Analysis of the Stabilization System of Mimbot Biped

 

M.E. Escobar*¹, H. Rubio², J.C. García-Prada³

 

^1,2,3 Departamento de Ingeniería Mecánica. Universidad Carlos III de Madrid. Av. Universidad 30, 28911. Madrid. Spain. *mescobar@ing.uc3m.es.

 

Abstract

Mimbot robot consists of a mechanical system with one degree of freedom activated by a single motor; this robot is capable of simulating the human gait. Mimbot has three essential mechanisms: the Chebyshev mechanism, the pantograph mechanism and a stabilization system. The studied mechanism is an articulated system of links used in the leg of of the Mimbot biped robot. The technology used in the Mimbot biped is characterized by keeping these design conditions; using a mechanical system based on classical mechanics, the biped must reproduce the trajectory of human gait, energy consumption should be minimal and the prototype should be a low-cost robot. The role of the original stabilization system is to guide the foot to provide support for both legs; however, the position of the foot is not completely parallel to the support surface, which causes variations in the trajectory of the mass center of the biped, causing loss of stability. This paper presents a study of stability in the sagittal plane of the robot, adding a new mechanism that ensures that the stabilizer link is parallel to the ground at all times. Finally, a study of the kinematic and dynamic behavior generated by the modification has been carried out through an analytical model created by Adams ® software.

Keywords: robot, stabilization, kinematic and dynamics of mechanism.

 

Resumen

El robot bípedo Mimbot es un dispositivo mecánico de un grado de libertad accionado por un solo motor y capaz de emular el movimiento del paso humano. El Mimbot cuenta con tres mecanismos esenciales: mecanismo de Chebyshev, mecanismo tipo pantógrafo y un sistema de estabilización. La tecnología empleada en el Mimbot bípedo se caracteriza por mantener estas condiciones de diseño; utilizando un sistema mecánico basado en la mecánica clásica, el bípedo reproduce la trayectoria de la marcha humana, el consumo de energía debe ser mínimo y el prototipo debe ser un robot de bajo costo. El sistema de estabilización original busca proporcionar cierta orientación al pie para que sirva de apoyo al bípedo; sin embargo, no logra posicionar el pie completamente paralelo a la superficie de apoyo, lo cual ocasiona variaciones extensibles en la trayectoria del centro de masas del bípedo originando la consecuente pérdida de estabilidad. Este artículo plantea el estudio de la estabilidad, en el plano sagital del robot propone la inserción de un nuevo mecanismo que asegura que el eslabón estabilizador esté en todo momento paralelo al suelo. Finalmente se efectúa un estudio del comportamiento cinemático y dinámico generado por esta modificación, mediante un modelo analítico, implementado en el software Adams.

 

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Acknowledgements

Acknowledgments are due to the Spanish CICYT Project DPI2006-15443-C0-JCGPRADA.

 

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