Study on adhesion force reduction and state estimation by piezo-transducer

Our previous paper presented a method for reducing adhesion forces by oscillation and showed the adhesion state can be checked by analyzing the data obtained by laser displacement meter. However, there are several problems in this method. 1) The end-effector must be located at the specific point where laser displacement meter can measure oscillation. 2) The adhesion state can not be checked if something blocks the light/laser or the target leaves the measuring point. 3) The total system becomes very large. To resolve these problems, this paper firstly presents a method for checking the adhesion state by piezo-transducer. Next, to achieve more precise manipulation, we propose a method to deform the end-effector by adding DC input to the piezo actuator which is also oscillated simultaneously to reduce adhesion forces. Furthermore, we find that the first mode resonance frequency shifts with the increase of the pushing force applied to the object by the end-effector. Using the shift amount, we develop a method for checking the adhesion state.