Design, Control, and Validation of a Symmetrical Hip and Straight-Legged Vertically-Compliant Bipedal Robot

Abstract

This paper presents the development, modeling, and control of L03, an underactuated 3D bipedal robot with symmetrical hips and straight legs. This innovative design requires only five actuators, two for the legs and three for the hips. This paper is divided into three parts: (1) mechanism design and kinematic analysis; (2) trajectory planning for the center of mass and foot landing points based on the Divergent Component of Motion (DCM), enabling lateral and forward walking capabilities for the robot; and (3) gait stability analysis through prototype experiments. The primary focus of this study is to explore the application of underactuated symmetrical designs and determine the number of motors required to achieve omnidirectional movement of a bipedal robot. Our simulation and experimental results demonstrate that L03 achieves simple walking with a stable and consistent gait. Due to its lightweight construction, low leg inertia, and straight-legged design, L03 can achieve ground perception and gentle ground contact without the need for force sensors. Compared to existing bipedal robots, L03 closely adheres to the characteristics of the linear inverted pendulum model, making it an invaluable platform for future algorithm research.

High Dynamic Bipedal Robot with Underactuated Telescopic Straight Legs

“…Straight-legged designs are more suitable for modeling and relatively easier for control. Humanoid robots featuring straight leg structures offer several advantages [22,23], including enhanced stability, heightened movement efficiency, versatile adaptability, and streamlined control. Straight legs provide superior static and dynamic stability, reducing swaying and oscillations.…”

“…Consequently, straight leg structures are also frequently chosen for the design of humanoid robots. Works like Tang [23] tend to use a single bar for each leg. Rarely do studies use double-bar design, as introduced in this paper, for legs, which can improve the standing and walking states of bipedal robots.…”

“…Udai [24] and Bhardwaj [25] both discussed the hip trajectory of bipedal robots. Previous work of Tang [23] also proposed a symmetrical hip design for bipedal robots.…”

A Hierarchical Control Strategy for a Rigid–Flexible Coupled Hexapod Bio-Robot

“…There is extensive current research on rigid-soft coupling robots, with the most direct solution being the optimization of the robot structure based on modern design methods [9,10]. K. Xu [11] proposed an optimized design method for the flexible joint linkage of a quadruped robot, which improves the payload capacity of the robot.…”