This research aims to formulate a new lubricant containing oxide nanoparticles for enhancing anti-wear ability and reducing friction. Different concentrations of copper oxide (CuO) and zinc oxide (ZnO) nanoparticles were separately added to an ionic liquid, methyltrioctylammonium bis(trifluoromethylsulfonyl)imide [N1888] [NTf2], to formulate the tested lubricants. The tribological properties of the lubricants were tested by performing ball-on-disc wear tests on a tribotester (MTM, PCS Instruments). The results show that both the CuO and ZnO nanoparticles can increase the friction reduction ability of the ionic liquid when used as a neat lubricant. The anti-wear characteristic of the ionic liquid is increased by adding ZnO nanoparticles but decreased by adding CuO nanoparticles. The best tribological performance observed for the concentration of 0.2 wt% ZnO, with the wear scar diameter is reduced by 32% compared to the pure ionic liquid. The results of SEM/EDX analysis on the worm morphologies show different lubrication mechanisms of the nanoparticles in the [N1888] [NTf2], which are tribo-sintering for CuO nanoparticles, and third body with pure rolling effect for ZnO nanoparticles.

The tribological and vibration behaviors of a lubricated system are often studied separately. However, in recent years, the combination of tribology and mechanical vibration significantly contributes in analyzing and solving many practical problems. The main objective of this study is to establish empirical equations that describe friction–-vibration interactions under dynamic (sliding) lubricated contacts. The effects of operating conditions on the tribological and vibration behaviors of lubricating oils having different viscosities were experimentally investigated using a four-ball wear test machine. The results indicated that the vibration velocity tends to increase with the sliding velocity. With a lower combination of ratio of the vibration velocity to the sliding velocity and the specific film thickness, lower friction coefficients were observed in the boundary and mixed lubrication regimes. The mean wear scar diameters exhibited positive correlations with the amplitudes of vibration accelerations. The empirical equations provide basic information for the prediction of friction variation by measuring vibration signals.

Generating nonlinear trajectories of walking patterns is one of the most important problems in stability a humanoid robot when it walks on different ground conditions. In order to solve this problem, a desired Zero Moment Point (ZMP) trajectory is firstly designed and then a Center of Mass (CoM) trajectory will be created based on this ZMP. Hence, the preview control formulation which follows the planned ZMP patterns while reducing the jerk (acceleration derivation) is considered to implement this trajectory. In this study, the walking pattern for bipedal robot is generated by using a cart-table model. The procedure of apply a preview controller to the cart-table model will be presented in this investigation. After that, the position of each leg joint of bipedal robot is also calculated by using the proposed CoM Jacobian. Finally, computer simulations are performed by utilizing RecurDyn and MATLAB softwares to validate the proposed preview control formulation for the nonlinear walking patterns generation of a Bioloid humanoid robot.