Stability Analysis and Implementation of a Wheel-Leg Robot Using the Force-Angle Method

Considering that stability is an inseparable part of mobile robots, in this paper, the stability of a wheeled-legged robot is investigated. A suitable method for stability analysis should be adopted regarding the robot mechanism and alteration in its height. One of the critical issues in this regard is the displacement of the center of mass for various reasons, such as the manipulator displacement or uncertainties in the robot mechanism. Thus, this paper brings novelty by considering a parameter for the position of the center of mass relative to the geometric center of the robot, which has not yet been discussed as an independent degree of freedom. In this regard, due to its ability to extend in three dimensions and determination of the applied torques according to the variable height of the robot, we propose a novel force-angle method That has been selected and applied for stability analysis. While a specific variable is defined for the relative position of the center of mass, which generalizes this stability method. Then, to validate the extended Force-Angle method, the theoretical results are compared with the obtained results of the constructed WLRIUST robot. The range of stability of the robot was determined at different points of the center of mass and with possible angles for the legs of the robot, and the torques were reported because torque jumps are an important factor in system instability. Hence, These results are also theoretically and practically compared concerning changes in joint torques when the robot is unstable.

Automated summary

In this study, the stability of a wheeled-legged robot is investigated by introducing the position of the center of mass relative to the geometric center of the robot as an independent degree of freedom. A novel force-angle method is proposed and applied for stability analysis, and its effectiveness is validated by comparing with the results of an actual robot.