The robot joint lubrication with ultra-thin hyperelastic superficial layers

The surface of humanoid robots is more or less deformable metal and plastic replica of human body. An advanced humanoid robot has human like behaviour – it can talk, run, jump or climb stairs in a very similar way a human does. Hence follows that operation of construction of the robots artificial joints to be similar for biological joints activities. This fact requires applying proper as well corresponding soft solid materials, and specific lubricants. To the interesting phenomena belong the fact, that as well the surfaces of an articular cartilage human joint as the soft surfaces of the robot joints, coated with ultra-thin hyperelastic multi-layers, plays an important role in the surface active lubrication, relative small friction forces and wear during the human limb or robot body activities in the movement. The presence of the ultra-thin hyperelastic layers consisting the soft bearing materials including hyperelastic nano-particles during the robot bearing lubrication enables to indicate numerous positive effects among other the decreases the friction coefficient values. Therefore, the results obtained in this paper may be applicable during the joint-endo-prosthesis or artificial joint design in new humanoid robots, where instead cartilage and synovial fluid are applied new soft materials with active hyperelastic micro- and nano- particles. In this paper is shortly presented the mathematical model of hydrodynamic lubrication of thin boundary layer describing the robot joint. Mathematical model in 3D for lubricant consists of three equations of motion, continuity equation, conservation of energy equation and Young-Kelvin-Laplace equation describing the thin layer interfacial energy.