Study on kinematics and inverse dynamics of legged mobile manipulator for determining feet-terrain reaction forces and joint torques

Abstract

Legged mobile manipulator is a robotic system that consists of a serial manipulator rigidly mounted on a multi-legged platform. Its high mobility and dexterity makes this robotic system more suitable to be used in disaster management and space applications, where there will be an uneven and unstructured terrain. However, its high power consumption and low stability under external disturbances are the challenges to be solved. In this paper, an attempt is made to determine the feet-terrain reaction forces and joint actuating torques, which ensures the minimum power consumption. Initially, the kinematic model of the robotic system is developed using general-purpose rigid body analysis. Newton–Euler approach is then utilized to formulate the coupled dynamics of this multi-body system. The developed inverse dynamics model considers the inertial effects of the manipulator and moving legs on the trunk body and stationary legs. However, it has no unique solution due to its high redundancy. Therefore, it has been formulated as an optimization problem in order to minimize the power consumption after satisfying some functional constraints. The performance of the developed approach has been tested on computer simulations. The results show that the developed model can efficiently study the kinematics and dynamics of the legged mobile manipulator and also explain the nature of shifting of center of gravity of the combined robotic system due to the movement of the manipulator links. The developed model is a generalized one and it can be used for carrying out stability analysis and designing suitable controller for the combined robotic system.