Development of a Permanent Magnet Elastomer (PME) Infused Soft Robot Skin for Tactile Sensing

The skin is an important organ which enables humans to interact with the unstructured environment around. It is perfectly soft and covers the entire body providing immediate feedback even when that part is not directly in the field of vision. With the human skin as an inspiration, in this paper, we develop a novel completely soft robot skin for tactile sensing. The skin utilizes a new type of material called as Permanent Magnet Elastomer (PME) to replace the traditionally used hard permanent magnet for hall effect based tactile sensors. PME is formed by mixing Neodymium particles in a polymer base and using strong magnetization (up to 6 T) for anisotropy and to achieve strong and complete magnetization. The 6-axis soft PME is a perfect replacement for powerful hard magnets. We also do a thorough analysis of this material by infusing it in different types of silicone and as a result the most suitable combinations are selected. Performance tests show that the sensor can detect minute forces like 0.1 N. Moreover, the hysteresis test is carried out and the hysteresis error for our skin is found to be only 1.402%. An overloading test is also performed by loading the skin up to 64 N to check the robustness. In conclusion, the skin can produce reliable Triaxial force measurements and we present two models of it for smaller and large force range measurements respectively.