Measurement and Control of the Contact Forces between Walking Robot legs and its Environment
Mohammed Ahmed, Yong-Ho Yoo, Frank Kirchner
In Proceedings of the Joint 9th Asia-Pacific ISTVS Conference and Annual Meeting of Japanese Society for Terramechanics, (ISTVS-10), 27.9.-30.9.2010, Sapporo, o.A., Sep/2010.
Interaction between a walking robot and its environment is one of the most important issues in robotic research. To achieve good dynamical locomotion behaviors such as compliance with unknown load on the walking pattern as well as for energy-efficient locomotion behaviors such as low friction, high-force fidelity, and large-force bandwidth are deeply related to the interaction between the robot and its environment.
For a good walking behavior, the robot should be capable of efficiently handling the forces resulting from the physical contact between its legs and the environment. Pure motion control turns out to be inadequate because the unavoidable modeling errors and uncertainties may cause a rise of the contact force, ultimately leading to an unstable behavior during the interaction, especially in the presence of rigid environments.
Force feedback and force control becomes mandatory to achieve a robust and versatile behavior of a robotic system in poorly structured environments as well as safe and dependable operation in the presence of humans.
In this paper, different approaches to measure the interaction forces between a legged robot and the environment that can be used for impedance control of its joint actuators are proposed with In addition, the analysis of indirect force control strategies, conceived to keep the contact forces limited by ensuring a suitable compliant behavior to the robot foot, with no need for an accurate model of the environment and formulation of the indirect force control via motion control scheme. This formulation is the essential premise to the synthesis of a hybrid impedance (admittance to be more specific) force/motion controller scheme. The results of experiments performed in a realistic simulation framework along with some analysis of the terrain force interaction between robot leg and the ground are presented.
Force measurement, terrain interaction, impedance control, legged robots, simulation