micromotors and microgenerators. Their microtribological behavior needs to be investigated for design and control of such micromachines. In this paper a vision-based, non-intrusive measurement method is presented for characterization of friction in linear microball bearings. Infrared imaging is used to directly observe the dynamics of microballs and track the motion of bearing components. It is verified that microballs roll most of the time with occasional sliding or bumping resulting from fabrication nonuniformity. The friction-velocity curve demonstrates evident hysteresis. The dependence of frictional behavior on several factors is studied. INTRODUCTIONMicroball bearings have potential to offer robust and low friction support in micromachines, such as micromotors and microengines. A careful study on their microtribological behavior is necessary for proper design and effective control of micromachines based on such bearings. A linear microball bearing structure was proposed and its static coefficient of friction (COF) measured by Ghodssi et al [1]. A vision-based experimental setup was developed to study the dynamic friction of linear ball bearings by Lin et al [2], where the underlying friction model consisted of the Coulomb friction only.As a continuation of the work in [2], this paper contains indepth characterization and understanding of the microtribological behavior using infrared imaging, scanning electron microscopy (SEM) imaging, and analysis. The contributions of this paper include: a) verification of rolling motions of microballs by directly observing trajectories of all bearing elements (stator, slider, balls); b) observation of the hysteresis between the friction and the relative velocity; and c) investigation of the influences of the ball number and oxide formation on the frictional behavior.

Microball-bearing-supported electrostatic micromachines with polymer dielectric films for electromechanical power conversion

“…The first demonstration of this device is a 6-phase, bottomdrive, linear, variable-capacitance micromotor (B-LVCM) [3] as shown in figure 1. The B-LVCM has been designed, fabricated and tested on the basis of our previous work on characterization and modeling of microball bearings [4][5][6][7], and characterization and process integration of BCB polymers [8][9][10][11]. The primary application of the B-LVCM is longrange, high-speed, linear micropositioning.…”

Modeling of Velocity-Dependent Rolling Friction in Linear Microball Bearings

“…Two parallel Vgrooves, which house the balls, are etched into the plates with potassium hydroxide (KOH). A non-intrusive, vision-based experimental setup was built [1] and then improved [2] to investigate the microtribological behavior of such linear bearings. It was found that the rolling friction demonstrates dependency on the relative velocity between the slider and the stator [3].…”