A Three-row Opposed Gripping Mechanism with Bioinspired Spiny Toes for Wall-climbing Robots

This paper presents a study of a three-row opposed gripping mechanism made of bioinspired spiny toes. An insect Serica orientalis Motschulsky’s tarsal system was first described and studied. A compliant single spiny toe model was established assuming that the contact asperities were spheres. Following the single toe contact model, a spiny toe array’s contact model was then developed using asperity height’s distribution function. By studying the engaging and disengaging process of the single toe, the mechanical behavior of the toe and toe array were addressed. The toes as well as the arrays were manufactured via rapid prototyping. A customized apparatus using displacement-control method has been carried out to measure the pull-in forces and pull-off positions of the single toe and toe array under various compression conditions. Based on the understanding, a three-row opposed gripping mechanism with radial configuration for wall-climbing robots was designed and fabricated according to the mechanical behaviors of the toe and array. Using an opposed spoke configuration with 3 rows of 31 toes on each linkage array, the mechanism designed as a foot of climbing robots can vertically resist at least 1 kg of load on rough inverted surface, while the maximum normal load is as high as 31 N. The findings may provide a way in developing a high payload wall-climbing robot system for practical applications.