The Design And Characterization Of Flexible Tactile Sensors For Robot Skin

Industrial automation is the developing trend of china's manufacturing and robots become increasingly prevalent in factories.Man-machine collaborating system will gradually substitute for traditional industrial robots to accomplish complex tasks.Under the man-machine collaboration mechanism,robots and operators work side by side without a security fence which would result in industrial accidents or personal injuries.In order to ensure the security of the robots and the people in the process of collaboration,the robots should be equipped with the capability of sense which can help robots improve the environment awareness and safely interact with people and objects.Flexible tactile sensors for robot skin are developed to meet this demand.According to the requirements of robotic obstacle avoidance and human-computer secure collaboration,a flexible tactile sensing array based on a capacitive mechanism was designed for sensitive robot skin.Microstructures atop a PDMS dielectric layer were well-designed and fabricated to enhance tactile sensitivity.By incorporating a tactile feedback control system,the flexible sensing array as the sensitive skin of a robotic manipulator demonstrated a potential capability of robotic obstacle avoidance.Due to the limitations in covering area and large-scale commercial application,the flexible tactile sensor was optimized into a large scale flexible triboelectric sensor for industrial robot skin.A tactile feedback control system was also built and achieved the goal of intelligently controlling the robot into emergency stop.The main contents of this paper are listed as follows:(1)A flexible capacitive tactile sensing array was designed and can transform external force variation into capacitance variation.It was composed of flexible polyethyleneterephthalate(PET)substrates and a polydimethylsiloxane(PDMS)dielectric layer.Four types of microstructures atop a PDMS dielectric layer were well-designed and fabricated to enhance tactile sensitivity.The optimal sensing unit achieved a high sensitivity of 35.9%/N in a force range of 0-1 N.(2)For the demonstration of robot obstacle avoidance,a tactile feedback system was built.The capacitance change of a sensing unit can be detected by a capacitance detection module and transformed into voltage variation.The trigger voltage was sent to a signal acquisition module,and a program interrupt occurred.The interrupt command enabled the robotic manipulator to change its motion and avoid obstacles.(3)A improved flexible tactile sensor based on triboelectric mechanism and electrostatic induction was designed.The device can transform external force variation into voltage and has the advantages of large area,easy fabrication and self-power supply.Roll-to-roll ultraviolet embossing was used to pattern PET.to increase the output.This process realized the capability of mass production of triboelectric material with high sensitivity.(4)We also demonstrated a tactile feedback system including triboelectric sensing array,signal acquisition module and relay control module.By integrating the tactile feedback system on an industrial robot,the experiment was successfully carried on and demonstrated a potential capability of robotic intelligent scram.The triboelectric sensing array as the sensitive skin showed high impact velocity detection sensitivity of 0.1184 m/s.The response time of the tactile feedback system is no more than 1.5 ms.