A Flexible Tactile Sensor Based On The Combination Of Capacitance And Triboelectricity

The robot market has huge demand for tactile sensing technology.This paper analyzes the current research status of tactile sensors and target object recognition methods at home and abroad,and designs a new type of flexible composite sensor based on capacitive and frictional electrical machinery applied to tactile systems for robotics.The sensor can measure the hardness and surface material information of the target object.The composite sensor is composed of a capacitive sensor with a porous polymer PDMS(polydimethylsiloxane)as a capacitive medium and a single-level friction generating electrode structure.The friction layer of the single-level friction power generation and the dielectric layer of the capacitor are integrally formed by filling a mixture of PDMS and NaCl through a cleverly designed mold.The step is to solidify and salt out the mixed precursor of PDMS and NaCl to form a porous PDMS layer,and then adhere to the double-sided FPC flexible circuit board.Finally,a composite tactile sensor capable of measuring target object information is obtained.Considering the requirements for high sensitivity and pressure measurement range and structural durability of composite sensors that can be applied to intelligent robotic arms,a lowcost,easy-to-control,and environmentally-friendly method for preparing flexible composite tactile sensors is proposed.The principle of hardness measurement and triboelectricity generation about the flexible composite sensor are described.In order to analyze the composite tactile sensor based on the capacitive and triboelectric,we processed and analyzed the experimental data from the two modules of capacitance and triboelectricity in the composite sensor.The stress-capacitance change curve of the composite tactile sensor and the triboelectric voltage information when different materials in contact are obtained.The greater the pressure when the composite sensor is in contact with the surface of the indenter,the greater the amount of change in capacitance,and when objects of different materials are in contact with the composite sensor,the friction voltage signal shows a significant difference.The PDMS: NaCl = 1: 2 composite sensor selected for the optimal preparation parameters has a measurable range of 0-200 kpa,a device response time of 9 ms,and still maintains stable performance after 3,000 cycles.We builds an intelligent tactile measurement system in subsequent application experiments.This system is based on a robotic arm and a flexible composite sensor based on capacitive and frictional electromechanics.First,debug and analyze the system under a large number of experiments to find the program parameter settings of grasping objects.Then conduct realworld grip simulation experiments,respectively,to perform non-injury grip recognition test on common balls(table tennis,tennis,training balls,etc.)and common fruits(kiwi,persimmon,mango,etc.)and fruit ripeness judgment.Through comprehensive analysis of the two electrical signals(capacitive signal and triboelectric signal)of the composite sensor during the gripping process,the experimental results show that the composite tactile sensor can effectively identify and distinguish various types of target objects.At the same time,it can also initially determine the hardness level of the object,whether the target object is damaged,and whether the fruit is ripe or not.Human recognition of target objects is a comprehensive recognition process.In order to indent the gap between robotic tactile sensation and human tactile sensation,the research and development of robotic tactile sensation system is proposed further.