# Design and Analysis of a Planar Six-Bar Crank-Driven Leg Mechanism for Walking Robots
## 1 Introduction
Simulation efforts were undertaken to evaluate key parameters such as movement velocity, spring deformation, and the dynamics of running gait, leading to prototype creation and treadmill testing. This research demonstrates the potential of applying biomechanical insights to the design of robotic leg mechanisms, specifically for achieving efficient high-speed locomotion. Additionally, a new study [12] presented the design of a 12-link single-leg walking mechanism for a single-DOF quadruped robot, focusing on simplicity, easy implementation, and minimal driving components. The mechanism features a series of crank-rocker and scaling mechanisms to achieve an \"inverted D\" walking gait trajectory, reducing the degrees of freedom and enhancing stability. An auxiliary mechanism improves its load-bearing capacity and motion stability, while a unique sole structure increases the contact area with the ground, supporting the lightweight design. The analytical expression of its foot displacement was derived, providing a foundation for dynamic analysis. Simulations using ADAMS software verified that the design meets motion requirements and stability, demonstrating its feasibility and reliability for engineering applications. Additionally, [PERSON] et al. [7] presented an eight-link novel single-degree-of-freedom crank-driven walking leg mechanism designed for walking machines and robots. The mechanism, based on the Peaucellier-Lipkin type, was thoroughly analyzed in terms of its geometry and working principles. The paper detailed various configurations and discussed the kinematic behavior of the leg mechanism. An eight-legged walking machine incorporating this mechanism was also built and tested, with the results showing a good agreement between the simulation and practical application. The leg mechanism's performance was compared with the [PERSON] and [PERSON]'s walking mechanisms, highlighting its advantages such as its stability, economical use of legs, compact design, and versatility in its stride length and height adjustments. The study concluded with a discussion on the practical applications of the walking leg mechanism in various fields, including industry, agriculture, and autonomous vehicles, while noting a limitation in positioning the linkage pair in the same plane as [PERSON]'s and the Klann linkages. [PERSON] et al. [13] developed a six-bar leg mechanism that enhances traditional four-bar linkage mechanisms by incorporating a symmetrical coupler point curve. This mechanism combines a four-bar linkage with an additional dyad, forming an embedded regular or skew pantograph. The primary advantage of this design is the amplification of the coupler curve at the output point, resulting in a compact mechanism that generates a relatively large coupler curve. This structural arrangement simplifies the analysis and synthesis process, allowing for the creation of mechanisms tailored to specific needs. The six-bar linkages, with their embedded skew pantographs, offer greater design flexibility compared to typical four-bar mechanisms. The authors highlight the ability of these mechanisms to produce large, symmetrical coupler curves and emphasize their potential in integrating the coupler curves of a four-bar linkage and a pantograph into a single system. However, the foot path generated by [PERSON] et al. 's mechanism is symmetrical without a flat portion, which limits its direct applicability as a leg mechanism for walking robots. This paper introduces a new leg mechanism for a robot designed to walk and overcome obstacles that traditional wheeled robots cannot handle. The proposed mechanism is a crank-driven, single-degree-of-freedom design featuring six links and an embedded skew pantograph. The primary objective was to modify the configuration of [PERSON] et al. 's mechanism to achieve a foot trajectory that includes a flat path in contact with the ground, making it highly suitable for walking robots.