Abstract
This study aims to develop mathematical model which can capture behavior of "wheel spider" that can perform rolling locomotion and analyze characteristics of the behavior to realize biologically inspired locomotion by robots. Therefore, a rolling wheel spider model is developed by applying constraint force on the ground to a wheel spider model without the ground and considering velocity transformation due to collision. As a result, it was found that the wheel spider goes downhill at a constant speed with rolling whether it is provided with initial velocity or not. In conclusion, the wheel spider can go down the slope over a certain pitch without providing initial velocity.