Design, Optimization and Evaluation of a New Cylinder Attachment Geometry to Improve the Hopping Height of the Bionic One-Legged Robot

Donglai Zhao,Wenjie Ge,Xiaojuan Mo,Yuzhu Li,Zhuo Wang

doi:10.3390/app11083676

Abstract

Due to the high power-to-weight ratio and robustness, hydraulic cylinders are widely used in the actuation area of the legged robot systems. Most of these applications are focused on the motion stability, gait planning, and impedance control. However, the energy efficiency of the legged robotic system is also a very important point to be considered. Hopping locomotion requires a fast extension of the tibia leg at the end of the take-off phase, which causes a continuous increment of the cylinder velocity under the normally direct attachment geometry (DAG) of the cylinder. This leads to a high flow requirement, large pressure drop, and low energy efficiency. Therefore, we propose a four-bar mechanism attachment geometry (FMAG) to improve the energy efficiency by refining the relationship between the joint angle and cylinder displacement trend. The kinematic and dynamic models of the bionic one-legged robot are built to calculate the hopping process during the take-off phase. Based on the established dynamic models, the design parameters in both the DAG and FMAG are optimized to maximize the hopping height, respectively. The hopping experiments are conducted to verify the effectiveness of the new attachment geometry. The experimental results show that the robot hopping energy at the end of the take-off phase increases 14.8% under the FMAG.

Highlights

The legged robots have superior mobility and adaptation on the rough road compared to the wheeled and tracked robots. This significant advantage has encouraged scholars to research the legged robot over the past decades
To explore the intrinsic reason and find how the four-bar mechanism attachment geometry (FMAG) achieves a higher hopping height than the direct attachment geometry (DAG), the experiment results combining the variation of the equivalent lever length are discussed in detail
From Equation (19), with the increments of the knee joint angle and the body velocity, the angular velocity of the knee joint continues to increase during the take-off phase

Summary

Introduction

The legged robots have superior mobility and adaptation on the rough road compared to the wheeled and tracked robots. This significant advantage has encouraged scholars to research the legged robot over the past decades. Raibert et al developed one-legged, biped, and quadruped running robots which performed highly dynamic ability in the 1980s [1,2,3]. All these robots used a pneumatic cylinder as a telescopic leg. The mechanical springs located at the telescopic leg and hip joint improved this robot’s hopping efficiency [4,5]

Methods

Results

Conclusion