The Development Of Slip Sensor Via The Micro-bending Effect

With the development of robot technology,slip as a kind of perceptual mode plays a more important role than before when judging the robot hand grasping successful or not.The existing slip sensors mainly use acceleration,visual recognition,voltage detection and other ways to detect relative sliding.However,due to the limitation of the technical level and the manufacturing cost,the research of the sliding sensor is still in exploration.This article proposes a sliding sensor based on the micro-bending effect of the fiber.Based on the principle of micro-bending effect,the sensor measures the friction between the object and the robot by a series of transformation: "force signal-displacement signal-luminous flux-voltage signal".A cantilever elastic tooth plate structure is designed to realize the transformation of the force signal-displacement signal.The advantage is that the deformation variable is small and has good repeatability.The important parameters of the cantilever elastic tooth plate are determined,including the tooth pitch,the radius of tooth profile,the coefficient of stiffness of the elastic cantilever group and so on.Using the photoelectric conversion circuit to convert the light flux into a voltage signal.The above system consists of a measuring unit.The sensor consists of two orthogonal measuring units,which are used to measure the two frictional forces in the X / Y direction,respectively.The calibration test is required to obtain the relationship between the force signal and the voltage signal of the sensor accurately.First,the two units in the X / Y direction are calibrated separately.The results show that the force signal and the voltage signal show a linear correlation,of which the coefficients are 0.99963 and 0.99869,respectively.The coefficients are different because the coefficients of stiffness of the elastic cantilever group of the two sensing units are different.And then,combined sensors are calibrated in all directions.It was found that the error was existed,due to the presence of the frictional force.After the friction gets furtherly compensated,the experimental shows that the overall error within ± 2%,when the angle between Load and X axis in the range of 30 ° ~ 60 °.It can suit the sensor detection needs,and indicating that the sensor design is valid.Set up the test platform to simulate the robot to grasp the test object,and measure the static friction and sliding friction separately between the sensor and the object,the results of the test show that there is a significant falling edge of the voltage signal when the sensor and the object change from static friction to sliding friction.When the load is 16 N,the voltage drop on the falling edge is about 1V.Thus,it is easy to capture the moment that the relative sliding occurs between the sensor and the object.