Evaluation of Error and Sensitivity for Force Sensor Using Shape-Memory Polymer

Robotic technology is being increasingly used in a variety of fields, including not only manufacturing, but also nursing and welfare. Applications of robotic technology in nursing and welfare require the measurement of a wide range of forces in order to grasp and lift objects accurately in different operating environments. In light of this, we have developed a force sensor that uses a shape-memory polymer (SMP) whose stiffness varies with temperature. The relationship between the applied force and the deformation of the SMP changes depending on the temperature, which allows the measurement range and sensitivity to be changed with temperature. Our sensor, which consists of strain gauges bonded to an SMP beam, senses the applied force by measuring the strain in the SMP as it bends. In the present study, four SMP force sensors with different numbers of strain gauges and steel plates were fabricated, and their accuracy and sensitivity were evaluated. Experiments using the prototypes demonstrated that the sensor with one steel plate had a small error and a large sensitivity range.