Control Strategies of Gecko’s Toe in Response to Reduced Gravity

Shear-induced adhesion is one of the key properties for the gecko moving safely and quickly in a three-dimensional environment. The control strategies of such locomotion strongly relying on adhesion are still not well understood. In this study, we measured foot alignment and three-dimensional reaction forces of the single toes of the Tokay gecko running on the ground freely (gravity condition) and running in a situation where the gravity force was counterbalanced (reduced gravity condition). The forelimb rotated from the outward position to the front-facing position and the hindlimb rotated from the outward position to the rear-facing position, when running with balanced force, which indicated that the adhesive system was employed behaviorally through the modulation of the foot alignment. The toe was compressed and pulled in the gravity condition, but it was tensed and pulled in the reduced gravity condition. There was an approximately linear relationship between peak normal forces and the corresponding shear forces in both the reduced gravity condition (FN = −0.40FS − 0.008) and the gravity condition (FN = 2.70FS − 0.12). The footpad was compressed and pushed in the gravity condition, whereas it was tensed and pulled in the reduced gravity condition. There was an approximately linear relationship between peak normal forces and the corresponding shear forces in both the reduced gravity condition (FN = −0.39FS − 0.001) and in the gravity condition (FN = −2.80FS − 0.08). The shear-induced adhesion of the gecko footpad is controlled by the coupling of the normal force and shear forces: that is why in this system adhesion was shear-sensitive and friction was load-sensitive. Our measurements of single toe reaction forces also show that geckos control their footpad attachment using ‘toe rolling-in and gripping’ motion in both gravity and reduced gravity conditions

Bio-Inspired Adhesive Footpad for Legged Robot Climbing under Reduced Gravity: Multiple Toes Facilitate Stable Attachment

This paper presents the design of a legged robot with gecko-mimicking mechanism and mushroom-shaped adhesive microstructure (MSAMS) that can climb surfaces under reduced gravity. The design principle, adhesion performance and roles of different toes of footpad are explored and discussed in this paper. The effect of the preload velocity, peeling velocity and thickness of backing layering on the reliability of the robot are investigated. Results show that pull-force is independent of preload velocity, while the peeling force is relying on peeling velocity, and the peel strength increased with the increasing thickness of the backing layer. The climbing experiments show that the robot can climb under mimic zero gravity by using multiple toes facilitating adhesion. The robot with new type of footpads also provides a good platform for testing different adhesive materials for the future space applications

Rans and detached-eddy simulation of the NASA trap wing for HILIFTPW-1.

This project aims to study and perform a turbulent flow simulation over the NASA Trap Wing by exploring the numerical aerodynamic predictions capacity of high lift configurations using two S-A, k-ω SST and DES method for comparison in ANSYS Fluent software, among which DES method has been paid key attention for its accuracy as a CFD high lift prediction tool. NASA Trap Wing geometry from High lift Prediction Workshop-1 is applied in this project with slat angle of 30° and flap angle of 25°. Prediction results are analysed for several flow characteristics including pressure distribution, force and moment coefficient as well as skin friction and some other flow visualization. Results show that the DES method performs the best flow prediction near stall, however, it fails to provide as good flow characteristics at low pitch angles as S-A model and fails to show stall patterns. Both S-A and k-ω SST model shows a premature stall due to massive separation at high AoAs, while k-ω SST model gives a worst prediction results among all the three turbulent models applied. Restarted S-A model, based on experience from the 1st AIAA High lift Prediction Workshop, means high pitch angle case restarted with the converged solution of lower pitch angle case, which improves the prediction results of original S-A model by delaying the separation in very limited extent. Further researches have been proposed including key local mesh adaption, further application of URANS model for comparison, higher AoA cases for DES model for testing its capability, increasing the pitch angles cases more gradually for better prediction.PhD in Aerospac