| Microgrippers is the important tool in micro-manipulation,and has a wide range of application prospects,such as in micro-machined parts machining,micromanipulation and assembly,biomedical engineering,and precision optical engineering.High-precision and high-quality micro-grippers could help improve the possibility of micromanipulation and assembly operations.However,current micro-grippers are not perfect in terms of displacement control and driving force control.In the process of prey capturing and food transporting,ants act like a microgripper’s clamping mechanism,which can not only transport soft materials such as ant eggs and water,but also fighting enemy,digging holes and prey capturing,this provides an excellent reference for designing new microgripper designs.This article selects the ant mandible as the research object,observed mandibles moving process,testing biting force,and analyzed its movement control mechanism.A mechanical model was established to analyze the motion control mechanism of the mandibles.Based on the theoretical analysis,an conceptual design of bionic micro-holder is proposed.This study will enrich and improve the ant predation mechanism,and has important theoretical significance and practical engineering value for the development of micro-grippers.Firstly,we have selected four different species of long-mandibles ants for research,a high-speed camera system is used to capture the dynamic process of ant predation.The mandibles moving process was observed,and various kinematic parameters such as speed,acceleration were obtained.The ants close their mandibles quickly and with different closing speeds when they prey,among them the highest average speed of the mandibles is 602 rad/s of ant Anochetus risii,followed by ant Harpegnathos venator,the speed is about 35.08 rad/s,which is about 4.8 times that of ant Camponotus japonica,and almost 8.7 times that of ant Polyrhachis dives.We measured the biting force by a membrane pressure sensor.It was found that the maximum biting force produced by Camponotus japonica,smaller in size and mandible speed can reach 40.3 mN,which is greater than the biting force of swift ants Harpegnathos venator with biting force 30.6 mN.Ant Polyrhachis dives has the smallest biting force,less than 1 mN.Secondly,we observe the microstructure and distribution of head muscles by frozen section technique.The adductor muscles mainly controlling the mandibles movement and can be divided into two types: filament-attached muscle fibers and direct attached muscle fibers.Camponotus japonica had more ffilament-attached muscle fibers with larger biting forces,and Harpegnathos venator had more direct attached muscle fibers with higher closing speed.Finally,a distributed driving model based on muscle geometry and physical properties was established.According to the muscular morphology,we simplify the directly attached fibers and filament attached fibers into cylindrical and conical structures,respectively,and build a muscle-driven model.Theoretical analysis and experimental results show that cylindrical muscles help to increase the speed of the mandibles when the muscles number,length,volume are the same,and the conical muscles help to provide gripping force.Therefore,Camponotus japonica can provide more than 1.3 times biting force than Harpegnathos venator,while Harpegnathos venator can produce more than 4 times mandible closing speed than Camponotus japonica.Through the theoretical analysis and modeling of the ant mandible’s movement,a conceptual design model of the bionic micro-clamp is given.The mandible,the apodeme,and the adductor muscle are equivalent to the clamping arm,connecting rod and motion control mechanism of the micro-gripper.The micro-gripper can achieve the effects of high speed and big driving force at the same time,and the structure of the micro-gripper is compact,and is suitable for a variety of micro-operation occasions. |
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