Research On Foot Adhesion Properties Of Gecko-like Robot For Climbing On The Surface Of Spacecraft

With the rapid development of space technology,in-orbit control will become an essential means to detect and repair faulty spacecraft.A mobile robot system can stick to and climb outside the spacecraft module is proposed.The robot can rely on the adhesion force of its foot to climb stably and reliably in zero gravity,vacuum,high or low-temperature space environment,and move to the target position to detect and repair the spacecraft.In order to study biomimetic adhesive structures with reliable adhesion properties,a lot of research has been done on biomimetic adhesive structures at home and abroad,but there is still a significant gap in the adhesion properties of gecko feet,and it isn’t easy to achieve reliable adhesion and rapid desorption at the same time.The excellent adhesion properties of gecko feet are due to their multi-scale fiber array structure with a certain oblique angle.Therefore,the adhesion mechanism of gecko feet needs to be studied while imita ting the microstructure of the gecko feet.This paper first studies the microstructure of the gecko foot and establishes a contact mechanics model,including the spatulae pad and spatulae shank structure based on van der Waals force and frictional self-locking force,and analyzes its adhesion mechanism in essence.Based on the geometric model of the spatulae structure,a discrete element simulation model of the gecko spatulae structure and the contact surface is established using particle accumulation.By simulating the dynamic process of the adhesion and desorption of the gecko spatulae structure to the contact surface under the action of normal and tangential external forces,the relationship between the normal adhesion force and the tangential adhesion force of the spatulae structure under different desorption angles is obtained.Variation curves to analyze the directional adhesion mechanical properties of the gecko spatulae structure.At the same time,a force test system was built based on a multi-degree-of-freedom nano manipulator and an atomic force probe in a scanning electron microscope.To test the adhesion characteristics of gecko spatulae and verify the correctness of the mechanical model of the adhesion of the spatulae structure.Based on the study of the adhesion mechanism of gecko foot spatulae structure,the bionic adhesion structure with different size parameters and structural parameters was mechanically modeled by imitating the microstructure of gecko foot end based on van der Waals adhesion.Th e adhesion and desorption mechanical models of the micron-scale columnar biomimetic structure array,micron-scale wedge-shaped,and nano-scale biomimetic structure array were established,respectively.The influence law of the microarray scale parameters,structural parameters,material stiffness and other parameters on the adhesion characteristics was analyzed.The discrete element model of the bionic microstructure array is established,and the influence law of the directional adhesion characteristics of the microstructure array is analyzed by simulating the dynamic process of adhesion and desorption of the microstructure array.The experimental study on the adhesion characteristics of microstructure arrays was combined with the space environment.The corr esponding preparation method is selected for the adhesion structure arrays with different size,structural,and material property parameters.The columnar biomimetic microstructure array is prepared by inductively coupled plasma technology.The flexible we dge-shaped microstructure is processed by water-assisted laser ablation technology.At the same time,a two-dimensional force test platform is built based on a two-dimensional motion system and a multi-dimensional force test system.The microadhesion structure is fixed on the end mechanism of the motion system,and the pre-pressure is generated by the movement of the mechanism to make the micro-adhesion structure entirely in contact with the test interface,and then the tangential sliding friction is performed until desorption,and the normal and tangential adhesion forces are obtained.The adhesion properties of the biomimetic micro-structure arrays with various parameters were tested,and the adhesion properties of the micro-adhesive structures were compared and evaluated.Based on the research on the adhesion characteristics of the robot foot,the design and experimental research of the crawling robot is carried out.Based on the analysis of the space environment,the surface structure characteristics of the target spacecraft,and the motion law of the gecko body structure,the body mechanism configuration of the crawling robot is designed based on the adhesion characteristics of the feet.The motion function of the robot’s foot-lifting and footfalling during the crawling process is realized by the rope-driven detachment mechanism,and the motion gait is analyzed.At the same time,the mechanical model of adhesion and desorption of the robot’s flexible adhesive foot during the lifting process was established,and the optimal desorption method was obtained.On this basis,the principle prototype of the climbing robot was developed,and the adhesion characteristics of the robot feet were tested experimentally.At the same time,the gravity compensation method is used to build a low-gravity experimental platform to simulate the microgravity environment for the robot’s adhesion and climbing test.Test the motion function of the crawling robot principle prototype with stable adhesion and crawling.The influence of motion gait on the adhesion and crawling function of the principle prototype was analyzed.Verify the feasibility of the overall solution of the crawling robot.