Development of 4-axis soft deformable sensor for humanoid sensor flesh

In order to achieve tactile sensing exterior for humanoid robots expected to have close interaction with humans or environments, not only the distribution of the sensors, but also softness of the sensor element itself and detection capability for multi-axis deformation are crucial. Although there´s some studies on developing tactile sensor with both softness and multi-axis deformation, few of them can be applicable to humanoid exterior from viewpoint of embedding them inside the soft thick exterior. In our previous works, 20 mm-cube 3-axis soft deformable sensor is developed. However, there is enough room to improve. In this paper, 4-axis soft deformable sensor unit is proposed. Proposed sensor can detect 3-axis rotational change including twisting direction, and 1-axis normal direction force. 3D rotation of the sensor is estimated by a pair of MEMS IMU boards. Although each of the outputs of IMUs are affected by motions or vibrations of the attached link, rotational deformation of the sensor can robustly estimated by monitoring the difference between them. Also, we have developed a prototype sensor flesh embedded with this deformation sensor for a humanoid robot, and the result of implemented reactive behavior against tactile sensation shows the feasibility of the proposed tactile sensor system.