A soft three-axis tactile sensor based on electromagnetic induction

A novel tactile sensor based on electromagnetic induction that can detect slippage in addition to three-axis force is proposed. The structure of this sensor is simple, and the sensor, which is essentially a displacement gauge, consists of a two-dimensional array of inductors and an elastic body containing a permanent magnet. Formulas to transform the output voltage of the proposed sensor into a force vector are derived, and analyses of both deformation of the proposed structure and magnetic field generated by a cylindrical permanent magnet are carried out to extract transformation parameters. In addition, it is shown that the sensor sensitivity can be designed using the aspect ratio of the cylindrical magnet. A prototype unit-cell of a tactile sensor is developed with four chip inductors, silicone gel as an elastic body and a neodymium magnet, and experiments are undertaken with a six-axis force/torque sensor as a reference. The contributions of inductors to sensor output are observed experimentally to be in agreement with analytical prediction and the reference sensor. Experimental results show that the proposed tactile sensor is useful for three-axis force measurement and slip detection simultaneously.