Design And Output Characteristics Of Magnetostrictive Tactile Sensor For Force And Stiffness Detection

Tactile sensing is an essential medium for intelligent robots to interact with environment.Compared with visual technology,tactile sensing and its applications develop slowly.With the development of smart home,bionic prosthesis and autonomous operation of medical procedures,tactile sensing technology has more and more significant application and broad prospects.As the hardware foundation of tactile sensing technology,tactile sensors need to be studied in design,manufacture and output characteristics.Most of the available tactile sensors only measure force,but can not obtain other tactile information interacting with the target objects.Based on structural characteristics of cantilever beam and piezomagnetic effect,a new tactile sensor is designed and fabricated by using flaky Galfenol alloy,which is used to test the gripping force and the stiffness of manipulated objects.In order to optimize the performance of the sensor,the static magnetic characteristics of the flaky Galfenol alloy were tested,including magnetostrictive effect and piezomagnetic effect.Meanwhile,the finite element simulation software COMSOL is used to analyze the structure of the flaky Galfenol alloy cantilever beam.Combined with the simulation results and experimental results,it is concluded that with the increase of magnetic field intensity,the piezomagnetic coefficient of the flaky Galfenol alloy increases at first,then decreases to be stable.When the stress is 0 MPa and the bias magnetic field intensity is 4.5 k A/m,the piezomagnetic coefficient reaches maximum 17.5 T/GPa.Considering finger skin tactile model,the structure of magnetostrictive tactile sensor is designed,and the working principle of the sensor is introduced.Based on the magnetostrictive linear constitutive equation,the force measurement model and the stiffness detection model have been established,which can be used to describe the relationship between output voltage of sensor and grasping force and stiffness of objects.The output characteristic of the sensor are calculated based on the model by MATLAB software,and the sensitivity of stiffness detection is determined according to the output characteristic curve of the sensor.Finally,the output characteristics of magnetostrictive tactile sensor were tested.A prototype of magnetostrictive tactile sensor was made and the testing system of tactilesensors was built.With the measurement of static force and dynamic force,it indicates that the sensor has a sensitivity of 114 m V/N,a resolution of 0.07 N and a linearity of 3%.The sensor possess a good response to dynamic force and a good sensing accuracy in the frequency range of 2-4 Hz.Based on the testing system of tactile sensors,the stiffness detection method of target object is proposed,and the estimated stiffness of four sample objects is obtained by the analysis of output voltage.Extracting gradient value and the steady value of output voltage as eigenvalues,object recognition based on target stiffness is realized with KNN algorithm,which recognition accuracy reaches 95%.