A gripping device provided in, for example, a robot hand is provided with a pressure-sensitive sensor so as to grip objects to be gripped (target objects) different in characteristics, such as shapes, hardnesses, surface properties, and weights, without breaking the objects to be gripped.
The grip state is detected in real time from an output signal of the pressure-sensitive sensor to control the gripping force (contact pressure), the moving speed, and the like. In recent years, in order to accurately handle a wide variety of objects to be gripped, there is a demand for sensitivity as a tactile sensor capable of providing sensation, such as sense of pressure and sense of slip, equivalent to human finger tips.
For example, a pressure-sensitive sensor in which conductive particles such as carbon are dispersed in a rubber material, and that is configured to grasp a change in applied current based on the relation between force and resistance value with a change in contact state of the conductive particles with pressure applied, is known.
The pressure-sensitive sensor having such a configuration requires a power supply and inevitably costs much.
Using a piezoelectric material that deforms to generate electricity as a pressure-sensitive sensor eliminates the need for a power supply.
A vibration-powered device including an elastic sheet deformed by a vibration load, a piezoelectric film placed on a surface of the elastic sheet, and electrodes disposed on both surfaces of the piezoelectric film is known (for example, Patent Literature 1). This vibration-powered device generates electricity using strain caused by tensile force or compression force of the piezoelectric film involved with deformation of the elastic sheet. Polyvinylidene fluoride (PVDF), which is a polymer piezoelectric material, is used for the piezoelectric film.