Application of Tactile Sensor Using Shape-memory Polymer to Robot Arm

Tactile sensors typically have elastic covers for reducing the impact of objects that make contact with the sensor. However, elastic covers decrease the spatial resolution of the sensor because of their low-pass spatial filtering characteristics, which vary based on the stiffness of each cover. Therefore, we propose a tactile sensor that uses shape-memory polymer (SMP) with stiffness that varies based on temperature. SMPs can be deformed above their glass transition temperature ( T g ) upon application of a small load. The reversible change in the elastic modulus between the glassy and rubbery states of an SMP can be on the order of several hundred-fold. These characteristics can be exploited to alter the spatial resolution and the rigidity of the sensor surface by adjusting the temperature of the SMP. In this study, a prototype sensor was fabricated using an SMP sheet with embedded electrical heating wires, and its fundamental performance was evaluated. The experimental re-sults of a preliminary proof-of-concept investigation conducted using the prototype confirm the feasibility of the proposed sensor. Moreover, using a 4 × 4 array of pressure sensors, it was possible to distinguish the shape of the object placed on the sensor above and below T g . The center of pressure applied on the prototype sensor could be measured by a developed program. In addition, we evaluated the control of the position of an object on the robot arm utilizing the prototype sensor attached on the arm. We could hold the constant position of the object on the sensor, although it took a longer time to stabilize the object above T g because of the deformation of the SMP.