Development of Triaxis Electromagnetic Tactile Sensor With Adjustable Sensitivity and Measurement Range for Robot Manipulation

Tactile sensor is one of the most important sensations for human to perceive the external world. This article proposed a novel triaxis soft electromagnetic (EM) tactile sensor based on the principle of a transformer, where the sensitivity or measurement range of the designed tactile sensor can be adjusted by changing the excitation voltage (frequency or amplitude) of the primary coil. It mainly contains a primary coil, four secondary coils, and a PDMS elastomer containing a magnet, where the coils are planar coils and the four secondary coils are a four-quadrant structure. Therefore, the displacement of the magnet in the 3-D space can be obtained by decoupling the output voltages of the four secondary coils, which is equivalent to being capable of detecting the triaxis force. Theoretical analysis and model simulation were first used to study the influence of the excitation voltage of the primary coil on the output voltage of the secondary coil, which provides a theoretical basis for the adjustable sensitivity of the sensor. Then, the designed tactile sensor was prepared, and the typical performances of the adjustable sensitivity were evaluated by a commercial six-axis force/torque sensor. The results have shown the relationship between the sensitivity of the sensor and the excitation voltage of the primary coil and verified its ability to measure the triaxis force. Finally, the adjustable ability of the designed tactile sensor to measure normal force and shear force was verified by a commercial robotic arm with an electric gripper.