This paper presents a study of bioinspired wall-climbing robot (WCR) using spiny toes. The first part of the paper describes a design of a flexible spiny toe inspired by the features of a typical wall-climbing insect Serica orientalis Motschulsky’s tarsal system. A simple contact model of the spiny toe is proposed by considering the contact asperities as spheres. With the help of the finite element method (FEM), the stiffness matrices as well as the directional adhesive properties of the spiny toe are obtained. A single spiny toe and its array are fabricated via fast prototyping. The adhesive forces and pull-off positions of the single toe are measured with a homebuilt apparatus using displacement-control method under different compressive deformations. As for the spiny array, the effect of the dragging path on the adhesive forces is evaluated. The results show that, both the single toe and array exhibit directional adhesive features. The value of compressive deformation of the single toe influences the contacting angle, as a consequence the directional adhesive behavior is achieved. When forming an array with numerous spiny toes, the adhesive ability is strengthened, which is also affected by the random distribution of the surface asperity height.
In the second part of the paper, a prototype of bioinspired WCR is designed and fabricated based on a fully understanding of the spiny contact mechanism. The robot has two feet, each of which has spring-actuated gripper. An inchworm gait is generated according to the trajectory planning of the feet. Using the proposed spiny arrays, the robot archives scaling on vertical and inverted rough surfaces, and can also transition between vertical and ceiling walls. The performance of the prototype of bioinspired WCR shows promising in developing an intelligent and maneuverable WCR system in practical applications.