Gait analysis of a radial symmetrical hexapod robot based on parallel mechanisms

Abstract

Most gait studies of multi-legged robots in past neglected the dexterity of robot body and the relationship between stride length and body height. This paper investigates the performance of a radial symmetrical hexapod robot based on the dexterity of parallel mechanism. Assuming the constraints between the supporting feet and the ground with hinges, the supporting legs and the hexapod body are taken as a parallel mechanism, and each swing leg is regarded as a serial manipulator. The hexapod robot can be considered as a series of hybrid serial-parallel mechanisms while walking on the ground. Locomotion performance can be got by analyzing these equivalent mechanisms. The kinematics of the whole robotic system is established, and the influence of foothold position on the workspace of robot body is analyzed. A new method to calculate the stride length of multi-legged robots is proposed by analyzing the relationship between the workspaces of two adjacent equivalent parallel mechanisms in one gait cycle. Referring to service region and service sphere, weight service sphere and weight service region are put forward to evaluate the dexterity of robot body. The dexterity of single point in workspace and the dexterity distribution in vertical and horizontal projection plane are demonstrated. Simulation shows when the foothold offset goes up to 174 mm, the dexterity of robot body achieves its maximum value 0.1644 in mixed gait. The proposed methods based on parallel mechanisms can be used to calculate the stride length and the dexterity of multi-legged robot, and provide new approach to determine the stride length, body height, footholds in gait planning of multi-legged robot.