Friction models for a mobile machine using piezo vibration

Micro-machines and micro-robots, recently under development for medical and industrial applications, need both manipulative and locomotive capabilities. We built a small mobile machine which has two legs made of bimorph piezoelectric actuators. It proceeds by vibrating one leg and making selective use of the friction between the legs and the floor. Simulations were made to investigate the dynamics of its mobility using different friction models. The simulation results were compared with the movement of the machine measured using an accelerometer, which showed that the viscous friction model explains the movement better than the Coulomb friction model. Four-legged machines were also built and tested for multidimensional mobility.