Dynamics, Stability Analysis and Control of a Mammal-Like Octopod Robot Driven by Different Central Pattern Generators

Abstract

In this paper, we studied numerically both kinematic and dynamic models of a biologically inspired mammal-like octopod robot walking with a tetrapod gait. Three different nonlinear oscillators were used to drive the robot’s legs working as central pattern generators. In addition, also a new, relatively simple and efficient model was proposed and investigated. The introduced model of the gait generator allowed us to obtain better both kinematic and dynamic parameters of motion of the robot walking in different directions. By changing the length and the height of a single step of the robot, we introduced in a simple way the initial, rhythmic and terminal phases of the robot gait. For numerical research and to visualization of the walking process, we developed a simulation model of the investigated robot in Mathematica software. We computed displacement, velocity and acceleration of the center of the robot’s body, fluctuations in the zero moment point of the robot and the ground reaction forces acting on the feet of the robot. The obtained results indicated some advantages of the proposed central pattern generator regarding fluctuations in the robot’s body, the minimum value of dynamic stability margin as well as the minimum value of a friction coefficient which is necessary to avoid slipping between the ground and the robot’s feet during walking process. Eventually, the proposed model of gait also allowed us to control the vertical position of the robot during walking in different directions.